[Dovecot] Stale imap processes

[Renaud Allard]

Brad wrote:
> On Tue, Aug 01, 2006 at 05:38:00PM -0700, Pete Slagle wrote:
>> Fran Fabrizio wrote:
>>
>>> Anyone have any theories or experiences as to why for a certain user, 
>>> some of his imap processes hang, and stay around for days and days?  He 
>>> just reported that his Thunderbird was timing out when trying to open 
>>> folders, I looked on the server, and he had 3 old imap processes from 1 
>>> week+ ago.  I killed those and his performance immediately improved.
>>>
>>> He checks mail with Thunderbird > 1.5 from both Win and Linux, 
>>> Squirrelmail webmail, and pine.  Of those, pine is the only one that is 
>>> somewhat rare around here - any specific problems with pine's imap 
>>> client code that anyone knows about?
>>>
>>> We have been using the dovecot-1.0-0.beta2.7 rpm for Fedora Core 5, I'm 
>>> updating to 1.0-0.beta8.2.fc5 to see if that helps, as well.  Just 
>>> curious if anyone else has seen this lately.
>>>
>>> Thanks,
>>> Fran
>> I have just seen this problem, big time. I was poking around on a
>> FreeBSD 6.1 server because of Thunderbird hangs (see thread
>> "dovecot-1.0rc2 problems with Thunderbird" if you are interested), and I
>> found over 900 (!) imap process. Only two users were using the dovecot
>> server at the time.
>>
>> I restarted dovecot, but this did NOT kill the multitudinous imap
>> processes. After another restart, with a 'killall imap' in the middle,
>> things were temporarily fine, but the number of imap processes
>> immediately started to grow again. Apparently they never exit. or use
>> any CPU, but just sit around in KQREAD state, eventually getting swapped
>> out. No error messages are generated.
> 
> Stop using the kqueue support! It is broken and has never fully worked
> properly. This is a known issue if you back in the list archives.
> 

Unfortunately, I had the problem on OpenBSD with dovecot 1.0rc2. Stale
imap processes when _NOT_ using kqueue (using poll). Using kqueue solved
the problem. Not sure if it's the same on FreeBSD, but it seems that
using kqueue solves the stale processes problem both on OpenBSD and
NetBSD. On linux, kqueue doesn't produce stale imap processes either.

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