[Dovecot] A few rc17 imap crashes

[Chris Wakelin]

Timo Sirainen wrote:
> On Thu, 2007-01-11 at 21:32 +0000, Chris Wakelin wrote:
>>> dovecot: Jan 11 11:39:59 Info: IMAP 5751 xxxxxxxx xxx.xxx.xxx.xxx : Opened Sent (18 msgs)
>>> dovecot: Jan 11 11:39:59 Error: child 5751 (imap) killed with signal 11
>>> dovecot: Jan 11 12:28:49 Info: IMAP 12765 xxxxxxxx xxx.xxx.xxx.xxx : Disconnected: Internal error occurred. Refer to server log for more information. [2007-01-11 12:28:49]
>>> dovecot: Jan 11 12:28:49 Error: child 12765 (imap) killed with signal 10
> 
> Didn't it log the internal error?

Sorry, yes, it was:
Corrupted Index file <path>/.imap/Gloria/dovecot.index: Record [2].uid=0

I've had four of these between 11th-15th January, all for different
folders/users, not always "Record [2]" but all of them had "uid=0".

...

> 
> These are all from malloc/free, which means there's memory corruption,
> which is bad. :( It can't really be debugged from the backtraces, since
> the actual bug could have occurred long before it crashed.
> 
> Do these happen for different users or only for a couple of users? Do
> the crashed users have unusually large mailboxes?

They seem to happen only the once for 3 or 4 different users each day. I
guess they're caused by corrupt indexes left over from the earlier
version of Dovecot. I don't think the folders are particularly large.
I'll look at restoring the relevant index files and folders from backup
for some of the users (i.e. before they were fixed by the new Dovecot)
and seeing if I can reproduce the crashes. We only backup some of the
indexes though (those not stored on a separate partition).

> Could you run Dovecot with this:
> http://dovecot.org/patches/debug/memdebug-bof.diff
> I don't think it'll affect performance much. Only the imap binary needs
> to be compiled with it.
> 
> There's also this patch:
> http://dovecot.org/patches/debug/memdebug-delayed.diff
> But it does hurt performance and probably makes Dovecot use a lot more
> memory, so it's useful only if you can run it only for a couple of users
> who have crashing problems (make mail_executable to be a script which
> checks the username and based on that executes different imap binary).

I'd rather not do these to the live server, but if I manage to reproduce
the crashes as above, I'll certainly do it.

Best Wishes,
Chris

-- 
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Christopher Wakelin,                           c.d.wakelin at reading.ac.uk
IT Services Centre, The University of Reading,  Tel: +44 (0)118 378 8439
Whiteknights, Reading, RG6 2AF, UK              Fax: +44 (0)118 975 3094