MySQL 8.0 新特性 - ARAF

ARAF 简介

Asynchronous Replication Automatic failover（ARAF），ARAF 是 MySQL 8.0.22 的新特性，当某个复制源不可用时，自动根据权重重新选择数据源进行同步。

其原理是在一条异步复制通道上配置多个可用复制源，当某个复制源不可用时(宕机、复制链路中断)，且slave的IO线程尝试重连无效，自动根据权重选择新的源继续同步。

配置 ARAF 功能

1. 创建复制通道

replica> CHANGE MASTER TO MASTER_USER='rpl_user', MASTER_PASSWORD='password', MASTER_HOST='node1', MASTER_PORT=3306, MASTER_RETRY_COUNT=2 FOR CHANNEL 'ch1';
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• MASTER_RETRY_COUNT：重试次数，默认86400次

• MASTER_CONNECT_RETRY：单次重试时间，默认60秒

mysql> change master to master_user='root',master_password='123456', master_host='172.26.55.66',master_auto_position=1,source_connection_auto_failover=1,master_port=3306,master_retry_count=6,master_connect_retry=20 for channel 'report';
Query OK, 0 rows affected, 2 warnings (0.07 sec)
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2. 从机配置复制通道备用源

SELECT asynchronous_connection_failover_add_source(channel, host, port, network_namespace, weight);
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• channel host port network_namespace：复制通道连接属性，备用源服务器信息

• weight：当有多个备用源服务器时，故障转移操作将尝试连接到权重最大的源服务器默认50

mysql> SELECT asynchronous_connection_failover_add_source('report','172.26.55.66',3306,null,100); 
+------------------------------------------------------------------------------------+
| asynchronous_connection_failover_add_source('report','172.26.55.66',3306,null,100) |
+------------------------------------------------------------------------------------+
| The UDF asynchronous_connection_failover_add_source() executed successfully.       |
+------------------------------------------------------------------------------------+
1 row in set (0.01 sec)

mysql> SELECT asynchronous_connection_failover_add_source('report','172.26.55.67',3306,null,80);
+-----------------------------------------------------------------------------------+
| asynchronous_connection_failover_add_source('report','172.26.55.67',3306,null,80) |
+-----------------------------------------------------------------------------------+
| The UDF asynchronous_connection_failover_add_source() executed successfully.      |
+-----------------------------------------------------------------------------------+
1 row in set (0.01 sec)

mysql> SELECT asynchronous_connection_failover_add_source('report','172.26.55.68',3306,null,50); 
+-----------------------------------------------------------------------------------+
| asynchronous_connection_failover_add_source('report','172.26.55.68',3306,null,50) |
+-----------------------------------------------------------------------------------+
| The UDF asynchronous_connection_failover_add_source() executed successfully.      |
+-----------------------------------------------------------------------------------+
1 row in set (0.01 sec)

SELECT CHANNEL_NAME, SOURCE_CONNECTION_AUTO_FAILOVER FROM performance_schema.replication_connection_configuration;

SELECT * FROM performance_schema.replication_asynchronous_connection_failover;
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3. 检查复制通道信息

mysql> SELECT CHANNEL_NAME, SOURCE_CONNECTION_AUTO_FAILOVER FROM performance_schema.replication_connection_configuration;
+--------------+---------------------------------+
| CHANNEL_NAME | SOURCE_CONNECTION_AUTO_FAILOVER |
+--------------+---------------------------------+
| report       | 1                               |
+--------------+---------------------------------+
1 row in set (0.00 sec)
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测试 ARAF

1. 关闭MGR的primary节点

mysql> select * from performance_schema.replication_group_members;
+---------------------------+--------------------------------------+--------------------+-------------+--------------+-------------+----------------+
| CHANNEL_NAME              | MEMBER_ID                            | MEMBER_HOST        | MEMBER_PORT | MEMBER_STATE | MEMBER_ROLE | MEMBER_VERSION |
+---------------------------+--------------------------------------+--------------------+-------------+--------------+-------------+----------------+
| group_replication_applier | f50abea0-e994-11e9-b149-525400f3f784 | test_mysql8_mgr_02 |        3306 | ONLINE       | PRIMARY     | 8.0.22         |
| group_replication_applier | f50abea0-e994-11e9-b149-525400f3f785 | test_mysql8_mgr_03 |        3306 | ONLINE       | SECONDARY   | 8.0.22         |
+---------------------------+--------------------------------------+--------------------+-------------+--------------+-------------+----------------+
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test_mysql8_mgr_01 已经被移除，test_mysql8_mgr_02变为新的 primary。

2. 查看从节点切换状态

可以看到在重试了6次后，将新的 master 切换到了 test_mysql8_mgr_02（172.26.55.67）上。

slave status 里也可以看到新 master 的信息。