import blobsynth;


Trivial vmod to use blobs for synthetic responses, intended only as a transitional solution until support for generating synthetic responses is generalised in Varnish Cache.


import blob;
import blobsynth;

sub vcl_init {
        new gif = blob.blob(BASE64,

sub vcl_synth {
        set resp.http.Content-Type = "image/gif";
        return (deliver);


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.



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:


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.


  • 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.