Re: [squid-users] running out of filedescriptors

From: Amos Jeffries <squid3_at_treenet.co.nz>
Date: Wed, 27 Jan 2010 23:12:05 +1300

Mike Rambo wrote:
> Landy Landy wrote:
>>
>> --- On Tue, 1/26/10, Mike Rambo <mrambo_at_lsd.k12.mi.us> wrote:
>>
>>> From: Mike Rambo <mrambo_at_lsd.k12.mi.us>
>>> Subject: Re: [squid-users] running out of filedescriptors
>>> To: "Landy Landy" <landysaccount_at_yahoo.com>
>>> Cc: "Squid-Users" <squid-users_at_squid-cache.org>
>>> Date: Tuesday, January 26, 2010, 11:48 AM
>>> Landy Landy wrote:
>>>> I restarted squid and it comes up ok. But I still
>>> get:
>>>> With 1024 file descriptors available
>>>>
>>>> 2010/01/26 10:27:43| Starting Squid Cache version
>>> 3.0.STABLE20 for i686-pc-linux-gnu...
>>>> 2010/01/26 10:27:43| Process ID 2768
>>>> 2010/01/26 10:27:43| With 1024 file descriptors
>>> available
>
> (SNIP)
>
>>>>
>>>>
>>>>
>>> Unless I'm totally missing it there isn't anything in this
>>> particular log that indicates a shortage of file
>>> descriptors. I do notice your redirectors are exiting
>>> though. I'd suggest running squid without the redirector
>>> just to see if the cache itself will stay up and process
>>> traffic that way. If it does it implies the problem is with
>>> the redirector.
>>>
>>> If you actually *are* running out of file descriptors and
>>> it just isn't identified in this particular log, and if you
>>> can't do anything with ulimit and recompiling squid to use
>>> more FD's as others have suggested, you can try setting
>>> persistent connections to off as that will reduce the FD
>>> pressure on squid.
>>>
>>> server_persistent_connections off
>>> client_persistent_connections off
>>>
>>
>> This actual log doesnt show any error since is a new reboot and squid
>> doesn't have any problems after a reload. The actual error is on a
>> previous post.
>>
>> Now, which are the pros and cons of enabling
>> server_persistent_connections on
>> client_persistent_connections on
>>
>
> They are enabled by default. We have had them disabled (at Henrik's
> suggestion) for several years now because of that exact FD problem when
> we first deployed squid. Since that original deployment we have
> increased the file descriptor pool to 4096 and for all I know may not
> have the FD problem at all any more but we've never re-enabled the
> persistent connections to see.

IIRC 2.x had a few minor issues around releasing or holding persistent
connections. 3.x handles them better according to RFC. But whether that
balances more to pro or con I'm not certain.

Pro:
   greatly reduces the number of FD used and TCP handshake delays when
talking to a client or server.

Cons:
  greatly increases the number of server FD left open after contact is
done and before a close timeout has happened on the server.

Amos

-- 
Please be using
   Current Stable Squid 2.7.STABLE7 or 3.0.STABLE21
   Current Beta Squid 3.1.0.15
Received on Wed Jan 27 2010 - 10:12:19 MST

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