数据库环境的部署：
两边安装好相同的数据库软件，初始化，可以启动起来。
检查事项：
两边防火墙是否开启，对应的端口号是否通（可以通过telnet的方式，或者远程登录的方式验证）
主库创建复制账号：
create user 'repl'@'192.168.56.%' identified by 'oracle';
grant replication slave on *.* to 'repl'@'192.168.56.%';
flush privileges;
创建完之后，在另外一台服务器测试是否能连接上。
mysql -h 192.168.56.156 -urepl -p
1.安装相关的插件
show plugins; 查看模块
help --uninstall; 查看卸载模块
判断是否支持动态加载安装插件（如果是NO，表示不支持）
show variables like 'have_dynamic_loading';
master:
mysql> install plugin rpl_semi_sync_master soname 'semisync_master.so';
slave:
mysql> install plugin rpl_semi_sync_slave soname 'semisync_slave.so';
mysql> install plugin rpl_semi_sync_master soname 'semisync_master.so';
2.修改的参数：
set global rpl_semi_sync_master_enabled=1;
set global rpl_semi_sync_master_timeout=1000;
set global rpl_semi_sync_slave_enabled=1;
也可以直接写到配置文件 [mysqld]
master:
[mysqld]
rpl_semi_sync_master_enabled = 1
rpl_semi_sync_master_timeout = 1000 # 1 second
slave：
[mysqld]
rpl_semi_sync_slave_enabled = 1
修改了参数需要重启：
查看修改的参数
master:
mysql> show global variables like '%rpl_semi%';
+-------------------------------------------+------------+
| 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_for_slave_count | 1 |
| rpl_semi_sync_master_wait_no_slave | ON |
| rpl_semi_sync_master_wait_point | AFTER_SYNC |
+-------------------------------------------+------------+
6 rows in set (0.00 sec)
slave:
root@localhost [(none)]>show global variables like '%rpl_semi%';
+-------------------------------------------+------------+
| 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_for_slave_count | 1 |
| rpl_semi_sync_master_wait_no_slave | ON |
| rpl_semi_sync_master_wait_point | AFTER_SYNC |
| rpl_semi_sync_slave_enabled | ON |
| rpl_semi_sync_slave_trace_level | 32 |
+-------------------------------------------+------------+
8 rows in set (0.00 sec)
如果：如果原来是已经建好的复制结构很简单，运行下面的语句之后就是半同步复制了：
stop slave io_thread;
start slave io_thread;
3.在从库上执行：
change master to master_host='192.168.56.156',master_user='repl',master_password='oracle',master_port=3306,MASTER_AUTO_POSITION = 1;
mysql> start slave;
mysql> show slave status \G;
*************************** 1. row ***************************
Slave_IO_State: Waiting for master to send event
Master_Host: 192.168.56.156
Master_User: repl
Master_Port: 3306
Connect_Retry: 60
Master_Log_File: mysql-bin.000004
Read_Master_Log_Pos: 769
Relay_Log_File: relay-bin.000002
Relay_Log_Pos: 982
Relay_Master_Log_File: mysql-bin.000004
Slave_IO_Running: Yes
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: 769
Relay_Log_Space: 1183
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: 1563306
Master_UUID: 4dc90770-e120-11e6-9fd7-000c29355816
Master_Info_File: mysql.slave_master_info
SQL_Delay: 0
SQL_Remaining_Delay: NULL
Slave_SQL_Running_State: Slave has read all relay log; waiting for more updates
Master_Retry_Count: 86400
Master_Bind:
Last_IO_Error_Timestamp:
Last_SQL_Error_Timestamp:
Master_SSL_Crl:
Master_SSL_Crlpath:
Retrieved_Gtid_Set: 4dc90770-e120-11e6-9fd7-000c29355816:1-3
Executed_Gtid_Set: 4dc90770-e120-11e6-9fd7-000c29355816:1-3
Auto_Position: 1
Replicate_Rewrite_DB:
Channel_Name:
Master_TLS_Version:
1 row in set (0.00 sec)
5.查看slave是否有数据
略
6. 怎么确认是同步还是半同步？
show global variables like '%semi%';
show global status like '%semi%';
master:
root@localhost [zw3306]>show global status like '%semi%';
+--------------------------------------------+-------+
| Variable_name | Value |
+--------------------------------------------+-------+
| Rpl_semi_sync_master_clients | 1 | 有多少个Semi-sync的备库
| Rpl_semi_sync_master_net_avg_wait_time | 0 | 事务提交后，等待备库响应的平均时间
| Rpl_semi_sync_master_net_wait_time | 0 | 等待网络响应的总次数
| Rpl_semi_sync_master_net_waits | 7 | 总的网络等待时间
| Rpl_semi_sync_master_no_times | 0 | 一共有几次从Semi-sync跌回普通状态
| Rpl_semi_sync_master_no_tx | 0 | 库未及时响应的事务数,如果这个值很大就有问题
| Rpl_semi_sync_master_status | ON | 主库上Semi-sync是否正常开启
| Rpl_semi_sync_master_timefunc_failures | 0 | 时间函数未正常工作的次数
| Rpl_semi_sync_master_tx_avg_wait_time | 410 | 开启Semi-sync，事务返回需要等待的平均时间
| Rpl_semi_sync_master_tx_wait_time | 2876 | 事务等待备库响应的总时间
| Rpl_semi_sync_master_tx_waits | 7 | 事务等待备库响应的总次数
| Rpl_semi_sync_master_wait_pos_backtraverse | 0 | 改变当前等待最小二进制日志的次数
| Rpl_semi_sync_master_wait_sessions | 0 | 当前有几个线程在等备库响应
| Rpl_semi_sync_master_yes_tx | 7 | Semi-sync模式下，成功的事务数
+--------------------------------------------+-------+
15 rows in set (0.00 sec)
root@localhost [zw3306]>show global variables like '%semi%';
+-------------------------------------------+------------+
| 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_for_slave_count | 1 |
| rpl_semi_sync_master_wait_no_slave | ON |
| rpl_semi_sync_master_wait_point | AFTER_SYNC |
| rpl_semi_sync_slave_enabled | ON |
| rpl_semi_sync_slave_trace_level | 32 |
+-------------------------------------------+------------+
8 rows in set (0.00 sec)
Rpl_semi_sync_master_no_tx 如果这个值很大就有问题
也有其他的原因；
mysql> 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 | 17 |
| Rpl_semi_sync_master_no_times | 1 |
| Rpl_semi_sync_master_no_tx | 10 | 不是用半同步复制的
| Rpl_semi_sync_master_status | OFF |
| Rpl_semi_sync_master_timefunc_failures | 0 |
| Rpl_semi_sync_master_tx_avg_wait_time | 410 |
| Rpl_semi_sync_master_tx_wait_time | 2876 |
| Rpl_semi_sync_master_tx_waits | 7 |
| Rpl_semi_sync_master_wait_pos_backtraverse | 0 |
| Rpl_semi_sync_master_wait_sessions | 0 |
| Rpl_semi_sync_master_yes_tx | 7 |
+--------------------------------------------+-------+
14 rows in set (0.01 sec)
操作10个事物，可以发现都是 Rpl_semi_sync_master_no_tx
master接收到N个slave的应答后，才commit事物，等待1s用户可以设置应道slave的数量。
rpl_semi_sync_master_wait_for_slave_count=1 默认是1
set global rpl_semi_sync_master_wait_for_slave_count=2;
意思是多少个半同步的slave;
监控：
show global status like 'rpl_semi_sync%';
浙公网安备 33010602011771号