Details
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Task
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Status: Open (View Workflow)
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Major
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Resolution: Unresolved
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None
Description
In a Galera Cluster environment, sometimes it can be useful to look at SHOW PROCESSLIST and SHOW ENGINE INNODB STATUS output to try to determine what the WSREP slave thread is currently doing. Unfortunately, since the thread is not actually executing raw SQL, some of the information shown isn't very useful for trying to determine what transaction is currently being executed. For example, you might see something like this in SHOW PROCESSLIST:
Id: 2
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User: system user
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Host:
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db: NULL
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Command: Sleep
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Time: 0
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State: Update_rows_log_event::find_row(442082)
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Info: NULL
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Progress: 0.000
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And you might see something like this in SHOW ENGINE INNODB STATUS:
---TRANSACTION 6372971, ACTIVE 1435 sec starting index read
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mysql tables in use 1, locked 1
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1572723 lock struct(s), heap size 224818728, 20603597 row lock(s), undo log entries 20659529
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MySQL thread id 2, OS thread handle 0x7fbf52b22b00, query id 4979324 Update_rows_log_event::find_row(442082)
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Trx #rec lock waits 0 #table lock waits 0
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Trx total rec lock wait time 0 SEC
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Trx total table lock wait time 0 SEC
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If the user wanted to try to match this specific transaction to another transaction in the master's binary log, this information doesn't really help the user does that. For WSREP slave threads, maybe it would be worth printing in SHOW PROCESSLIST and SHOW ENGINE INNODB STATUS the "Xid" or GTID of the transaction? e.g. see the "Xid" and GTID values in the mysqlbinlog output below:
# at 463
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#170110 17:55:58 server id 1 end_log_pos 501 GTID 1-1-11 trans
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/*!100001 SET @@session.gtid_seq_no=11*//*!*/;
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BEGIN
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/*!*/;
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# at 501
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#170110 17:55:58 server id 1 end_log_pos 545 Table_map: `db1`.`tab` mapped to number 18
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# at 545
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#170110 17:55:58 server id 1 end_log_pos 584 Write_rows: table id 18 flags: STMT_END_F
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BINLOG '
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fmZ1WBMBAAAALAAAACECAAAAABIAAAAAAAEAA2RiMQADdGFiAAIDDwIyAAI=
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fmZ1WBcBAAAAJwAAAEgCAAAAABIAAAAAAAEAAgP8AQAAAARzdHIx
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'/*!*/;
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### INSERT INTO `db1`.`tab`
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### SET
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### @1=1
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### @2='str1'
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# at 584
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#170110 17:55:58 server id 1 end_log_pos 611 Xid = 11
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COMMIT/*!*/;
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