mysql5.7 开启增强半同步复制
前提是主从异步复制环境要提前搭建好，然后再开启mysql增强半同步
环境：mysql5.7.26 主从异步复制早已部署好。
1.加载plugin插件
建议master和slave上全部执行（考虑到MHA的主从自动切换的环境）
在主库安装semisync_master.so和semisync_slave.so插件：
linux服务器上的master库执行：
root@localhost [(none)]>INSTALL PLUGIN rpl_semi_sync_master SONAME 'semisync_master.so'; Query OK, 0 rows affected (4.52 sec) root@localhost [(none)]>INSTALL PLUGIN rpl_semi_sync_slave SONAME 'semisync_slave.so'; Query OK, 0 rows affected (0.07 sec)
linux服务器上的slave库执行：
root@localhost [(none)]>INSTALL PLUGIN rpl_semi_sync_master SONAME 'semisync_master.so'; Query OK, 0 rows affected (4.52 sec) root@localhost [(none)]>INSTALL PLUGIN rpl_semi_sync_slave SONAME 'semisync_slave.so'; Query OK, 0 rows affected (0.07 sec)
查看时候已经安装了插件
root@localhost 07:52: [fengjian]> show plugins; +----------------------------+----------+--------------------+--------------------+---------+ | Name | Status | Type | Library | License | +----------------------------+----------+--------------------+--------------------+---------+ | binlog | ACTIVE | STORAGE ENGINE | NULL | GPL | | mysql_native_password | ACTIVE | AUTHENTICATION | NULL | GPL | | sha256_password | ACTIVE | AUTHENTICATION | NULL | GPL | | MyISAM | ACTIVE | STORAGE ENGINE | NULL | GPL | | CSV | ACTIVE | STORAGE ENGINE | NULL | GPL | | PERFORMANCE_SCHEMA | ACTIVE | STORAGE ENGINE | NULL | GPL | | MEMORY | ACTIVE | STORAGE ENGINE | NULL | GPL | | MRG_MYISAM | ACTIVE | STORAGE ENGINE | NULL | GPL | | InnoDB | ACTIVE | STORAGE ENGINE | NULL | GPL | | INNODB_TRX | ACTIVE | INFORMATION SCHEMA | NULL | GPL | | INNODB_LOCKS | ACTIVE | INFORMATION SCHEMA | NULL | GPL | | INNODB_LOCK_WAITS | ACTIVE | INFORMATION SCHEMA | NULL | GPL | | INNODB_CMP | ACTIVE | INFORMATION SCHEMA | NULL | GPL | | INNODB_CMP_RESET | ACTIVE | INFORMATION SCHEMA | NULL | GPL | | INNODB_CMPMEM | ACTIVE | INFORMATION SCHEMA | NULL | GPL | | INNODB_CMPMEM_RESET | ACTIVE | INFORMATION SCHEMA | NULL | GPL | | INNODB_CMP_PER_INDEX | ACTIVE | INFORMATION SCHEMA | NULL | GPL | | INNODB_CMP_PER_INDEX_RESET | ACTIVE | INFORMATION SCHEMA | NULL | GPL | | INNODB_BUFFER_PAGE | ACTIVE | INFORMATION SCHEMA | NULL | GPL | | INNODB_BUFFER_PAGE_LRU | ACTIVE | INFORMATION SCHEMA | NULL | GPL | | INNODB_BUFFER_POOL_STATS | ACTIVE | INFORMATION SCHEMA | NULL | GPL | | INNODB_TEMP_TABLE_INFO | ACTIVE | INFORMATION SCHEMA | NULL | GPL | | INNODB_METRICS | ACTIVE | INFORMATION SCHEMA | NULL | GPL | | INNODB_FT_DEFAULT_STOPWORD | ACTIVE | INFORMATION SCHEMA | NULL | GPL | | INNODB_FT_DELETED | ACTIVE | INFORMATION SCHEMA | NULL | GPL | | INNODB_FT_BEING_DELETED | ACTIVE | INFORMATION SCHEMA | NULL | GPL | | INNODB_FT_CONFIG | ACTIVE | INFORMATION SCHEMA | NULL | GPL | | INNODB_FT_INDEX_CACHE | ACTIVE | INFORMATION SCHEMA | NULL | GPL | | INNODB_FT_INDEX_TABLE | ACTIVE | INFORMATION SCHEMA | NULL | GPL | | INNODB_SYS_TABLES | ACTIVE | INFORMATION SCHEMA | NULL | GPL | | INNODB_SYS_TABLESTATS | ACTIVE | INFORMATION SCHEMA | NULL | GPL | | INNODB_SYS_INDEXES | ACTIVE | INFORMATION SCHEMA | NULL | GPL | | INNODB_SYS_COLUMNS | ACTIVE | INFORMATION SCHEMA | NULL | GPL | | INNODB_SYS_FIELDS | ACTIVE | INFORMATION SCHEMA | NULL | GPL | | INNODB_SYS_FOREIGN | ACTIVE | INFORMATION SCHEMA | NULL | GPL | | INNODB_SYS_FOREIGN_COLS | ACTIVE | INFORMATION SCHEMA | NULL | GPL | | INNODB_SYS_TABLESPACES | ACTIVE | INFORMATION SCHEMA | NULL | GPL | | INNODB_SYS_DATAFILES | ACTIVE | INFORMATION SCHEMA | NULL | GPL | | INNODB_SYS_VIRTUAL | ACTIVE | INFORMATION SCHEMA | NULL | GPL | | ARCHIVE | ACTIVE | STORAGE ENGINE | NULL | GPL | | FEDERATED | DISABLED | STORAGE ENGINE | NULL | GPL | | BLACKHOLE | ACTIVE | STORAGE ENGINE | NULL | GPL | | partition | ACTIVE | STORAGE ENGINE | NULL | GPL | | ngram | ACTIVE | FTPARSER | NULL | GPL | | rpl_semi_sync_master | ACTIVE | REPLICATION | semisync_master.so | GPL | | rpl_semi_sync_slave | ACTIVE | REPLICATION | semisync_slave.so | GPL | +----------------------------+----------+--------------------+--------------------+---------+ 46 rows in set (0.11 sec)
2.slave和master开启增强半同步参数
生产环境上建议先在slave库上的开启 增强半同步参数
set global rpl_semi_sync_slave_enabled =1； stop slave io_thread;start slave io_thread;
此刻观察master的错误日志：提示开启了Semi-sync replication 复制
2020-02-24T07:39:39.445151-00:00 584 [Note] Start binlog_dump to master_thread_id(584) slave_server(255506), pos(, 4) 2020-02-24T07:44:44.300106-00:00 586 [Note] While initializing dump thread for slave with UUID <22da22b2-56af-11ea-9b23-0242ac120c03>, found a zombie dump thread with the same UUID. Master is killing the zombie dump thread(584). 2020-02-24T07:44:44.300345-00:00 586 [Note] Start binlog_dump to master_thread_id(586) slave_server(255506), pos(, 4) 2020-02-24T07:44:44.300371-00:00 586 [Note] Start semi-sync binlog_dump to slave (server_id: 255506), pos(, 4) 2020-02-24T07:44:44.300809-00:00 584 [Note] Stop asynchronous binlog_dump to slave (server_id: 255506) 2020-02-24T07:46:09.373869-00:00 585 [Note] Semi-sync replication initialized for transactions. 2020-02-24T07:46:09.373908-00:00 585 [Note] Semi-sync replication enabled on the master. 2020-02-24T07:46:09.374779-00:00 0 [Note] Starting ack receiver thread
然后master上再开启增强半同步参数
set global rpl_semi_sync_master_enabled =1 set global rpl_semi_sync_master_timeout =1000 #增强半同步的个数 rpl_semi_sync_master_wait_for_slave_count = 1
3.MySQL官网配置方法
rpl_semi_sync_master_enabled =1 # 0 rpl_semi_sync_slave_enabled =1 # 0 rpl_semi_sync_master_timeout =1000 # 1000(1 second) 同步复制中由于网络原因导致复制时间超过1s后，增强半同步复制就变成了异步复制了 rpl_semi_sync_master_wait_for_slave_count=N plugin_load_add =semisync_master.so # plugin_load_add =semisync_slave.so
重启master和slave数据库。
4.实际生产环境配置方法
当然实际操作中还是不建议把参数rpl_semi_sync_master_enabled 和rpl_semi_sync_slave_enabled 直接写入配置文件的。
原因：把参数加入my.cnf配置文件时，在slave库挂掉，重新开启slave库或者是slave库重启后，会自动开启增强半同步复制。
如果在slave库断开master库时间较长时，最好是先开启mysql异步复制，让slave库追赶上master库后，然后再开启增强半同步复制。这样不会拖垮master库。要是直接开启增强半同步复制是会拖垮主库的。
rpl_semi_sync_master_timeout =1000 ##1s 这个转化为异步复制的超时参数是可以写入配置文件的。
5.案例
当线上运行的MySQL增强半同步复制架构中，当其中的一台slave库挂掉了应该如何正确重新添加到原先的增强半同步复制架构？？
正确的做法如下：
1. 此2个参数rpl_semi_sync_master_enabled 和rpl_semi_sync_slave_enabled 不要直接写入到my.cnf配置文件开启。 2.在slave库上先 stop slave io_thread ;set global rpl_semi_sync_slave_enabled=0 关闭此参数。然后start slave io_thread 或者start slave 开启异步复制，让slave库追赶上master库。 3.然后在slave库 set global rpl_semi_sync_slave_enabled=1 ；stop slave io_thread;start slave io_thread;
转载于:https://blog.51cto.com/wujianwei/2409754
