RE: Replication check script

(No, I don't have a script, but...)

1. SHOW SLAVE STATUS tells you if both threads are running -- important. Checking how far behind each thread is is messy, but sometimes useful. Also, last-err tells you if repl is stuck due to corruption.
2. Tough one. You should alter your application to avoid such.

There have been times when SLAVE STOP; SLAVE STOP; was all it took to get a stuck slave going again. Never figured out what the cause was.

> -----Original Message-----
> From: Matt Juszczak [mailto:matt@atopia.net]
> Sent: Friday, August 10, 2007 8:49 AM
> To: replication@lists.mysql.com
> Subject: Replication check script
>
> Does anyone have a decent replication check script that
> checks the following:
>
> A) Does multiple polls to verify exec_master_log_pos and
> relay_master_log_pos are changing, so that, even if
> replication is behind,
> we still know that it is actually working (IE: I've seen
> seconds behind
> master as 0 because the slave lost connection to the master
> but didn't
> actually know it. Checking exec_master_log_pos verifies that
> indeed, the
> replication aspect of things is working, even if its behind.
>
> B) Can tell the difference between replication actually being behind
> (lagging behind) and the times of replication being behind
> because of a
> slow running query or a locked query on the slave (As in, the
> SQL thread
> and I/O threads are working fine, but they are just waiting
> for a query on
> the slave to finish, so seconds behind master is showing a 10 or 15
> second value, but as soon as the query is done, replication
> catches up: in
> my opinion, this is only something to warn about, not take
> replication
> down for).
>
> Thanks,
>
> Matt
>
>
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