https://dev.mysql.com/doc/refman/5.7/en/replication-solutions-unexpected-slave-halt.html

https://dev.mysql.com/doc/refman/5.7/en/replication-features-transaction-inconsistencies.html

##slave_preserve_commit_order=0  ##开了性能太差，一定要设置成0。测试丢20%-30%性能。开启主从一致性更高

 set global rpl_semi_sync_master_enabled=1;开启半同步安全性更高，性能影响10%-20%左右

无损半同步复制：rpl_semi_sync_master_wait_point   = AFTER_SYNC 性能无影响。

relay_log_recovery=1

crash-safe