Re: Squid opens too much icap connections

From: Alex Rousskov <>
Date: Tue, 02 Mar 2010 22:49:26 -0700

On 03/01/2010 02:05 AM, akinf wrote:
> I have implemnted a icap server, and configured squid to forward request to
> this server.
> Everything works fine but, Squid opens too much icap connections and exhaust
> my filedescriptors.
> I upgraded my squid to latest version Squid Cache: Version
> Bu it still opens too much icap connections, Sometimes i see in log files ,
> such a warning
> 2010/02/28 00:32:31| okToAccept: WARNING! Your cache is
> running out of filedescriptors

> I configured squid to use persistent_connections on but it did not help.

When connection establishment time is relatively small, persistent ICAP
connections cannot reduce the number of open concurrent connections by
much and may even increase it.

> Can you please help.

How many ICAP connections do you observe? What is your HTTP request
rate? What is your ICAP service response time? What is your hit ratio?
Do you use REQMOD and RESPMOD for all HTTP messages?

How do you define "too much"? In other words, why do you think Squid
should open less ICAP connections?

It is difficult to come up with a good generic formula for the number of
ICAP connections that Squid should open because the answer depends on
many factors such as icap_service ACLs, hit ratio, and ICAP service
response time.

Please note that Squid does not honor ICAP Max-Connections response
header but even if that [rather complex!] feature is added, it is of
little help in this context unless you are OK with some HTTP messages
not being sent to your ICAP service due to the connection limit.

Received on Wed Mar 03 2010 - 05:49:33 MST

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