Re: [squid-users] Slow Internet with squid

 On Wed, 20 Jul 2011 11:12:04 -0400, Wilson Hernandez wrote:
> Hello.
>
> I am puzzled to see how my bandwidth is used when running squid. I
> have
> a total of 25M/3M of bandwidth, lately I've noticed with iptraf that
> my
> external interface traffic/bandwidth is almost maxed out at 24.8M and
> my
> internal interface (squid) is only at 2.9M as a result most clients
> have
> been calling saying "their internet is slow".
>
> I'm wondering why that big of a difference on the interfaces'
> traffic.
>
> This is what cachemgr shows:
>
> Squid Object Cache: Version 3.1.14
>
> Start Time: Fri, 15 Jul 2011 08:01:48 GMT
> Current Time: Wed, 20 Jul 2011 14:39:02 GMT
>
>
> Connection information for squid:
> Number of clients accessing cache: 113
> Number of HTTP requests received: 5198204
> Number of ICP messages received: 0
> Number of ICP messages sent: 0
> Number of queued ICP replies: 0
> Number of HTCP messages received: 0
> Number of HTCP messages sent: 0
> Request failure ratio: 0.00
> Average HTTP requests per minute since start: 684.2
> Average ICP messages per minute since start: 0.0
> Select loop called: 479758718 times, 0.950 ms avg
> Cache information for squid:
> Hits as % of all requests: 5min: 23.2%, 60min: 19.4%
> Hits as % of bytes sent: 5min: -219.3%, 60min: -314.7%
> Memory hits as % of hit requests: 5min: 13.2%, 60min: 9.5%
> Disk hits as % of hit requests: 5min: 64.6%, 60min: 62.5%
> Storage Swap size: 66028580 KB
> Storage Swap capacity: 64.5% used, 35.5% free
> Storage Mem size: 1042556 KB
> Storage Mem capacity: 100.0% used, 0.0% free
> Mean Object Size: 23.52 KB
> Requests given to unlinkd: 0
> Median Service Times (seconds) 5 min 60 min:
> HTTP Requests (All): 0.12106 0.02069
> Cache Misses: 0.24524 0.30459
> Cache Hits: 0.05046 0.02899
> Near Hits: 0.17711 0.22004
> Not-Modified Replies: 0.00307 0.00091
> DNS Lookups: 0.31806 0.17048

 DNS is very slow as well. Probably due to remote queries over this full
 link.

>
> Please help me understand why this is happening and if there is a
> solution to make squid perform better.

 Squid "optimizes web delivery" as the slogan goes. So when the server
 side is acting very inefficiently it can consume more than the client
 side. Could be any of these or a few other things I'm not aware of:

 1) client requests an object. Squid has it cached, but server is
 requiring 'must-revalidate'. While revalidating the server forces an
 entire new object back at squid, along with a timestamp stating it has
 not changed. Squid only sends the small no-change reply to the client.

 2a) client requests a small range of an object. Squid passes this on.
 Server replies with again, forcing an entire new object back at squid.
 Squid only sends the small range asked for to the client.

 2b) client requests a small range of an object. Squid passes this on
 but requests the full object (refresh_offset_limit). Server replies with
 the whole object. Squid stores it and only sends the small range asked
 for to the client.

 3) client requests info about an object (HEAD). Squid relays this
 request on. Server replies, forcing an entire new object back at squid.
 Squid only sends the small header asked for to the client.

 4) client requests an object, then abandons it before receiving the
 reply. Squid continues to wait and receive it, in hopes that it can be
 stored. If not storable it may be discarded and the cycle repeat. Or it
 could be stored but never again requested. This behaviour is modified by
 the quick_abort_* directives.

 Or it could be you configured an open proxy. Configuration problems can
 allow external access to external sites. When discovered attackers can
 use this and consume all your external bandwidth. Usually its caused by
 mistakenly removing or bypassing the controls on CONNECT tunnels. Though
 it can also happen on other requests.

 Amos
Received on Thu Jul 21 2011 - 01:12:45 MDT