vmod_example

Varnish Example Module

Date:	2015-03-03
Version:	1.0
Manual section:	3

SYNOPSIS

import example;

DESCRIPTION

Example Varnish vmod demonstrating how to write an out-of-tree Varnish vmod.

Implements the traditional Hello World as a vmod.

FUNCTIONS

hello

Prototype

hello(STRING S)

Return value

STRING

Description

Returns "Hello, " prepended to S

Example

set resp.http.hello = example.hello("World");

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.

Building requires the Varnish header files and uses pkg-config to find the necessary paths.

Pre-requisites:

sudo apt-get install -y autotools-dev make automake libtool pkg-config libvarnishapi1 libvarnishapi-dev

Usage:

./autogen.sh
./configure

If you have installed Varnish to a non-standard directory, call autogen.sh and configure with PKG_CONFIG_PATH pointing to the appropriate path. For example, when varnishd configure was called with --prefix=$PREFIX, use

PKG_CONFIG_PATH=${PREFIX}/lib/pkgconfig export PKG_CONFIG_PATH

Make targets:

• make - builds the vmod.
• make install - installs your vmod.
• make check - runs the unit tests in src/tests/*.vtc
• make distcheck - run check and prepare a tarball of the vmod.

Installation directories

By default, the vmod configure script installs the built vmod in the same directory as Varnish, determined via pkg-config(1). The vmod installation directory can be overridden by passing the VMOD_DIR variable to configure.

Other files like man-pages and documentation are installed in the locations determined by configure, which inherits its default --prefix setting from Varnish.

USAGE EXAMPLE

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

import example;

sub vcl_deliver {
        # This sets resp.http.hello to "Hello, World"
        set resp.http.hello = example.hello("World");
}

COMMON PROBLEMS

• configure: error: Need varnish.m4 -- see README.rst

  Check if PKG_CONFIG_PATH has been set correctly before calling autogen.sh and configure

• Incompatibilities with different Varnish Cache versions

  Make sure you build this vmod against its correspondent Varnish Cache version. For example, to build against Varnish Cache 4.0, this vmod must be built from branch 4.0.