[Dovecot] Corrupted index cache file and high CPU usage

[Timo Sirainen]

On 21.12.2011, at 18.38, hydra wrote:

> I suspect, that dovecot v2.0.16 under Linux (tested on Gentoo 3.0.4
> Hardened, Gentoo 3.0.6, Gentoo 3.1.4) causes 100% cpu utilization when
> index.cache is broken and doveadm is lanched. Dovecot uses LDAP as the
> userdb and provides IMAP and LDA. Because each user has a quota, the
> doveadm's expunge functionality is used to get rid of old trashed mail.
> 
> The mail log:
> Dec 12 07:38:59 www dovecot: imap(user): Error: Corrupted index cache file
> /var/data/mail/domain.tld/user/mail/dovecot.index.cache: invalid record size

OK..

> Mail is stored on ext4 and flush will use all of the CPU capacity like this:
> load average: 4.00, 4.01, 4.05
> 
> ps:
> root     26401 98.2  0.0      0     0 ?        R    Dec20 1369:49
> [flush-253:1]

That's a kernel process..

> I suspect, that this is something to do with Dovecot, because after
> deleting the dovecot.index.cache file, everything went back to normal. When
> this happens, I cannot unmount the drive nor a system reboot works.

That's a kernel bug..

I think you're thinking it the wrong way: Dovecot isn't causing your system to break. Your system is causing Dovecot to break. Faulty hardware or faulty kernel.