1. 主库报错

2017-07-19T13:07:07.229901+08:00 0 [Note] Failed to select() on semi-sync dump sockets, error: errno=9

2017-07-19T13:38:23.464859+08:00 0 [Note] Failed to select() on semi-sync dump sockets, error: errno=9

2. 从库报错

2017-07-19T17:28:30.314448+08:00 1234432 [ERROR] Semi-sync slave net_flush() reply failed

2017-07-19T17:28:30.320069+08:00 1234432 [ERROR] Semi-sync slave net_flush() reply failed

2017-07-19T17:28:30.329480+08:00 1234432 [ERROR] Semi-sync slave net_flush() reply failed

2017-07-19T17:28:30.330239+08:00 1234432 [ERROR] Semi-sync slave net_flush() reply failed

2017-07-19T17:28:30.342473+08:00 1234432 [ERROR] Semi-sync slave net_flush() reply failed

2017-07-19T17:28:30.349666+08:00 1234432 [ERROR] Semi-sync slave net_flush() reply failed

2017-07-19T17:28:30.354800+08:00 1234432 [ERROR] Semi-sync slave net_flush() reply failed

2017-07-19T17:28:30.357032+08:00 1234432 [ERROR] Semi-sync slave net_flush() reply failed

2017-07-19T17:28:30.360438+08:00 1234432 [ERROR] Semi-sync slave net_flush() reply failed

2017-07-19T17:28:30.365723+08:00 1234432 [ERROR] Semi-sync slave net_flush() reply failed

2017-07-19T17:28:30.371208+08:00 1234432 [ERROR] Semi-sync slave net_flush() reply failed

2017-07-19T17:28:30.376451+08:00 1234432 [ERROR] Semi-sync slave net_flush() reply failed

2017-07-19T17:28:30.471915+08:00 1234432 [ERROR] Semi-sync slave net_flush() reply failed

2017-07-19T17:28:30.484752+08:00 1234432 [ERROR] Semi-sync slave net_flush() reply failed

2017-07-19T17:28:30.490855+08:00 1234432 [ERROR] Semi-sync slave net_flush() reply failed

2017-07-19T17:28:30.506901+08:00 1234432 [ERROR] Semi-sync slave net_flush() reply failed

2017-07-19T17:28:30.512776+08:00 1234432 [ERROR] Semi-sync slave net_flush() reply failed

3. 查看网上有类似报错  应该是半同步复制bug

io复用 使用的select()   而不是poll     epoll  ，有硬限制1024  FD   5.7.17 版本才修复，查看5.7.18 版本源码是使用了poll方式检查socket 检查

只能禁用半同步复制

长时间的报错信息，会导致error_log  很大的

参考：

http://www.xuchunyang.com/2016/11/13/net-flush-reply-failed/

http://bugs.mysql.com/bug.php?id=79865