Deadlock problem with agents,queues and PRI (stop accepting incoming calls in PRI line)

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Deadlock problem with agents,queues and PRI (st...
\ Ted Brown (23 May 2007)

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Subject:	Deadlock problem with agents,queues and PRI (stop accepting incoming calls in PRI line)
Group:	Asterisk-users
From:	Ted Brown
Date:	23 May 2007

Hi everyone,

We have a Asterisk-based call center deployment with around 40 SIP users,
attending incoming calls from two PRI lines (2xE1) using agents and queues.

The problem is that Asterisk stops accepting new incoming calls to the PRI
lines without reason, although there should be free channels to make room
for new incoming calls, but Asterisk thinks these channels are being used.
SIP calls can be placed without problemsbetween internal users.

PRI lines shouldn't be the origin of the problem, as an old legacy PBX works
perfectly with the same lines, so the problem seems to be related with
agents or queues.

After the crash, performing an "zap show channels" shows that all channels
are busy, and calls seems that have been queued for a long time in different
queues (and they are not really there - users don't wait 50 minutes to be
attended listening to the music on hold).

There is no other services running on the server, CDR is being stored to
disk and we are not using any kind of AGI's or reporting tools.

Currently the only solution is to reboot the machine, as rebooting Asterisk
is not enough. Using any command on the CLI results in no output at all.

The crash is not easily reproduceable, as it doesn't follow a clear pattern.
Asterisk just seem to get blocked when it manages around 30-40 calls in the
queues. During last week, we had 2-3 crashed each day.

Based on users lists mails, it seems that other users have had a similar
problem within the same scenario, at least with 1.2.x. More precisely, we
have observed the same problem in bug ID 0006147, but it has been closed
without a clear answer.

Hardware and software specs:

Platform: Suse Linux Enterprise Server 10
Machine: IBM xSeries 226, 1 GB RAM, Intel CPU
PRI card: Digium TE212 with echo cancellation module
Asterisk version: 1.2.18

Follows a list of the most relevant messages before and after the crash:

DEBUG[28519] chan_sip.c: Stopping retransmission on
'NzNmZWM0ZDc0OTYyNWI5YWM2ZTBhZjY3NDM4N2RjNmQ.' of Response 12: Match Found
(lots of messages like that)

DEBUG[28511] chan_zap.c: Ring requested on channel 0/13 already in use or
previously requested on span 1. Attempting to renegotiating channel.

DEBUG[28511] chan_zap.c: Found empty available channel 0/9

DEBUG[29939] app_dial.c: Exiting with DIALSTATUS=CONGESTION.

I would very appreciate any help on this. I can provide backtrace if needed.

Best regards,

Ted.

--
Ted Brown
tedbrown75 REMOVE_THIS gmail.com

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