How to Setup MySQL Master-Master Replication (Circular Replication)

How to Setup MySQL Master-Master Replication (Circular Replication)


Master-Master Replication
(Circular Replication) also known as ring topology in MySQL, this setup requires two or more MySQL servers which act as a master. All masters receive writes and generate binlogs.

Below points should be considered while doing the master-master setup.

  • You need to set an auto-increment offset on each server to avoid primary key collisions.
  • There is no conflict resolution.
  • MySQL Replication currently does not support the atomicity of updates across two different servers.


We have already set up 2 mysql instances in test-machine01 server running on port 3306 (Server_ID : 1) & 3307 (Server_ID : 3), We have also changed the mysql prompt to Master-1Master-2, and Replica for easy understanding.

HostnameIPRole
Server_ID
Port
Installation Link
test-machine01192.168.114.177Master-113306Click Here
test-machine01192.168.114.177Master-233307Click Here

Master-1: Below are the Master-1 configuration parameters

mysql> prompt mysql Master-1>
PROMPT set to 'mysql Master-1>'
mysql Master-1>

mysql Master-1>select @@server_uuid;
+--------------------------------------+
| @@server_uuid                        |
+--------------------------------------+
| 13ecba9c-444a-11eb-a397-000c29f9d9e6 |
+--------------------------------------+
1 row in set (0.00 sec)

mysql Master-1>
mysql Master-1>
mysql Master-1>select @@server_id;
+-------------+
| @@server_id |
+-------------+
|           1 |
+-------------+
1 row in set (0.00 sec)

mysql Master-1>select @@port;
+--------+
| @@port |
+--------+
|   3306 |
+--------+
1 row in set (0.00 sec)

mysql Master-1>


[mysqld@inst1]
#General
user = mysql
port = 3306
server_id = 1
socket=/var/lib/mysql/mysql.sock
pid_file=/var/run/mysqld/mysqld.pid

# Data Storage
datadir=/var/lib/mysql
innodb_directories="/u01/mysql/"

#Logging
log_bin = /var/lib/mysql/binlog
log_error = /var/lib/mysql/mysqld.log
expire_logs_days = 7
relay_log = /var/lib/mysql/relay_bin01
relay_log_index = /var/lib/mysql/relay_bin.index
relay_log_recovery = on
master_info_repository = TABLE
relay_log_info_repository = TABLE

# GTID Based Replication Parameter
gtid-mode=on
enforce-gtid-consistency=1
log_slave_updates= 1
auto_increment_increment=2
auto_increment_offset=1


Master-1: Below are the Master-2 configuration parameters

mysql> prompt mysql Master-2>
PROMPT set to 'mysql Master-2>'
mysql Master-2>

mysql Master-2>select @@server_uuid;
+--------------------------------------+
| @@server_uuid                        |
+--------------------------------------+
| 98411332-6aad-11eb-809a-000c29f9d9e6 |
+--------------------------------------+
1 row in set (0.00 sec)

mysql Master-2>select @@server_id;
+-------------+
| @@server_id |
+-------------+
|           3 |
+-------------+
1 row in set (0.00 sec)

mysql Master-2>select @@port;
+--------+
| @@port |
+--------+
|   3307 |
+--------+
1 row in set (0.00 sec)

mysql Master-2>


[mysqld@inst2]
#General
user = mysql
port=3307
server_id = 3
socket=/u01/mysql-2/mysql.sock
pid_file=/u01/mysql-2/mysqld.pid

# Data Storage
basedir=/u01/mysql-2
datadir=/u01/mysql-2/data
innodb_directories="/u01/mysql/"
plugin_dir=/usr/lib64/mysql/plugin

#Logging
log_bin = /u01/mysql-2/data/binlog
log_error = /u01/mysql-2/data/mysqld.log
expire_logs_days = 7
relay_log = /u01/mysql-2/data/relay_bin01
relay_log_index = /u01/mysql-2/data/relay_bin.index
relay_log_recovery = on
master_info_repository = TABLE
relay_log_info_repository = TABLE

# GTID Based Replication Parameter
gtid-mode=on
enforce-gtid-consistency=1
log_slave_updates= 1
auto_increment_increment=2
auto_increment_offset=2


Step 1. Configuration Setup: Setup above parameters in masters configuration file (my.cnf) and restart both mysql instance.

[root@test-machine01 ~]# systemctl restart mysqld@inst1
[root@test-machine01 ~]#
[root@test-machine01 ~]# systemctl restart mysqld@inst2
[root@test-machine01 ~]#


Step 2.: Create Replication User: Create replication user in both master mysql instances. This user will be used by replica to connect to the master instance.

mysql Master-1>CREATE USER IF NOT EXISTS 'repluser'@'%' IDENTIFIED BY 'Password123#@!';
Query OK, 0 rows affected (0.06 sec)
 
mysql Master-1>GRANT REPLICATION SLAVE, REPLICATION CLIENT ON *.* TO 'repluser'@'%';
Query OK, 0 rows affected (0.00 sec)
 
mysql Master-1>ALTER USER 'repluser'@'%' IDENTIFIED WITH mysql_native_password BY 'Password123#@!';
Query OK, 0 rows affected (0.00 sec)
 
mysql Master-1>flush privileges;
Query OK, 0 rows affected (0.00 sec)
 
mysql Master-1>
 
mysql Master-2>CREATE USER IF NOT EXISTS 'repluser'@'%' IDENTIFIED BY 'Password123#@!';
Query OK, 0 rows affected (0.06 sec)
 
mysql Master-2>GRANT REPLICATION SLAVE, REPLICATION CLIENT ON *.* TO 'repluser'@'%';
Query OK, 0 rows affected (0.00 sec)
 
mysql Master-2>ALTER USER 'repluser'@'%' IDENTIFIED WITH mysql_native_password BY 'Password123#@!';
Query OK, 0 rows affected (0.00 sec)
 
mysql Master-2>flush privileges;
Query OK, 0 rows affected (0.00 sec)
 
mysql master2 >


Step 3. Reset Master: Execute reset master command to reset Executed_Gtid_Set variable in both masters mysql instances.


Master-1

mysql Master-1>show master status;
+---------------+----------+--------------+------------------+------------------------------------------+
| File          | Position | Binlog_Do_DB | Binlog_Ignore_DB | Executed_Gtid_Set                        |
+---------------+----------+--------------+------------------+------------------------------------------+
| binlog.000004 |      196 |              |                  | 13ecba9c-444a-11eb-a397-000c29f9d9e6:1-7 |
+---------------+----------+--------------+------------------+------------------------------------------+
1 row in set (0.00 sec)

mysql Master-1>
mysql Master-1>reset master;
Query OK, 0 rows affected (0.07 sec)

mysql Master-1>show master status;
+---------------+----------+--------------+------------------+-------------------+
| File          | Position | Binlog_Do_DB | Binlog_Ignore_DB | Executed_Gtid_Set |
+---------------+----------+--------------+------------------+-------------------+
| binlog.000001 |      156 |              |                  |                   |
+---------------+----------+--------------+------------------+-------------------+
1 row in set (0.00 sec)

mysql Master-1>


Master-2

mysql Master-2>show master status;
+---------------+----------+--------------+------------------+------------------------------------------+
| File          | Position | Binlog_Do_DB | Binlog_Ignore_DB | Executed_Gtid_Set                        |
+---------------+----------+--------------+------------------+------------------------------------------+
| binlog.000002 |      196 |              |                  | 98411332-6aad-11eb-809a-000c29f9d9e6:1-9 |
+---------------+----------+--------------+------------------+------------------------------------------+
1 row in set (0.00 sec)

mysql Master-2>
mysql Master-2>
mysql Master-2>reset master;
Query OK, 0 rows affected (0.07 sec)

mysql Master-2>show master status;
+---------------+----------+--------------+------------------+-------------------+
| File          | Position | Binlog_Do_DB | Binlog_Ignore_DB | Executed_Gtid_Set |
+---------------+----------+--------------+------------------+-------------------+
| binlog.000001 |      156 |              |                  |                   |
+---------------+----------+--------------+------------------+-------------------+
1 row in set (0.00 sec)

mysql Master-2>
mysql Master-2>


Step 4. Dummy Transaction: Execute dummy transaction in both masters mysql instances to increment Executed_Gtid_Set variable to 1 and note down Executed_Gtid_Set value.


Master-1

mysql Master-1>use repl_test;
Database changed
mysql Master-1>create table dummy ( id int);
Query OK, 0 rows affected (0.06 sec)

mysql Master-1>show master status;
+---------------+----------+--------------+------------------+----------------------------------------+
| File          | Position | Binlog_Do_DB | Binlog_Ignore_DB | Executed_Gtid_Set                      |
+---------------+----------+--------------+------------------+----------------------------------------+
| binlog.000001 |      363 |              |                  | 13ecba9c-444a-11eb-a397-000c29f9d9e6:1 |
+---------------+----------+--------------+------------------+----------------------------------------+
1 row in set (0.00 sec)

mysql Master-1>


Master-2

mysql Master-2>use repl_test;
Database changed

mysql Master-2>create dummy test ( id int);
Query OK, 0 rows affected (0.07 sec)

mysql Master-2>show master status;
+---------------+----------+--------------+------------------+----------------------------------------+
| File          | Position | Binlog_Do_DB | Binlog_Ignore_DB | Executed_Gtid_Set                      |
+---------------+----------+--------------+------------------+----------------------------------------+
| binlog.000001 |      363 |              |                  | 98411332-6aad-11eb-809a-000c29f9d9e6:1 |
+---------------+----------+--------------+------------------+----------------------------------------+
1 row in set (0.00 sec)

mysql Master-


Step 5: Update Executed_Gtid_Set: Update variable gtid_purged with Executed_Gtid_Set value from the above output and update master information and then start replica.


Master-1

mysql Master-1>
mysql Master-1>SET @@GLOBAL.gtid_purged = "98411332-6aad-11eb-809a-000c29f9d9e6:1";
Query OK, 0 rows affected (0.00 sec)

mysql Master-1>

mysql Master-1>CHANGE MASTER TO MASTER_HOST='192.168.114.177',MASTER_USER='repluser',MASTER_PASSWORD='Password123#@!',MASTER_PORT=3307,MASTER_AUTO_POSITION=1;
Query OK, 0 rows affected, 2 warnings (0.03 sec)

mysql Master-1>start replica ;
Query OK, 0 rows affected (0.00 sec)

mysql Master-1>


Master-2

mysql Master-2>SET @@GLOBAL.gtid_purged = "13ecba9c-444a-11eb-a397-000c29f9d9e6:1";
Query OK, 0 rows affected (0.07 sec)

mysql Master-2>
mysql Master-2>CHANGE MASTER TO MASTER_HOST='192.168.114.177',MASTER_USER='repluser',MASTER_PASSWORD='Password123#@!',MASTER_PORT=3306,MASTER_AUTO_POSITION=1;
Query OK, 0 rows affected, 2 warnings (0.08 sec)

mysql Master-2>start replica ;
Query OK, 0 rows affected (0.01 sec)

mysql Master-2>


Step 6: Check Status: Execute command show replica status to validate the status.

Master-1

mysql Master-1>show replica status \G;
*************************** 1. row ***************************
               Slave_IO_State: Waiting for master to send event
                  Master_Host: 192.168.114.177
                  Master_User: repluser
                  Master_Port: 3307
                Connect_Retry: 60
              Master_Log_File: binlog.000001
          Read_Master_Log_Pos: 363
               Relay_Log_File: relay_bin01.000002
                Relay_Log_Pos: 409
        Relay_Master_Log_File: binlog.000001
             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: 363
              Relay_Log_Space: 614
              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: 3
                  Master_UUID: 98411332-6aad-11eb-809a-000c29f9d9e6
             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 more updates
           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: 13ecba9c-444a-11eb-a397-000c29f9d9e6:1,
98411332-6aad-11eb-809a-000c29f9d9e6:1
                Auto_Position: 1
         Replicate_Rewrite_DB:
                 Channel_Name:
           Master_TLS_Version:
       Master_public_key_path:
        Get_master_public_key: 0
            Network_Namespace:
1 row in set, 1 warning (0.00 sec)

ERROR:
No query specified

mysql Master-1>


Master-2

mysql Master-2>show replica status \G;
*************************** 1. row ***************************
               Slave_IO_State: Waiting for master to send event
                  Master_Host: 192.168.114.177
                  Master_User: repluser
                  Master_Port: 3306
                Connect_Retry: 60
              Master_Log_File: binlog.000001
          Read_Master_Log_Pos: 363
               Relay_Log_File: relay_bin01.000002
                Relay_Log_Pos: 409
        Relay_Master_Log_File: binlog.000001
             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: 363
              Relay_Log_Space: 614
              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: 13ecba9c-444a-11eb-a397-000c29f9d9e6
             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 more updates
           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: 13ecba9c-444a-11eb-a397-000c29f9d9e6:1,
98411332-6aad-11eb-809a-000c29f9d9e6:1
                Auto_Position: 1
         Replicate_Rewrite_DB:
                 Channel_Name:
           Master_TLS_Version:
       Master_public_key_path:
        Get_master_public_key: 0
            Network_Namespace:
1 row in set, 1 warning (0.00 sec)

ERROR:
No query specified

mysql Master-2>


Step 7: Test replication configuration: Execute transaction in both master mysql instances and validate if the same transaction replicated in other master instances.


Master-1

mysql Master-1>use repl_test;
Database changed

mysql Master-1>create table repl_test8 as select *from repl_test7;
Query OK, 28 rows affected (0.07 sec)
Records: 28  Duplicates: 0  Warnings: 0


Master-2

mysql Master-2>show tables ;
+---------------------+
| Tables_in_repl_test |
+---------------------+
| repl_test           |
| repl_test1          |
| repl_test2          |
| repl_test3          |
| repl_test4          |
| repl_test5          |
| repl_test6          |
| repl_test8          |
| test                |
+---------------------+
9 rows in set (0.00 sec)


Master-2

mysql Master-2>create table repl_test9 as select *from repl_test8;
Query OK, 28 rows affected (0.01 sec)
Records: 28  Duplicates: 0  Warnings: 0

mysql Master-2>


Master-1

mysql Master-1>show tables ;
+---------------------+
| Tables_in_repl_test |
+---------------------+
| repl_test1          |
| repl_test2          |
| repl_test3          |
| repl_test4          |
| repl_test5          |
| repl_test6          |
| repl_test7          |
| repl_test8          |
| repl_test9          |
| test                |
+---------------------+
10 rows in set (0.01 sec)

mysql Master-1>

This document is only for learning purpose and always validate in the LAB environment first before applying in the LIVE environment.


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