vmod_softpurge

Softpurge in Varnish

Author:	Lasse Karstensen
Date:	2012-08-21
Version:	1.0
Manual section:	1

SYNOPSIS

import softpurge;

DESCRIPTION

Softpurge is cache invalidation in Varnish that reduces TTL but keeps the grace value of a resource.

This makes it possible to serve purged content to users if a backend is unavailable and fresh content can not be fetched.

FUNCTIONS

softpurge

Prototype

softpurge()

Return value

NULL

Description

Performs a soft purge. Valid in vcl_hit and vcl_miss.

Example

sub vcl_hit {
        if (req.method == "PURGE") {
                softpurge.softpurge();
        }
}

INSTALLATION

The source tree is based on autotools to configure the building, and does also have the necessary bits in place to do functional unit tests using the varnishtest tool.

Usage:

./configure VARNISHSRC=DIR [VMODDIR=DIR]

VARNISHSRC is the directory of the Varnish source tree for which to compile your vmod. Both the VARNISHSRC and VARNISHSRC/include will be added to the include search paths for your module.

Optionally you can also set the vmod install directory by adding VMODDIR=DIR (defaults to the pkg-config discovered directory from your Varnish installation).

Make targets:

• make - builds the vmod
• make install - installs your vmod in VMODDIR
• make check - runs the unit tests in src/tests/*.vtc

In your VCL you could then use this vmod along the following lines:

import softpurge;

sub vcl_recv {
        if (req.method == "PURGE") { return(hash); }
}
sub vcl_fetch { set beresp.grace = 10m; }

sub vcl_hit {
        if (req.method == "PURGE) {
                softpurge.softpurge();
                return (synth(200, "Successful softpurge"));
        }
}
sub vcl_miss {
        if (req.method == "PURGE) {
                softpurge.softpurge();
                return (synth(200, "Successful softpurge"));
        }
}

COPYRIGHT

• Copyright (c) 2014 Varnish Software