Re: httpd_accelerator mode and virtual hosts

Dear Folks,
Henrik Nordstrom wrote:

> Nick Urbanik wrote:
>
> > 1. combine two servers (serving different material) and have them
> > appear as one machine
>
> This is done via a redirector which splits the received URL space to two
> (or more) backend URL spaces.

I guess squirm might do the job here, with squirm.local set to allow all
hosts. (Yes? No?)

> > 2. One of the web servers has a number of virtual hosts. The Squid
> > docs are very sketchy on the use of httpd_accel_host virtual.
>
> httpd_accel_host virual is when you need one Squid to accelerate
> multiple official IP servers. It is not needed for Host: based virtual
> servers.

I'm still not clear here. Does that mean that the Squid machine has a
number of IP addresses, and a request is somehow (how?) transformed into a
request to a particular web server?

> There are three relevant components here:
>
> 1. httpd_accel_host
> 2. httpd_accel_uses_host_header
> 3. The redirector process
>
> httpd_accel_uses_host_header tells Squid to look for a Host header on
> accelerated requests and use that as host part in the reconstructed URL
> if available.

I imagine that this is really the only solution (together with the
redirector, such as squirm). Yes? No?

> httpd_accel_hosts tells Squid what to use if there is no Host header
> available (or if httpd_accel_uses_host_header isn't used). If a hostname
> is configured then Squid will assume the request is for this host.

Can there be only one httpd_accel_host entry in squid.conf? If so, then
does that mean it is not possible to help me?

> If
> the word virtual is used then Squid reconstruct request URL using the IP
> addr where the request is received.

This part (httpd_accel_host virtual) I do not understand. How does Squid
reconstruct the request?

> After this URL reconstruction phase and some other steps (like access
> control) the redirector is called. The job if the redirector is to
> transform the received URL space to a URL space which Squid can in turn
> fetch and cache.

Thank you for your time, Henrik.

--
Nick Urbanik, Dept. of Electrical & Communications Engineering
Hong Kong Institute of Vocational Education (Tsing Yi)
email: nicku@vtc.edu.hk, nicku@iohk.com
Tel:   (852) 2436 8660, (825) 2436 8674   Fax: (852) 2436 8643
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