pt-table-checksum, replication filters

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1

Hi all,

I’m getting an error with pt-table-checksum.

Cannot checksum with --replicate because replication filters are set on these hosts:
P=3306,S=/var/lib/mysql/mysql.sock,h=localhost,p=…,u=root
replicate_ignore_table = prod_thr.semaphore
P=3306,S=/var/lib/mysql/mysql.sock,h=pldnyi05.pgmedia.org,p= …,u=root
replicate_ignore_table = prod_thr.semaphore
P=3306,S=/var/lib/mysql/mysql.sock,h=10.17.33.72,p=…,u=roo t
replicate_ignore_table = prod_aw.semaphore
Please read the --check-replication-filters documentation to learn how to solve this problem. at /usr/bin/pt-table-checksum line 5315.

From the docs it is clear that this is caused by a replication filter. Yes I just added one for a SINGLE table, the drupal semaphore table. It’s MyISAM and periodically (maybe once a month or so) we find replication dying due to this table. Since it doesn’t need to replicate, we use a replicate_ignore_table option in our my.cnf file.

Unfortunately it has broken our pt-table-checksum checks, which I REALLY want to have in place.

How risky is this --nocheck-replication-filters flag? What exactly does it do?

If the ONLY replication filter I have in place is this one rule to ignore the semaphore table, could that introduce serious problems? Obviously I don’t want replication to break because of pt-table-checksum gathering on the master.

Thoughts?

Thx in advance!

-Sean

2

The option is there to scare you into making sure you will be safe. We’d rather you are scared than that you blame us for breaking replication :slight_smile:

Without knowing exact details about your replication topology I can’t give firm advice, but you shouldn’t have any trouble knowing if this is unsafe. You should be able to pass the --ignore-tables option to the tool and then disable the check.

3

Thx Baron. For the tool and the reply!

I have no idea how you find the time to do all the stuff you do.

PS: Just received your new book from Amazon. I’m 150 pages into it. Full of useful nuggets on every page. Will have a review of it posted soon enough.

Cheers!
-Sean