Re: [squid-users] Squid behaviour with gzip responses from origin server

On 17/04/2013 8:19 p.m., anita wrote:
> Hi All,
>
> I am using Squid 3.1.16.
> I had modified the request header in Squid to include: "Accept-Encoding:
> gzip".
>
> The request is also sent to the Apache server. The server seems to even
> compress the object and return with proper headers.
>
> But the squid seems to drop the "content-encoding" header. It also seems to
> drop the content-length header.
>
> I am not able to understand why Squid replaces the Content-Encoding header
> with something else and why it was marking as internal?
>
> These are my tcpdumps for the request and response from the Apache:
>
> Request sent to Apache (tcpdump)
> ----------------------------------
> GET./compres
> s.html.HTTP/1.1.
> .User-Agent:.Wge
> t/1.12.(linux-gn
> u)..Accept:.*/*.
> .Host:.10.145.66
> .205..Referer:.h
> ttp://10.145.66.
> 205/fetchcompres
> s.html..Accept-E
> ncoding:.gzip..V
> ia:.1.1.prefetch
> .net.(squid/3.1.
> 16)..X-Forwarded
> -For:.unknown..C
> ache-Control:.ma
> x-age=259200..Co
> nnection:.keep-a
> live....
>
> Reply header as sent by Apache (tcpdump)
> HTTP/1.1.200
> .OK..Date:.Wed,.
> 17.Apr.2013.02:1
> 3:13.GMT..Server
> :.Apache/2.2.15.
> (Red.Hat)..Last-
> Modified:.Wed,.1
> 7.Apr.2013.01:21
> :00.GMT..ETag:."
> 1208df-282-4da84
> 4c80d89e"..Accep
> t-Ranges:.bytes.
> .Vary:.Accept-En
> coding..Content-
> Encoding:.gzip..
> Content-Length:.
> 125..Connection:
> .close..Content-
> Type:.text/html;
> .charset=UTF-8..
>
> Reply header (as given by Squid) after it receives data from Apache
> -----------------------------------------------------------------
> HTTP/1.0 200 Internal marker object
> Server: squid/3.1.16
> Mime-Version: 1.0
> Date: Wed, 17 Apr 2013 07:16:30 GMT
> Content-Type: x-squid-internal/vary
> Expires: Thu, 18 Apr 2013 11:03:10 GMT
> Vary: Accept-Encoding
>

This is an internal object used by Squid to manage variant caching. It
is telling Squid that future requests for this URL needs to be combined
with the clients Accept-Encoding header to determine what object to
return. With normal operation the Accept-Encoding sent to the server
would be created by the client and the server response would be stored
at the location the server request URL and Accept-Encoding headers.

I suspect that what is happening is that the client did not send any
Accept-Encoding header. Which makes the client URL plus client
Accept-Encoding header point back at this marker object instead of the
intended serve response. Please confirm that by looking at the client
request received by Squid.

Amos
Received on Wed Apr 17 2013 - 09:10:54 MDT