MariaDB主从半同步复制详解

Posted

tags:

篇首语:本文由小常识网(cha138.com)小编为大家整理,主要介绍了MariaDB主从半同步复制详解相关的知识,希望对你有一定的参考价值。

半同步复制(Semisynchronous replication)

介于异步复制和全同步复制之间,主库在执行完客户端提交的事务后不是立刻返回给客户端,而是等待至少一个从库接收到并写到relay log中才返回给客户端。相对于异步复制,半同步复制提高了数据的安全性,同时它也造成了一定程度的延迟,这个延迟最少是一个TCP/IP往返的时间。所以,半同步复制最好在低延时的网络中使用。

  
潜在的问题

客户端事务在存储引擎层提交后,在得到从库确认的过程中,主库宕机了,此时,可能的情况有两种:
 1.事务还没发送到从库上:此时,客户端会收到事务提交失败的信息,客户端会重新提交该事务到新的主上,当宕机的主库重新启动后,以从库的身份重新加入到该主从结构中,会发现,该事务在从库中被提交了两次,一次是之前作为主的时候,一次是被新主同步过来的。
 2.事务已经发送到从库上:此时,从库已经收到并应用了该事务,但是客户端仍然会收到事务提交失败的信息,重新提交该事务到新的主上。


半同步复制支持多种插件:/usr/lib64/mysql/plugin/*

需要安装方可使用:

MariaDB [mydb]> INSTALL PLUGIN plugin_name SONAME ‘shared_library_name‘; 

 

半同步复制插件:
 semisync_master.so
 semisync_slave.so


主从复制演示示例:

分别在配置文件server.cnf的[mysqld]段添加如下配置:
主节点:

[[email protected] ~]# vim /etc/my.cnf.d/server.cnf
 [mysqld]
 skip_name_resolve=ON
 innodb_file_per_table=ON
 server_id=1
 log_bin=log-bin

 

从节点:

[[email protected] ~]# vim /etc/my.cnf.d/server.cnf
 [mysqld]
 skip_name_resolve=ON
 innodb_file_per_table=ON
 server_id=2
 relay_log=relay-log

 

查看插件是否安装:

MariaDB [mydb]> SHOW PLUGINS;
+--------------------------------+----------+--------------------+---------+---------+
| 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     |
| MRG_MYISAM                     | ACTIVE   | STORAGE ENGINE     | NULL    | GPL     |
| MEMORY                         | ACTIVE   | STORAGE ENGINE     | NULL    | GPL     |
| MyISAM                         | ACTIVE   | STORAGE ENGINE     | NULL    | GPL     |
| CSV                            | ACTIVE   | STORAGE ENGINE     | NULL    | GPL     |
| PERFORMANCE_SCHEMA             | ACTIVE   | STORAGE ENGINE     | NULL    | GPL     |
| ARCHIVE                        | ACTIVE   | STORAGE ENGINE     | NULL    | GPL     |
| InnoDB                         | ACTIVE   | STORAGE ENGINE     | NULL    | GPL     |
| INNODB_RSEG                    | ACTIVE   | INFORMATION SCHEMA | NULL    | GPL     |
| INNODB_UNDO_LOGS               | ACTIVE   | INFORMATION SCHEMA | 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_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_STATS               | ACTIVE   | INFORMATION SCHEMA | NULL    | GPL     |
| INNODB_TABLE_STATS             | ACTIVE   | INFORMATION SCHEMA | NULL    | GPL     |
| INNODB_INDEX_STATS             | ACTIVE   | INFORMATION SCHEMA | NULL    | GPL     |
| INNODB_BUFFER_POOL_PAGES       | ACTIVE   | INFORMATION SCHEMA | NULL    | GPL     |
| INNODB_BUFFER_POOL_PAGES_INDEX | ACTIVE   | INFORMATION SCHEMA | NULL    | GPL     |
| INNODB_BUFFER_POOL_PAGES_BLOB  | ACTIVE   | INFORMATION SCHEMA | NULL    | GPL     |
| XTRADB_ADMIN_COMMAND           | ACTIVE   | INFORMATION SCHEMA | NULL    | GPL     |
| INNODB_CHANGED_PAGES           | 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     |
| FEDERATED                      | ACTIVE   | STORAGE ENGINE     | NULL    | GPL     |
| BLACKHOLE                      | ACTIVE   | STORAGE ENGINE     | NULL    | GPL     |
| Aria                           | ACTIVE   | STORAGE ENGINE     | NULL    | GPL     |
| FEEDBACK                       | DISABLED | INFORMATION SCHEMA | NULL    | GPL     |
| partition                      | ACTIVE   | STORAGE ENGINE     | NULL    | GPL     |
+--------------------------------+----------+--------------------+---------+---------+

 

经过查看半同步插件并没有安装,我们需要安装上去:

MariaDB [mydb]> HELP INSTALL;
 Name: ‘INSTALL PLUGIN‘
 Description:
 Syntax:
 INSTALL PLUGIN plugin_name SONAME ‘shared_library_name‘

 

在主节点安装插件:

MariaDB [(none)]> INSTALL PLUGIN rpl_semi_sync_master SONAME ‘semisync_master.so‘;
MariaDB [(none)]> SHOW PLUGINS;
+--------------------------------+----------+--------------------+--------------------+---------+
| Name                           | Status   | Type               | Library            | License |
+--------------------------------+----------+--------------------+--------------------+---------+
| rpl_semi_sync_master           | ACTIVE   | REPLICATION        | semisync_master.so | GPL     |
+--------------------------------+----------+--------------------+--------------------+---------+
MariaDB [(none)]> SHOW GLOBAL VARIABLES LIKE ‘%semi%‘;
+------------------------------------+-------+
| Variable_name                      | Value |
+------------------------------------+-------+
| rpl_semi_sync_master_enabled       | OFF   |
| rpl_semi_sync_master_timeout       | 10000 |
| rpl_semi_sync_master_trace_level   | 32    |
| rpl_semi_sync_master_wait_no_slave | ON    |
+------------------------------------+-------+
MariaDB [(none)]> SET @@global.rpl_semi_sync_master_enabled=ON;
MariaDB [(none)]> SHOW GLOBAL 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    |
+------------------------------------+-------+

 

在从节点安装插件:

MariaDB [(none)]> INSTALL PLUGIN rpl_semi_sync_slave SONAME ‘semisync_slave.so‘;
MariaDB [(none)]> SHOW PLUGINS;
+--------------------------------+----------+--------------------+-------------------+---------+
| Name                           | Status   | Type               | Library           | License |
+--------------------------------+----------+--------------------+-------------------+---------+
| rpl_semi_sync_slave            | ACTIVE   | REPLICATION        | semisync_slave.so | GPL     |
+--------------------------------+----------+--------------------+-------------------+---------+
MariaDB [(none)]> SHOW GLOBAL VARIABLES LIKE ‘%semi%‘;
+---------------------------------+-------+
| Variable_name                   | Value |
+---------------------------------+-------+
| rpl_semi_sync_slave_enabled     | OFF   |
| rpl_semi_sync_slave_trace_level | 32    |
+---------------------------------+-------+
MariaDB [(none)]> SET @@global.rpl_semi_sync_slave_enabled=ON;
MariaDB [(none)]> SHOW GLOBAL VARIABLES LIKE ‘%semi%‘;
+---------------------------------+-------+
| Variable_name                   | Value |
+---------------------------------+-------+
| rpl_semi_sync_slave_enabled     | ON    |
| rpl_semi_sync_slave_trace_level | 32    |
+---------------------------------+-------+

 

主节点:

MariaDB [(none)]> SHOW GLOBAL STATUS LIKE ‘%semi%‘;
+--------------------------------------------+-------+
| Variable_name                              | Value |
+--------------------------------------------+-------+
| Rpl_semi_sync_master_clients               | 0     |
| 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     |
+--------------------------------------------+-------+

 

从节点启动IO线程:

MariaDB [(none)]> STOP SLAVE IO_THREAD;
MariaDB [(none)]> START SLAVE IO_THREAD;

 

主节点:

MariaDB [(none)]> SHOW GLOBAL STATUS LIKE ‘%semi%‘;
+--------------------------------------------+-------+
| Variable_name                              | Value |
+--------------------------------------------+-------+
| Rpl_semi_sync_master_clients               | 1     |
| 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     |
+--------------------------------------------+-------+

 

在主节点为事先创建的用户进行主从复制授权:

MariaDB [(none)]> GRANT REPLICATION SLAVE,REPLICATION CLIENT ON *.* TO ‘repluser‘@‘172.18.67.%‘ IDENTIFIED BY ‘replpass‘;
MariaDB [(none)]> FLUSH PRIVILEGES;
MariaDB [(none)]> SHOW MASTER STATUS;
+----------------+----------+--------------+------------------+
| File           | Position | Binlog_Do_DB | Binlog_Ignore_DB |
+----------------+----------+--------------+------------------+
| log-bin.000003 |      497 |              |                  |
+----------------+----------+--------------+------------------+

 

从节点:

MariaDB [(none)]> CHANGE MASTER TO MASTER_HOST=‘172.18.67.11‘,MASTER_USER=‘repluser‘,MASTER_PASSWORD=‘replpass‘,MASTER_LOG_FILE=‘log-bin.000003‘,MASTER_LOG_POS=497;
MariaDB [(none)]> START SLAVE;

 

在主节点创建数据库mydb:

MariaDB [(none)]> CREATE DATABASE mydb CHARACTER SET ‘utf8‘;

 

在从节点查看数据库是否复制成功:

MariaDB [(none)]> SHOW DATABASES;
+--------------------+
| Database           |
+--------------------+
| information_schema |
| mydb               |
| mysql              |
| performance_schema |
| test               |
+--------------------+

 

发现数据库mydb成功复制

使用数据库mydb在主节点进行数据操作:

MariaDB [(none)]> use mydb;
MariaDB [mydb]> CREATE TABLE tbl1 (id INT,name VARCHAR(100));

 

在从节点上观察:

MariaDB [mydb]> SHOW GLOBAL STATUS LIKE ‘%semi%‘;
+--------------------------------------------+-------+
| Variable_name                              | Value |
+--------------------------------------------+-------+
| Rpl_semi_sync_master_clients               | 1     |
| Rpl_semi_sync_master_net_avg_wait_time     | 487   |
| Rpl_semi_sync_master_net_wait_time         | 487   |
| Rpl_semi_sync_master_net_waits             | 1     |
| 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      | 646   |
| Rpl_semi_sync_master_tx_wait_time          | 646   |
| Rpl_semi_sync_master_tx_waits              | 1     |
| Rpl_semi_sync_master_wait_pos_backtraverse | 0     |
| Rpl_semi_sync_master_wait_sessions         | 0     |
| Rpl_semi_sync_master_yes_tx                | 1     |
+--------------------------------------------+-------+

 

主节点继续操作:

MariaDB [mydb]> INSERT INTO tbl1 VALUES (1,‘tom‘);

 

我们发现从节点的数据都在变化:

MariaDB [mydb]> SHOW GLOBAL STATUS LIKE ‘%semi%‘;
+--------------------------------------------+-------+
| Variable_name                              | Value |
+--------------------------------------------+-------+
| Rpl_semi_sync_master_clients               | 1     |
| Rpl_semi_sync_master_net_avg_wait_time     | 910   |
| Rpl_semi_sync_master_net_wait_time         | 1821  |
| Rpl_semi_sync_master_net_waits             | 2     |
| 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      | 734   |
| Rpl_semi_sync_master_tx_wait_time          | 1469  |
| Rpl_semi_sync_master_tx_waits              | 2     |
| Rpl_semi_sync_master_wait_pos_backtraverse | 0     |
| Rpl_semi_sync_master_wait_sessions         | 0     |
| Rpl_semi_sync_master_yes_tx                | 2     |
+--------------------------------------------+-------+

 









以上是关于MariaDB主从半同步复制详解的主要内容,如果未能解决你的问题,请参考以下文章

Mariadb的半同步复制

Mariadb半同步复制,主从复制与双主复制

MariaDB主从复制及半同步复制

MariaDB 10.3 主主半同步复制

Mariadb数据库之主从复制同步配置实战

初识MariaDB之6——半同步复制