MySQL中show slave status关键值和MGRrelay log的清理策略

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一、show slave status关键值

*************************** 1. row ***************************
Slave_io_State: Waiting for master to send event (IO THREAD状态)
Master_Host: 192.168.99.42(通道主库IP)
Master_User: repl991(同步用户名)
Master_Port: 3310(端口)
Connect_Retry: 60(IO thread 重试时间)
Master_Log_File: binlog.000002(读取到的binlog文件名)
Read_Master_Log_Pos: 44688(读取到的binlog位置)
Relay_Log_File: test-relay-bin.000003(本IO THREAD replay文件名)
Relay_Log_Pos: 24360(当前写到relay log的位置)
Relay_Master_Log_File: binlog.000002(sql thread应用到的binlog的文件名)
Slave_IO_Running: Yes (IO thread状态是否正常)
Slave_SQL_Running: Yes (SQL THREAD状态是否正常)
...
Last_Errno: 0 (错误号)
Last_Error: (错误信息)
Skip_Counter: 0
Exec_Master_Log_Pos: 44688 (SQL thread应用到的binlog的位置)
Relay_Log_Space: 44599 (relay 日志文件总的的大小)
...
Seconds_Behind_Master: 0 (延迟)
...
Master_Server_Id: 9942 (主库的server_id)
Master_UUID: 0e733bbb-a594-11e7-ab07-52540020afef (主库的UUID)
Master_Info_File: /root/mysql5.7.14/percona-server-5.7.14-7/mysql-test/var/mysqld.1/data/master.info (master info的文件或者表)
SQL_Delay: 0(是否配置延时应用)
...
Slave_SQL_Running_State: Slave has read all relay log; waiting for more updates (sql thread状态)
Master_Retry_Count: 86400 (可以重试的总次数)
...
Retrieved_Gtid_Set: 0e733bbb-a594-11e7-ab07-52540020afef:9-129 (收到的GTID)
Executed_Gtid_Set: 0e733bbb-a594-11e7-ab07-52540020afef:1-129 (应用的GTID)
Auto_Position: 1 (是否通过GTID自动寻找binlog位置)
...
Channel_Name: 通道名
...

二、MGR relaylog 清理策略

普通sql线程删除relay文件

#0  MYSQL_BIN_LOG::purge_logs (this=0x37ea570, to_log=0x7fff2400d1a0 "./test-relay-bin.000004", included=false, need_lock_index=false, need_update_threads=false, 
    decrease_log_space=0x37ec628, auto_purge=true) at /root/mysql5.7.14/percona-server-5.7.14-7/sql/binlog.cc:5950#1  0x000000000185073f in MYSQL_BIN_LOG::purge_first_log (this=0x37ea570, rli=0x37e9b30, included=false)
    at /root/mysql5.7.14/percona-server-5.7.14-7/sql/binlog.cc:5818#2  0x0000000001892224 in next_event (rli=0x37e9b30) at /root/mysql5.7.14/percona-server-5.7.14-7/sql/rpl_slave.cc:9299#3  0x0000000001886443 in exec_relay_log_event (thd=0x7fff24000950, rli=0x37e9b30) at /root/mysql5.7.14/percona-server-5.7.14-7/sql/rpl_slave.cc:5145#4  0x000000000188d092 in handle_slave_sql (arg=0x3790690) at /root/mysql5.7.14/percona-server-5.7.14-7/sql/rpl_slave.cc:7387#5  0x0000000001d7b4b0 in pfs_spawn_thread (arg=0x7fff3c01b5f0) at /root/mysql5.7.14/percona-server-5.7.14-7/storage/perfschema/pfs.cc:2188#6  0x0000003f74807aa1 in start_thread () from /lib64/libpthread.so.0#7  0x0000003f740e8bcd in clone () from /lib64/libc.so.6

MGR group_replication_applier通道的sql线程删除relay文件

#0  MYSQL_BIN_LOG::purge_logs (this=0x7fff9c0562f0, to_log=0x7fff800160b0 "./gp4-relay-bin-group_replication_applier.000006", included=false, need_lock_index=false, 
    need_update_threads=false, decrease_log_space=0x7fff9c058320, auto_purge=true) at /root/softm/percona-server-5.7.22-22/sql/binlog.cc:6391#1  0x0000000001870333 in MYSQL_BIN_LOG::purge_first_log (this=0x7fff9c0562f0, rli=0x7fff9c0558a0, included=false)
    at /root/softm/percona-server-5.7.22-22/sql/binlog.cc:6259#2  0x00000000018b6bcf in next_event (rli=0x7fff9c0558a0) at /root/softm/percona-server-5.7.22-22/sql/rpl_slave.cc:9480#3  0x00000000018aa5a6 in exec_relay_log_event (thd=0x7fff80007e10, rli=0x7fff9c0558a0) at /root/softm/percona-server-5.7.22-22/sql/rpl_slave.cc:5193#4  0x00000000018b1980 in handle_slave_sql (arg=0x7fff9c04e850) at /root/softm/percona-server-5.7.22-22/sql/rpl_slave.cc:7543#5  0x0000000001932112 in pfs_spawn_thread (arg=0x7fff9803ff60) at /root/softm/percona-server-5.7.22-22/storage/perfschema/pfs.cc:2190#6  0x00007ffff7bc6aa1 in start_thread () from /lib64/libpthread.so.0#7  0x00007ffff6719bcd in clone () from /lib64/libc.so.6

可以看出没有什么区别。实际上都是一样的还是通过sql线程应用了event后删除。当然有如下代码 受到参数relay_log_purge控制

      if (relay_log_purge)
      {        
        if (rli->relay_log.purge_first_log
            (rli,
             rli->get_group_relay_log_pos() == rli->get_event_relay_log_pos()
             && !strcmp(rli->get_group_relay_log_name(),rli->get_event_relay_log_name())))
        {
          errmsg = "Error purging processed logs";          Goto err;
        }
        DBUG_PRINT("info", ("next_event group master %s %lu  group relay %s %lu event %s %lu\n",
          rli->get_group_master_log_name(),
          (ulong) rli->get_group_master_log_pos(),
          rli->get_group_relay_log_name(),
          (ulong) rli->get_group_relay_log_pos(),
          rli->get_event_relay_log_name(),
          (ulong) rli->get_event_relay_log_pos()));
      }      else

• flush logs等命令不会影响MGR的repay log包括recovery通道和applier通道

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