Re: httpd_accelerator mode and virtual hosts

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.

> 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.

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.

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

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.

--
Henrik Nordstrom
Spare time Squid hacker