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varnishkafka - varnish log collector with Apache Kafka integration

Copyright (c) 2018 Wikimedia Foundation

Copyright (c) 2013 Magnus Edenhill


varnishkafka is a varnish log collector with an integrated Apache Kafka producer. It was written from scratch with performance and modularity in mind.

Supported outputs and formats

Currently supported outputs:

  • kafka - produce messages to one or more Apache Kafka brokers
  • stdout - write log messages to stdout (as varnishncsa does)

Currently supported output formats:

  • string - arbitrary text output according to the configured formatting.
  • json - output as JSON with configurable field, field types and names.

New formats and outputs can easily be added.

Varnish compatibility

The Varnish cache upstream project radically changed a lot of times their API to read the shared memory log (introducing non backward compatible changes), and Varnishkafka had to adapt as consequence. We chose to keep this convention:

  • The master branch works from Varnish 5.2 to 6.0.
  • The varnishv51 branch works from Varnish 4.x to 5.1.
  • The varnishv3 branch works with Varnish up to 3.x.

The Wikimedia foundation now runs Varnish 5.1 and the last varnishv51 Varnishkafka version, so the most recent changes in master have not been battle tested on our production environment.

Important notes about internal settings

The initial position of the Varnish log cursor is fixed and set to start from the tail of the log. This implies that varnishkafka collects log entries that occur while it is running.


varnishkafka is configured with a configuration file and is designed to operate as a system daemon.

Please see the configuration file example, varnishkafka.conf.example, for a full description of configuration properties.

The standard Varnish VSL command line arguments are supported, both through the command line and configuration file.

TLS/SSL Support

varnishkafka leverages TLS support offered by librdkafka simply passing the right configuration parameters to it as indicated in this tutorial: Using-SSL-with-librdkafka.

It requires a recent (>= 0.9) version of librdkafka. Please check the TLS/SSL section of varnishkafka.conf.example for more information.


varnishkafka is licensed under the 2-clause BSD license.

The Apache Kafka support is provided by librdkafka



glibc >=2.19
libvarnishapi >=4.1
librdkafka >=0.9

Please note that the entire codebase assumes the use of glibc, so other C library implementations might not compile or work as expected.

Varnishkafka uses daemon(), which is included by default in glibc 2.19 and later. glibc 2.19 or a later version is available in Ubuntu 14.04 or Debian 8. To use an earlier version of glibc, compile with the -D_BSD_SOURCE flag.



  sudo make install
  # or to install in another location than /usr/local, set DESTDIR env
  # to the filesystem root of your choice.
  sudo make DESTDIR=/usr make install


# If /etc/varnishkafka.conf exists

# Alternative configuration path
varnishkafka -S /path/to/varnishkafka.conf

# Read a specific log file
varnishkafka -S /path/to/varnishkafka.conf -N /path/to/_.vsm

# Read a specific Varnish instance log file
varnishkafka -S /path/to/varnishkafka.conf -n varnish_instance_name

# Usage description
varnishkafka -h


Varnish log collector with Apache Kafka integration. This is a mirror from See for contributing.




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