在mysql5.7中如何开启半同步复制

show plugins; 查看模块
help --uninstall; 查看卸载模块

master:
mysql> install plugin rpl_semi_sync_master soname 'semisync_master.so'; --安装 semisync_master.so插件 
Query OK, 0 rows affected (0.03 sec)
slave:
root@localhost [zw3306]>install plugin rpl_semi_sync_slave soname 'semisync_slave.so'; --安装 semisync_slave.so插件
Query OK, 0 rows affected (0.00 sec)
root@localhost [zw3306]>install plugin rpl_semi_sync_master soname 'semisync_master.so';
Query OK, 0 rows affected (0.00 sec)

set global rpl_semi_sync_master_enabled=1;
set global rpl_semi_sync_master_timeout=1000;
set global rpl_semi_sync_slave_enabled=1;

master:
[mysqld]
rpl_semi_sync_master_enabled = 1 
rpl_semi_sync_master_timeout = 1000 # 1 second
slave：
[mysqld]
rpl_semi_sync_slave_enabled = 1

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%';

stop slave io_thread;
start slave io_thread;

change master to master_host='192.168.26.233', master_port=3306, master_user='repl',master_password='repl', master_auto_position=1;
 
root@localhost [(none)]>start slave;
Query OK, 0 rows affected (0.01 sec)
root@localhost [(none)]>show slave status\G;
*************************** 1. row ***************************
 Slave_IO_State: Waiting for master to send event
 Master_Host: 192.168.26.233
 Master_User: repl
 Master_Port: 3306
 Connect_Retry: 60
 Master_Log_File: mysql-bin.000002
 Read_Master_Log_Pos: 194
 Relay_Log_File: relay-bin.000004
 Relay_Log_Pos: 407
 Relay_Master_Log_File: mysql-bin.000002
 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: 194
 Relay_Log_Space: 861
 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: 3306100
 Master_UUID: 7e354a2c-6f5f-11e6-997d-005056a36f08
 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: 7e354a2c-6f5f-11e6-997d-005056a36f08:1-9
 Executed_Gtid_Set: 7e354a2c-6f5f-11e6-997d-005056a36f08:1-9,
ba0d5587-74d6-11e6-ab5c-005056a3f46e:1-2
 Auto_Position: 1
 Replicate_Rewrite_DB: 
 Channel_Name: 
 Master_TLS_Version: 
1 row in set (0.00 sec)
ERROR: 
No query specified

root@localhost [zw3306]>show tables;

+------------------+
| Tables_in_zw3306 |
+------------------+
| t1 |
+------------------+
1 row in set (0.00 sec)

root@localhost [zw3306]>select * from t1;

+------+
| id |
+------+
| 1 |
| 2 |
| 3 |
| 4 |
+------+
4 rows in set (0.00 sec)

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%';

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;