MySQL复制卡住

Question

我将MySQL复制从一个主设置为一个奴隶。“显示从状态\G”显示一个不断增加的Seconds_Behind_Master。以下是从最老(顶部)到最新(底部)的连续三个结果。谁知道wrong?.................................................................................................................是什么.........................................................................................................................

1

    mysql> SHOW SLAVE STATUS\G
*************************** 1. row ***************************
               Slave_IO_State: Queueing master event to the relay log
                  Master_Host: <excluding>
                  Master_User: <excluding>
                  Master_Port: 3306
                Connect_Retry: 60
              Master_Log_File: mysql-bin.002723
          Read_Master_Log_Pos: 893947806
               Relay_Log_File: design-hotels-database-relay-bin.000002
                Relay_Log_Pos: 7692403
        Relay_Master_Log_File: mysql-bin.002723
             Slave_IO_Running: Yes
            Slave_SQL_Running: Yes
              Replicate_Do_DB:
          Replicate_Ignore_DB: starwood_sop,starwood_blp
           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: 192464416
              Relay_Log_Space: 709176017
              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: 76613
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: 3
                  Master_UUID:
             Master_Info_File: /var/lib/mysql/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
         Replicate_Rewrite_DB:
                 Channel_Name:
           Master_TLS_Version:
1 row in set (0.04 sec)

2

mysql> SHOW SLAVE STATUS\G
*************************** 1. row ***************************
               Slave_IO_State: Queueing master event to the relay log
                  Master_Host: <excluding>
                  Master_User: <excluding>
                  Master_Port: 3306
                Connect_Retry: 60
              Master_Log_File: mysql-bin.002723
          Read_Master_Log_Pos: 908310158
               Relay_Log_File: design-hotels-database-relay-bin.000002
                Relay_Log_Pos: 7906291
        Relay_Master_Log_File: mysql-bin.002723
             Slave_IO_Running: Yes
            Slave_SQL_Running: Yes
              Replicate_Do_DB:
          Replicate_Ignore_DB: starwood_sop,starwood_blp
           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: 192678304
              Relay_Log_Space: 723538369
              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: 76698
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: 3
                  Master_UUID:
             Master_Info_File: /var/lib/mysql/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
         Replicate_Rewrite_DB:
                 Channel_Name:
           Master_TLS_Version:
1 row in set (0.06 sec)

3

mysql> SHOW SLAVE STATUS\G
*************************** 1. row ***************************
               Slave_IO_State: Queueing master event to the relay log
                  Master_Host: <excluding>
                  Master_User: <excluding>
                  Master_Port: 3306
                Connect_Retry: 60
              Master_Log_File: mysql-bin.002723
          Read_Master_Log_Pos: 945765663
               Relay_Log_File: design-hotels-database-relay-bin.000002
                Relay_Log_Pos: 8389913
        Relay_Master_Log_File: mysql-bin.002723
             Slave_IO_Running: Yes
            Slave_SQL_Running: Yes
              Replicate_Do_DB:
          Replicate_Ignore_DB: starwood_sop,starwood_blp
           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: 193161926
              Relay_Log_Space: 760993874
              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: 76870
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: 3
                  Master_UUID:
             Master_Info_File: /var/lib/mysql/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
         Replicate_Rewrite_DB:
                 Channel_Name:
           Master_TLS_Version:
1 row in set (0.04 sec)

Answer 1

好的，Exec_Master_Log_Pos也在增加，这表明SQL线程实际上正在工作并应用更改。只是速度不够快，无法跟上输入的日志，Read_Master_Log_Pos的增长率表明了这一点。

    Exec-pos              Read-pos
1:  192464416             893947806
2:  192678304 (+213,888)  908310158 (+14,362,352
3:  193161926 (+483,622)  945765663 (+37,455,505) 

因此，传入日志(读-pos)到达的速率比复制能够在从实例上执行更改的速率高出许多倍。

复制滞后是一个复杂的问题，其原因是多方面的。您可以使用许多配置设置来帮助提高从站的吞吐量。您没有描述任何关于当前配置或数据库更改的性质或正在更改的表的任何内容，因此我无法提供真正知情的建议。但是下面是我通常做的一些典型的改变：

innodb_buffer_pool_size = <high> # depends on server RAM and other factors 
innodb_log_file_size = 1G # or more
innodb_flush_log_at_trx_commit = 2
master_info_repository = TABLE
relay_log_info_repository = TABLE
relay_log_recovery = ON
sync_master_info = 0
binlog_format = ROW # make sure all tables have PRIMARY KEY constraints

有关这些选项的详细信息，请参阅MySQL文档。

即使有了所有这些调优技巧，最终您也可能遇到一个限制，即奴隶在单个线程中重播在主服务器上的许多线程中创建的更改的能力。

您可能可以使用多线程从属程序，但这并不像听起来那么简单，因此您需要在尝试之前阅读更多有关它的信息。

即使使用调优和多线程从服务器，您也有可能达到硬件的极限。它根本无法足够快地处理这些变化。您可以将硬件升级为更快的CPU和更快的存储。

另一种选择是降低主数据库的更改率。要么在主服务器上进行节气门更改，要么通过各自的从站部署多个主程序，并在多个主服务器上平衡更改。