1.背景概述

在一次主從復制架構中，由于主節點binlog損壞，導致從節點無法正常同步數據，只能重做從節點；因此使用MySQL 8.0.17開始提供的clone技術進行恢復，恢復后的2天都發生了主從報錯數據沖突。

通過解析binlog發現，同一時刻主從節點都在執行同一條語句，因此詢問業務是否在主從節點都執行了定時任務，業務回復定時任務只在主節點執行。

最后排查發現，克隆后的從節點的定時任務也會是開啟的狀態，因此同一時刻，主從節點同時執行定時任務，導致主從報錯，最終將從節點的定時任務關閉后解決此問題。

2.問題復現

本次測試基于 GreatSQL 8.0.32-24

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greatsql>?SELECT?VERSION();
+-----------+
|?VERSION()?|
+-----------+
|?8.0.32-24?|
+-----------+
1?row?in?set?(0.00?sec)

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1.搭建一套主從架構

略

2.創建event

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greatsql>?create?database?test;
greatsql>?use?test;
greatsql>?CREATE?TABLE?`test`?(
?`id`?int(11)?unsigned?NOT?NULL?AUTO_INCREMENT?COMMENT?'ID',
?`now`?datetime?DEFAULT?NULL?COMMENT?'時間',
?PRIMARY?KEY?(`id`)
);

greatsql>?CREATE?EVENT?event_test?
ON?SCHEDULE?EVERY?1?MINUTE
ON?COMPLETION?PRESERVE?
ENABLE?
COMMENT?'每隔1分鐘向test表插入記錄'
DO?INSERT?INTO?test?VALUES(NULL,?now());

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3.查看event狀態

主節點，默認情況下event狀態為 ENABLED

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greatsql>?show?events;
+------+------------+---------+-----------+-----------+------------+----------------+----------------+---------------------+------+---------+------------+----------------------+----------------------+--------------------+
|?Db??|?Name????|?Definer?|?Time?zone?|?Type????|?Execute?at?|?Interval?value?|?Interval?field?|?Starts????????|?Ends?|?Status??|?Originator?|?character_set_client?|?collation_connection?|?Database?Collation?|
+------+------------+---------+-----------+-----------+------------+----------------+----------------+---------------------+------+---------+------------+----------------------+----------------------+--------------------+
|?test?|?event_test?|?root@%??|?SYSTEM???|?RECURRING?|?NULL????|?1????????|?MINUTE?????|?2023-10-12?17:11:14?|?NULL?|?ENABLED?|??????1?|?utf8mb4????????|?utf8mb4_unicode_ci??|?utf8mb4_unicode_ci?|
+------+------------+---------+-----------+-----------+------------+----------------+----------------+---------------------+------+---------+------------+----------------------+----------------------+--------------------+
1?row?in?set?(0.00?sec)

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從節點，默認情況下event狀態為 SLAVESIDE_DISABLED

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greatsql>?show?events;
+------+------------+---------+-----------+-----------+------------+----------------+----------------+---------------------+------+--------------------+------------+----------------------+----------------------+--------------------+
|?Db??|?Name????|?Definer?|?Time?zone?|?Type????|?Execute?at?|?Interval?value?|?Interval?field?|?Starts????????|?Ends?|?Status???????|?Originator?|?character_set_client?|?collation_connection?|?Database?Collation?|
+------+------------+---------+-----------+-----------+------------+----------------+----------------+---------------------+------+--------------------+------------+----------------------+----------------------+--------------------+
|?test?|?event_test?|?root@%??|?SYSTEM???|?RECURRING?|?NULL????|?1????????|?MINUTE?????|?2023-10-12?17:11:14?|?NULL?|?SLAVESIDE_DISABLED?|??????1?|?utf8mb4????????|?utf8mb4_unicode_ci??|?utf8mb4_unicode_ci?|
+------+------------+---------+-----------+-----------+------------+----------------+----------------+---------------------+------+--------------------+------------+----------------------+----------------------+--------------------+
1?row?in?set?(0.00?sec)

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4.查看數據

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greatsql>?select?*?from?test.test;
+----+---------------------+
|?id?|?now?????????|
+----+---------------------+
|??1?|?2023-08-08?1639?|
|??2?|?2023-08-08?1639?|
|??3?|?2023-08-08 1639?|
+----+---------------------+
3?rows?in?set?(0.00?sec)

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5.從節點進行克隆

# 安裝克隆插件，主從節點都需要

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greatsql>?install?plugin?clone?soname?'mysql_clone.so';

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# 從節點進行clone

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greatsql>?set?global?clone_valid_donor_list='172.17.137.162:6001';

greatsql>?clone?instance?from?root@'172.17.137.162':6001?identified?by?'greatsql';

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6.重新建立主從復制

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greatsql>?change?master?to?master_user='root',master_password='greatsql',master_host='172.17.137.162',master_port=6001,master_auto_position=1;
Query?OK,?0?rows?affected,?7?warnings?(0.04?sec)

greatsql>?start?slave;
Query?OK,?0?rows?affected,?1?warning?(0.04?sec)

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7.查看主從狀態

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greatsql>?show?slave?statusG
***************************?1.?row?***************************
???????????????Slave_IO_State:?Waiting?for?source?to?send?event
??????????????????Master_Host:?172.17.137.162
??????????????????Master_User:?root
??????????????????Master_Port:?6001
????????????????Connect_Retry:?60
??????????????Master_Log_File:?binlog.000001
??????????Read_Master_Log_Pos:?2959
???????????????Relay_Log_File:?relaylog.000002
????????????????Relay_Log_Pos:?395
????????Relay_Master_Log_File:?binlog.000001
?????????????Slave_IO_Running:?Yes
????????????Slave_SQL_Running:?No
??????????????Replicate_Do_DB:?
??????????Replicate_Ignore_DB:?
???????????Replicate_Do_Table:?
???????Replicate_Ignore_Table:?
??????Replicate_Wild_Do_Table:?
??Replicate_Wild_Ignore_Table:?
???????????????????Last_Errno:?1062
???????????????????Last_Error:?Coordinator?stopped?because?there?were?error(s)?in?the?worker(s).?The?most?recent?failure?being:?Worker?1?failed?executing?transaction?'e8bf88f9-2acd-11ee-a98a-00163e605c74:8'?at?master?log?binlog.000001,?end_log_pos?2606.?See?error?log?and/or?performance_schema.replication_applier_status_by_worker?table?for?more?details?about?this?failure?or?others,?if?any.
?????????????????Skip_Counter:?0
??????????Exec_Master_Log_Pos:?2307
??????????????Relay_Log_Space:?1242
??????????????Until_Condition:?None
???????????????Until_Log_File:?
greatsql>?select?*?from?performance_schema.replication_applier_status_by_worker?limit?1G
***************************?1.?row?***************************
???????????????????????????????????????????CHANNEL_NAME:?
??????????????????????????????????????????????WORKER_ID:?1
??????????????????????????????????????????????THREAD_ID:?NULL
??????????????????????????????????????????SERVICE_STATE:?OFF
??????????????????????????????????????LAST_ERROR_NUMBER:?1062
?????????????????????????????????????LAST_ERROR_MESSAGE:?Worker?1?failed?executing?transaction?'e8bf88f9-2acd-11ee-a98a-00163e605c74:8'?at?master?log?binlog.000001,?end_log_pos?2606;?Could?not?execute?Write_rows?event?on?table?test.test;?Duplicate?entry?'5'?for?key?'test.PRIMARY',?Error_code:?1062;?handler?error?HA_ERR_FOUND_DUPP_KEY;?the?event's?master?log?FIRST,?end_log_pos?2606
???????????????????????????????????LAST_ERROR_TIMESTAMP:?2023-08-08?1639.033240
???????????????????????????????LAST_APPLIED_TRANSACTION:?
?????LAST_APPLIED_TRANSACTION_ORIGINAL_COMMIT_TIMESTAMP:?0000-00-00?0000.000000
????LAST_APPLIED_TRANSACTION_IMMEDIATE_COMMIT_TIMESTAMP:?0000-00-00?0000.000000
?????????LAST_APPLIED_TRANSACTION_START_APPLY_TIMESTAMP:?0000-00-00?0000.000000
???????????LAST_APPLIED_TRANSACTION_END_APPLY_TIMESTAMP:?0000-00-00?0000.000000
???????????????????????????????????APPLYING_TRANSACTION:?e8bf88f9-2acd-11ee-a98a-00163e605c74:8
?????????APPLYING_TRANSACTION_ORIGINAL_COMMIT_TIMESTAMP:?2023-08-08?1645.795753
????????APPLYING_TRANSACTION_IMMEDIATE_COMMIT_TIMESTAMP:?2023-08-08?1645.795753
?????????????APPLYING_TRANSACTION_START_APPLY_TIMESTAMP:?2023-08-08?1639.032510
?????????????????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?0000.000000
?????????????????????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?0000.000000
1?row?in?set?(0.00?sec）

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可以看到從節點報錯發生了主鍵沖突。

8.查看從節點定時任務狀態

當前從節點定時任務狀態為 ENABLED

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greatsql>?show?events;
+------+------------+---------+-----------+-----------+------------+----------------+----------------+---------------------+------+---------+------------+----------------------+----------------------+--------------------+
|?Db??|?Name????|?Definer?|?Time?zone?|?Type????|?Execute?at?|?Interval?value?|?Interval?field?|?Starts????????|?Ends?|?Status??|?Originator?|?character_set_client?|?collation_connection?|?Database?Collation?|
+------+------------+---------+-----------+-----------+------------+----------------+----------------+---------------------+------+---------+------------+----------------------+----------------------+--------------------+
|?test?|?event_test?|?root@%??|?SYSTEM???|?RECURRING?|?NULL????|?1????????|?MINUTE?????|?2023-08-08?15:58:45?|?NULL?|?ENABLED?|??????1?|?utf8mb4????????|?utf8mb4_unicode_ci??|?utf8mb4_unicode_ci?|
+------+------------+---------+-----------+-----------+------------+----------------+----------------+---------------------+------+---------+------------+---------------------+----------------------+--------------------+
1?row?in?set?(0.00?sec)

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可以看到由于從節點的定時任務也執行了，從節點寫入數據，導致主鍵沖突。

9.故障解決

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greatsql>?alter?event?event_test?DISABLE;
Query?OK,?0?rows?affected?(0.01?sec)

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關閉從節點的定時任務event，然后跳過主鍵沖突的報錯，最后重新啟動主從復制。

3.總結

1.如果主庫有定時任務，通過clone的方式搭建從庫，在從庫恢復之后需要關閉定時任務，避免主從同時執行定時任務導致主從故障。

2.克隆時，如果捐贈節點有主從復制信息，則克隆后的接收節點也會克隆此復制信息，并在克隆完成自動重啟實例后，自動啟動復制；避免此問題可以在接收節點的配置文件中增加 skip-slave-start，避免節點重啟后自動啟動復制。

編輯：黃飛

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