MySQL Bugs: #70410: DDL queries increases rpl_semi_sync_master_yes

Bug #70410	DDL queries increases rpl_semi_sync_master_yes_tx by a value of 2
Submitted:	24 Sep 2013 18:49	Modified:	27 Nov 2013 17:03
Reporter:	Santosh Praneeth Banda	Email Updates:
Status:	Closed	Impact on me:	None
Category:	MySQL Server: Replication	Severity:	S3 (Non-critical)
Version:	mysql 5.6.13, 5.6.14	OS:	Any
Assigned to:		CPU Architecture:	Any

Description:
see how to repeat

How to repeat:
1) Install semisync master and slave plugin on both master and slave
2) use test; create table t1 (a int);
3) check out the output of show status like 'rpl_semi_sync_master_yes_tx'; rpl_semi_sync_master_yes_tx increased by 2

Suggested fix:
It seems semisync master plugin is called twice in case of DDL queries

Hello Santosh,

Thank you for the bug report and test case.
Verified as described.

Thanks,
Umesh

Fixed in 5.6+. Noted as follows in the 5.6.16 and 5.7.4 changelogs:

        The semisynchronous replication plugin was called twice for a
        DDL statement, incrementing rpl_semi_sync_master_yes_tx by 2
        instead of 1 each time such a statement was executed.

Closed.

5.6$ bzr log -r 5652
------------------------------------------------------------
revno: 5652
committer: Luis Soares <luis.soares@oracle.com>
branch nick: mysql-5.6
timestamp: Wed 2013-11-27 09:19:19 +0000
message:
  BUG#17509011: DDL QUERIES INCREASES RPL_SEMI_SYNC_MASTER_YES_TX 
  BY A VALUE OF 2
  
  The problem is that the after_commit hook is being called twice during
  the DDL execution: first on the COMMIT stage of the binlog group
  commit procedure (MYSQL_BIN_LOG::process_after_commit_stage_queue) and
  a second time during the transaction implicit commit
  (trans_commit_implicit). And this happens even though the first time
  the hook is called, the flag transaction->run_hooks is set to false.
  
  The smallest and quickest fix for this issue is to deploy checks when
  we call the after_commit hook, to verify that we have not called the
  hook already during this "transaction" lifecycle.