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I have two mysql servers setup with default my.cnf config apart from server-id's and enabling binlogs on masters. Replication is setup and working and i have a simple bash scrip on master feeding in random data.

I am testing a script which stops and starts the replication periodically on the slave. The script records the Exec_Master_Log_Pos value and master binlog which will be used with the next CHANGE MASTER TO..

The problem i have is, if i poll the SHOW SLAVE STATUS every second i have noticed that during binlog rotation on the master i see the Read_Master_Log_Pos jumping very high, far to high to be actual written data to master which in turn seems to cause a knock on affect to the Exec_Master_Log_Pos so that is also wrong. So when i log this value and use it in the next CHANGE MASTER i get errors on slave about impossible position.

Interestingly at the same time of polling SHOW SLAVE i also log the output of SHOW MASTER STATUS and i don't see the same wrong binlog or position reported so it seems to be a slave thing only.

So my question is, does anyone know of recent bugs in mysql that could cause this? Is there a my.cnf setting i can magically enable to prevent this from happening or has anyone seem similar behavior as this?

This is running on Debian Wheezy 7.0 with MySQL 5.5.31.

Thanks Scott

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That might be a bug, though it's not clear why you would want to reposition the slave in a setup that is working. Are both the master and the slave both 5.5.31? When do you see the incorrect values -- after stopping the slave or before? What's an example of the "too high" value? Insanely out of range? Could it be the end of the previous log? Are you using any of the replicate-* options to limit what replicates, or are you replicating everything (the default)? –  Michael - sqlbot Oct 22 '13 at 2:18
Hi, yes both are on 5.5.31 and the incorrect values occur/are logged after stopping slave either via STOP SLAVE or independently via STOP SLAVE IO_THREAD and STOP SLAVE SQL_THERAD. I don't have the logs to hand but lets say the Exec_Master_Log_Pos was 20000 then the Read_Master_Log_Pos would be 70000. So significantly different considering there were only 5 rows being added to the master every couple seconds. No replicate-* options are used.. just the default replicate everything. Thanks. –  Flo Woo Oct 22 '13 at 6:02
possibly related? bugs.mysql.com/bug.php?id=66921 –  Jonathan Nicol Feb 28 '14 at 19:37

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