[Dovecot] Dovecot hangs randomly

[Timo Sirainen]

On Thu, 2005-07-28 at 12:19 -0400, Jacob Elder wrote:
> I have been run into a weird problem with dovecot. We have 4  
> identical servers running dovecot, serving both IMAP and POP3  
> clients. Every few hours, clients start timing out after the PASS  
> command. Here is what the process tree looks like at that time:
> 
>   6718 ?        Ss     0:00 /usr/sbin/dovecot
> 6719 ?        S      0:00  \_ dovecot-auth
> 6881 ?        S      0:00  |   \_ dovecot-auth
> 6883 ?        S      0:00  |   \_ dovecot-auth
> 6890 ?        S      0:00  |   \_ dovecot-auth
> 6928 ?        S      0:00  |   \_ dovecot-auth
> 6929 ?        S      0:00  |   \_ dovecot-auth
> 6934 ?        S      0:00  |   \_ dovecot-auth
> 6936 ?        S      0:00  |   \_ dovecot-auth
> 6939 ?        S      0:00  |   \_ dovecot-auth
..
> If I run "killall -9 dovecot-auth pop3-login; invoke-rc.d dovecot  
> start", service resumes for a few hours. This happens both on 2.6.8  
> and 2.4.27. This is Debian testing, 512 MB RAM, about 20 users per  
> server. We use libnss-ldap and libpam-ldap for all users other than  
> root. Samba, SSH, saslauthd (for Postfix), login, etc all work as  
> expected. There is a 5th server that is identical to the other 4  
> except is NOT using libpam-ldap, and dovecot does not hang on this  
> machine. Any ideas?

Looks like you have several dovecot-auth processes hanging there.
Dovecot creates a new process for each PAM lookup, so that's probably
the reason. You could try to check with strace what those dovecot-auth
processes are doing? I guess Dovecot should itself also do some
timeouting and start killing PAM processes if they don't finish within a
minute..

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