yum實現MariaDB5.5.6半同步複製

爲什麼需要半同步複製
默認情況下，MySQL的複製功能是異步的，異步複製可以提供最佳的性能，主庫把Binlog日誌發送給從
庫即結束，並不驗證從庫是否接收完畢。這意味着當主服務器或從服務器端發生故障時，有可能從服務
器沒有接收到主服務器發送過來的binlog日誌，這就會造成主服務器和從服務器的數據不一致，甚至在
恢復時造成數據的丟失
什麼是半同步複製
在一主多從的環境下，如果一個從收到了來自主服務器的同步信息，那麼立即返回給主，表示已同步完成；不需要等所有從都同步才返回信息，繼而保障了主機異常宕機時，數據不會丟失，可提升爲已完成備份的從服務器提升爲主，保障服務的持續集成。如果主存活，slave全部宕機，主服務器寫入數據後等待time超時時間過期後，就會返回成功信息，不同繼續等待slave，如果slave再次上線，繼而同步成功。

官方文檔: https://mariadb.com/kb/en/library/semisynchronous-replication/

實驗環境

OS	IP	Dabase	Type
centos7.6	192.168.146.97	MariaDB5.5.6	Master
centos7.6	192.168.146.97	MariaDB5.5.6	Slave1
centos7.6	192.168.146.97	MariaDB5.5.6	Slave2

配置YUM倉庫: 本示例採用阿里yum源

[root@97 /etc/yum.repos.d]#curl -o /etc/yum.repos.d/CentOS-Base.repo http://mirrors.aliyun.com/repo/Centos-7.repo

[root@97 /etc/yum.repos.d]#yum install mariadb-server -y

Master1配置

[root@97 /etc/yum.repos.d]#cat /etc/my.cnf.d/server.cnf 
[mysqld]
server-id=97   #服務器ID
log-bin=myqsl-bin  #二進制日誌
log-error  #錯誤日誌

啓動服務，並配置mariadbserver

[root@97 ~]# systemctl start mariadb

[root@97 ~]# mysql

先搭建三臺機器的主從配置，後續接入半同步配置

Master

MariaDB [(none)]> grant replication slave on *.* to 'repluser'@'192.168.146.%' identified by 'replpasswd';  創建可複製的用戶
Query OK, 0 rows affected (0.00 sec)

MariaDB [(none)]> show master logs;  #查看當前bin-log日誌位置
+------------------+-----------+
| Log_name         | File_size |
+------------------+-----------+
| mysql-bin.000001 |     30322 |
| mysql-bin.000002 |   1038814 |
| mysql-bin.000003 |       407 |
+------------------+-----------+
3 rows in set (0.00 sec)

slave1配置

[root@107 ~]#cat /etc/my.cnf
[mysqld]
server-id=107
log-error
datadir=/var/lib/mysql
socket=/var/lib/mysql/mysql.sock

[root@107 ~]#systemctl start mariadb

[root@107 ~]#mysql

MariaDB [(none)]> CHANGE MASTER TO MASTER_HOST='192.168.146.97', MASTER_USER='repluser', MASTER_PASSWORD='replpasswd', MASTER_LOG_FILE='mysql-bin.000003', MASTER_LOG_POS=407;
Query OK, 0 rows affected (0.01 sec)

MariaDB [(none)]> start slave;
Query OK, 0 rows affected (0.00 sec)

MariaDB [(none)]> SHOW SLAVE STATUS\G
*************************** 1. row ***************************
               Slave_IO_State: Waiting for master to send event
                  Master_Host: 192.168.146.97
                  Master_User: repluser
                  Master_Port: 3306
                Connect_Retry: 60
              Master_Log_File: mysql-bin.000003
          Read_Master_Log_Pos: 407
               Relay_Log_File: mariadb-relay-bin.000002
                Relay_Log_Pos: 529
        Relay_Master_Log_File: mysql-bin.000003
             Slave_IO_Running: Yes  #同步已成功
            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: 407
              Relay_Log_Space: 825
              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: 97
1 row in set (0.00 sec)

測試
Master創建db1測試

MariaDB [(none)]> create database db1;
Query OK, 1 row affected (0.00 sec)

MariaDB [(none)]> show databases;
+--------------------+
| Database           |
+--------------------+
| information_schema |
| db1                |
| mysql              |
| performance_schema |
| test               |
+--------------------+
5 rows in set (0.00 sec)

slave查看

MariaDB [(none)]> show databases;
+--------------------+
| Database           |
+--------------------+
| information_schema |
| db1                |    #至此主從已完成
| mysql              |
| performance_schema |
| test               |
+--------------------+
5 rows in set (0.01 sec)

半同步設置

Master

MariaDB [(none)]> INSTALL SONAME 'semisync_master';  #安裝master插件，無須重啓
Query OK, 0 rows affected (0.00 sec)


MariaDB [(none)]> SET GLOBAL rpl_semi_sync_master_enabled=ON;  #開啓master_sync
Query OK, 0 rows affected (0.001 sec)

MariaDB [(none)]> SET GLOBAL rpl_semi_sync_master_timeout = 1000; #設置超時時長爲1s
Query OK, 0 rows affected (0.000 sec)

MariaDB [(none)]> SHOW GLOBAL VARIABLES LIKE '%semi%';  #查看相關全局變量
+---------------------------------------+--------------+
| Variable_name                         | Value        |
+---------------------------------------+--------------+
| rpl_semi_sync_master_enabled          | ON           |
| rpl_semi_sync_master_timeout          | 1000         |
| rpl_semi_sync_master_trace_level      | 32           |
| rpl_semi_sync_master_wait_no_slave    | ON           |
| rpl_semi_sync_master_wait_point       | AFTER_COMMIT |
| rpl_semi_sync_slave_delay_master      | OFF          |
| rpl_semi_sync_slave_enabled           | OFF          |
| rpl_semi_sync_slave_kill_conn_timeout | 5            |
| rpl_semi_sync_slave_trace_level       | 32           |
+---------------------------------------+--------------+
9 rows in set (0.001 sec)

MariaDB [(none)]> SHOW GLOBAL STATUS LIKE '%semi%';  #查看當前狀態信息
+--------------------------------------------+-------+
| Variable_name                              | Value |
+--------------------------------------------+-------+
| Rpl_semi_sync_master_clients               | 0     |  #此時雖然master插件已就緒，還沒有slave就緒
| Rpl_semi_sync_master_get_ack               | 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_request_ack           | 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     |
| Rpl_semi_sync_slave_send_ack               | 0     |
| Rpl_semi_sync_slave_status                 | OFF   |
+--------------------------------------------+-------+
18 rows in set (0.001 sec)

slave1.2設置

MariaDB [(none)]> INSTALL PLUGIN rpl_semi_sync_slave SONAME 'semisync_slave.so';  #安裝從插件
Query OK, 0 rows affected (0.01 sec)

MariaDB [(none)]> SET GLOBAL rpl_semi_sync_slave_enabled=1;   #啓動從插件
Query OK, 0 rows affected (0.00 sec)

MariaDB [(none)]> SHOW GLOBAL 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)

MariaDB [(none)]> SHOW GLOBAL STATUS LIKE '%semi%';  #此時發現slave是關閉的
+----------------------------+-------+
| Variable_name              | Value |
+----------------------------+-------+
| Rpl_semi_sync_slave_status | OFF   |
+----------------------------+-------+
1 row in set (0.01 sec)

MariaDB [(none)]> STOP SLAVE IO_THREAD;   #重啓線程
Query OK, 0 rows affected (0.00 sec)

MariaDB [(none)]> START SLAVE IO_THREAD;
Query OK, 0 rows affected (0.00 sec)

MariaDB [(none)]> SHOW GLOBAL STATUS LIKE '%semi%';  #插件開啓
+----------------------------+-------+
| Variable_name              | Value |
+----------------------------+-------+
| Rpl_semi_sync_slave_status | ON    |
+----------------------------+-------+
1 row in set (0.00 sec)

master上查看slave插件線程是否啓動且同步到了master

MariaDB [(none)]> SHOW GLOBAL STATUS LIKE '%semi%';
+--------------------------------------------+-------+
| Variable_name                              | Value |
+--------------------------------------------+-------+
| Rpl_semi_sync_master_clients               | 2     |  #此時檢測到兩個線程已連接，配置成功
| 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)

測試半同步

#在master實現，創建數據庫，立即成功

MariaDB [(none)]> create database db2;
Query OK, 1 row affected (1.00 sec)
MariaDB [(none)]> show databases;
+--------------------+
| Database           |
+--------------------+
| information_schema |
| db1                |
| db2                |
| mysql              |
| performance_schema |
| test               |
+--------------------+
6 rows in set (0.00 sec)

MariaDB [(none)]> show databases;
+--------------------+
| Database           |
+--------------------+
| information_schema |
| db1                |
| db2                |
| mysql              |
| performance_schema |
| test               |
+--------------------+
7 rows in set (0.00 sec)

#在所有slave節點實現，停止複製線程

MariaDB [(none)]> stop slave;
Query OK, 0 rows affected (0.011 sec)

#在master實現，創建數據庫，等待3s才能成功

MariaDB [(none)]> create database db3
Query OK, 1 row affected (1.00 sec)

MariaDB [(none)]> show databases;
+--------------------+
| Database           |
+--------------------+
| information_schema |
| db1                |
| db2                |
| db3                |
| mysql              |
| performance_schema |
| test               |
+--------------------+
6 rows in set (0.00 sec)

此時slave上沒有同步信息，因爲線程已關閉
MariaDB [(none)]> show databases;
+--------------------+
| Database           |
+--------------------+
| information_schema |
| db1                |
| db2                |
| mysql              |
| performance_schema |
| test               |
+--------------------+
5 rows in set (0.00 sec)

#在任意一個slave節點實現，恢復複製線程

MariaDB [(none)]> start slave;
Query OK, 0 rows affected (0.006 sec)

MariaDB [(none)]> start slave;
Query OK, 0 rows affected (0.00 sec)

MariaDB [(none)]> show databases;
+--------------------+
| Database           |
+--------------------+
| information_schema |
| db1                |
| db2                |
| db3                |   #數據馬上同步成功
| mysql              |
| performance_schema |
| test               |
+--------------------+
6 rows in set (0.00 sec)

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yum實現MariaDB5.5.6半同步複製

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