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From:Johan De Meersman Date:May 24 2011 4:25pm
Subject:Re: After long semaphore waits MySQL becomes unresponsive.
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----- Original Message -----
> From: "Rik Wasmus" <rik@stripped>
> 
> OK, but that would mean that the answer to the question:
> 
> "I may be wrong here, but I tend to interpret this as
> '140054029002496' is trying to get an exclusive lock on 0x78733f8, on which it
> already has
> an exclusive lock, and hence is deadlocked in some manner" is  'no there
> is another query' (i.e.: it isn't locked on mistakingly acquiring a lock
> it already has) rather then 'that seems likely' :)

Ah, misread that. Yes, the former behaviour seems more like a bug; which is not entirely
impossible of course.

> And in my case, the server became unusable (kept running into
> semaphore locks at 769 seconds before a kill & start was given). Query timeouts
> /
> crashes I can live with, an unresponsive server I cannot...

Which is what kind of mystifies me - it should detect deadlocks as soon as they happen.

> OK, let's hope I never get to show that output (i.e: that the problem
> doesn't reoccur). Since the server has been restarted since-start counters
> will probably be pretty useless.

Yups. A trending database (munin, cacti or something) may or may not offer much hindsight
in this case (mostly a matter of luck at when it last checked); but it's definitely
something useful to have at hand for plenty of other purposes.

> Yup, right there it did, And that's the way I like it: kill the/a
> query, which issues an error somewhere else we know if and how to handle in some
> application, rather then letting a database server with a light load
> grind to a halt.
> 
> My main problem at hand is why the server did nothing but seize up
> gracelessly, rather then either dying (a last resort, but something
> we have failovers for) or killing queries (which we can handle).

Uhuh. You may want to take this to the mysql-dev mailinglist, the good people there might
have a bit more insight about the error runes you posted.


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Is als mosterd by den wyn
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Thread
After long semaphore waits MySQL becomes unresponsive.rik24 May
  • Re: After long semaphore waits MySQL becomes unresponsive.Johan De Meersman24 May
    • Re: After long semaphore waits MySQL becomes unresponsive.Rik Wasmus24 May
      • Re: After long semaphore waits MySQL becomes unresponsive.Johan De Meersman24 May
        • Re: After long semaphore waits MySQL becomes unresponsive.Rik Wasmus24 May
          • Re: After long semaphore waits MySQL becomes unresponsive.Johan De Meersman24 May
            • Re: After long semaphore waits MySQL becomes unresponsive.Rik Wasmus25 May
              • Re: After long semaphore waits MySQL becomes unresponsive.Johan De Meersman25 May
                • Re: After long semaphore waits MySQL becomes unresponsive.Rik Wasmus25 May
                  • Re: After long semaphore waits MySQL becomes unresponsive.Johan De Meersman25 May