Re: [squid-users] TCP connections keep alive problem after 302 HTTP response from web

Good detective work! I'm not sure whether this is a requirement or
not. Henrik would know better.

Henrik, is this worthy of a bugzilla report?

adrian

2008/11/30 Itzcak Pechtalt <itzcak_at_gmail.com>:
> Hi
>
> I found some inefficiency in Squid TCP connection handling toward servers .
> In some cases Squid closes TCP connection to servers immediately after
> 304 not modified response and doesn't save it for reuse.
> There is no visbible reason why Squid closes the connection. Squid
> Sends "Connection: Keep-Alive" in HTTP request and the web server
> returns "Connection: Keep-Alive" on the response, Also pconn_timeout
> is configured to 1 minute.
>
> After digging into the problem, I found that the the problem occurs
> only in cases the object type is PRIVATE. It seems like when
> client_side code hadnles 304 not modified reply it calls
> store_unregister which closes store entry and TCP connection in turn.
>
> To reproduce it do the following
> 1) Browse www.cnn.com
> 2) Delete browser cache.
> 3) Browse again. The case will occur here.
>
> Does someone know about it ?
>
> Itzcak
>
> Following short Wireshark sniff with 1 sample, 10.50.0.100 is Squid
> IP. See FIN packet from Squid.
>
> 0.000000 10.50.0.100 -> 205.128.90.126 TCP 4006 > http [SYN] Seq=0
> Len=0 MSS=1460 WS=2
> 0.085216 205.128.90.126 -> 10.50.0.100 TCP http > 4006 [SYN, ACK]
> Seq=0 Ack=1 Win=5840 Len=0 MSS=1460 WS=7
> 0.085226 10.50.0.100 -> 205.128.90.126 TCP 4006 > http [ACK] Seq=1
> Ack=1 Win=5840 Len=0
> 0.085230 10.50.0.100 -> 205.128.90.126 HTTP GET
> /cnn/.element/css/2.0/common.css HTTP/1.0
> GET /cnn/.element/css/2.0/common.css HTTP/1.0
> If-Modified-Since: Tue, 16 Sep 2008 14:48:32 GMT
> Accept: */*
> Referer: http://www.cnn.com/
> Accept-Language: en-us
> UA-CPU: x86
> User-Agent: Mozilla/4.0 (compatible; MSIE 7.0; Windows NT 5.1; .NET
> CLR 2.0.50727; .NET CLR 3.0.04506.30)
> Host: i.cdn.turner.com
> Cache-Control: max-age=259200
> Connection: keep-alive
>
> 0.172250 205.128.90.126 -> 10.50.0.100 TCP http > 4006 [ACK] Seq=1
> Ack=366 Win=6912 Len=0
> 0.172934 205.128.90.126 -> 10.50.0.100 HTTP HTTP/1.1 304 Not Modified
> HTTP/1.1 304 Not Modified
> Date: Wed, 26 Nov 2008 12:33:33 GMT
> Expires: Wed, 26 Nov 2008 13:03:51 GMT
> Last-Modified: Tue, 16 Sep 2008 14:48:32 GMT
> Cache-Control: max-age=3600
> Connection: keep-alive
>
> 0.173145 10.50.0.100 -> 205.128.90.126 TCP 4006 > http [ACK] Seq=366
> Ack=206 Win=6912 Len=0
> 0.173238 10.50.0.100 -> 205.128.90.126 TCP 4006 > http [FIN, ACK]
> Seq=366 Ack=206 Win=6912 Len=0
> 0.259520 205.128.90.126 -> 10.50.0.100 TCP http > 4006 [FIN, ACK]
> Seq=206 Ack=367 Win=6912 Len=0
> 0.259906 10.50.0.100 -> 205.128.90.126 TCP 4006 > http [ACK] Seq=367
> Ack=207 Win=6912 Len=0
> 0.565702 205.128.90.126 -> 10.50.0.100 TCP http > 4006 [FIN, ACK]
> Seq=206 Ack=367 Win=6912 Len=0
> 0.565842 10.50.0.100 -> 205.128.90.126 TCP [TCP Dup ACK 10#1] 4006 >
> http [ACK] Seq=367 Ack=207 Win=6912 Len=0
>
>
Received on Sun Nov 30 2008 - 17:14:52 MST