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Infrastructure

Trying MySQL Replication on Docker

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Using a Docker Ubuntu image, I will try setting up MySQL 8 replication.

First, prepare containers to host MySQL.

Since the MySQL master and slave communicate with each other for replication, run master and slave containers on a Docker Bridge network.

> docker network create mysql-replica
> docker network ls
> docker network inspect mysql-replica
> docker run --name mysql-master --network mysql-replica -it ubuntu /bin/bash
> docker run --name mysql-slave --network mysql-replica -it ubuntu /bin/bash

Install the packages needed to verify connectivity between master and slave. Also install vim for file editing.

# apt update -y
# apt install dnsutils -y
# apt install iputils-ping -y
# apt install vim -y

Confirm that name resolution works and that ping responds.

# nslookup mysql-master
# nslookup mysql-slave
# ping mysql-master
# ping mysql-slave

Install the MySQL server and start it with service ... start. Installing mysql-server also installs the mysql client.

# apt install mysql-server -y
# service mysql start

MySQL server preparation is now complete. Next, configure replication.

Perform the following configuration on both master and slave.

Master-side configuration

  • Set server_id
  • Set GTID and enforce_gtid_consistency (not required if not using GTID)
  • Configure remote connection settings
  • Create an account for slave connection
  • Enable binary logging (not required as it is enabled by default)

Slave-side configuration

  • Set server_id
  • Set GTID and enforce_gtid_consistency (not required if not using GTID)
  • Configure replication settings
  • Start replication

Start with the master-side configuration.

Set server_id and GTID. Append the following to /etc/mysql/my.cnf.

# vi /etc/mysql/my.cnf

Make sure server_id does not overlap with the slave.

[mysqld]
server_id = 201
gtid_mode=ON
enforce_gtid_consistency

Restart to apply the configuration changes.

# service mysql restart

To allow remote connections, comment out the bound address.

In /etc/mysql/mysql.conf.d/mysqld.cnf, comment out the following line.

# bind-address          = 127.0.0.1

The slave acts as the mysql client, and the master acts as the mysql server for MySQL replication.

That is, the slave accesses the master using a user account to retrieve the binlog.

Create the user account to be used by the slave.

The slave's hostname will be mysql-slave.mysql-replica.

# mysql
mysql> CREATE USE repl@'mysql-slave.mysql-replica' IDENTIFIED BY 'secret';

Since we want the slave to access using password authentication, set the authentication method to mysql_native_password.

ALTER USER repl@'mysql-slave.mysql-replica' IDENTIFIED WITH 'mysql_native_password' BY 'secret';

Master-side configuration is now complete.

Configure the slave side.

Set server_id and GTID. Append the following to /etc/mysql/my.cnf.

[mysqld]
server_id = 211
gtid_mode=ON
enforce_gtid_consistency

Restart to apply the configuration changes.

# service mysql restart

Configure replication and start it.

# mysql
mysql> change master to MASTER_HOST='mysql-master' , MASTER_PORT=3306, MASTER_AUTO_POSITION=1, MASTER_HEARTBEAT_PERIOD=60;
mysql> start replica user='repl' password='secret';

The replication status can be checked with the following command. Actually verify that databases and tables created on the master side are also replicated on the slave side.

mysql> show replica status\G;
*************************** 1. row ***************************
             Replica_IO_State: Waiting for source to send event
                  Source_Host: mysql-master
                  Source_User: repl
                  Source_Port: 3306
                Connect_Retry: 60
              Source_Log_File: binlog.000008
          Read_Source_Log_Pos: 157
               Relay_Log_File: 7db1994e1293-relay-bin.000002
                Relay_Log_Pos: 367
        Relay_Source_Log_File: binlog.000008
           Replica_IO_Running: Yes
          Replica_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_Source_Log_Pos: 157
              Relay_Log_Space: 584
              Until_Condition: None
               Until_Log_File:
                Until_Log_Pos: 0
           Source_SSL_Allowed: No
           Source_SSL_CA_File:
           Source_SSL_CA_Path:
              Source_SSL_Cert:
            Source_SSL_Cipher:
               Source_SSL_Key:
        Seconds_Behind_Source: 0
Source_SSL_Verify_Server_Cert: No
                Last_IO_Errno: 0
                Last_IO_Error:
               Last_SQL_Errno: 0
               Last_SQL_Error:
  Replicate_Ignore_Server_Ids:
             Source_Server_Id: 201
                  Source_UUID: 0700aae6-15ad-11ef-82bc-0242ac140002
             Source_Info_File: mysql.slave_master_info
                    SQL_Delay: 0
          SQL_Remaining_Delay: NULL
    Replica_SQL_Running_State: Replica has read all relay log; waiting for more updates
           Source_Retry_Count: 86400
                  Source_Bind:
      Last_IO_Error_Timestamp:
     Last_SQL_Error_Timestamp:
               Source_SSL_Crl:
           Source_SSL_Crlpath:
           Retrieved_Gtid_Set:
            Executed_Gtid_Set:
                Auto_Position: 1
         Replicate_Rewrite_DB:
                 Channel_Name:
           Source_TLS_Version:
       Source_public_key_path:
        Get_Source_public_key: 0
            Network_Namespace:
1 row in set (0.01 sec)

That's it.

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