主从半同步复制是目前用得最多的MySQL复制方案,日常工作中我们一般通过show slave status语句查看当前复制过程中状态信息,基本上能满足大多数场景下的需求。Performance_schema中提供了16个关于复制的监控表(包括组复制、过滤复制等,这里我们先不讨论),show slave status中的大多数信息都来自Performance_schema中的复制系列表,这些表有利于更好的收集主从复制中的状态,报错,配置等信息,并且比show slave status提供了更全面的主从复制的诊断信息。这些表主要可以分为两类,分别为IO进程和SQL进程的信息:
replication_connection_configuration
这张表主要显示了从库连接到主库的配置参数,包括复制用户、主库地址、端口等,随着change master to命令语句改变。
replication_connection_status
主要包括当前IO线程的状态信息,IO线程相关错误信息,relaylog中上个排队和当前正在排队的事务信息。当因为连接失败等问题导致IO进程停止时,可以通过这张表排查错误信息。
mysql> select * from performance_schema.replication_connection_status\G *************************** 1. row *************************** CHANNEL_NAME: GROUP_NAME: SOURCE_UUID: c8e82820-16c4-11ed-8677-005056b65258 THREAD_ID: 341 SERVICE_STATE: ON COUNT_RECEIVED_HEARTBEATS: 67076 LAST_HEARTBEAT_TIMESTAMP: 2023-04-27 15:20:29.393141 RECEIVED_TRANSACTION_SET: c8e82820-16c4-11ed-8677-005056b65258:12-37 LAST_ERROR_NUMBER: 0 LAST_ERROR_MESSAGE: LAST_ERROR_TIMESTAMP: 0000-00-00 00:00:00.000000 LAST_QUEUED_TRANSACTION: c8e82820-16c4-11ed-8677-005056b65258:37 LAST_QUEUED_TRANSACTION_ORIGINAL_COMMIT_TIMESTAMP: 2023-04-26 14:37:27.673466 LAST_QUEUED_TRANSACTION_IMMEDIATE_COMMIT_TIMESTAMP: 2023-04-26 14:37:27.673466 LAST_QUEUED_TRANSACTION_START_QUEUE_TIMESTAMP: 2023-04-26 14:40:51.513510 LAST_QUEUED_TRANSACTION_END_QUEUE_TIMESTAMP: 2023-04-26 14:40:51.513521 QUEUEING_TRANSACTION: QUEUEING_TRANSACTION_ORIGINAL_COMMIT_TIMESTAMP: 0000-00-00 00:00:00.000000 QUEUEING_TRANSACTION_IMMEDIATE_COMMIT_TIMESTAMP: 0000-00-00 00:00:00.000000 QUEUEING_TRANSACTION_START_QUEUE_TIMESTAMP: 0000-00-00 00:00:00.000000 1 row in set (0.00 sec)
replication_applier_configuration
这个表包含影响从库回放事务的配置参数,比如REQUIRE_TABLE_PRIMARY_KEY_CHECK(开启主键校验)、DESIRED_DELAY(延迟复制配置)。
replication_applier_status
这个表显示从库SQL线程的状态总信息,现在生产中一般都开启了多线程复制,多线程复制下SQL线程状态主要看replication_applier_status_by_coordinator table 和replication_applier_status_by_worker这两张表。
replication_applier_status_by_coordinator
对于多线程复制,从库使用了多个复制线程(work thread),并且开启了一个协调线程(coordinator thread)来管理它们。这个表显示了协调线程的状态信息和错误信息,并且包括上一个被协调线程buffer的事务,以及当前协调线程正在buffer的事务。在多线程复制中,首先由协调线程从relaylog中读取并缓存需要执行事务,然后再把事务分配给其中一个复制线程。
mysql> select * from performance_schema.replication_applier_status_by_coordinator\G *************************** 1. row *************************** CHANNEL_NAME: THREAD_ID: 342 SERVICE_STATE: ON LAST_ERROR_NUMBER: 0 LAST_ERROR_MESSAGE: LAST_ERROR_TIMESTAMP: 0000-00-00 00:00:00.000000 LAST_PROCESSED_TRANSACTION: c8e82820-16c4-11ed-8677-005056b65258:37 LAST_PROCESSED_TRANSACTION_ORIGINAL_COMMIT_TIMESTAMP: 2023-04-26 14:37:27.673466 LAST_PROCESSED_TRANSACTION_IMMEDIATE_COMMIT_TIMESTAMP: 2023-04-26 14:37:27.673466 LAST_PROCESSED_TRANSACTION_START_BUFFER_TIMESTAMP: 2023-04-26 14:42:29.097360 LAST_PROCESSED_TRANSACTION_END_BUFFER_TIMESTAMP: 2023-04-26 14:42:29.098834 PROCESSING_TRANSACTION: PROCESSING_TRANSACTION_ORIGINAL_COMMIT_TIMESTAMP: 0000-00-00 00:00:00.000000 PROCESSING_TRANSACTION_IMMEDIATE_COMMIT_TIMESTAMP: 0000-00-00 00:00:00.000000 PROCESSING_TRANSACTION_START_BUFFER_TIMESTAMP: 0000-00-00 00:00:00.000000 1 row in set (0.00 sec)
replication_applier_status_by_worker
这个表显示了多线程复制中从库各个回放线程(applier thread)的状态及错误信息,applier thread也称workers。如果从库SQL线程在回放事务中报错,需要查询这个表获取详细的报错信息。如下图所示,下面的报错显示了SQL线程在回放事务过程中由于notest表中的某条记录不存在导致写入失败:
mysql> select * from performance_schema.replication_applier_status_by_worker where last_error_message != ''\G *************************** 1. row *************************** CHANNEL_NAME: WORKER_ID: 1 THREAD_ID: NULL SERVICE_STATE: OFF LAST_ERROR_NUMBER: 1032 LAST_ERROR_MESSAGE: Worker 1 failed executing transaction 'c8e82820-16c4-11ed-8677-005056b65258:38' at master log bin.000012, end_log_pos 3315; Could not execute Update_rows event on table test.notest; Can't find record in 'notest', Error_code: 1032; handler error HA_ERR_KEY_NOT_FOUND; the event's master log FIRST, end_log_pos 3315 LAST_ERROR_TIMESTAMP: 2023-04-28 09:45:59.684586 LAST_APPLIED_TRANSACTION: LAST_APPLIED_TRANSACTION_ORIGINAL_COMMIT_TIMESTAMP: 0000-00-00 00:00:00.000000 LAST_APPLIED_TRANSACTION_IMMEDIATE_COMMIT_TIMESTAMP: 0000-00-00 00:00:00.000000 LAST_APPLIED_TRANSACTION_START_APPLY_TIMESTAMP: 0000-00-00 00:00:00.000000 LAST_APPLIED_TRANSACTION_END_APPLY_TIMESTAMP: 0000-00-00 00:00:00.000000 APPLYING_TRANSACTION: c8e82820-16c4-11ed-8677-005056b65258:38 APPLYING_TRANSACTION_ORIGINAL_COMMIT_TIMESTAMP: 2023-04-28 09:45:59.673804 APPLYING_TRANSACTION_IMMEDIATE_COMMIT_TIMESTAMP: 2023-04-28 09:45:59.673804 APPLYING_TRANSACTION_START_APPLY_TIMESTAMP: 2023-04-28 09:45:59.684183 LAST_APPLIED_TRANSACTION_RETRIES_COUNT: 0 LAST_APPLIED_TRANSACTION_LAST_TRANSIENT_ERROR_NUMBER: 0 LAST_APPLIED_TRANSACTION_LAST_TRANSIENT_ERROR_MESSAGE: LAST_APPLIED_TRANSACTION_LAST_TRANSIENT_ERROR_TIMESTAMP: 0000-00-00 00:00:00.000000 APPLYING_TRANSACTION_RETRIES_COUNT: 0 APPLYING_TRANSACTION_LAST_TRANSIENT_ERROR_NUMBER: 0 APPLYING_TRANSACTION_LAST_TRANSIENT_ERROR_MESSAGE: APPLYING_TRANSACTION_LAST_TRANSIENT_ERROR_TIMESTAMP: 0000-00-00 00:00:00.000000 1 row in set (0.00 sec)
mysql.slave_master_info
此外mysql.slave_master_info这个表也需要注意,这个表显示了复制用户的明文密码,因此需要注意两点:
1.不要给复制用户repl授予除了REPLICATION SLAVE以外的权限,防止被获取明文密码后,利用这个用户进行一些高危操作。
2.在给数据库重建主从复制或者新加从库时,如果忘记了复制用户的密码,不需要再重置,可以通过这个表获取。
mysql> select * from mysql.slave_master_info\G *************************** 1. row *************************** Number_of_lines: 33 Master_log_name: bin.000012 Master_log_pos: 197 Host: 10.3.111.102 User_name: repl User_password: PASSW0RD Port: 3306 Connect_retry: 60 Enabled_ssl: 0 Ssl_ca: Ssl_capath: Ssl_cert: Ssl_cipher: Ssl_key: Ssl_verify_server_cert: 0 Heartbeat: 30 Bind: Ignored_server_ids: 0 Uuid: c8e82820-16c4-11ed-8677-005056b65258 Retry_count: 86400 Ssl_crl: Ssl_crlpath: Enabled_auto_position: 1 Channel_name: Tls_version: Public_key_path: Get_public_key: 0 Network_namespace: Master_compression_algorithm: uncompressed Master_zstd_compression_level: 3 Tls_ciphersuites: NULL Source_connection_auto_failover: 0 Gtid_only: 0
总结一下,show slave status已经是一个比较全面的监控了,其他用的比较多的performance_schema中的关于复制的表有replication_applier_status_by_worker、The replication_applier_status_by_coordinator、replication_connection_status。工作中需要注意结合这些表的使用更好的排查问题。
原文链接:https://www.cnblogs.com/coygfly/p/17361132.html
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