今天收到邮件报警,mysql主从延迟>1h,导致新的数据无法进行同步。
mysql工作目录下积累了很多的mysqld-relay文件
Seconds_Behind_Master: 越来越大。
Slave_SQL_Running_State: 一直处于Reading event from the relay log 状态
mysql> show slave status\G
*************************** 1. row ***************************
Slave_IO_State: Waiting for master to send event
Master_Host: 10.52.35.185
Master_User: repl
Master_Port: 3306
Connect_Retry: 60
Master_Log_File: mysql-bin.011374
Read_Master_Log_Pos: 88856621
Relay_Log_File: mysqld-relay-bin.034139
Relay_Log_Pos: 7119391
Relay_Master_Log_File: mysql-bin.011371
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: performance_schema.*,test.%,information_schema.%
Last_Errno: 0
Last_Error:
Skip_Counter: 0
Exec_Master_Log_Pos: 7119228
Relay_Log_Space: 2116679529
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: 5430
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: 185
Master_UUID: 870ab79e-2a14-11ea-ba96-00505697e312
Master_Info_File: /data/mysql/db/master.info
SQL_Delay: 0
SQL_Remaining_Delay: NULL
Slave_SQL_Running_State: Reading event from the relay log
Master_Retry_Count: 86400
Master_Bind:
Last_IO_Error_Timestamp:
Last_SQL_Error_Timestamp:
Master_SSL_Crl:
Master_SSL_Crlpath:
Retrieved_Gtid_Set:
Executed_Gtid_Set:
Auto_Position: 0
1 row in set (0.00 sec)
如果innodb_flush_log_at_trx_commit设置为0,log buffer将每秒一次地写入log file中,并且log file的flush(刷到磁盘)操作同时进行.该模式下,在事务提交的时候,不会主动触发写入磁盘的操作。
如果innodb_flush_log_at_trx_commit设置为1,每次事务提交时MySQL都会把log buffer的数据写入log file,并且flush(刷到磁盘)中去.
如果innodb_flush_log_at_trx_commit设置为2,每次事务提交时MySQL都会把log buffer的数据写入log file.但是flush(刷到磁盘)操作并不会同时进行。该模式下,MySQL会每秒执行一次 flush(刷到磁盘)操作。
注意:
由于进程调度策略问题,这个“每秒执行一次 flush(刷到磁盘)操作”并不是保证100%的“每秒”。
sync_binlog
sync_binlog 的默认值是0,像操作系统刷其他文件的机制一样,MySQL不会同步到磁盘中去而是依赖操作系统来刷新binary log。
当sync_binlog =N (N>0) ,MySQL 在每写 N次 二进制日志binary log时,会使用fdatasync()函数将它的写二进制日志binary log同步到磁盘中去。
注意:
如果启用了autocommit,那么每一个语句statement就会有一次写操作;否则每个事务对应一个写操作。
而且mysql服务默认是autocommit打开的
解决办法mysql> set global sync_binlog=20;
Query OK, 0 rows affected (0.00 sec)
mysql> set global innodb_flush_log_at_trx_commit=2;
Query OK, 0 rows affected (0.00 sec)
修改配置文件my.cnf 重启生效。
sync_binlog=20
innodb_flush_log_at_trx_commit=2
再次查看一下主从是否恢复正常
mysql> show slave status\G
*************************** 1. row ***************************
Slave_IO_State: Waiting for master to send event
Master_Host: 10.52.35.185
Master_User: repl
Master_Port: 3306
Connect_Retry: 60
Master_Log_File: mysql-bin.011387
Read_Master_Log_Pos: 52242714
Relay_Log_File: mysqld-relay-bin.034269
Relay_Log_Pos: 52242877
Relay_Master_Log_File: mysql-bin.011387
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: performance_schema.*,test.%,information_schema.%
Last_Errno: 0
Last_Error:
Skip_Counter: 0
Exec_Master_Log_Pos: 52242714
Relay_Log_Space: 52243098
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: 185
Master_UUID: 870ab79e-2a14-11ea-ba96-00505697e312
Master_Info_File: /data/mysql/db/master.info
SQL_Delay: 0
SQL_Remaining_Delay: NULL
Slave_SQL_Running_State: Slave has read all relay log; waiting for the slave I/O thread to update it
Master_Retry_Count: 86400
Master_Bind:
Last_IO_Error_Timestamp:
Last_SQL_Error_Timestamp:
Master_SSL_Crl:
Master_SSL_Crlpath:
Retrieved_Gtid_Set:
Executed_Gtid_Set:
Auto_Position: 0
1 row in set (0.00 sec)
↑ 可以看到Seconds_Behind_Master 已经0延迟了