Mailing List Archive

As promised, here is a proposal for a new definition of what varnish is for the FAQ (links in <>, changes in bold, comments in []). I did compile some mails exchanged the last days on varnish-dev, credit for this goes to many people.

My mother tongue not being english, there might be quite a few spelling/grammatical errors.

What is varnish ? [new]

Varnish is a HTTP accelerator : a high performance HTTP server to be put in front of a slow one (like apache) to speed up an existing website. Rather than a true reverse proxy (as in <RFC2616>), varnish is a "HTTP surrogate", as defined in the <Edge Architecture Specification> w3c draft. Varnish can be very easily adapted to any website, and <become a reverse proxy> with a few lines of configuration [link to the section in the FAQ, below].

Why bother with Varnish - why not use Squid ? [modified]

Varnish was written from the ground up to be a high performance HTTP accelerator. Squid is a forward proxy that can be configured as a reverse proxy, that, as a side effect, can provide HTTP accelerating features. Besides - Squid is rather old, bloated and designed like computer programs where supposed to be designed in 1980. Please see <ArchitectNotes <http://varnish.projects.linpro.no/wiki/ArchitectNotes> > for details.

How do I configure varnish to act like a classical reverse proxy ? [new]

Here is a sample VCL to do this :

backend default {
set backend.host = "backend.example.com";
set backend.port = "http";
}

sub vcl_recv {

if (req.request != "GET" && req.request != "HEAD") {
pipe;
}
if (req.http.Expect) {
pipe;
}
if (req.http.Authenticate) {
pass;
}
if (req.http.Cache-Control ~ "no-cache") {
pass;
}
lookup;
}

sub vcl_pipe {
pipe;
}

sub vcl_pass {
pass;
}

sub vcl_hash {
set req.hash += req.url;
set req.hash += req.http.host;
hash;
}

sub vcl_hit {
if (!obj.cacheable) {
pass;
}
deliver;
}

sub vcl_miss {
fetch;
}

sub vcl_fetch {
if (!obj.valid) {
error;
}
if (!obj.cacheable) {
pass;
}
if (obj.http.Set-Cookie) {
pass;
}
if (obj.http.Pragma ~ "no-cache" || obj.http.Cache-Control ~ "(no-cache|private)" ) {
pass;
}
insert;
}

sub vcl_deliver {
deliver;
}

sub vcl_timeout {
discard;
}

sub vcl_discard {
discard;
}

What do you think of this ?

Jean-Fran?ois Bustarret
WAT - Responsable technique
http://www.wat.tv

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