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-1, Master-2, and Replica for easy understanding.
| Hostname | IP | Role | Server_ID | Port | Installation Link |
| test-machine01 | 192.168.114.177 | Master-1 | 1 | 3306 | Click Here |
| test-machine01 | 192.168.114.177 | Master-2 | 3 | 3307 | Click 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.
Hope so you like this article!
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