============
vmod-example
============

notice
------

For new developments, we recommend to consider using
https://github.com/Dridi/vcdk

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.

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 instance, when varnishd configure was called
with ``--prefix=$PREFIX``, use

::

 export PKG_CONFIG_PATH=${PREFIX}/lib/pkgconfig
 export ACLOCAL_PATH=${PREFIX}/share/aclocal

The module will inherit its prefix from Varnish, unless you specify a
different ``--prefix`` when running the ``configure`` script for this
module.

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.

If you build a dist tarball, you don't need any of the autotools or
pkg-config. You can build the module simply by running::

 ./configure
 make

Installation directories
------------------------

By default, the vmod ``configure`` script installs the built vmod in the
directory relevant to the prefix. The vmod installation directory can be
overridden by passing the ``vmoddir`` variable to ``make install``.

USAGE
=====

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 whether ``PKG_CONFIG_PATH`` and ``ACLOCAL_PATH`` were 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 instance, to build against Varnish Cache 4.1, this vmod must be built from
  branch 4.1.

START YOUR OWN VMOD
===================

The basic steps to start a new vmod from this example are::

  name=myvmod
  git clone libvmod-example libvmod-$name
  cd libvmod-$name
  ./rename-vmod-script $name

and follow the instructions output by rename-vmod-script

.. image:: https://circleci.com/gh/varnishcache/libvmod-example/tree/master.svg?style=svg
    :target: https://app.circleci.com/pipelines/github/varnishcache/libvmod-example?branch=master