MySQL 5.7 multi-source replication – automatically combining data from multiple databases into one

MySQL’s multi-source replication allows you to replicate data from multiple databases into one database in parallel (at the same time). This post will explain and show you how to set up multi-source replication. (WARNING: This is a very long and detailed post. You might want to grab a sandwich and a drink.)

In most replication environments, you have one master database and one or more slave databases. This topology is used for high-availability scenarios, where the reads and writes are split between multiple servers. Your application sends the writes to the master, and reads data from the slaves. This is one way to scale MySQL horizontally for reads, as you can have more than one slave. Multi-source replication allows you to write to multiple MySQL instances, and then combine the data into one server.

Here is a quick overview of MySQL multi-source replication:

MySQL Multi-Source Replication enables a replication slave to receive transactions from multiple sources simultaneously. Multi-source replication can be used to back up multiple servers to a single server, to merge table shards, and consolidate data from multiple servers to a single server. Multi-source replication does not implement any conflict detection or resolution when applying the transactions, and those tasks are left to the application if required. In a multi-source replication topology, a slave creates a replication channel for each master that it should receive transactions from. (from https://dev.mysql.com/doc/refman/5.7/en/replication-multi-source-overview.html)

In this post, I will demonstrate how to setup multi-source replication with two masters and one slave (as shown in the right side of the above picture). This will involve a new installation of MySQL 5.7.10 for each server.

I am not going to explain how to install MySQL, but you do need to follow the post-installation instructions for your operating system. If you don’t run the mysqld initialize post-installation process for each install, you will run into a lot of problems (I will explain this later). I will start with what you need to do post-installation, after the server is up and running. In this example, I have turned off GTID’s, and I will enable GTID later in the process. I have written several posts on replication, so I am going to assume you have some knowledge on how to setup replication, what GTID’s are, and how replication works. I will also show you some errors you may encounter.

You may visit these posts to learn more about replication:

MySQL Replication with Global Transaction Identifiers – Step-by-Step Install and Addition of Slaves – Part One
MySQL Replication with Global Transaction Identifiers – Step-by-Step Install and Addition of Slaves – Part Two
MySQL Replication – Creating a New Master/Slave Topology with or without Virtual Machines
MySQL Replication – Multi-Threaded Slaves (Parallel Event Execution)
MySQL 5.6 Delayed Replication – Making a Slave Deliberately Lag Behind a Master

Prior to installation, you will need to make sure the repositories on the slave are being stored in a table. I have this enabled on all three servers, but it is only required for the slave. If you don’t have this enabled, you can enable it via your configuration (my.cnf or my.ini) file:

[mysqld]
master-info-repository=TABLE
relay-log-info-repository=TABLE

If you did not enable this earlier, you will want to modify your configuration file and restart MySQL. You can check to see if this is enabled via this command:

mysql> SHOW VARIABLES LIKE '%repository%';
+---------------------------+-------+
| Variable_name             | Value |
+---------------------------+-------+
| master_info_repository    | TABLE |
| relay_log_info_repository | TABLE |
+---------------------------+-------+
2 rows in set (0.00 sec)

You will also need to modify your configuration files (my.cnf or my.ini) to make sure each server has a unique server_id. I use the last three digits of the IP address for each server as my server_id, as in this example:

[mysqld]
server-id=141

To view the server_id for a given server, execute this command:

mysql> SHOW VARIABLES WHERE VARIABLE_NAME = 'server_id';
+---------------+-------+
| Variable_name | Value |
+---------------+-------+
| server_id     | 141   |
+---------------+-------+
1 row in set (0.00 sec)

I will be using three servers, and each one has MySQL 5.7.10 installed:

Server #1 – Slave – IP 192.168.1.141
Server #2 – Master #1 – IP 192.168.1.142
Server #3 – Master #2 – IP 192.168.1.143

I will refer to each of these servers as either Slave, Master #1 or Master #2.


NOTE: With MySQL 5.7, if you use a GUI-installation, a password is generated for root during the install process, and it should appear in the installation GUI. If you don’t see the password, it will be in your error log file. Also, when you run the post-installation process, a new root password may be generated again, and this password will also be located in your error log file.

# grep root error.log
2015-12-09T05:34:01.639797Z 1 [Note] A temporary password is generated for root@localhost: T<e-hd0cgI!d

You will need this password to continue using MySQL, and you will need to change it before issuing any other commands. Here is the command to change the password for root:

ALTER USER 'root'@'localhost' IDENTIFIED BY 'password';

The key to making multi-source replication work is to ensure you don’t have the same primary keys on your two masters. This is true especially if you are using AUTO_INCREMENT columns. If both masters have the same primary key for two different records, the data could be corrupted once it reaches the slave. I will show you one way to setup alternating key values using AUTO_INCREMENT. Of course, there are other ways to do this, including having your application generate the value for the keys.

If you don’t turn off GTID’s (via your configuration file) prior to running the post-installation steps, you will encounter a problem in that GTID’s will be created for the mysqld initialize process, and these transactions will be replicated to the slave. Let’s assume you enabled GTID’s from the start, before you ran the post-installation steps, and then you attempted to start replication on the slave. When you run the SHOW MASTER STATUS command, you will see something like this, showing you the 138 transactions which were executed on the master, and would now be replicated to the slave:

mysql> SHOW MASTER STATUS\G
*************************** 1. row ***************************
             File: mysql-bin.000002
         Position: 1286
     Binlog_Do_DB: 
 Binlog_Ignore_DB: 
Executed_Gtid_Set: 73fdfd2a-9e36-11e5-8592-00a64151d129:1-138
1 row in set (0.00 sec)

On the slave, you would see an error in the SHOW SLAVE STATUS:

Last_Error: Error 'Can't create database 'mysql'; database exists' on query. Default database: 'mysql'. Query: 'CREATE DATABASE mysql;

And the RETRIEVED GTID SET would look like this, showing you the 138 transactions which have already been copied to the slave.

mysql> SHOW SLAVE STATUS\G
...
Retrieved_Gtid_Set: 73fdfd2a-9e36-11e5-8592-00a64151d129:1-138
...

You can attempt to skip these transactions, but it is much easier to wait and enable GTID’s later.

After the post-installation steps, you will get the same results on all three servers for a SHOW MASTER STATUS command:

mysql> SHOW MASTER STATUS\G
*************************** 1. row ***************************
             File: mysql-bin.000002
         Position: 398
     Binlog_Do_DB: 
 Binlog_Ignore_DB: 
Executed_Gtid_Set: 
1 row in set (0.00 sec)

Next, you will need to create the replication user on each of the master servers (where 192.168.1.141 is the IP address of your slave).

mysql> CREATE USER 'replicate'@'192.168.1.141' IDENTIFIED BY 'password';
Query OK, 0 rows affected (0.05 sec)

mysql> GRANT REPLICATION SLAVE ON *.* TO 'replicate'@'192.168.1.141';
Query OK, 0 rows affected (0.01 sec)

After, you can see the additional changes (from creating the user and granting permissions) to the binary log via the SHOW MASTER STATUS command:

mysql> show master status\G
*************************** 1. row ***************************
             File: mysql-bin.000002
         Position: 873
     Binlog_Do_DB: 
 Binlog_Ignore_DB: 
Executed_Gtid_Set:
1 row in set (0.00 sec)

Now we are ready to create our schemas on the slave and the master servers. For this example, I have created a small table to be used for storing information about a comic book collection. Here are the CREATE DATABASE and CREATE TABLE commands:

Slave

CREATE DATABASE `comicbookdb`;
use comicbookdb;
CREATE TABLE `comics` (
  `comic_id` int(9) NOT NULL AUTO_INCREMENT,
  `comic_title` varchar(60) NOT NULL,
  `issue_number` decimal(9,0) NOT NULL,
  `pub_year` varchar(60) NOT NULL,
  `pub_month` varchar(60) NOT NULL,
  PRIMARY KEY (`comic_id`)
) ENGINE=InnoDB AUTO_INCREMENT=1;

You can use the same SQL to create tables on the slave as you do on the master. Since we will using AUTO_INCREMENT values on the master, you might think you would not want to use AUTO_INCREMENT in the CREATE TABLE statement on the slave. But, since we will not be doing any writes to the slave, you can use the same CREATE TABLE statement as you use on a master. You will only need to modify the CREATE TABLE statements for the masters to create alternate primary keys values. (More on this later)

When the data replicates to the slave from the master, replication will handle the AUTO_INCREMENT columns.

Here is what happens when you create the comics table on the slave without specifying the AUTO_INCREMENT for the comic_id column, and then you start replication. From the SHOW SLAVE STATUS\G command:

mysql> SHOW SLAVE STATUS\G...
Last_SQL_Error: Error 'Field 'comic_id' doesn't have a default value' on query. Default database: 'comicbookdb'. Query: 'INSERT INTO COMICS (comic_title, issue_number, pub_year, pub_month) VALUES('Fly Man','5','2014','03')'
...

We now need to find a way to create different and alternating values for our primary key column – comic_id. You could have your application do this, but an easy way is to use the auto_increment_increment variable. In your configuration file (my.cnf or my.ini), you will want to add this for both master databases:

[mysqld]
auto_increment_increment = 2

Adding this variable will require a reboot of MySQL. But, you can set it during the mysql session if you don’t want to reboot. Just make sure to add it to your configuration file (my.cnf or my.ini), or it won’t take effect after the session ends.

mysql> SET @@auto_increment_increment=2;
Query OK, 0 rows affected (0.00 sec)

You can verify to see if this variable is enabled with this command:

mysql> SHOW VARIABLES WHERE VARIABLES_NAME = 'auto_increment_increment';
+-----------------------------+-------+
| Variable_name               | Value |
+-----------------------------+-------+
| auto_increment_increment    | 2     |
+-----------------------------+-------+
1 row in set (0.00 sec)

The auto_increment_increment variable will increment the AUTO_INCREMENT value by two (2) for each new primary key value. We will also need to use different initial primary key values for each master. You can’t simply use 0 (zero) and 1 (one) for the AUTO_INCREMENT value, as when you use the value of 0 (zero), it defaults back to a value of 1 (one). It is easier to set the AUTO_INCREMENT values to a higher number, with the last digits being 0 (zero) and 1 (one) for each master. Here are the CREATE DATABASE and CREATE TABLE commands for each master:

Master #1

CREATE DATABASE `comicbookdb`;
use comicbookdb;
CREATE TABLE `comics` (
  `comic_id` int(9) NOT NULL AUTO_INCREMENT,
  `comic_title` varchar(60) NOT NULL,
  `issue_number` decimal(9,0) NOT NULL,
  `pub_year` varchar(60) NOT NULL,
  `pub_month` varchar(60) NOT NULL,
  PRIMARY KEY (`comic_id`)
) ENGINE=InnoDB AUTO_INCREMENT=100000;

Master #2

CREATE DATABASE `comicbookdb`;
use comicbookdb;
CREATE TABLE `comics` (
  `comic_id` int(9) NOT NULL AUTO_INCREMENT,
  `comic_title` varchar(60) NOT NULL,
  `issue_number` decimal(9,0) NOT NULL,
  `pub_year` varchar(60) NOT NULL,
  `pub_month` varchar(60) NOT NULL,
  PRIMARY KEY (`comic_id`)
) ENGINE=InnoDB AUTO_INCREMENT=100001;

Now that we have all of our tables and users created, we can implement GTID’s on the master servers. I also implemented GTID’s on the slave, in case I wanted to add another slave to this slave. To enable GTID’s, I put the following my the configuration file (my.cnf or my.ini), and restarted MySQL. I added these variable below the auto_increment_increment variable.

[mysqld]
auto_increment_increment = 2
gtid-mode = on
enforce-gtid-consistency = 1

After you have restarted each server, you can take a look at the MASTER STATUS for each server, and the status should be the same:

mysql> SHOW MASTER STATUS\G
*************************** 1. row ***************************
             File: mysql-bin.000005
         Position: 154
     Binlog_Do_DB: 
 Binlog_Ignore_DB: 
Executed_Gtid_Set: 
1 row in set (0.00 sec)

You don’t have to do this, but I like to reset the master status on both masters and the slave. Resetting the master deletes all binary log files listed in the index file, resets the binary log index file to be empty, and creates a new binary log file. On each server (both masters and slave servers), I ran this:

mysql> RESET MASTER;
Query OK, 0 rows affected (0.00 sec)

mysql> SHOW MASTER STATUS\G
*************************** 1. row ***************************
             File: mysql-bin.000001
         Position: 154
     Binlog_Do_DB: 
 Binlog_Ignore_DB: 
Executed_Gtid_Set: 
1 row in set (0.00 sec)

You can see the new binary log (mysql-bin.000001), and the beginning position in the binary log (154). Let’s insert some data into one of the master databases, and then check the master’s status again. (And yes, we haven’t turned on replication yet).

Master #1

mysql> INSERT INTO COMICS (comic_title, issue_number, pub_year, pub_month) VALUES('Fly Man','1','2014','01');
Query OK, 1 row affected (0.02 sec)

mysql> SHOW MASTER STATUS\G
*************************** 1. row ***************************
             File: mysql-bin.000001
         Position: 574
     Binlog_Do_DB: 
 Binlog_Ignore_DB: 
Executed_Gtid_Set: 63a7971c-b48c-11e5-87cf-f7b6a723ba3d:1
1 row in set (0.00 sec)

You can see the GTID created for the INSERT statement – 63a7971c-b48c-11e5-87cf-f7b6a723ba3d:1. The first part of the GTID (63a7971c-b48c-11e5-87cf-f7b6a723ba3d) is the UUID of the master. The UUID information can be found in the auto.cnf file, located in the data directory.

Master #1

# cat auto.cnf
[auto]
server-uuid=63a7971c-b48c-11e5-87cf-f7b6a723ba3d

Let’s insert another row of data, check the master status, and then look at the entries of the comics table:

Master #1

mysql> INSERT INTO COMICS (comic_title, issue_number, pub_year, pub_month) VALUES('Fly Man','2','2014','02');
Query OK, 1 row affected (0.05 sec)

mysql> show master status\G
*************************** 1. row ***************************
             File: mysql-bin.000001
         Position: 994
     Binlog_Do_DB: 
 Binlog_Ignore_DB: 
Executed_Gtid_Set: 63a7971c-b48c-11e5-87cf-f7b6a723ba3d:1-2
1 row in set (0.00 sec)

mysql> select * from comics;
+----------+-------------+--------------+----------+-----------+
| comic_id | comic_title | issue_number | pub_year | pub_month |
+----------+-------------+--------------+----------+-----------+
|   100001 | Fly Man     |            1 | 2014     | 01        |
|   100003 | Fly Man     |            2 | 2014     | 02        |
+----------+-------------+--------------+----------+-----------+
2 rows in set (0.00 sec)

You can see how the values for the comic_id table are now incremented by two (2). Now we can insert two lines of data into the second master, look at the master’s status, and look at the entries in the comics database:

Master #2

mysql> INSERT INTO COMICS (comic_title, issue_number, pub_year, pub_month) VALUES('Fly Man','3','2014','03');
mysql> INSERT INTO COMICS (comic_title, issue_number, pub_year, pub_month) VALUES('Fly Man','4','2014','04');

mysql> show master status\G
*************************** 1. row ***************************
             File: mysql-bin.000005
         Position: 974
     Binlog_Do_DB: 
 Binlog_Ignore_DB: 
Executed_Gtid_Set: 75e2e1dc-b48e-11e5-83bb-1438deb0d51e:1-2
1 row in set (0.00 sec)

mysql> select * from comics;
+----------+-------------+--------------+----------+-----------+
| comic_id | comic_title | issue_number | pub_year | pub_month |
+----------+-------------+--------------+----------+-----------+
|   100002 | Fly Man     |            3 | 2014     | 03        |
|   100004 | Fly Man     |            4 | 2014     | 04        |
+----------+-------------+--------------+----------+-----------+
2 rows in set (0.00 sec)

The second master has a different UUID than the first master, and that is how we can tell what GTID’s belong to which master. We now have two sets of GTID’s to replicate over to the slave. Of course, the slave will have it’s own UUID as well.

Master #1 and Master #2 GTID sets:

63a7971c-b48c-11e5-87cf-f7b6a723ba3d:1-2
75e2e1dc-b48e-11e5-83bb-1438deb0d51e:1-2

I always check to make sure the slave isn’t running before I do anything:

Slave

mysql> show slave status\G
Empty set (0.00 sec)

Unlike regular replication, in multi-source replication, you have to create a CHANNEL specific to each master. You will need to also name this channel, and I simply named the channels “master-142” and “master-143” to match their server_id‘s (as well as their IP addresses). Here is how you start replication for Master #1 (server_id=142).

Slave

mysql> CHANGE MASTER TO MASTER_HOST='192.168.1.142', MASTER_USER='replicate', MASTER_PASSWORD='password', MASTER_AUTO_POSITION = 1 FOR CHANNEL 'master-142';
Query OK, 0 rows affected, 2 warnings (0.23 sec)

This statement produced two warnings, but they can be ignored. I am following the same instructions on the MySQL Manual Page.

Slave

mysql> SHOW WARNINGS\G
*************************** 1. row ***************************
  Level: Note
   Code: 1759
Message: Sending passwords in plain text without SSL/TLS is extremely insecure.
*************************** 2. row ***************************
  Level: Note
   Code: 1760
Message: Storing MySQL user name or password information in the master info repository is not secure and is therefore not recommended. Please consider using the USER and PASSWORD connection options for START SLAVE; see the 'START SLAVE Syntax' in the MySQL Manual for more information.
2 rows in set (0.00 sec)

Now we can start the slave for channel ‘master-142‘:

Slave

mysql> START SLAVE FOR CHANNEL 'master-142';
Query OK, 0 rows affected (0.03 sec)

This command is the same as starting the SQL_THREAD and the IO_THREAD at the same time. There may be times when you will want to stop and stop either of these threads, so here is the syntax – as you have to specify which channel you want to modify:

START SLAVE SQL_THREAD FOR CHANNEL 'master-142';
START SLAVE IO_THREAD FOR CHANNEL 'master-142';

You can also issue a simple START SLAVE command, and it will start both threads for all currently configured replication channels. The slave has been started, and we should see the GTID’s from Master #1 already retrieved and applied to the database. (I am not going to display the entire SHOW SLAVE STATUS output, as it very long)

Slave

mysql> SHOW SLAVE STATUS FOR CHANNEL 'master-142'\G
*************************** 1. row ***************************
               Slave_IO_State: Waiting for master to send event
                  Master_Host: 192.168.1.142
...
                  Master_UUID: 63a7971c-b48c-11e5-87cf-f7b6a723ba3d
...
      Slave_SQL_Running_State: Slave has read all relay log; waiting for more updates
...
           Retrieved_Gtid_Set: 63a7971c-b48c-11e5-87cf-f7b6a723ba3d:1-2
            Executed_Gtid_Set: 63a7971c-b48c-11e5-87cf-f7b6a723ba3d:1-2
                Auto_Position: 1
...
                 Channel_Name: master-142

We can take a look at the comics table, and see the two entries from the Master #1 database (channel master-142):

Slave

mysql> select * from comics;
+----------+-------------+--------------+----------+-----------+
| comic_id | comic_title | issue_number | pub_year | pub_month |
+----------+-------------+--------------+----------+-----------+
|   100001 | Fly Man     |            1 | 2014     | 01        |
|   100003 | Fly Man     |            2 | 2014     | 02        |
+----------+-------------+--------------+----------+-----------+
2 rows in set (0.00 sec)

Since we have the first master up and running with replication, let’s start replication for the second master:

CHANGE MASTER TO MASTER_HOST='192.168.1.143', MASTER_USER='replicate', MASTER_PASSWORD='password', MASTER_AUTO_POSITION = 1 FOR CHANNEL 'master-143';

And we can check the SLAVE STATUS for this master: (Again, not all of the results are displayed below)

Slave

mysql> SHOW SLAVE STATUS FOR CHANNEL 'master-143'\G
*************************** 1. row ***************************
               Slave_IO_State: Waiting for master to send event
                  Master_Host: 192.168.1.143
...
                  Master_UUID: 75e2e1dc-b48e-11e5-83bb-1438deb0d51e
...
      Slave_SQL_Running_State: Slave has read all relay log; waiting for more updates
...
           Retrieved_Gtid_Set: 75e2e1dc-b48e-11e5-83bb-1438deb0d51e:1-2
            Executed_Gtid_Set: 63a7971c-b48c-11e5-87cf-f7b6a723ba3d:1-2,
75e2e1dc-b48e-11e5-83bb-1438deb0d51e:1-2,
                Auto_Position: 1
...
                 Channel_Name: master-143

We can see the slave has retrieved the two GTID’s (75e2e1dc-b48e-11e5-83bb-1438deb0d51e:1-2) and executed them as well. Looking at the comics table, we can see all four comics have been transferred from two different masters:

Slave

mysql> select * from comics;
+----------+-------------+--------------+----------+-----------+
| comic_id | comic_title | issue_number | pub_year | pub_month |
+----------+-------------+--------------+----------+-----------+
|   100001 | Fly Man     |            1 | 2014     | 01        |
|   100002 | Fly Man     |            3 | 2014     | 03        |
|   100003 | Fly Man     |            2 | 2014     | 02        |
|   100004 | Fly Man     |            4 | 2014     | 04        |
+----------+-------------+--------------+----------+-----------+
4 rows in set (0.01 sec)

Replication took care of the AUTO_INCREMENT values. However, if you were able to see the SQL statements which were being replicated, you would have seen the original INSERT statements:

INSERT INTO COMICS (comic_title, issue_number, pub_year, pub_month) VALUES('Fly Man','1','2014','01')
INSERT INTO COMICS (comic_title, issue_number, pub_year, pub_month) VALUES('Fly Man','2','2014','02');
INSERT INTO COMICS (comic_title, issue_number, pub_year, pub_month) VALUES('Fly Man','3','2014','03');
INSERT INTO COMICS (comic_title, issue_number, pub_year, pub_month) VALUES('Fly Man','4','2014','04');

The way replication handles the different AUTO_INCREMENT values is by sending over (from the master to the slave via the IO thread), the value for the comic_id column (which uses AUTO_INCREMENT). The value for this column (generated by the master) is transmitted along with the statement. We can take a look at the binary log on the master to see the SET INSERT_ID=100001 information, which is the value for the comic_id column, being transmitted to the slave along with the original SQL statement:

Slave

# mysqlbinlog mysql-bin.000001
...
# at 349
#160106 21:08:01 server id 142  end_log_pos 349 CRC32 0x48fb16a2 	Intvar
SET INSERT_ID=100001/*!*/;
#160106 21:08:01 server id 142  end_log_pos 543 CRC32 0xbaf55210 	Query	thread_id=1exec_time=0	error_code=0
use `comicbookdb`/*!*/;
SET TIMESTAMP=1452132481/*!*/;
INSERT INTO COMICS (comic_title, issue_number, pub_year, pub_month) VALUES('Fly Man','1','2014','01')
/*!*/;
...

You now have two master MySQL databases replicating data to a single MySQL slave database. Let me know if you have any problems following this tutorial. And follow me on Twitter at ScriptingMySQL.

 


Tony Darnell is a Principal Sales Consultant for MySQL, a division of Oracle, Inc. MySQL is the world’s most popular open-source database program. Tony may be reached at info [at] ScriptingMySQL.com and on LinkedIn.
Tony is the author of Twenty Forty-Four: The League of Patriots

 

Visit http://2044thebook.com for more information.

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Upgrade MySQL to a new version with a fresh installation & use shell scripts and mysqldump to reload your data

There are several ways to upgrade MySQL. In this post, we will use a combination of shell scripts and the mysqldump application to export our MySQL data, and then re-import it back into the upgraded version of MySQL.

In this example, we will be doing a minor version upgrade. We will be going from 5.6.17 to 5.6.19. This method may not work if you are upgrading from one major release to another – from 5.1 to 5.5, or 5.5 to 5.6. You will want to check each version and review the new features/functions and also what features/functions have been deprecated. We are also assuming that no one will be using the database during the time it takes for us to do the upgrade.

If you want to upgrade from a version that is more than one major release apart from your current version, then you will want to upgrade to each successive version. For example, if you want to upgrade from 5.0 to 5.6, you will want to upgrade from 5.0 to 5.1, then 5.1 to 5.5, and then 5.5 to 5.6.

You don’t have to export all of your data when you upgrade MySQL. There are ways of upgrading without doing anything to your data. But in this post, I will be exporting the data and re-importing it, for a fresh installation. I don’t have that much data, so I don’t mind doing the export and import. If you have a lot of data, you might want to consider other options.

To get an idea of the size of your database(s), here is a quick script that you can use:

SELECT table_schema "Data Base Name", sum( data_length + index_length ) / 1024 / 1024 "Data Base Size in MB" 
FROM information_schema.TABLES GROUP BY table_schema ; 

When I perform an export/import, I like to export each database as a separate mysqldump file, and then also export all of the databases together in one large file. By exporting/importing the individual databases, if you have an error importing one of the database dump files, you can isolate the error to a single database. It is much easier to fix the error in one smaller data dump file than with a larger all-inclusive dump file.

I am also going to create some simple shell scripts to help me create the commands that I need to make this task much easier. First, you will want to create a directory to store all of the scripts and dump files. Do all of your work inside that directory.

Next, I want to get a list of all of my databases. I will log into mysql, and then issue the show databases; command: (which is the same command as: select schema_name from information_schema.schemata;)

mysql> show databases;
+--------------------+
| Database           |
+--------------------+
| information_schema |
| 12thmedia          |
| cbgc               |
| comicbookdb        |
| coupons            |
| healthcheck        |
| innodb_memcache    |
| landwatch          |
| laurelsprings      |
| ls_directory       |
| mem                |
| mysql              |
| performance_schema |
| protech            |
| scripts            |
| stacy              |
| storelist          |
| test               |
| testcert           |
| tony               |
| twtr               |
| watchdb            |
+--------------------+
22 rows in set (1.08 sec)

I can then just highlight and copy the list of databases, and put that list into a text file named “list.txt“. I do not want to include these databases in my export:

information_schema
mysql
performance_schema
test

However, I will export the mysql table later. You need to check with the MySQL manual to make sure that there haven’t been any changes to the MySQL table from one version to the next.

I will need to manually remove those databases from my list.txt file. I then want to remove all of the spaces and pipe symbols from the text file – assuming that you do not have any spaces in your database names. Instead of using spaces in a database name, I prefer to use an underline character “_“. These scripts assume that you don’t have any spaces in your database names.

If you know how to use the vi editor, you can so a substitution for the pipes and spaces with these commands:

:%s/ //g
:%s/|//g

Otherwise, you will want to use another text editor and manually edit the list to remove the spaces and pipe symbols. Your finished list.txt file should look like this:

12thmedia cbgc
comicbookdb
coupons
healthcheck
innodb_memcache
landwatch
laurelsprings
ls_directory
mem
protech
scripts
stacy
storelist
testcert
tony
twtr
watchdb

You can then create a simple shell script to help create your mysqldump commands – one command for each database. You will want to create this script and the other scripts in the directory you created earlier. Name the script export.sh. You can also change the mysqldump options to meet your needs. I am using GTID’s for replication, so I want to use this option –set-gtid-purged=OFF. You will also want to change the value of my password my_pass to your mysql password. You can also skip including the password by using the -p option, and just enter the password each time you run the mysqldump command.

# export.sh
# script to create the database export commands
k=""
for i in `cat list.txt`
do

echo "mysqldump -uroot --password=my_pass --set-gtid-purged=OFF --triggers --quick --skip-opt --add-drop-database --create-options --databases $i > "$i"_backup.sql"

k="$k $i"

done

# Optional - export the entire database
# use the file extention of .txt so that your script won't import it later
echo "mysqldump -uroot --password=my_pass --set-gtid-purged=OFF --triggers --quick --skip-opt --add-drop-database --create-options --databases $k > all_db_backup.txt"

For the individual databases, I am using the suffix of .sql. For the dump file that contains all of the databases, I am using the prefix .txt – as I use a wildcard search later to get a list of the dump files, and I don’t want to import the one dump file that contains all of the databases.

Now you can run the export.sh script to create a list of your mysqldump commands, and you are going to direct the output into another shell script named export_list.sh.

# sh export.sh > export_list.sh

We can now take a look at what is in the export_list.sh file

# cat export_list.sh
mysqldump -uroot --set-gtid-purged=OFF --password=my_pass --triggers --quick --skip-opt --add-drop-database --create-options --databases 12thmedia > 12thmedia_backup.sql
mysqldump -uroot --set-gtid-purged=OFF --password=my_pass --triggers --quick --skip-opt --add-drop-database --create-options --databases cbgc > cbgc_backup.sql
mysqldump -uroot --set-gtid-purged=OFF --password=my_pass --triggers --quick --skip-opt --add-drop-database --create-options --databases comicbookdb > comicbookdb_backup.sql
mysqldump -uroot --set-gtid-purged=OFF --password=my_pass --triggers --quick --skip-opt --add-drop-database --create-options --databases coupons > coupons_backup.sql
mysqldump -uroot --set-gtid-purged=OFF --password=my_pass --triggers --quick --skip-opt --add-drop-database --create-options --databases healthcheck > healthcheck_backup.sql
mysqldump -uroot --set-gtid-purged=OFF --password=my_pass --triggers --quick --skip-opt --add-drop-database --create-options --databases innodb_memcache > innodb_memcache_backup.sql
mysqldump -uroot --set-gtid-purged=OFF --password=my_pass --triggers --quick --skip-opt --add-drop-database --create-options --databases landwatch > landwatch_backup.sql
mysqldump -uroot --set-gtid-purged=OFF --password=my_pass --triggers --quick --skip-opt --add-drop-database --create-options --databases laurelsprings > laurelsprings_backup.sql
mysqldump -uroot --set-gtid-purged=OFF --password=my_pass --triggers --quick --skip-opt --add-drop-database --create-options --databases ls_directory > ls_directory_backup.sql
mysqldump -uroot --set-gtid-purged=OFF --password=my_pass --triggers --quick --skip-opt --add-drop-database --create-options --databases mem > mem_backup.sql
mysqldump -uroot --set-gtid-purged=OFF --password=my_pass --triggers --quick --skip-opt --add-drop-database --create-options --databases protech > protech_backup.sql
mysqldump -uroot --set-gtid-purged=OFF --password=my_pass --triggers --quick --skip-opt --add-drop-database --create-options --databases scripts > scripts_backup.sql
mysqldump -uroot --set-gtid-purged=OFF --password=my_pass --triggers --quick --skip-opt --add-drop-database --create-options --databases stacy > stacy_backup.sql
mysqldump -uroot --set-gtid-purged=OFF --password=my_pass --triggers --quick --skip-opt --add-drop-database --create-options --databases storelist > storelist_backup.sql
mysqldump -uroot --set-gtid-purged=OFF --password=my_pass --triggers --quick --skip-opt --add-drop-database --create-options --databases testcert > testcert_backup.sql
mysqldump -uroot --set-gtid-purged=OFF --password=my_pass --triggers --quick --skip-opt --add-drop-database --create-options --databases tony > tony_backup.sql
mysqldump -uroot --set-gtid-purged=OFF --password=my_pass --triggers --quick --skip-opt --add-drop-database --create-options --databases twtr > twtr_backup.sql
mysqldump -uroot --set-gtid-purged=OFF --password=my_pass --triggers --quick --skip-opt --add-drop-database --create-options --databases watchdb > watchdb_backup.sql

mysqldump -uroot -p --set-gtid-purged=OFF --password=my_psss --triggers --quick --skip-opt --add-drop-database --create-options --databases  12thmedia cbgc comicbookdb coupons healthcheck innodb_memcache landwatch laurelsprings ls_directory mem protech scripts stacy storelist testcert tony twtr watchdb > all_db_backup.txt

Now you have created a list of mysqldump commands that you can execute to dump all of your databases. You can now go ahead and execute your mysqldump commands by running the export_list.sh script:

# sh export_list.sh
Warning: Using a password on the command line interface can be insecure.
Warning: Using a password on the command line interface can be insecure.
Warning: Using a password on the command line interface can be insecure.
....

The message “Warning: Using a password on the command line interface can be insecure.” is shown because you included the value for “–password“. If you don’t want to put your password on the command line, just change that option to “-p“, and you will have to manually enter your MySQL root user’s password after each mysqldump command.

Here is a list of the dump files that was produced:

# ls -l
total 21424
-rw-r--r--  1 root  staff    26690 Aug  1 16:25 12thmedia_backup.sql
-rw-r--r--  1 root  staff  5455275 Aug  1 16:26 all_db_backup.txt
-rw-r--r--  1 root  staff  1746820 Aug  1 16:25 cbgc_backup.sql
-rw-r--r--  1 root  staff   492943 Aug  1 16:25 comicbookdb_backup.sql
-rw-r--r--  1 root  staff     1057 Aug  1 16:25 coupons_backup.sql
-rw-r--r--  1 root  staff     3366 Aug  1 16:25 export_list.sh
-rw-r--r--  1 root  staff     1077 Aug  1 16:25 healthcheck_backup.sql
-rw-r--r--  1 root  staff     3429 Aug  1 16:25 innodb_memcache_backup.sql
-rw-r--r--  1 root  staff  1815839 Aug  1 16:25 landwatch_backup.sql
-rw-r--r--  1 root  staff   642965 Aug  1 16:25 laurelsprings_backup.sql
-rw-r--r--  1 root  staff   660254 Aug  1 16:25 ls_directory_backup.sql
-rw-r--r--  1 root  staff     1037 Aug  1 16:25 mem_backup.sql
-rw-r--r--  1 root  staff     1057 Aug  1 16:25 protech_backup.sql
-rw-r--r--  1 root  staff     2889 Aug  1 16:25 scripts_backup.sql
-rw-r--r--  1 root  staff    11107 Aug  1 16:25 stacy_backup.sql
-rw-r--r--  1 root  staff     4002 Aug  1 16:25 storelist_backup.sql
-rw-r--r--  1 root  staff     1062 Aug  1 16:25 testcert_backup.sql
-rw-r--r--  1 root  staff     4467 Aug  1 16:25 tony_backup.sql
-rw-r--r--  1 root  staff     1042 Aug  1 16:25 twtr_backup.sql
-rw-r--r--  1 root  staff    52209 Aug  1 16:25 watchdb_backup.sql

You will now want to dump your MySQL table, so you don’t have to recreate all of the MySQL information, including the users, passwords and privileges after the new install.

mysqldump -uroot --password=my_pass --set-gtid-purged=OFF mysql > mysql_user_backup.txt

I am once again using the .txt prefix for this file.

After you execute the above command, make sure that the dump file was created:

# ls -l mysql_user_backup.txt
-rw-r--r--  1 root  staff  9672 Aug  1 16:32 mysql_user_backup.txt

We have now finished exporting all of our data, including our MySQL table data. You will need to shutdown MySQL. You may use mysqladmin to shutdown your database, or here is a link on ways to shutdown MySQL.

# mysqladmin -uroot --password=my_pass shutdown
Warning: Using a password on the command line interface can be insecure.

Before continuing, you might want to check to make sure that the mysqld process isn’t still active.

# ps -ef|grep mysqld
    0 18380 17762   0   0:00.00 ttys002    0:00.00 grep mysqld

You are now going to want to change the name of your mysql directory. This will give you access to the old directory in case the upgrade fails. For my OS (Mac OS 10.9), my MySQL home directory is a symbolic link to another directory that contains the actual MySQL data. All I have to do is to remove the symbolic link. A new symbolic link will be created with the new install. Otherwise, just use the mv command to rename your old MySQL directory.

# cd /usr/local/
# ls -ld mysql* 
lrwxr-xr-x   1 root  wheel   36 Aug  9  2013 mysql -> mysql-advanced-5.6.17-osx10.6-x86_64
drwxr-xr-x  18 root  wheel  612 Jan 16  2014 mysql-advanced-5.6.17-osx10.6-x86_64

All I have to do is to remove the link, and the MySQL directory will still be there:

# rm mysql
# ls -ld mysql* 
drwxr-xr-x  18 root  wheel  612 Jan 16  2014 mysql-advanced-5.6.17-osx10.6-x86_64

Now I am ready to install the new version of MySQL. I won’t cover the installation process, but here is the link to the installation page.

Tip: After you have installed MySQL, don’t forget to run this script from your MySQL home directory. This will install your mysql database tables. Otherwise, you will get an error when you try to start the mysqld process.

# ./scripts/mysql_install_db

Now you can start the mysqld process. See this page if you don’t know how to start MySQL.

You can test to see if the new installation of MySQL is running by either checking the process table, or logging into mysql. With a fresh install of 5.6, you should not have to include a user name or password.

Note: (Future versions of MySQL may automatically create a random root password and put it in your data directory. You will then need to use that password to login to MySQL for the first time. Check the user’s manual for any MySQL versions beyond 5.6.)

# mysql
Welcome to the mysql monitor.  Commands end with ; or \g.
Your mysql connection id is 3
....

mysql>

Now that MySQL is up and running, leave the mysql terminal window open, and open another terminal window so you can import your mysql table information from your dump file:

# mysql < /users/tonydarnell/mysql_2014_0731/2014_0731_mysql_backup.sql

You won't be able to login with your old user names and passwords until you execute the flush privileges command. So, in your other terminal window with the mysql prompt:

mysql> flush privileges;
Query OK, 0 rows affected (0.00 sec)

Open another terminal window and see if you can login with your old mysql user name and password:

# mysql -uroot -p
Enter password: 
Welcome to the mysql monitor.  Commands end with ; or \g.
Your mysql connection id is 3
....

mysql>

You can then look at your the user names and passwords in the mysql.user table:

mysql> select user, host, password from mysql.user order by user, host;
+----------------+---------------+-------------------------------------------+
| user           | host          | password                                  |
+----------------+---------------+-------------------------------------------+
| root           | 127.0.0.1     | *BF6F71512345332CAB67E7608EBE63005BEB705C |
| root           | 192.168.1.2   | *BF6F71512345332CAB67E7608EBE63005BEB705C |
| root           | 192.168.1.5   | *BF6F71512345332CAB67E7608EBE63005BEB705C |
| root           | 192.168.1.50  | *BF6F71512345332CAB67E7608EBE63005BEB705C |
| root           | localhost     | *BF6F71512345332CAB67E7608EBE63005BEB705C |
+----------------+---------------+-------------------------------------------+
5 rows in set (0.00 sec)


OPTIONAL:
Since I am using GTID’s for replication, I can check to see how many transactions have been completed, by issuing the show master status command:

mysql> show master status\G
*************************** 1. row ***************************
             File: mysql-bin.000005
         Position: 644455
     Binlog_Do_DB: 
 Binlog_Ignore_DB: coupons,usta,ls_directory,landwatch
Executed_Gtid_Set: e1eb3f38-18da-11e4-aa44-0a1a64a61679:1-124
1 row in set (0.00 sec)

We are now ready to import the database dump files. We can use this script to create the import commands. Copy this into a text file named import.sh:

# import.sh
# script to import all of the export files
# run this script in the same directory as the exported dump files
#
> import_files.sh
directory=`pwd`
for file in `ls *sql`
do

if [[ $(grep -c '.txt' $file) != 0 ]];then

echo "# found mysql - do nothing"

else

echo "mysql -uroot -p"my_pass"  < $directory/$file"
echo "mysql -uroot -p"my_pass"  > import_files.sh

fi

done

Then run the import.sh script. The script will print the output to the terminal window as well as into a new script file named import_files.sh.

# sh import.sh
mysql -uroot -pmy_pass < 12thmedia_backup.sql
mysql -uroot -pmy_pass < cbgc_backup.sql
mysql -uroot -pmy_pass < comicbookdb_backup.sql
mysql -uroot -pmy_pass < coupons_backup.sql
mysql -uroot -pmy_pass < healthcheck_backup.sql
mysql -uroot -pmy_pass < innodb_memcache_backup.sql
mysql -uroot -pmy_pass < landwatch_backup.sql
mysql -uroot -pmy_pass < laurelsprings_backup.sql
mysql -uroot -pmy_pass < ls_directory_backup.sql
mysql -uroot -pmy_pass < mem_backup.sql
mysql -uroot -pmy_pass < protech_backup.sql
mysql -uroot -pmy_pass < scripts_backup.sql
mysql -uroot -pmy_pass < stacy_backup.sql
mysql -uroot -pmy_pass < storelist_backup.sql
mysql -uroot -pmy_pass < testcert_backup.sql
mysql -uroot -pmy_pass < tony_backup.sql
mysql -uroot -pmy_pass < twtr_backup.sql
mysql -uroot -pmy_pass < watchdb_backup.sql

Look at the contents of the new script file – import_files.sh – to make sure that it contains all of the database files. You will use this file to help you import your dump files.

# cat import_files.sh
mysql -uroot -pmy_pass < 12thmedia_backup.sql
mysql -uroot -pmy_pass < cbgc_backup.sql
mysql -uroot -pmy_pass < comicbookdb_backup.sql
mysql -uroot -pmy_pass < coupons_backup.sql
mysql -uroot -pmy_pass < healthcheck_backup.sql
mysql -uroot -pmy_pass < innodb_memcache_backup.sql
mysql -uroot -pmy_pass < landwatch_backup.sql
mysql -uroot -pmy_pass < laurelsprings_backup.sql
mysql -uroot -pmy_pass < ls_directory_backup.sql
mysql -uroot -pmy_pass < mem_backup.sql
mysql -uroot -pmy_pass < protech_backup.sql
mysql -uroot -pmy_pass < scripts_backup.sql
mysql -uroot -pmy_pass < stacy_backup.sql
mysql -uroot -pmy_pass < storelist_backup.sql
mysql -uroot -pmy_pass < testcert_backup.sql
mysql -uroot -pmy_pass < tony_backup.sql
mysql -uroot -pmy_pass < twtr_backup.sql
mysql -uroot -pmy_pass < watchdb_backup.sql

WARNING: Be sure that this script file does not contain the main dump file or the mysql user’s file that we created.


I was exporting and importing eighteen (18) database files, so I can also check the line count of the import_files.sh script to make sure it matches:

# wc -l import_files.sh
      18 import_files.sh

I am now ready to import my files.


Optional: add the -v for verbose mode – sh -v import_files.sh


# sh import_files.sh
Warning: Using a password on the command line interface can be insecure.
Warning: Using a password on the command line interface can be insecure.
....

You databases should now be imported into your new instance of MySQL. You can always re-run the script to make sure that the databases are the same size.


OPTIONAL:
Since I am using GTID’s for replication, I can check to see how many transactions have been completed after importing the dump files, by issuing the show master status command:

mysql> show master status\G
*************************** 1. row ***************************
             File: mysql-bin.000003
         Position: 16884001
     Binlog_Do_DB: 
 Binlog_Ignore_DB: coupons,usta,ls_directory,landwatch
Executed_Gtid_Set: cc68d008-18f3-11e4-aae6-470d6cf89709:1-43160
1 row in set (0.00 sec)

Your new and fresh installation of MySQL should be ready to use.

NOTE:A thank-you to Daniel Van Eeden for pointing out a mistake that I had made.

 


Tony Darnell is a Principal Sales Consultant for MySQL, a division of Oracle, Inc. MySQL is the world’s most popular open-source database program. Tony may be reached at info [at] ScriptingMySQL.com and on LinkedIn.
Tony is the author of Twenty Forty-Four: The League of Patriots

 

Visit http://2044thebook.com for more information.

Creating and restoring database backups with mysqldump and MySQL Enterprise Backup – Part 1 of 2

Be sure to check out my other posts on mysqldump:
Scripting Backups of MySQL with Perl via mysqldump
Splitting a MySQL Dump File Into Smaller Files Via Perl

Part 1 of 2: (part two)
If you have used MySQL for a while, you have probably used mysqldump to backup your database. In part one of this blog, I am going to show you how to create a simple full and partial backup using mysqldump. In part two, I will show you how to use MySQL Enterprise Backup (which is the successor to the InnoDB Hot Backup product). MySQL Enterprise Backup allows you to backup your database while it is online and it keeps the database available to users during backup operations (you don’t have to take the database offline or lock any databases/tables – but to do this, you need to use the –no-locking option).

This post will deal with mysqldump. For those of you that aren’t familiar with mysqldump:

The mysqldump client is a utility that performs logical backups, producing a set of SQL statements that can be run to reproduce the original schema objects, table data, or both. It dumps one or more MySQL database for backup or transfer to another SQL server. The mysqldump command can also generate output in CSV, other delimited text, or XML format.

The best feature about mysqldump is that it is easy to use. The main problem with using mysqldump occurs when you need to restore a database. When you execute mysqldump, the database backup (output) is an SQL file that contains all of the necessary SQL statements to restore the database – but restoring requires that you execute these SQL statements to essentially rebuild the database. Since you are recreating your database, the tables and all of your data from this file, the restoration procedure can take a long time to execute if you have a very large database.

There are a lot of features and options with mysqldump – (a complete list is here). I won’t review all of the features, but I will explain some of the ones that I use.

Here is the command to use mysqldump to simply backup all of your databases (assuming you have InnoDB tables). This command will create a dump (backup) file named all_databases.sql.

mysqldump --all-databases --single-transaction --user=root --password > all_databases.sql

After you hit return, you will have to enter your password. You can include the password after the –password option (example: –password=my_password), but this is less secure and you will get the following error:

Warning: Using a password on the command line interface can be insecure.

Here is some information about the options that were used:

--all-databases - this dumps all of the tables in all of the databases
--user - The MySQL user name you want to use for the backup
--password - The password for this user.  You can leave this blank or include the password value (which is less secure)
--single-transaction - for InnoDB tables

If you are using Global Transaction Identifier’s (GTID’s) with InnoDB (GTID’s aren’t available with MyISAM), you will want to use the –set-gtid-purged=OFF option. Then you would issue this command:

mysqldump --all-databases --single-transaction --set-gtid-purged=OFF --user=root --password > all_databases.sql

Otherwise you will see this error:

Warning: A partial dump from a server that has GTIDs will by default include the GTIDs of all transactions, even those that changed suppressed parts of the database. If you don't want to restore GTIDs, pass --set-gtid-purged=OFF. To make a complete dump, pass --all-databases --triggers --routines --events.

You can also execute a partial backup of all of your databases. This example will be a partial backup because I am not going to backup the default databases for MySQL (which are created during installation) – mysql, test, PERFORMANCE_SCHEMA and INFORMATION_SCHEMA

Note: mysqldump does not dump the INFORMATION_SCHEMA database by default. To dump INFORMATION_SCHEMA, name it explicitly on the command line and also use the –skip-lock-tables option.

mysqldump never dumps the performance_schema database.

mysqldump also does not dump the MySQL Cluster ndbinfo information database.

Before MySQL 5.6.6, mysqldump does not dump the general_log or slow_query_log tables for dumps of the mysql database. As of 5.6.6, the dump includes statements to recreate those tables so that they are not missing after reloading the dump file. Log table contents are not dumped.

If you encounter problems backing up views due to insufficient privileges, see Section E.5, “Restrictions on Views” for a workaround.
(from: http://dev.mysql.com/doc/refman/5.6/en/mysqldump.html)

To do a partial backup, you will need a list of the databases that you want to backup. You may retrieve a list of all of the databases by simply executing the SHOW DATABASES command from a mysql prompt:

mysql> SHOW DATABASES;
+--------------------+
| Database           |
+--------------------+
| information_schema |
| comicbookdb        |
| coupons            |
| mysql              |
| performance_schema |
| scripts            |
| test               |
| watchdb            |
+--------------------+
8 rows in set (0.00 sec)

In this example, since I don’t want to backup the default mysql databases, I am only going to backup the comicbookdb, coupons, scripts and watchdb databases. I am going to use the following options:

--databases - This allows you to specify the databases that you want to backup.  You can also specify certain tables that you want to backup.  If you want to do a full backup of all of the databases, then leave out this option
--add-drop-database - This will insert a DROP DATABASE statement before each CREATE DATABASE statement.  This is useful if you need to import the data to an existing MySQL instance where you want to overwrite the existing data.  You can also use this to import your backup onto a new MySQL instance, and it will create the databases and tables for you.
--triggers - this will include the triggers for each dumped table
--routines - this will include the stored routines (procedures and functions) from the dumped databases
--events - this will include any events from the dumped databases
--set-gtid-purged=OFF - since I am using replication on this database (it is the master), I like to include this in case I want to create a new slave using the data that I have dumped.  This option enables control over global transaction identifiers (GTID) information written to the dump file, by indicating whether to add a SET @@global.gtid_purged statement to the output.
--user - The MySQL user name you want to use
--password - Again, you can add the actual value of the password (ex. --password=mypassword), but it is less secure than typing in the password manually.  This is useful for when you want to put the backup in a script, in cron or in Windows Task Scheduler.
--single-transaction - Since I am using InnoDB tables, I will want to use this option.

Here is the command that I will run from a prompt:

mysqldump --databases comicbookdb coupons scripts watchdb --single-transaction --set-gtid-purged=OFF --add-drop-database --triggers --routines --events --user=root --password > partial_database_backup.sql

I will need to enter my password on the command line. After the backup has completed, if your backup file isn’t too large, you can open it and see the actual SQL statements that will be used if you decide that you need to recreate the database(s). If you accidentally dump all of the databases into one file, and you want to separate the dump file into smaller files, see my post on using Perl to split the dump file.

For example, here is the section of the dump file (partial_database_backup.db) for the comicbookdb database (without the table definitions). (I omitted the headers from the dump file.)

--
-- Current Database: `comicbookdb`
--

/*!40000 DROP DATABASE IF EXISTS `comicbookdb`*/;

CREATE DATABASE /*!32312 IF NOT EXISTS*/ `comicbookdb` /*!40100 DEFAULT CHARACTER SET latin1 */;

USE `comicbookdb`;

--
-- Table structure for table `comics`
--

DROP TABLE IF EXISTS `comics`;
/*!40101 SET @saved_cs_client     = @@character_set_client */;
/*!40101 SET character_set_client = utf8 */;
CREATE TABLE `comics` (
  `serial_id` int(7) NOT NULL AUTO_INCREMENT,
  `date_time_added` datetime NOT NULL,
  `publisher_id` int(6) NOT NULL,
....

If you are using the dump file to create a slave server, you can use the –master-data option, which includes the CHANGE MASTER information, which looks like this:

--
-- Position to start replication or point-in-time recovery from
--

CHANGE MASTER TO MASTER_LOG_FILE='mysql-bin.000013', MASTER_LOG_POS=79338;

If you used the –set-gtid-purged=ON option, you would see the value of the Global Transaction Identifier’s (GTID’s):

--
--GTID state at the beginning of the backup 
--

SET @@GLOBAL.GTID_PURGED='82F20158-5A16-11E2-88F9-C4A801092ABB:1-168523';

You may also test your backup without exporting any data by using the –no-data option. This will show you all of the information for creating the databases and tables, but it will not export any data. This is also useful for recreating a blank database on the same or on another server.

When you export your data, mysqldump will create INSERT INTO statements to import the data into the tables. However, the default is for the INSERT INTO statements to contain multiple-row INSERT syntax that includes several VALUES lists. This allows for a quicker import of the data. But, if you think that your data might be corrupt, and you want to be able to isolate a given row of data – or if you simply want to have one INSERT INTO statement per row of data, then you can use the –skip-extended-insert option. If you use the –skip-extended-insert option, importing the data will take much longer to complete, and the backup file size will be larger.

Importing and restoring the data is easy. To import the backup file into a new, blank instance of MySQL, you can simply use the mysql command to import the data:

mysql -uroot -p < partial_database_backup.sql

Again, you will need to enter your password or you can include the value after the -p option (less secure).

There are many more options that you can use with a href=”http://dev.mysql.com/doc/refman/5.6/en/mysqldump.html”>mysqldump. The main thing to remember is that you should backup your data on a regular basis, and move a copy of the backup file off the MySQL server.

Finally, here is a Perl script that I use in cron to backup my databases. This script allows you to specify which databases you want to backup via the mysql_bak.config file. This config file is simply a list of the databases that you want to backup, with an option to ignore any databases that are commented out with a #. This isn’t a secure script, as you have to embed the MySQL user password in the script.

#!/usr/bin/perl
# Perform a mysqldump on all the databases specified in the dbbackup.config file

use warnings;
use File::Basename;

# set the directory where you will keep the backup files
$backup_folder = '/Users/tonydarnell/mysqlbak';

# the config file is a text file with a list of the databases to backup
# this should be in the same location as this script, but you can modify this
# if you want to put the file somewhere else
my $config_file = dirname($0) . "/mysql_bak.config";

# example config file
# You may use a comment to bypass any database that you don't want to backup
# # Unwanted_DB    (commented - will not be backed up)
# twtr
# cbgc

# retrieve a list of the databases from the config file
my @databases = removeComments(getFileContents($config_file));

# change to the directory of the backup files.
chdir($backup_folder) or die("Cannot go to folder '$backup_folder'");

# grab the local time variables
my ($sec,$min,$hour,$mday,$mon,$year,$wday,$yday,$isdst) = localtime(time);
$year += 1900;
$mon++;
#Zero padding
$mday = '0'.$mday if ($mday<10);
$mon = '0'.$mon if ($mon<10);

$hour = "0$hour" if $hour < 10;
$min = "0$min" if $min  $folder/$file.Z`;

	print "Done\n";
}
print "Done\n\n";

# this subroutine simply creates an array of the list of the databases

sub getFileContents {
	my $file = shift;
	open (FILE,$file) || die("Can't open '$file': $!");
	my @lines=;
	close(FILE);

	return @lines;
}

# remove any commented tables from the @lines array

sub removeComments {
	my @lines = @_;

	@cleaned = grep(!/^\s*#/, @lines); #Remove Comments
	@cleaned = grep(!/^\s*$/, @cleaned); #Remove Empty lines

	return @cleaned;
}

 


Tony Darnell is a Principal Sales Consultant for MySQL, a division of Oracle, Inc. MySQL is the world’s most popular open-source database program. Tony may be reached at info [at] ScriptingMySQL.com and on LinkedIn.
Tony is the author of Twenty Forty-Four: The League of Patriots

 

Visit http://2044thebook.com for more information.

MySQL Replication – Creating a New Master/Slave Topology with or without Virtual Machines

In my last few posts, I wrote about “How to install MySQL replication using GTID’s” (Part One, Part Two). In this post, I will show you how to install MySQL 5.6 and set up replication between two MySQL servers the “old fashioned way” using the binary log and binary log position.

I am going to create some virtual machines instead of using individual servers. But, you can also use these instructions to create a MySQL replication (master/slave) setup with real servers.

Here is how replication works. On the master server, when there are updates (inserts, updates, deletes, alter, etc.) to the database, MySQL will write the appropriate information to the binlog (binary log), depending upon which replication method you choose.

From: http://dev.mysql.com/doc/refman/5.6/en/binary-log.html

The binary log contains “events” that describe database changes such as table creation operations or changes to table data. It also contains events for statements that potentially could have made changes (for example, a DELETE which matched no rows), unless row-based logging is used. The binary log also contains information about how long each statement took that updated data. The binary log has two important purposes:

For replication, the binary log on a master replication server provides a record of the data changes to be sent to slave servers. The master server sends the events contained in its binary log to its slaves, which execute those events to make the same data changes that were made on the master. See Section 16.2, “Replication Implementation“.

Certain data recovery operations require use of the binary log. After a backup has been restored, the events in the binary log that were recorded after the backup was made are re-executed. These events bring databases up to date from the point of the backup. See Section 7.5, “Point-in-Time (Incremental) Recovery Using the Binary Log“.

The binary log is not used for statements such as SELECT or SHOW that do not modify data. To log all statements (for example, to identify a problem query), use the general query log. See Section 5.2.3, “The General Query Log“.

Running a server with binary logging enabled makes performance slightly slower. However, the benefits of the binary log in enabling you to set up replication and for restore operations generally outweigh this minor performance decrement.

From: http://dev.mysql.com/doc/refman/5.6/en/replication-formats.html

Replication works because events written to the binary log are read from the master and then processed on the slave. The events are recorded within the binary log in different formats according to the type of event. The different replication formats used correspond to the binary logging format used when the events were recorded in the master’s binary log. The correlation between binary logging formats and the terms used during replication are:

  • Replication capabilities in MySQL originally were based on propagation of SQL statements from master to slave. This is called statement-based replication (often abbreviated as SBR), which corresponds to the standard statement-based binary logging format. In older versions of MySQL (5.1.4 and earlier), binary logging and replication used this format exclusively.
  • Row-based binary logging logs changes in individual table rows. When used with MySQL replication, this is known as row-based replication (often abbreviated as RBR). In row-based replication, the master writes events to the binary log that indicate how individual table rows are changed.
  • The server can change the binary logging format in real time according to the type of event using mixed-format logging. When the mixed format is in effect, statement-based logging is used by default, but automatically switches to row-based logging in particular cases as described later. Replication using the mixed format is often referred to as mixed-based replication or mixed-format replication. For more information, see Section 5.2.4.3, “Mixed Binary Logging Format”.

Once a slave has the binlog and binlog position, the slave will connect to the master and retrieve all of the binlog entries from the specified binlog file and after a specified binlog position. The slave creates a thread (IO thread) that connects to the master server. The master server then creates a binlog dump thread, and sends the data to the slave’s IO thread. The slave will in effect retrieve the data that was written to the specified binary log starting after a specific binlog position and then write it to the slave’s relay log (see IO thread states). The slave will then take the data from the relay log and apply it to the slave’s database via the SQL thread. If this isn’t confusing enough, maybe this poorly drawn diagram will help you understand the steps in replication:

For this example, I am starting with a fresh install on one virtual machine running Mac OS X 10.8. MySQL doesn’t have a version specific to 10.8, but I found that the version for 10.7 will work. I am not going to cover how to install MySQL, but I will show you what you need to change in order to make MySQL replication work.

MySQL uses a configuration file (my.cnf or my.ini for Windows) for all of the database variables that will be read by MySQL at startup. After I install MySQL – but before I start MySQL, I will need to choose a copy of the my.cnf file to use, and then modify that file to match my specific use of MySQL. For this example, I am going to just copy the my.cnf file in my MySQL home directory to /etc/my.cnf and then edit the /etc/my.cnf file. You may use the following variables for your my.cnf options file. There are quite a few variables in this file that you will need to change or add. Since the version of the my.cnf file that I copied is mostly blank, here is what I have in my my.cnf file: (And yes, these are not all of the variables that you might need – these are just the basic variables for this example)

[mysqld_safe]
socket = /tmp/mysql.sock

[client]
port=3306

[mysqld]
port = 3306
user = mysql
tmpdir = /tmp
socket = /tmp/mysql.sock
basedir = /usr/local/mysql
datadir = /usr/local/mysql/data
log_error = /usr/local/mysql/error.log

Since InnoDB is the default storage engine for MySQL (as of 5.5), I want to provide some InnoDB-specific variables:

innodb_data_home_dir = /usr/local/mysql/data
innodb_data_file_path = ibdata1:25M:autoextend
innodb_log_group_home_dir = /usr/local/mysql/data

innodb_log_files_in_group = 2
innodb_log_file_size = 25M
innodb_buffer_pool_size = 16M

And then to enable replication, MySQL will need to write all of the select, insert, update and delete etc. statements to the binary log (binlog). I also need to choose the binlog format. I will use “mixed“, which allows MySQL to determine whether or not to use row or statement-based binlog format for each separate SQL statement. The slave will retrieve these statements from the master and then write them to the slave’s relay log before applying these statements to the slave database.

log-bin=mysql-bin
binlog_format=mixed

I need to give each server a unique ID. I always give my master server the id of one (1), and then for the slaves, I will assign a sequential number starting at two for the server-id‘s.

server-id = 1

If you want to possibly use the slave for failover (where you promote the slave to be the master), then you will need to log the updates that are on the slave to the slave’s binary log as well. This will allow any other slaves to use this server as a master. Even though this is a master, if it ever becomes a slave I might want to re-promote it to master at a future date.

log-slave-updates

And in order to enable auto crash recovery on the slaves, enable:

relay-log-recovery

You may now run the installation script for the version of MySQL that you are installing. After you install the new database, you will want to execute the mysql_install_db script. You can also refer to the post-installation procedures on the MySQL web site. Start MySQL, and run the script:

root@macserver01: # ./scripts/mysql_install_db
Installing MySQL system tables...OK

Filling help tables...OK

To start mysqld at boot time you have to copy
support-files/mysql.server to the right place for your system

PLEASE REMEMBER TO SET A PASSWORD FOR THE MySQL root USER !
To do so, start the server, then issue the following commands:

  ./bin/mysqladmin -u root password 'new-password'
  ./bin/mysqladmin -u root -h macserver01 password 'new-password'

Alternatively you can run:

  ./bin/mysql_secure_installation

which will also give you the option of removing the test
databases and anonymous user created by default.  This is
strongly recommended for production servers.

See the manual for more instructions.

You can start the MySQL daemon with:

  cd . ; ./bin/mysqld_safe &

You can test the MySQL daemon with mysql-test-run.pl

  cd mysql-test ; perl mysql-test-run.pl

Please report any problems with the ./bin/mysqlbug script!

The latest information about MySQL is available on the web at

  http://www.mysql.com

Support MySQL by buying support/licenses at http://shop.mysql.com

WARNING: Found existing config file ./my.cnf on the system.
Because this file might be in use, it was not replaced,
but was used in bootstrap (unless you used --defaults-file)
and when you later start the server.
The new default config file was created as ./my-new.cnf,
please compare it with your file and take the changes you need.

WARNING: Default config file /etc/my.cnf exists on the system
This file will be read by default by the MySQL server
If you do not want to use this, either remove it, or use the
--defaults-file argument to mysqld_safe when starting the server

If you ran this script as root, you will need to change the ownership of the mysql-bin and mysql-bin.index files in the mysql data directory to the mysql Unix user.

Now you can start the MySQL server (if it isn’t already started). When you executed the mysql_install_db script, it created the grant tables. You are going to want to change the root password and delete any anonymous accounts. See Securing the Initial MySQL Accounts for specific information for your operating system.

An easy way to change the root password is to use mysqladmin from a command prompt:

$ ./bin/mysqladmin -u root password 'new-password'

Right after you change the root password, you will want to test the new root password by logging in with mysql as root at a Unix prompt:

root@macserver01: $ mysql -uroot -p
Enter password: 
Welcome to the MySQL monitor.  Commands end with ; or \g.
Your MySQL connection id is 2259
Server version: 5.6.9-rc-log MySQL Community Server (GPL)

Copyright (c) 2000, 2012, Oracle and/or its affiliates. All rights reserved.

Oracle is a registered trademark of Oracle Corporation and/or its
affiliates. Other names may be trademarks of their respective
owners.

Type 'help;' or '\h' for help. Type '\c' to clear the current input statement.

mysql> 

Running the mysqladmin program (above) only changed your root password for the localhost.

mysql> select host, user, password from user;
+-----------+------+-------------------------------------------+
| host      | user | password                                  |
+-----------+------+-------------------------------------------+
| localhost | root | *8B7D321C58724D1990BB8DE02FBD22FE19DB0D0A |
| 127.0.0.1 | root |                                           |
| ::1       | root |                                           |
| localhost |      |                                           |
+-----------+------+-------------------------------------------+
4 rows in set (0.00 sec)

Now that you have logged in, you can change your password for all of your root accounts:

mysql> UPDATE mysql.user SET Password=PASSWORD('new-password') WHERE User='root';
Query OK, 2 rows affected (0.00 sec)
Rows matched: 3  Changed: 2  Warnings: 0

mysql> flush privileges;
Query OK, 0 rows affected (0.00 sec)

mysql> select host, user, password from user;
+-----------+------+-------------------------------------------+
| host      | user | password                                  |
+-----------+------+-------------------------------------------+
| localhost | root | *8B7D321C58724D1990BB8DE02FBD22FE19DB0D0A |
| 127.0.0.1 | root | *8B7D321C58724D1990BB8DE02FBD22FE19DB0D0A |
| ::1       | root | *8B7D321C58724D1990BB8DE02FBD22FE19DB0D0A |
| localhost |      |                                           |
+-----------+------+-------------------------------------------+
4 rows in set (0.00 sec)

To find and delete the anonymous accounts, you can find a list of all of the accounts. From a mysql prompt:

mysql> use mysql;
Database changed
mysql> SELECT user, host FROM user;
+------+-----------+
| user | host      |
+------+-----------+
| root | 127.0.0.1 |
| root | ::1       |
|      | localhost |
| root | localhost |
+------+-----------+
4 rows in set (0.00 sec)

The users that are blank are anonymous users. You can double-check the blank users with this statement:

mysql> select user, host from user where user = '';
+------+-----------+
| user | host      |
+------+-----------+
|      | localhost |
+------+-----------+
1 row in set (0.00 sec)

You may now delete the blank users:

mysql> delete from user where user = '';
Query OK, 1 row affected (0.00 sec)

These are the users that are remaining:

mysql> select user, host from user;
+------+-----------+
| user | host      |
+------+-----------+
| root | 127.0.0.1 |
| root | ::1       |
| root | localhost |
+------+-----------+
3 rows in set (0.00 sec)

Since we are installing MySQL for the first time on your master, you will need to create a replication user for replication. See Creating a User for Replication for more details, but here is a sample replication user creation statement:

mysql> CREATE USER 'replicate'@'%.mydomain.com' IDENTIFIED BY 'password';
mysql> GRANT REPLICATION SLAVE ON *.* TO 'replicate'@'%.mydomain.com';

mysql> select user, host from user;
+-----------+-----------+
| user      | host      |
+-----------+-----------+
| replicate | %         |
| root      | 127.0.0.1 |
| root      | ::1       |
| root      | localhost |
+-----------+-----------+
4 rows in set (0.00 sec)

You will need to make sure that your replication user matches the domain names or IP addresses, so that it has permissions to access the other server(s).

MySQL should now be up and running on your master server. If you aren’t using VM’s, you may now duplicate these same installation steps on your slave server(s) – but you must change the value of server-id in your my.cnf file for each server – to something other than the value that you have for your master server.

If you are working with virtual machines, you will need to:

  • Stop the mysqld process
  • Stop the virtual machine (shutdown the instance)
  • Copy/duplicate the virtual machine
  • Change the IP address of the new virtual machine
  • Change the server-id in the my.cnf file of the new virtual machine
  • Change my server name for use in file sharing (if file sharing is turned on)
  • Generate a new UUID for the new slave servers and edit the auto.cnf file. (more on this below)

Beginning with MySQL 5.6, the MySQL server generates a unique ID (UUID) in addition to the server-id supplied by the user. This is available as the global, read-only variable server_uuid. If you aren’t using VM’s, a new UUID will be installed when you install MySQL. On the new VM copies, we will need to generate a new UUID and then edit the auto.cnf file. You can run the select UUID(); command from the master server:

mysql> select UUID();
+--------------------------------------+
| UUID()                               |
+--------------------------------------+
| 1da4ab9c-7baf-11e2-930f-6a4c3f56f0b5 |
+--------------------------------------+
1 row in set (0.00 sec)

Next, edit the auto.cnf file that is in the MySQL home data directory:

# cat auto.cnf 
[auto]
server-uuid=1da4ab9c-7baf-11e2-930f-6a4c3f56f0b5

Edit the auto.cnf file with a text editor (or use vi) and change the old UUID to the new UUID (example – change 33e3daac-79e5-11e2-9862-ec1bc27a1e29 to 1da4ab9c-7baf-11e2-930f-6a4c3f56f0b5).

After you have installed MySQL on the new slave or copied the original VM and repeated the steps above, you can check to see if your servers have unique server-id‘s and UUID‘s. Login to each instance of mysql:

# mysql -uroot -p
Enter password: 
Welcome to the MySQL monitor.  Commands end with ; or \g.
Your MySQL connection id is 3
Server version: 5.6.10-enterprise-commercial-advanced-log MySQL Enterprise Server - Advanced Edition (Commercial)

Copyright (c) 2000, 2013, Oracle and/or its affiliates. All rights reserved.

Oracle is a registered trademark of Oracle Corporation and/or its
affiliates. Other names may be trademarks of their respective
owners.

Type 'help;' or '\h' for help. Type '\c' to clear the current input statement.

mysql> use mysql;
Database changed
mysql> show variables where variable_name = 'server_id';
+---------------+-------+
| Variable_name | Value |
+---------------+-------+
| server_id     | 2     |
+---------------+-------+
1 row in set (0.00 sec)

mysql> show variables where variable_name = 'server_uuid';
+---------------+--------------------------------------+
| Variable_name | Value                                |
+---------------+--------------------------------------+
| server_uuid   | 33e3daac-79e5-11e2-9862-ec1bc27a1e29 |
+---------------+--------------------------------------+
1 row in set (0.00 sec)

Now that we have our servers up and running, we need to tell our slave server(s) about the master server. If we have already started inserting data into our master servers, we need to put a read lock on the master, show the master status to get the binlog and binlog position of the master, and then release the lock. You may do this on one line separated by a semi-colon to reduce the amount of time that the lock is in place:

mysql> FLUSH TABLES WITH READ LOCK;SHOW MASTER STATUS;UNLOCK TABLES;
Query OK, 0 rows affected (0.00 sec)

+------------------+----------+--------------+------------------+-------------------+
| File             | Position | Binlog_Do_DB | Binlog_Ignore_DB | Executed_Gtid_Set |
+------------------+----------+--------------+------------------+-------------------+
| mysql-bin.000015 |      540 |              |                  |                   |
+------------------+----------+--------------+------------------+-------------------+
1 row in set (0.00 sec)

Query OK, 0 rows affected (0.00 sec)

It is important that you save the SHOW MASTER STATUS information, as you will need this for each slave.

Now we need to tell the slave where the master is located, which binlog file to use, and which position to start. Issue this CHANGE MASTER TO command on the slave server(s): (don’t forget to change the values to match your master server)

mysql> CHANGE MASTER TO
    ->   MASTER_HOST='master IP address',
    ->   MASTER_USER='replication user',
    ->   MASTER_PASSWORD='replication user password',
    ->   MASTER_PORT=3306,
    ->   MASTER_LOG_FILE='mysql-bin.000015',
    ->   MASTER_LOG_POS=540,
    ->   MASTER_CONNECT_RETRY=10;
Query OK, 0 rows affected, 2 warnings (0.27 sec)

We have two warnings from the above statement. Let’s look at the warnings:

mysql> show warnings\G
*************************** 1. row ***************************
  Level: Note
   Code: 1759
Message: Sending passwords in plain text without SSL/TLS is extremely insecure.
*************************** 2. row ***************************
  Level: Note
   Code: 1760
Message: Storing MySQL user name or password information in the master.info repository 
is not secure and is therefore not recommended. Please see the MySQL Manual for more 
about this issue and possible alternatives.
2 rows in set (0.00 sec)

The first error “Sending passwords in plain text…” can be ignored. Since we are setting up replication using this method, we have to send the user name and password as plain text. The second error explains that the information in the CHANGE MASTER TO statement is stored in a non-secure file named master.info in your MySQL data directory:

# pwd
/usr/local/mysql/data
# ls -l master.info
-rw-rw----  1 _mysql  wheel  99 Feb 20 15:26 master.info
# cat master.info
23
mysql-bin.000015
540
192.168.1.2
replicate
replicate999
3306
10
....

There are options to not using the master.info file: “MySQL 5.6 extends the replication START SLAVE command to enable DBAs to specify master user and password as part of the replication slave options and to authenticate the account used to connect to the master through an external authentication plugin (user defined or those provided under MySQL Enterprise Edition). With these options the user and password no longer need to be exposed in plain text in the master.info file.” (from https://blogs.oracle.com/MySQL/entry/mysql_5_6_is_a)

For this example, we don’t need to worry about these errors. To begin replication, we need to start the slave:

mysql> start slave;
Query OK, 0 rows affected (0.01 sec)

We now can check the status of the slave to see if it is working as a slave, with the SHOW SLAVE STATUS\G command:

mysql> show slave status\G
*************************** 1. row ***************************
               Slave_IO_State: Waiting for master to send event
                  Master_Host: 192.168.1.181
                  Master_User: replicate
                  Master_Port: 3306
                Connect_Retry: 10
              Master_Log_File: mysql-bin.000015
          Read_Master_Log_Pos: 540
               Relay_Log_File: macos-108-repl02-relay-bin.000002
                Relay_Log_Pos: 1551
        Relay_Master_Log_File: mysql-bin.000015
             Slave_IO_Running: Yes
            Slave_SQL_Running: Yes
              Replicate_Do_DB: 
          Replicate_Ignore_DB: 
           Replicate_Do_Table: 
       Replicate_Ignore_Table: 
      Replicate_Wild_Do_Table: 
  Replicate_Wild_Ignore_Table: 
                   Last_Errno: 0
                   Last_Error: 
                 Skip_Counter: 0
          Exec_Master_Log_Pos: 540
              Relay_Log_Space: 1735
              Until_Condition: None
               Until_Log_File: 
                Until_Log_Pos: 0
           Master_SSL_Allowed: No
           Master_SSL_CA_File: 
           Master_SSL_CA_Path: 
              Master_SSL_Cert: 
            Master_SSL_Cipher: 
               Master_SSL_Key: 
        Seconds_Behind_Master: 0
Master_SSL_Verify_Server_Cert: No
                Last_IO_Errno: 0
                Last_IO_Error: 
               Last_SQL_Errno: 0
               Last_SQL_Error: 
  Replicate_Ignore_Server_Ids: 
             Master_Server_Id: 1
                  Master_UUID: 33e3daac-79e5-11e2-9862-ec1bc27a1e29
             Master_Info_File: /usr/local/mysql-advanced-5.6.10-osx10.7-x86_64/data/master.info
                    SQL_Delay: 0
          SQL_Remaining_Delay: NULL
      Slave_SQL_Running_State: Slave has read all relay log; waiting for the slave I/O thread to update it
           Master_Retry_Count: 86400
                  Master_Bind: 
      Last_IO_Error_Timestamp: 
     Last_SQL_Error_Timestamp: 
               Master_SSL_Crl: 
           Master_SSL_Crlpath: 
           Retrieved_Gtid_Set: 
            Executed_Gtid_Set: 
                Auto_Position: 0
1 row in set (0.00 sec)

Two values to note in the slave status shows us that our CHANGE MASTER TO statement worked:

              Master_Log_File: mysql-bin.000015
          Read_Master_Log_Pos: 540

We can now execute a statement on the master, to see if it propagates to the slave database. Let’s see what databases are on the master:

mysql> show databases;
+--------------------+
| Database           |
+--------------------+
| information_schema |
| mysql              |
| performance_schema |
| test               |
+--------------------+
4 rows in set (0.01 sec)

When we execute the same command on the slave, we get the same results. Since we already have a test database, let’s create a table in that database. We can check to see if there are any tables in that database already:

mysql> use test;
Database changed
mysql> show tables;
Empty set (0.00 sec)

Currently there aren’t any tables in the test database. We can now create one on the master database:

mysql> CREATE TABLE `address` (
    ->   `serial_number` int(6) NOT NULL AUTO_INCREMENT,
    ->   `last_name` char(40) NOT NULL DEFAULT '',
    ->   `first_name` char(40) NOT NULL DEFAULT '',
    ->   `address_01` char(40) NOT NULL DEFAULT '',
    ->   `city` char(30) NOT NULL DEFAULT '',
    ->   `state` char(20) NOT NULL DEFAULT '',
    ->   `zip` char(11) NOT NULL DEFAULT '',
    ->   `phone` char(15) NOT NULL DEFAULT '',
    ->   PRIMARY KEY (`serial_number`)
    -> ) ENGINE=InnoDB AUTO_INCREMENT=100000 DEFAULT CHARSET=latin1;
Query OK, 0 rows affected (0.07 sec)

mysql> show tables;
+----------------+
| Tables_in_test |
+----------------+
| address        |
+----------------+
1 row in set (0.00 sec)

And let’s take a look at the new master status;

mysql> show master status;
+------------------+----------+--------------+------------------+-------------------+
| File             | Position | Binlog_Do_DB | Binlog_Ignore_DB | Executed_Gtid_Set |
+------------------+----------+--------------+------------------+-------------------+
| mysql-bin.000015 |     1808 |              |                  |                   |
+------------------+----------+--------------+------------------+-------------------+

So, if we have replication set up correctly, when we go to the slave, we should see this table on the slave as well. Let’s execute the same same show table statement on the slave:

mysql> use test;
Database changed
mysql> show tables;
+----------------+
| Tables_in_test |
+----------------+
| address        |
+----------------+
1 row in set (0.00 sec)

Replication is now up and running. You may continue these steps for additional slaves that you install manually or slaves where you copy the VM.

I can also use the MySQL Utility script mysqldbcompare to see if both tables are the same. I wrote about mysqldbcompare in an earlier post. Just like this post, on the master and slave databases, I will create a user named “scripts” to execute the mysqldbcompare script: I don’t need to actually create the user on the slave, as when I execute this command on the master, it will be replicated over to the slave.

mysql> CREATE USER 'scripts'@'%' IDENTIFIED BY 'scripts999';
Query OK, 0 rows affected (0.00 sec)
mysql> GRANT ALL PRIVILEGES ON *.* TO 'scripts'@'%' WITH GRANT OPTION;
Query OK, 0 rows affected (0.00 sec)

I can now run the mysqldbcompare script:

$ mysqldbcompare --server1=scripts:scripts999@192.168.1.181 --server2=scripts:scripts999@192.168.1.182 test:test --run-all-tests --changes-for=server2 --difftype=sql
# server1 on 192.168.1.181: ... connected.
# server2 on 192.168.1.182: ... connected.
# Checking databases test on server1 and test on server2
#
#                                                   Defn    Row     Data   
# Type      Object Name                             Diff    Count   Check  
# ------------------------------------------------------------------------- 
# TABLE     address                                 pass    pass    pass   

Databases are consistent.
#
# ...done

The SQL statement that I executed on the master to create the table “address” has been replicated on the slave, so replication is running and confirmed to be working.

 


Tony Darnell is a Principal Sales Consultant for MySQL, a division of Oracle, Inc. MySQL is the world’s most popular open-source database program. Tony may be reached at info [at] ScriptingMySQL.com and on LinkedIn.
Tony is the author of Twenty Forty-Four: The League of Patriots

 

Visit http://2044thebook.com for more information.

Using MySQL Utilities Workbench Script mysqldbcompare To Compare Two Databases In Replication

In my last two posts, I wrote about setting up replication with MySQL 5.6 using Global Transaction Identifiers. Even when I set up replication “the old-fashioned way“, one thought always enters my mind – did all of the data copy over to the slave? And, even after the master/slave has been running for a while, I am always wondering if the data in the slave matches the master. Or did the change that I made to that table make it over to the slave? It is probably more of a case of paranoia on my part, as MySQL replication is very reliable and works really well.

A few months ago, I started writing about the MySQL Utilities. If you haven’t heard about the MySQL Utilities:

“MySQL Utilities is a package of utilities that are used for maintenance and administration of MySQL servers. These utilities encapsulate a set of primitive commands, and bundles them so they can be used to perform macro operations with a single command. MySQL Utilities may be installed via MySQL Workbench, or as a standalone package. The utilities are written in Python, available under the GPLv2 license, and are extendable using the supplied library. They are designed to work with Python 2.x greater than 2.6.” (from the introduction to MySQL Utilities page)

In order to reduce my paranoia (I will never be able to eliminate it), I can simply use the mysqldbcompare utility. The mysqldbcompare utility “compares the objects and data from two databases to find differences. It identifies objects having different definitions in the two databases and presents them in a diff-style format of choice. Differences in the data are shown using a similar diff-style format. Changed or missing rows are shown in a standard format of GRID, CSV, TAB, or VERTICAL.” (from: mysqldbcompare — Compare Two Databases and Identify Differences)

You don’t have to use mysqldcompare to compare two databases in replication. You may compare any two databases, even if they are on the same server. But for this post, I will be comparing two databases on two separate servers in a master/slave replication topology.

The utility is fairly easy to use. You just identify the two servers and which databases you want to compare. You will need to refer to my earlier post on using the MySQL Utilities for more information on how to execute the scripts.

I will be comparing a database that is on my master server (at 192.168.1.2) and the same database that is on one of the slaves (at 192.168.1.122) connected to that master. Instead of using root to execute the scripts, I create and use a MySQL user named “scripts” to use when I run a script. The syntax for mysqldbcompare is fairly easy, and you can refer to the mysqldbcompare man page for more of the commands and their usage:

I need to specify the servers, user name and passwords:

--server1=scripts:scripts999@192.168.1.2 
--server2=scripts:scripts999@192.168.1.122 

The name of the databases to compare (database_server1:database_server2):

cbgc:cbgc 

Do not stop the script at the first difference that is found. Process all objects.

--run-all-tests 

Specify the server to show transformations to match the other server.

--changes-for=server2 

Specify the difference display format. Permitted format values are unified, context, differ, and sql. The default is unified.

--difftype=sql

Now that I have decided on which options to use, I can run the scripts from within the MySQL Workbench Utilities shell:

$ mysqldbcompare --server1=scripts:scripts999@192.168.1.2 \
  --server2=scripts:scripts999@192.168.1.122 \
  cbgc:cbgc --run-all-tests --changes-for=server2 --difftype=sql
# server1 on 192.168.1.2: ... connected.
# server2 on 192.168.1.122: ... connected.
# Checking databases cbgc on server1 and cbgc on server2
#
#                                                   Defn    Row     Data   
# Type      Object Name                             Diff    Count   Check  
# ------------------------------------------------------------------------- 
# TABLE     Activity_Affiliate                      pass    pass    pass    
# TABLE     FedEx_2nd_Day                           pass    pass    pass    
# TABLE     FedEx_Express_Saver                     pass    pass    pass    
# TABLE     FedEx_Ground                            pass    pass    pass    
# TABLE     FedEx_Home                              pass    pass    pass    
# TABLE     FedEx_Priority_Overnight                pass    pass    pass    
# TABLE     FedEx_Standard_Overnight                pass    pass    pass    
# TABLE     Orders                                  pass    pass    pass    
# TABLE     USPS                                    pass    pass    pass    
# TABLE     activity                                pass    pass    pass    
# TABLE     comics                                  pass    pass    pass    
# TABLE     coupons                                 pass    pass    pass    
# TABLE     customer                                pass    pass    pass    
# TABLE     giftcert                                pass    pass    pass   

Databases are consistent.
#
# ...done

The output shows that my databases are consistent. I have a rather small database, and I re-executed the script again with the “time” command, and here are the time results:

real	0m4.519s
user	0m0.429s
sys	0m0.068s

It took about 4.5 seconds to execute on my database which is about 25 megabytes in size. Obviously, the time will increase relative to the complexity and size of your database. And the time will increase relative to the number of differences that the script finds.

In order to show you what happens when the databases are not in sync, I will now stop the slave database (at 192.168.1.122), and then add a line to one of the tables in the master database (at 192.168.1.2), and re-run the script (while the slave is still stopped).

On the slave server:

mysql> stop slave;
Query OK, 0 rows affected, 1 warning (0.00 sec)

On the master server:

mysql> insert into `cbgc`.`activity` ( `Customer_Serial_Number`, `Customer_Activity_Action`) \
          values ( '1201201', 'Test Visit');
Query OK, 1 row affected (0.96 sec)

Now I can run the mysqldbcompare script again. The slave is still turned off:

$ mysqldbcompare --server1=scripts:scripts999@192.168.1.2 \
  --server2=scripts:scripts999@192.168.1.122 cbgc:cbgc \ 
  --run-all-tests --changes-for=server2 --difftype=sql
# server1 on 192.168.1.2: ... connected.
# server2 on 192.168.1.122: ... connected.
# Checking databases cbgc on server1 and cbgc on server2
#
#                                                   Defn    Row     Data   
# Type      Object Name                             Diff    Count   Check  
# ------------------------------------------------------------------------- 
# TABLE     Activity_Affiliate                      pass    pass    pass    
# TABLE     FedEx_2nd_Day                           pass    pass    pass    
# TABLE     FedEx_Express_Saver                     pass    pass    pass    
# TABLE     FedEx_Ground                            pass    pass    pass    
# TABLE     FedEx_Home                              pass    pass    pass    
# TABLE     FedEx_Priority_Overnight                pass    pass    pass    
# TABLE     FedEx_Standard_Overnight                pass    pass    pass    
# TABLE     Orders                                  pass    pass    pass    
# TABLE     USPS                                    pass    pass    pass    
# TABLE     activity                                FAIL    FAIL    FAIL    
#
# Transformation for --changes-for=server2:
#

ALTER TABLE cbgc.activity 
  DROP PRIMARY KEY, 
  ADD PRIMARY KEY(serial_id), 
AUTO_INCREMENT=7542;

# Row counts are not the same among cbgc.activity and cbgc.activity.
#
# Transformation for --changes-for=server2:
#

INSERT INTO cbgc.activity (serial_id, Customer_Serial_Number, Customer_Activity_Action, 
Customer_Activity_Date_Time, Customer_Activity_Info, Notes, HTTP_REFERER) 
VALUES('7541', '1201201', 'Test Visit', NULL, NULL, NULL, NULL);


# TABLE     comics                                  pass    pass    pass    
# TABLE     coupons                                 pass    pass    pass    
# TABLE     customer                                pass    pass    pass    
# TABLE     giftcert                                pass    pass    pass   

# Database consistency check failed.
#
# ...done

The script alerted me to two issues. It tells me that I have one row of data missing (from the insert statement), but it also notices that my auto-increment on the activity database needs to be updated as well. If I simply run the insert statement, my auto-increment value will be incorrect. So, I need to run the auto-increment change first, and then I can execute the insert statement.

There are other choices of output that you can use besides sql – unified, context and differ. You can try each one and see which one will fit your needs. I prefer the sql output.

Since I stopped the slave, I can just start it again and it will catch up with the master. But, if you are working with an active master, you might want to put a read lock on the database, run the script again, and then make your changes. This is especially true if the changes involve something dynamic like a primary key or auto-increment column, as those values could change while you are trying to run the statements.

Let’s see what happens when we someone else makes some changes and we aren’t aware of the changes. But first, I will start the slave so it can catch up to the master (for the earlier missing statements). We will then stop the slave and let someone else make a few changes. And then we can run the mysqldbcompare utility again:

$ mysqldbcompare --server1=scripts:scripts999@192.168.1.2 \
  --server2=scripts:scripts999@192.168.1.122 cbgc:cbgc \
  --run-all-tests --changes-for=server2 --difftype=sql
# server1 on 192.168.1.2: ... connected.
# server2 on 192.168.1.122: ... connected.
# Checking databases cbgc on server1 and cbgc on server2
#
#                                                   Defn    Row     Data   
# Type      Object Name                             Diff    Count   Check  
# ------------------------------------------------------------------------- 
# TABLE     Activity_Affiliate                      pass    pass    pass    
# TABLE     FedEx_2nd_Day                           pass    pass    pass    
# TABLE     FedEx_Express_Saver                     pass    pass    pass    
# TABLE     FedEx_Ground                            pass    pass    pass    
# TABLE     FedEx_Home                              pass    pass    pass    
# TABLE     FedEx_Priority_Overnight                pass    pass    pass    
# TABLE     FedEx_Standard_Overnight                pass    pass    pass    
# TABLE     Orders                                  pass    pass    pass    
# TABLE     USPS                                    pass    pass    pass    
# TABLE     activity                                FAIL    pass    pass    
#
# Transformation for --changes-for=server2:
#

ALTER TABLE cbgc.activity 
  DROP PRIMARY KEY, 
  DROP COLUMN Dummy_Field, 
  ADD PRIMARY KEY(serial_id);


# TABLE     comics                                  pass    pass    pass    
# TABLE     coupons                                 FAIL    pass    pass    
#
# Transformation for --changes-for=server2:
#

ALTER TABLE cbgc.coupons 
  CHANGE COLUMN Coupon_Notes Coupon_Notes varchar(100) NULL;


# TABLE     customer                                pass    pass    pass    
# TABLE     giftcert                                pass    pass    pass   

Databases are consistent.
#
# ...done

This time, the script took about 20 seconds to run:

real	0m20.058s
user	0m0.452s
sys	0m0.224s

We can see from the output that a column named Dummy_Field was dropped. We can also see that the Coupon_Notes column has changed (or is different on the master). I can now take these changes and implement them on the slave (again assuming that these changes aren’t waiting to be sent to the slave). In my case, once I start the slave, the changes will propagate over to the slave, but there may be cases where that transaction was lost or skipped on the slave (for example, if you had to do a SET GLOBAL sql_slave_skip_counter = N on the slave). You now have the ability to easily make the slave the same as the master by executing these differences. If the changes are too complicated, then you might want to look at re-creating your slave.

There are many different options and output possibilities, so I would encourage you to just try mysqldbcompare and see how it works for you. And as always, feel free to post your feedback in the comments section.

 


Tony Darnell is a Principal Sales Consultant for MySQL, a division of Oracle, Inc. MySQL is the world’s most popular open-source database program. Tony may be reached at info [at] ScriptingMySQL.com and on LinkedIn.
Tony is the author of Twenty Forty-Four: The League of Patriots

 

Visit http://2044thebook.com for more information.

MySQL Replication with Global Transaction Identifiers – Step-by-Step Install and Addition of Slaves – Part Two

This post is part two of MySQL Replication with Global Transaction Identifiers – Step-by-Step Install and Addition of Slaves. In this post, I will be showing you how to use the MySQL Utility Script mysqlreplicate to create a new replication slave off a master database.

This is also the fourth in a series that I will be doing on MySQL Workbench Utilities – Administer MySQL with Python Scripts. You may want to read the first half of this post to understand how MySQL Workbench Utilities work and how you access the scripts. These scripts were written by Chuck Bell (a MySQL employee) and are available as stand-alone scripts (see Chuck’s blog for more information) or as part of the MySQL Workbench utility.

The mysqlreplicate “utility permits an administrator to start replication from one server (the master) to another (the slave). The user provides login information for the slave and connection information for connecting to the master.” (From: http://dev.mysql.com/doc/workbench/en/mysqlreplicate.html)

In the first post, I showed you how to create a slave off a master. The mysqlreplicate utility takes care of the manual steps for you, and makes it easy to create a slave database. I am not going to rewrite a lot of the details from the first post, so you may refer to that post for more information.

The first step is to install the MySQL database on a new server that is going to be your slave server. In this example, I am installing MySQL version 5.6.9 (Community Edition) on a Macintosh with OS 10.6.8. This tutorials should work for any platform, with just a few tweaks for Windows users.

After the install, I will need to change the permissions on my mysql directory, since I installed the database as root:

# ls -l
total 8
lrwxr-xr-x   1 root  wheel   29 Jan 25 11:50 mysql -> mysql-5.6.9-rc-osx10.7-x86_64
drwxr-xr-x  18 root  wheel  612 Jan 25 11:51 mysql-5.6.9-rc-osx10.7-x86_64
# chown -R _mysql mysql*
# ls -l
total 8
lrwxr-xr-x   1 _mysql  wheel   29 Jan 25 11:50 mysql -> mysql-5.6.9-rc-osx10.7-x86_64
drwxr-xr-x  18 _mysql  wheel  612 Jan 25 11:51 mysql-5.6.9-rc-osx10.7-x86_64

Next, I will run the mysql_install_db script from my mysql home directory (/usr/local/mysql) – /usr/local/mysql:

root# cd /usr/local/mysql
root# ls -l scripts
total 72
-rwxr-xr-x  1 _mysql  wheel  33018 Nov 22 10:28 mysql_install_db
root# ./scripts/mysql_install_db
Installing MySQL system tables...OK

Filling help tables...OK

To start mysqld at boot time you have to copy
support-files/mysql.server to the right place for your system

PLEASE REMEMBER TO SET A PASSWORD FOR THE MySQL root USER !
To do so, start the server, then issue the following commands:

  ./bin/mysqladmin -u root password 'new-password'
  ./bin/mysqladmin -u root -h VM-Mac-1081-122.local password 'new-password'

Alternatively you can run:

  ./bin/mysql_secure_installation

which will also give you the option of removing the test
databases and anonymous user created by default.  This is
strongly recommended for production servers.

See the manual for more instructions.

You can start the MySQL daemon with:

  cd . ; ./bin/mysqld_safe &

You can test the MySQL daemon with mysql-test-run.pl

  cd mysql-test ; perl mysql-test-run.pl

Please report any problems with the ./bin/mysqlbug script!

The latest information about MySQL is available on the web at

  http://www.mysql.com

Support MySQL by buying support/licenses at http://shop.mysql.com

WARNING: Found existing config file ./my.cnf on the system.
Because this file might be in use, it was not replaced,
but was used in bootstrap (unless you used --defaults-file)
and when you later start the server.
The new default config file was created as ./my-new.cnf,
please compare it with your file and take the changes you need.

WARNING: Default config file /etc/my.cnf exists on the system
This file will be read by default by the MySQL server
If you do not want to use this, either remove it, or use the
--defaults-file argument to mysqld_safe when starting the server

Again, since I ran this as root, I will need to change permissions on a few files in the mysql directory to the mysql user. There are some files in the data directory that are owned by root, but I can just do a change ownership of the entire mysql directory.

I will now need to start mysql, and then change the root password. I can change the password with the mysqladmin client application:

./bin/mysqladmin -u root password 'newpassword'

I then check to make sure that my password change worked. I can do this by logging into mysql and I will also list the users in the database:

root# mysql -uroot -p

mysql> use mysql;
Database changed
mysql> select user, host, password from users;
ERROR 1146 (42S02): Table 'mysql.users' doesn't exist
mysql> select user, host, password from user;
+---------+-----------------------+-------------------------------------------+
| user    | host                  | password                                  |
+---------+-----------------------+-------------------------------------------+
| root    | localhost             | *8FF7274XXF360A5BB33835F544D6617707C23968 |
| root    | VM-Mac-1081-122.local |                                           |
| root    | 127.0.0.1             |                                           |
| root    | ::1                   |                                           |
|         | localhost             |                                           |
|         | VM-Mac-1081-122.local |                                           |
+---------+-----------------------+-------------------------------------------+
6 rows in set (0.00 sec)

You can see that mysqladmin only changed the root password for the localhost (the rest of the password fields were blank). I can change the rest of the root passwords once I am in mysql:

mysql> UPDATE mysql.user SET Password=PASSWORD('newpassword') WHERE User='root';
Query OK, 3 rows affected (0.00 sec)
Rows matched: 4  Changed: 3  Warnings: 0
mysql> flush privileges;
Query OK, 0 rows affected (0.00 sec)

I will also want to delete the anonymous users.

mysql> delete from user where user = '';
Query OK, 2 rows affected (0.00 sec)

Prior to starting this server as a slave, we can see that there are only the four mysql databases:

mysql> show databases;
+--------------------+
| Database           |
+--------------------+
| information_schema |
| mysql              |
| performance_schema |
| test               |
+--------------------+
4 rows in set (0.00 sec)

And since we haven’t started it as a slave, the SHOW SLAVE STATUS is empty:

mysql> show slave status\G
Empty set (0.00 sec)

I prefer to run all of my scripts with a user named “scripts” versus using the root mysql user, so I will create the scripts user:

CREATE USER 'scripts'@'192.168.1.122' IDENTIFIED BY 'scripts123';
GRANT ALL PRIVILEGES ON *.* TO 'scripts'@'192.168.1.122' WITH GRANT OPTION;

You can just use the root user if you want. But the mysqlreplicate script does not allow for special characters in the password field, so you will want to use a password without any special characters.

We will need to create a replication use on the master for the slave, which is at 192.168.1.2.

CREATE USER 'replicate'@'192.168.1.122' IDENTIFIED BY 'replicate123';
GRANT REPLICATION SLAVE ON *.* TO 'replicate'@'192.168.1.122';

Now we are ready to run the mysqlreplicate script. You will want to review the mysqlreplicate man page for the variables and their use:

$ mysqlreplicate --master=scripts:scripts123@192.168.1.2:3306 \
   --slave=scripts:scripts123@192.168.1.122:3306 \ 
   --rpl-user=replicate:replicate123 --start-from-beginning -vvv
# master on 192.168.1.2: ... connected.
# slave on 192.168.1.122: ... connected.
# master id = 1
#  slave id = 5
# Checking InnoDB statistics for type and version conflicts.
# Checking storage engines...
# Checking for binary logging on master...
# Setting up replication...
# Connecting slave to master...
# CHANGE MASTER TO MASTER_HOST = '192.168.1.2', MASTER_USER = 'replicate', MASTER_PASSWORD = 'replicate123', MASTER_PORT = 3306
# Starting slave from the beginning...
# status: Queueing master event to the relay log
# Waiting for slave to synchronize with master
# status: Queueing master event to the relay log
# Waiting for slave to synchronize with master
# status: Waiting for master to send event
# ...done.

That’s it! The mysqlreplicate utility has done all of the steps necessary to start the slave. After a few minutes, we can now look at the slave status:

mysql> show slave status\G
*************************** 1. row ***************************
               Slave_IO_State: Waiting for master to send event
                  Master_Host: 192.168.1.2
                  Master_User: replicate
                  Master_Port: 3306
                Connect_Retry: 60
              Master_Log_File: mysql-bin.000007
          Read_Master_Log_Pos: 137301
               Relay_Log_File: WEB_SERVER_01-relay-bin.000012
                Relay_Log_Pos: 354
        Relay_Master_Log_File: mysql-bin.000007
             Slave_IO_Running: Yes
            Slave_SQL_Running: Yes
              Replicate_Do_DB: 
          Replicate_Ignore_DB: 
           Replicate_Do_Table: 
       Replicate_Ignore_Table: 
      Replicate_Wild_Do_Table: 
  Replicate_Wild_Ignore_Table: 
                   Last_Errno: 0
                   Last_Error: 
                 Skip_Counter: 0
          Exec_Master_Log_Pos: 137301
              Relay_Log_Space: 769
              Until_Condition: None
               Until_Log_File: 
                Until_Log_Pos: 0
           Master_SSL_Allowed: No
           Master_SSL_CA_File: 
           Master_SSL_CA_Path: 
              Master_SSL_Cert: 
            Master_SSL_Cipher: 
               Master_SSL_Key: 
        Seconds_Behind_Master: 0
Master_SSL_Verify_Server_Cert: No
                Last_IO_Errno: 0
                Last_IO_Error: 
               Last_SQL_Errno: 0
               Last_SQL_Error: 
  Replicate_Ignore_Server_Ids: 
             Master_Server_Id: 1
                  Master_UUID: 82f20158-5a16-11e2-88f9-c4a801092abb
             Master_Info_File: mysql.slave_master_info
                    SQL_Delay: 0
          SQL_Remaining_Delay: NULL
      Slave_SQL_Running_State: Slave has read all relay log; waiting for the slave I/O thread to update it
           Master_Retry_Count: 86400
                  Master_Bind: 
      Last_IO_Error_Timestamp: 
     Last_SQL_Error_Timestamp: 
               Master_SSL_Crl: 
           Master_SSL_Crlpath: 
           Retrieved_Gtid_Set: 82F20158-5A16-11E2-88F9-C4A801092ABB:1-162868
            Executed_Gtid_Set: 82F20158-5A16-11E2-88F9-C4A801092ABB:1-162868,
                               B7DB3608-6729-11E2-9E3C-BDE2366761B1:1-4
1 row in set (0.00 sec)

mysql> 

If your slave hasn’t caught up with the master yet, the values for Retrieved_Gtid_Set and Executed_Gtid_Set will not match. It only took my slave a few minutes to catch up to my master, but your situation will be different. We can now compare the status of the Executed_Gtid_Set to the master, and it matches:

mysql> show master status\G
*************************** 1. row ***************************
             File: mysql-bin.000007
         Position: 137301
     Binlog_Do_DB: 
 Binlog_Ignore_DB: 
Executed_Gtid_Set: 82F20158-5A16-11E2-88F9-C4A801092ABB:1-162868
1 row in set (0.00 sec)

If your master database was active with write transactions, then master’s Executed_Gtid_Set value may be higher and not match the slave. But your slave is now ready for use.

 


Tony Darnell is a Principal Sales Consultant for MySQL, a division of Oracle, Inc. MySQL is the world’s most popular open-source database program. Tony may be reached at info [at] ScriptingMySQL.com and on LinkedIn.
Tony is the author of Twenty Forty-Four: The League of Patriots

 

Visit http://2044thebook.com for more information.

MySQL Replication with Global Transaction Identifiers – Step-by-Step Install and Addition of Slaves – Part One

One of my favorite features of MySQL is replication. Replication provides you with the ability to have MySQL automatically copy data from one MySQL instance to another. There are many benefits to using replication, but I just like having an extra copy of my data on another server in case the main server crashes. But if the master crashes, I can then use the MySQL mysqlfailover script to automatically failover from the master to the slave. (see my earlier post – Using the MySQL Script mysqlfailover for Automatic Failover with MySQL 5.6 GTID Replication).

MySQL Replication automatically copies the data from the main database (master) to another database (slave). You can have multiple slaves pulling data from a single master, and you can have slaves replicating data off other slaves. If you are new to replication, check out the MySQL Replication FAQ page.

In this post, I will explain how to install or upgrade MySQL (by exporting and importing the data for a “fresh” upgrade), create a master and slave server, and start replication. If you have never installed MySQL or if you have never used replication, then this blog should be able to help you do this without too many headaches. One warning – this is a long post with a lot of details. And, this is not the only way to setup replication. This is just one way to do it. I will show you a different way in part two of this post. In order to try and keep this post as short as possible, I will not explain each command or feature, but instead I will post as many links as possible. This install was performed on a Macintosh with OS version 10.6.8 (for the master) and 10.8.1 (for the slave). This post should apply to most Unix installs, and it should work with Windows as well, with a few modifications.

I currently have one master database with three slaves attached. I will be upgrading from MySQL 5.6.8 to 5.6.9 and all of the servers are GTID-enabled. This post will be relevant if you are able to stop both the master and the slave during the upgrade process – or if you are installing a new master and a slave (without an existing database on either system).

When I upgrade my master server, I like to export the data and do a fresh install, and then re-import my data back into MySQL. Yes, there are ways to upgrade without doing having to export your data. But since I have a relatively small database (<100MB), I like starting with a new server and re-importing the data. This is just my preference.

The first thing that I will need to do is to export my data with mysqldump. I like to export my databases one at a time, in case I have problems with the import, then I can narrow the problem down to a specific database. I need a list of my databases, so from a MySQL prompt, I execute the show databases command.

mysql> show databases;
+--------------------+
| Database           |
+--------------------+
| addressbook        |
| comicbooks         |
| genealogy          |
| information_schema |
| inventory          |
| mysql              |
| performance_schema |
| scripting          |
| test               |
| twtr               |
| website            |
+--------------------+
11 rows in set (0.92 sec)

I don’t want to export the four MySQL databases – information_schema, mysql, performance_schema or test – as these will be created in the new install. You are going to want to make sure that you don’t have any activity on your database before you export your data. From a mysql prompt (on the server you want to export data), you can use the FLUSH TABLES WITH READ LOCK command to prevent any additional inserts into the database and to allow all current transactions to be completed.

mysql> flush tables with read lock;
Query OK, 0 rows affected (0.00 sec)

I then export each database separately (my preference – you could do all of your databases at one time as well with the –all-databases option). In the command below, you will need to change DATABASE_NAME to the actual name of each of your databases:

/usr/local/mysql/bin/mysqldump --user=root --password --quick --skip-opt --create-options \
   --add-drop-database DATABASE_NAME > $HOME/mysql_backups/DATABASE_NAME.sql

Here is some information from the mysqldump page that explains each of the options that I used:

--quick, -q
This option is useful for dumping large tables. It forces mysqldump to retrieve rows for a table 
from the server a row at a time rather than retrieving the entire row set and buffering it in 
memory before writing it out.  I use this option in case I have problems importing the data, 
I easily edit the dump file and remove the bad data

--skip-opt
The --opt option is enabled by default, and --opt is shorthand for the combination of 
--add-drop-table --add-locks --create-options --disable-keys --extended-insert --lock-tables 
--quick --set-charset. It gives a fast dump operation and produces a dump file that can be 
reloaded into a MySQL server quickly.  Because the --opt option is enabled by default, you only 
specify its converse, the --skip-opt to turn off several default settings. See the discussion 
of mysqldump option groups for information about selectively enabling or disabling a subset 
of the options affected by --opt.

--create-options
Include all MySQL-specific table options in the CREATE TABLE statements.

--add-drop-database
Add a DROP DATABASE statement before each CREATE DATABASE statement. This option is typically used 
in conjunction with the --all-databases or --databases option because no CREATE DATABASE statements 
are written unless one of those options is specified.

You might want to read the mysqldump page to see which options you will want to use.

Once I have exported my data, I look at the export files to make sure that they were created. You might even want to open one of the smaller dump files (if the file isn’t too large) in a text-editor and just take a look to make sure everything looks good. If you used the same commands for each dump, then the smaller file will show you if the export is in the format you want.

If you have an existing MySQL database, you can also export the user and grant information so you can import this back into the new database. See my last blog post “Retrieving List of MySQL Users and Grants with Perl” to find out how to export your users and grants. You don’t have to use Perl to do this – you can manually use the commands explained in the post.

Now you can shutdown your MySQL instance.

Once the database has shutdown, you can now install the new version of MySQL. In this case, I am installing version 5.6.9. If you are on Unix or Mac, and you are installing as root, you will need to change ownership to the mysql user of the files in your home MySQL directory after the install process.

After you install the new database, you will want to execute the mysql_install_db script. You can also refer to the post-installation procedures on the MySQL web site. Start MySQL, and run the script:

root@macserver01: # ./scripts/mysql_install_db
Installing MySQL system tables...OK

Filling help tables...OK

To start mysqld at boot time you have to copy
support-files/mysql.server to the right place for your system

PLEASE REMEMBER TO SET A PASSWORD FOR THE MySQL root USER !
To do so, start the server, then issue the following commands:

  ./bin/mysqladmin -u root password 'new-password'
  ./bin/mysqladmin -u root -h macserver01 password 'new-password'

Alternatively you can run:

  ./bin/mysql_secure_installation

which will also give you the option of removing the test
databases and anonymous user created by default.  This is
strongly recommended for production servers.

See the manual for more instructions.

You can start the MySQL daemon with:

  cd . ; ./bin/mysqld_safe &

You can test the MySQL daemon with mysql-test-run.pl

  cd mysql-test ; perl mysql-test-run.pl

Please report any problems with the ./bin/mysqlbug script!

The latest information about MySQL is available on the web at

  http://www.mysql.com

Support MySQL by buying support/licenses at http://shop.mysql.com

WARNING: Found existing config file ./my.cnf on the system.
Because this file might be in use, it was not replaced,
but was used in bootstrap (unless you used --defaults-file)
and when you later start the server.
The new default config file was created as ./my-new.cnf,
please compare it with your file and take the changes you need.

WARNING: Default config file /etc/my.cnf exists on the system
This file will be read by default by the MySQL server
If you do not want to use this, either remove it, or use the
--defaults-file argument to mysqld_safe when starting the server

If you ran this script as root, you will need to change the ownership of the mysql-bin and mysql-bin.index files in the mysql data directory to the mysql Unix user.

If you intend to use this server as a master server, you will need to edit the my.cnf (my.ini on Windows) file to make it ready to be a master server. The minimum you must change is to add these lines under the [mysqld] section of your my.cnf option file.

log-bin=mysql-bin
server-id=1

The “server-id” must be unique to each server. I usually set my master server-id = 1. Check out the Setting the Replication Master Configuration page on the MySQL web site to make sure you have the correct settings for your server.

We will be using global transaction identifiers (GTID) for replication. GTID’s are a new replication feature as of MySQL 5.6.5. To enable GTID, you will need to add these lines under the [mysqld] section of your my.cnf option file.

gtid_mode=ON
enforce-gtid-consistency
log-bin
log-slave-updates
binlog_format=mixed

Now you can start the MySQL server (if it isn’t already started). When you executed the mysql_install_db script, it created the grant tables. You are going to want to change the root password and delete any anonymous accounts. See Securing the Initial MySQL Accounts for specific information for your operating system.

An easy way to change the root password is to use mysqladmin from a command prompt:

$ ./bin/mysqladmin -u root password 'new-password'

Right after you change the root password, you will want to test the new root password by logging in with mysql as root at a Unix prompt:

root@macserver01: $ mysql -uroot -p
Enter password: 
Welcome to the MySQL monitor.  Commands end with ; or \g.
Your MySQL connection id is 2259
Server version: 5.6.9-rc-log MySQL Community Server (GPL)

Copyright (c) 2000, 2012, Oracle and/or its affiliates. All rights reserved.

Oracle is a registered trademark of Oracle Corporation and/or its
affiliates. Other names may be trademarks of their respective
owners.

Type 'help;' or '\h' for help. Type '\c' to clear the current input statement.

mysql> 

Before we perform any more transactions, we need to make sure that we have GTID enabled. To see if GTID has been enabled, we can execute this statement from the mysql prompt:

mysql> show global variables like '%GTID%';
+--------------------------+-----------------------------------------------+
| Variable_name            | Value                                         |
+--------------------------+-----------------------------------------------+
| enforce_gtid_consistency | ON                                            |
| gtid_executed            | 82F20158-5A16-11E2-88F9-C4A801092ABB:1-26     |
| gtid_mode                | ON                                            |
| gtid_owned               |                                               |
| gtid_purged              |                                               |
+--------------------------+-----------------------------------------------+
5 rows in set (0.00 sec)

The variables enforce_gtid_consistency and gtid_mode should have the value of “ON”. The variable value for gtid_executed shows the UUID of the server, and the 1-26 shows that transactions one through 26 were executed. See GTID Concepts for more information about this value. Now that we know GTID has been enabled and our root password has been changed and confirmed, we can continue with deleting the anonymous accounts, creating our users and importing our data.

To find and delete the anonymous accounts, from a mysql prompt:

mysql> use mysql;
Database changed
mysql> SELECT user, host FROM user;
+------+-----------------------+
| user | host                  |
+------+-----------------------+
| root | 127.0.0.1             |
| root | ::1                   |
|      | macserver01.local     |
| root | macserver01.local     |
|      | localhost             |
| root | localhost             |
+------+-----------------------+
6 rows in set (0.00 sec)

The users that are blank are anonymous users. You can double-check the blank users with this statement:

mysql> select user, host from user where user = '';
+------+-----------------------+
| user | host                  |
+------+-----------------------+
|      | VM-Mac-1081-128.local |
|      | localhost             |
+------+-----------------------+
2 rows in set (0.00 sec)

You may now delete the blank users:

mysql> delete from user where user = '';
Query OK, 2 rows affected (0.00 sec)

These are the users that are remaining:

mysql> select user, host from user;
+------+-----------------------+
| user | host                  |
+------+-----------------------+
| root | 127.0.0.1             |
| root | ::1                   |
| root | VM-Mac-1081-128.local |
| root | localhost             |
+------+-----------------------+
4 rows in set (0.00 sec)

You can now create the users that you exported from your previous instance, or if this is a new install, you may create the users that you think you will need for this instance. If you exported the users, then you will want to remove the “CREATE USER” statement for the root users that match the user and host values above. If you had grants for these users that were different than the default grants, you can still execute the grant statements.

If you are installing MySQL for the first time on your master or if you did not have a replication user in your previous instance, you will need a replication user for replication. See Creating a User for Replication for more details, but here is a sample replication user creation statement:

mysql> CREATE USER 'replicate'@'%.mydomain.com' IDENTIFIED BY 'password';
mysql> GRANT REPLICATION SLAVE ON *.* TO 'replicate'@'%.mydomain.com';

Now that our users have been created, we can import the data from our earlier export. If this is a new install, then you may skip this step. Before we import the data, let’s look at the master status. We will use this information later, so save the output to a text file.

mysql> show master status\G
*************************** 1. row ***************************
             File: mysql-bin.000006
         Position: 71046480
     Binlog_Do_DB: 
 Binlog_Ignore_DB: 
Executed_Gtid_Set: 82F20158-5A16-11E2-88F9-C4A801092ABB:1-26
1 row in set (0.00 sec)

We can use the mysql program to import the data from the backups that we created earlier. You will need to execute this command for each database backup file:

mysql -uroot -p DATABASE_NAME < $HOME/mysql_backups/DATABASE_NAME.sql

Once you have imported the data, you can check the master status to see how many transactions were executed. Since I exported my data with one insert statement per line, the total number of insert statements that I had in my import should be close to the number of transactions that were executed.

mysql -uroot -p DATABASE_NAME  show master status\G
*************************** 1. row ***************************
             File: mysql-bin.000006
         Position: 71046480
     Binlog_Do_DB: 
 Binlog_Ignore_DB: 
Executed_Gtid_Set: 82F20158-5A16-11E2-88F9-C4A801092ABB:1-162551
1 row in set (0.00 sec)

The value of Executed_Gtid_Set contains the same type of information from the variable gtid_executed that we looked at previously. The value 82F20158-5A16-11E2-88F9-C4A801092ABB:1-162551 contains the UUID of the server and shows that transactions one through 162551 have been executed on this new instance. Since we exported the original data with each data row on an individual INSERT line, we can now figure out how many rows of data we imported. Before we imported the data, the value of Executed_Gtid_Set was 82F20158-5A16-11E2-88F9-C4A801092ABB:1-26 – so we executed 26 transactions before the data import. The difference in the total number of rows from the data import less the number of transactions that were executed earlier, minus the total number of any other statements (such as CREATE TABLE) should give us a count of the number of lines of data we imported. This step isn’t really necessary, but I like to do it just to make sure that I didn’t lose any data. And yes, it might be overkill.

We can do a line count for all of the data files that we imported earlier that contained an “INSERT” statement. This will give us a count of the total number of inserts from our import.

$ ls -l $HOME/mysql_backups/*sql
total 61832
-rw-r--r--  1 root  staff   1151006 Jan  9 00:12 addressbook.sql
-rw-r--r--  1 root  staff    492652 Jan  8 23:11 comicbooks.sql
-rw-r--r--  1 root  staff  27485322 Jan  8 23:11 genealogy.sql
-rw-r--r--  1 root  staff    603943 Jan  8 23:11 inventory.sql
-rw-r--r--  1 root  staff    779634 Jan  8 23:11 scripting.sql
-rw-r--r--  1 root  staff   1077248 Jan  8 23:11 twtr.sql
-rw-r--r--  1 root  staff     50643 Jan  8 23:11 website.sql
$ grep INSERT *sql | wc -l
  162444

Now we can get the total number of CREATE statements:

root@macserver01: $ grep CREATE *sql | wc -l
      81

The total number of transactions executed so far is 162551. If we subtract the number of INSERT lines from the import (162444) and CREATE statements (81), we get the total of transactions that had taken place before the data import, which was 26. We can now confirm that all of our data was imported successfully. We can now install MySQL on the slave and start replication.

For the slave, we will want to do the same steps for the install process as we did on the master, but we will stop at importing any data. Also, we will not have to create our additional users (with the exception of the replication user) and we will not have to import any data. Once we turn on the slave instance, the users will be replicated and the data we imported will be copied to the slave. Here are the steps:

  • Install MySQL version 5.6.9 (change ownership of the files in the mysql directory to mysql if you installed as root)
  • Run the post-install script mysql_install_db (change ownership of the mysql-bin and mysql-bin.index files in the data directory if you installed as root)
  • Change the root password and test it.
  • You don’t have to remove the anonymous accounts, as the SQL statements that we performed on the master will also be executed on the slave.
  • Create the replication user.
  • Shutdown the mysql server.
  • Edit the my.cnf options file (my.ini on Windows) and insert the GTID variables as shown earlier. But, the server-id value must be something other than the value from the master server. You can set this value to 2.
  • Start the server
  • Test to make sure GTID is enabled.
  • Stop the slave by logging into mysql as root and executing “stop slave;”
mysql> stop slave;
Query OK, 0 rows affected, 1 warning (0.00 sec)

We can now provide the slave with the information on which master to use. Before GTID, you would have to tell mysql which binary log you wanted to use, and the position within that binary log. With GTID, you only need to set MASTER_AUTO_POSITION = 1“;

mysql> CHANGE MASTER TO 
    -> MASTER_HOST = '',
    -> MASTER_PORT = 3306,
    -> MASTER_USER = 'replication_user_name',
    -> MASTER_PASSWORD = 'replication_user_password',
    -> MASTER_AUTO_POSITION = 1;
Query OK, 0 rows affected, 2 warnings (0.20 sec)

You will need to change the replication_user_name and replication_user_password to match the values you used when you created the replication user.

Before we turn on the slave, you may check the status of the slave:

mysql> show slave status\G
*************************** 1. row ***************************
               Slave_IO_State: 
                  Master_Host: 192.168.1.2
                  Master_User: replicate
                  Master_Port: 3306
                Connect_Retry: 60
              Master_Log_File: 
          Read_Master_Log_Pos: 4
               Relay_Log_File: WEB_SERVER_01-relay-bin.000001
                Relay_Log_Pos: 4
        Relay_Master_Log_File: 
             Slave_IO_Running: No
            Slave_SQL_Running: No
              Replicate_Do_DB: 
          Replicate_Ignore_DB: 
           Replicate_Do_Table: 
       Replicate_Ignore_Table: 
      Replicate_Wild_Do_Table: 
  Replicate_Wild_Ignore_Table: 
                   Last_Errno: 0
                   Last_Error: 
                 Skip_Counter: 0
          Exec_Master_Log_Pos: 0
              Relay_Log_Space: 151
              Until_Condition: None
               Until_Log_File: 
                Until_Log_Pos: 0
           Master_SSL_Allowed: No
           Master_SSL_CA_File: 
           Master_SSL_CA_Path: 
              Master_SSL_Cert: 
            Master_SSL_Cipher: 
               Master_SSL_Key: 
        Seconds_Behind_Master: NULL
Master_SSL_Verify_Server_Cert: No
                Last_IO_Errno: 0
                Last_IO_Error: 
               Last_SQL_Errno: 0
               Last_SQL_Error: 
  Replicate_Ignore_Server_Ids: 
             Master_Server_Id: 0
                  Master_UUID: 
             Master_Info_File: mysql.slave_master_info
                    SQL_Delay: 0
          SQL_Remaining_Delay: NULL
      Slave_SQL_Running_State: 
           Master_Retry_Count: 86400
                  Master_Bind: 
      Last_IO_Error_Timestamp: 
     Last_SQL_Error_Timestamp: 
               Master_SSL_Crl: 
           Master_SSL_Crlpath: 
           Retrieved_Gtid_Set: 
            Executed_Gtid_Set: C242A198-5AAA-11E2-8CC0-387DCB822A4B:1-2
1 row in set (0.00 sec)

We can check the values for Master_Host and Master_User to make sure they match our master server. Since the slave hasn’t been started yet, the value for Retrieved_Gtid_Set is blank – as we haven’t retrieved any data from the master. Once we start the slave, the value for Retrieved_Gtid_Set will show us how many transactions have been retrieved from the master. The value for Executed_Gtid_Set shows that we have executed two transactions on this new slave instance – changing the root password and creating the replication user. Now we can start the slave:

mysql> start slave;
Query OK, 0 rows affected (0.00 sec)

After a few moments, you can check on the slave status again.

mysql> show slave status\G
*************************** 1. row ***************************
               Slave_IO_State: Waiting for master to send event
                  Master_Host: 192.168.1.2
                  Master_User: replicate
                  Master_Port: 3306
                Connect_Retry: 60
              Master_Log_File: mysql-bin.000007
          Read_Master_Log_Pos: 1914
               Relay_Log_File: WEB_SERVER_01-relay-bin.000007
                Relay_Log_Pos: 1024
        Relay_Master_Log_File: mysql-bin.000006
             Slave_IO_Running: Yes
            Slave_SQL_Running: No
              Replicate_Do_DB: 
          Replicate_Ignore_DB: 
           Replicate_Do_Table: 
       Replicate_Ignore_Table: 
      Replicate_Wild_Do_Table: 
  Replicate_Wild_Ignore_Table: 
                   Last_Errno: 1396
                   Last_Error: Error 'Operation CREATE USER failed for 'replicate'@'%'' on query. 
                               Default database: ''. Query: 'CREATE USER 'replicate'@'%' 
                               IDENTIFIED BY PASSWORD '*BE1BDEC0AA74B4XCB07X943E70X28096CXA985F8''
                 Skip_Counter: 0
          Exec_Master_Log_Pos: 814
              Relay_Log_Space: 71051295
              Until_Condition: None
               Until_Log_File: 
                Until_Log_Pos: 0
           Master_SSL_Allowed: No
           Master_SSL_CA_File: 
           Master_SSL_CA_Path: 
              Master_SSL_Cert: 
            Master_SSL_Cipher: 
               Master_SSL_Key: 
        Seconds_Behind_Master: NULL
Master_SSL_Verify_Server_Cert: No
                Last_IO_Errno: 0
                Last_IO_Error: 
               Last_SQL_Errno: 1396
               Last_SQL_Error: Error 'Operation CREATE USER failed for 'replicate'@'%'' on query. 
                               Default database: ''. Query: 'CREATE USER 'replicate'@'%' 
                               IDENTIFIED BY PASSWORD '*BE1BDEC0AA74B4DCB079943E70528096CCA985F8''
  Replicate_Ignore_Server_Ids: 
             Master_Server_Id: 1
                  Master_UUID: 82f20158-5a16-11e2-88f9-c4a801092abb
             Master_Info_File: mysql.slave_master_info
                    SQL_Delay: 0
          SQL_Remaining_Delay: NULL
      Slave_SQL_Running_State: 
           Master_Retry_Count: 86400
                  Master_Bind: 
      Last_IO_Error_Timestamp: 
     Last_SQL_Error_Timestamp: 130109 21:50:45
               Master_SSL_Crl: 
           Master_SSL_Crlpath: 
           Retrieved_Gtid_Set: 82F20158-5A16-11E2-88F9-C4A801092ABB:1-162562
            Executed_Gtid_Set: 82F20158-5A16-11E2-88F9-C4A801092ABB:1-3,
C242A198-5AAA-11E2-8CC0-387DCB822A4B:1-2

We can see from the value for Retrieved_Gtid_Set is 82F20158-5A16-11E2-88F9-C4A801092ABB:1-162562, which shows that we have already retrieved all of the transactions from the master. The Executed_Gtid_Set value of 82F20158-5A16-11E2-88F9-C4A801092ABB:1-3 shows that we have processed the first three transactions from the master, and the value of C242A198-5AAA-11E2-8CC0-387DCB822A4B:1-2 shows we have executed two transactions from the slave.

The variable Last_Error shows that we also have an error because the CREATE USER statement for the replication user from the master database fails on the slave, as we have already created a replication user. I purposely created the same user to show you what happens when you have an error on the slave. In the above list of installation actions to do on the slave, you can skip “create replication user”.

To skip this error and continue with replication, you can set the SQL_SLAVE_SKIP_COUNTER to “1”, which tells the slave to skip one transaction. You must stop the slave, set SQL_SLAVE_SKIP_COUNTER = 1 and restart the slave.

mysql> stop slave;SET GLOBAL SQL_SLAVE_SKIP_COUNTER = 1;start slave;
Query OK, 0 rows affected (0.16 sec)

Let’s look at the slave status again: (the output is truncated as we only need to look at the values for Retrieved_Gtid_Set and Executed_Gtid_Set)

mysql> show slave status\G
....
           Retrieved_Gtid_Set: 82F20158-5A16-11E2-88F9-C4A801092ABB:1-162562
            Executed_Gtid_Set: 82F20158-5A16-11E2-88F9-C4A801092ABB:1-3:5-15401,
C242A198-5AAA-11E2-8CC0-387DCB822A4B:1-12
....

You can see that the value of the Executed_Gtid_Set has changed to 82F20158-5A16-11E2-88F9-C4A801092ABB:1-3:5-15401, which means that the slave is starting to process the transactions from the master, and is on transaction 15401. You can also see that transaction number four was skipped (when we executed the SET GLOBAL SQL_SLAVE_SKIP_COUNTER command). This was the transaction to create the replication slave user.

You can check the slave status until you see that all of the transactions that were retrieved from the master have been completed on the slave:

mysql> show slave status\G
....
           Retrieved_Gtid_Set: 82F20158-5A16-11E2-88F9-C4A801092ABB:1-162562
            Executed_Gtid_Set: 82F20158-5A16-11E2-88F9-C4A801092ABB:1-3:5-162562,
C242A198-5AAA-11E2-8CC0-387DCB822A4B:1-12
....

You can go back to the master and see the master’s status:

mysql> show master status\G
*************************** 1. row ***************************
             File: mysql-bin.000007
         Position: 1914
     Binlog_Do_DB: 
 Binlog_Ignore_DB: 
Executed_Gtid_Set: 82F20158-5A16-11E2-88F9-C4A801092ABB:1-162562
1 row in set (0.00 sec)

We can now see that the value for Executed_Gtid_Set on the master is the same as the value on the slave (not including the transactions executed on the slave itself). So, the slave now has the same data as the master, and it is up to date and not lagging behind the master. If you have a busy master server, your slave might lag behind while it updates the records on the slave.

We can also check to make sure that all of the users that we created on the master are also now on the slave:

SLAVE:

mysql> select user, host from user order by user, host;
+-------------+-----------------------+
| user        | host                  |
+-------------+-----------------------+
| WebSite     | 192.168.1.2           |
| WebSite     | localhost             |
| replicate   | 192.168.1.121         |
| replicate   | 192.168.1.2           |
| replicate   | 192.168.1.4           |
| replicate   | localhost             |
| root        | 127.0.0.1             |
| root        | 192.168.1.2           |
| root        | VM-Mac-1081-128.local |
| root        | localhost             |
| scripting   | 192.168.1.121         |
| scripting   | 192.168.1.122         |
| scripting   | 192.168.1.2           |
+-----------+-------------------------+
13 rows in set (0.01 sec)

MASTER:

mysql> select user, host from user order by user, host;
+-------------+---------------+
| user        | host          |
+-------------+---------------+
| WebSite     | 192.168.1.2   |
| WebSite     | localhost     |
| replicate   | 192.168.1.121 |
| replicate   | 192.168.1.2   |
| replicate   | 192.168.1.4   |
| replicate   | localhost     |
| root        | 127.0.0.1     |
| root        | 192.168.1.2   |
| root        | localhost     |
| root        | macserver01   |
| scripting   | 192.168.1.121 |
| scripting   | 192.168.1.122 |
| scripting   | 192.168.1.2   |
+-----------+-----------------+
13 rows in set (0.00 sec)

The only difference in the users on the master and slave is the root user for each machine:

Slave - root, VM-Mac-1081-128.local
Master - root, macserver01

The master and slave are now ready for use. If you have an Enterprise subscription to MySQL, you can use MySQL Enterprise Monitor to look at the status of the master and the slave:

Otherwise, you may just do a periodic “show master status\G” and “show slave status\G” to see if the slave is lagging behind the master.

 


Tony Darnell is a Principal Sales Consultant for MySQL, a division of Oracle, Inc. MySQL is the world’s most popular open-source database program. Tony may be reached at info [at] ScriptingMySQL.com and on LinkedIn.
Tony is the author of Twenty Forty-Four: The League of Patriots

 

Visit http://2044thebook.com for more information.