Re: [squid-users] why three connection attemps to the same IP ?

On 2/6/10, Amos Jeffries <squid3_at_treenet.co.nz> wrote:
> Adrian Buciuman wrote:
> > Hi,
> >
> > Running squid 2.6 STABLE 21 from Centos 5.
> >
> > I've seen a issue with a site. The problem is that the browser locks
> > for some time, and only afterwards the user is able to interact with
> > the site. (The site has Flash based content or something similar). My
> > feeling is that this annoying delay is bigger when using squid than
> > when using direct connection to Internet. I believe the browser is
> > waiting for some tracking/adware gifs to load, and the webserver is
> > down. If using direct connection, the connection to the ads-server
> > will timeout in 20-30 seconds, the browser will display a
> > gif-placeholder, and the user can happily use the site (or they can
> > reload the page to see all the ads :-) ). If using squid, the timeout
> > will occur after a longer time.
> >
> > I've used tcpdump to find how is squid managing timeouts and retries.
> > Is looks squid is retrying a TCP connection to the origin webserver
> > for 3 times.This retry happens even if the webserver has only one IP.
> > Each of the three connection attempts consists of multiple SYN sent.
> > In the default config, Squid will return a failure to the browser
> > after 3 minutes (connect_timeout is set to 1 minute)
> >
>
> Lucky you. Squid-2.6 tries 10 times. But something is timing it out before
> all 10 are completed.

It tries only 3 times because of the fix for this:
http://bugs.squid-cache.org/show_bug.cgi?id=14

I'll use wireshark to find out how are the Firefox and IE handling
timeouts, especially for sites with multiple IPs. If their behavior
differs significantly from that of Squid, I'll open a bug report about
this. Users should not see a lack of responsiveness when their network
is switch from direct access to proxy-based access to the Internet.

Adrian Buciuman
Received on Fri Feb 19 2010 - 15:21:50 MST