[Dovecot] IMAP timeout problem

[Vasantha Narayan]

Hello,

We are running dovecot 1.1.2 on a Solaris 10 box. We have been running the same configuration for about a year without a problem. We have a different cert for POP and IMAP.

Recently we made two changes. The cert for IMAP expired and we had to install a new one. We applied some patches to the SAN disks that hosts the mail partition. These changes were made over a weekend and the system was rebooted. There were no errors in the logs and everything worked fine until the following Monday morning when IMAP connections increased. When IMAP ports started getting hammered in the morning, IMAP clients started getting "IMAP time out" errors. When this error occurs, IMAP freezes and IMAP clients such as, Thunderbird and Squirrelmail are not able to connect to the IMAP server (both IMAP and IMAPS). We cannot get a telnet connection to the IMAP port or a openssl connection to the IMAPS port. Kill -HUP of the dovecot server solves the problem. But again, when the usage increases, the problem surfaces again. There is no problem with POP or POPS. It continues to function normally while IMAP times out and freezes two or three times a day.

Any clue where the problem might be? The debug log does not have any useful pointers.

Thanks.

Vasantha

[Timo Sirainen]

Post by Vasantha Narayan
We cannot get a telnet connection to the IMAP port or a openssl
connection to the IMAPS port. Kill -HUP of the dovecot server solves
the problem. But again, when the usage increases, the problem
surfaces again. There is no problem with POP or POPS. It continues
to function normally while IMAP times out and freezes two or three
times a day.

How many imap-login processes do you have at those times? See if
changing login_* settings helps. http://wiki.dovecot.org/LoginProcess

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[Ken A]

Post by Vasantha Narayan
Hello,
We are running dovecot 1.1.2 on a Solaris 10 box. We have been
running the same configuration for about a year without a problem.
We have a different cert for POP and IMAP.
Recently we made two changes. The cert for IMAP expired and we had
to install a new one. We applied some patches to the SAN disks that
hosts the mail partition. These changes were made over a weekend and
the system was rebooted.

Do you have any baseline benchmarks for your SAN?
What does vmstat 2 or iostat -c 2 say about i/o wait?

Ken

There were no errors in the logs and

Post by Vasantha Narayan
everything worked fine until the following Monday morning when IMAP
connections increased. When IMAP ports started getting hammered in
the morning, IMAP clients started getting "IMAP time out" errors.
When this error occurs, IMAP freezes and IMAP clients such as,
Thunderbird and Squirrelmail are not able to connect to the IMAP
server (both IMAP and IMAPS). We cannot get a telnet connection to
the IMAP port or a openssl connection to the IMAPS port. Kill -HUP
of the dovecot server solves the problem. But again, when the usage
increases, the problem surfaces again. There is no problem with POP
or POPS. It continues to function normally while IMAP times out and
freezes two or three times a day.
Any clue where the problem might be? The debug log does not have any useful pointers.
Thanks.
Vasantha