mysql半同步复制实现
半同步复制简介mysql
何为半同步复制模式呢？在此咱们先了解异步复制模式，这是MySQL的默认复制选项。异步复制便是master数据库把binlog日志发送给slave数据库，而后就没有了而后了。在此暴露一个问题，当slave服务器发生故障了，那么确定会致使主从数据库服务器的数据不一致。
为了解决上面的问题，MySQL5.5引入一种叫作半同步复制模式。开启这种模式，能够保证slave数据库接收完master数据库发送过来的binlog日志并写入本身的中继日志中，而后反馈给master数据库，告知已经复制完毕。
开启这种模式后，当出现超时，主数据库将会自动转为异步复制模式，直到至少有一台从服务器接受到主数据库的binlog，而且反馈给主数据库。这时主数据库才会切换回半同步复制模式。sql
注意：
(1)半同步复制模式必须在主服务器和从服务器同时中开启，不然将会默认为异步复制模式；
且MySQL5.5或者以上版本才有这个功能
(2)对于开启半同步复制的集群，当某一台slave响应超时，会自动切换为异步复制模式；半同步复制模式存在的好处是，集群里的slave不可能同时全跪了，这个几率过小；只要存在同步正常的，就保证了数据的安全性数据库
环境：安全
CentOS系统
主库：192.168.0.1
从库：192.168.0.2
MySQL:5.6 服务器
开始配置半同步复制session
第一步：MySQL必须有自动加载功能，即have_dynamic_loading变量为YES（由于咱们是在MySQL里面来加载安装这个功能插件）异步
mysql>>show variables like 'have_dynamic_loading'; #检查是否具备自动加载功能 +----------------------+-------+ | Variable_name | Value | +----------------------+-------+ | have_dynamic_loading | YES | +----------------------+-------+ 1 row in set (0.00 sec) mysql>>show variables like 'plugin%'; +---------------+----------------------+ | Variable_name | Value | +---------------+----------------------+ | plugin_dir | /d/mysql/lib/plugin/ | +---------------+----------------------+ 1 row in set (0.00 sec) mysql>>system ls /d/mysql/lib/plugin/ mysql> system ls /d/mysql/lib/plugin/ adt_null.so auth_test_plugin.so debug libmemcached.so qa_auth_client.so semisync_master.so validate_password.so auth.so connection_control.so innodb_engine.so mypluglib.so qa_auth_interface.so semisync_slave.so auth_socket.so daemon_example.ini libdaemon_example.so mysql_no_login.so qa_auth_server.so test_udf_services.so
第二步：主库(192.168.0.1)配置:socket
mysql>>install plugin rpl_semi_sync_master soname 'semisync_master.so'; #加载主库半同步插件 mysql>>show plugins; #查看是否加载成功 +----------------------------+----------+--------------------+--------------------+---------+ | Name | Status | Type | Library | License | +----------------------------+----------+--------------------+--------------------+---------+ | binlog | ACTIVE | STORAGE ENGINE | NULL | GPL | | mysql_native_password | ACTIVE | AUTHENTICATION | NULL | GPL | | mysql_old_password | ACTIVE | AUTHENTICATION | NULL | GPL | | sha256_password | ACTIVE | AUTHENTICATION | NULL | GPL | | MyISAM | ACTIVE | STORAGE ENGINE | NULL | GPL | | MRG_MYISAM | ACTIVE | STORAGE ENGINE | NULL | GPL | | MEMORY | ACTIVE | STORAGE ENGINE | NULL | GPL | | CSV | ACTIVE | STORAGE ENGINE | NULL | GPL | | BLACKHOLE | ACTIVE | STORAGE ENGINE | NULL | GPL | | ARCHIVE | 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_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 | | FEDERATED | DISABLED | STORAGE ENGINE | NULL | GPL | | PERFORMANCE_SCHEMA | ACTIVE | STORAGE ENGINE | NULL | GPL | | partition | ACTIVE | STORAGE ENGINE | NULL | GPL | | rpl_semi_sync_master | ACTIVE | REPLICATION | semisync_master.so | GPL | +----------------------------+----------+--------------------+--------------------+---------+ mysql>>SET GLOBAL rpl_semi_sync_master_enabled = 1; #开启半同步复制，默认是关闭的
第三步：从库(192.168.0.2)配置:memcached
mysql>>INSTALL PLUGIN rpl_semi_sync_slave SONAME 'semisync_slave.so'; #加载从库半同步插件 mysql>>show plugins; #查看是否加载成功 +----------------------------+----------+--------------------+-------------------+---------+ | Name | Status | Type | Library | License | +----------------------------+----------+--------------------+-------------------+---------+ | binlog | ACTIVE | STORAGE ENGINE | NULL | GPL | | mysql_native_password | ACTIVE | AUTHENTICATION | NULL | GPL | | mysql_old_password | ACTIVE | AUTHENTICATION | NULL | GPL | | sha256_password | ACTIVE | AUTHENTICATION | NULL | GPL | | MyISAM | ACTIVE | STORAGE ENGINE | NULL | GPL | | MRG_MYISAM | ACTIVE | STORAGE ENGINE | NULL | GPL | | MEMORY | ACTIVE | STORAGE ENGINE | NULL | GPL | | CSV | ACTIVE | STORAGE ENGINE | NULL | GPL | | BLACKHOLE | ACTIVE | STORAGE ENGINE | NULL | GPL | | ARCHIVE | 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_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 | | FEDERATED | DISABLED | STORAGE ENGINE | NULL | GPL | | PERFORMANCE_SCHEMA | ACTIVE | STORAGE ENGINE | NULL | GPL | | partition | ACTIVE | STORAGE ENGINE | NULL | GPL | | rpl_semi_sync_slave | ACTIVE | REPLICATION | semisync_slave.so | GPL | +----------------------------+----------+--------------------+-------------------+---------+ 43 rows in set (0.03 sec) mysql>>SET GLOBAL rpl_semi_sync_slave_enabled = 1; #开启半同步复制，默认是关闭的
第四步：重启从服务器IO线程，手动将异步模式切换为半同步模式插件
mysql>>STOP SLAVE IO_THREAD; mysql>>START SLAVE IO_THREAD; ##能够把开启半同步写入my.cnf文件配置里，以后启动mysql服务后自动开启 rpl_semi_sync_master_enabled=1 #主库配置文件添加，表示之后启动MySQL将会自动开启半同步复制 rpl_semi_sync_slave_enabled=1 #从库配置文件添加，表示之后启动MySQL将会自动开启半同步复制
###########################################
查看是否配置成功
(1)参数确认：
主库执行命令show variables like '%semi%'; +------------------------------------+-------+ | Variable_name | Value | +------------------------------------+-------+ | rpl_semi_sync_master_enabled | ON | | rpl_semi_sync_master_timeout | 10000 | | rpl_semi_sync_master_trace_level | 32 | | rpl_semi_sync_master_wait_no_slave | ON | +------------------------------------+-------+ 4 rows in set (0.00 sec) Rpl_semi_sync_master_enabled=ON #表示开启半同步复制 Rpl_semi_sync_master_timeout=10000 #默认10000毫秒，即10秒超时，将切换为异步复制 Rpl_semi_sync_master_wait_no_slave #表示是否容许master每一个事物都要等待slave接收确认，默认为ON Rpl_semi_sync_master_trace_level=32 #表示用于开启半同步复制时的调试级别，默认32 从库执行命令show variables like '%semi%'; +---------------------------------+-------+ | Variable_name | Value | +---------------------------------+-------+ | rpl_semi_sync_slave_enabled | ON | | rpl_semi_sync_slave_trace_level | 32 | +---------------------------------+-------+ 2 rows in set (0.00 sec) Rpl_semi_sync_slave_enabled=ON #表示在slave已经开始半同步复制模式 Rpl_semi_sync_slave_trace_level=32 #表示用于开启半同步复制时的调试级别，默认32
(2)查看当前半同步状态
主库执行命令show status like '%semi%'; +--------------------------------------------+-------+ | Variable_name | Value | +--------------------------------------------+-------+ | Rpl_semi_sync_master_clients | 2 | | Rpl_semi_sync_master_net_avg_wait_time | 0 | | Rpl_semi_sync_master_net_wait_time | 0 | | Rpl_semi_sync_master_net_waits | 0 | | Rpl_semi_sync_master_no_times | 0 | | Rpl_semi_sync_master_no_tx | 0 | | Rpl_semi_sync_master_status | ON | | Rpl_semi_sync_master_timefunc_failures | 0 | | Rpl_semi_sync_master_tx_avg_wait_time | 0 | | Rpl_semi_sync_master_tx_wait_time | 0 | | Rpl_semi_sync_master_tx_waits | 0 | | Rpl_semi_sync_master_wait_pos_backtraverse | 0 | | Rpl_semi_sync_master_wait_sessions | 0 | | Rpl_semi_sync_master_yes_tx | 0 | +--------------------------------------------+-------+ 14 rows in set (0.00 sec) Rpl_semi_sync_master_status #表示主服务器使用是异步仍是半同步复制 Rpl_semi_sync_master_clients #表示从服务器有多少个配置成半同步复制 Rpl_semi_sync_master_yes_tx #表示从服务器确认成功提交的数量 Rpl_semi_sync_master_no_tx #表示从服务器确认失败提交的数量 从库执行命令show status like '%semi%'; +----------------------------+-------+ | Variable_name | Value | +----------------------------+-------+ | Rpl_semi_sync_slave_status | ON | +----------------------------+-------+ 1 row in set (0.00 sec) Rpl_semi_sync_slave_status #表示从服务器开启半同步复制
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