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Quick reference

• Maintained by:
  the Varnish Docker Community

• Where to get help:
  the Docker Community Slack, Server Fault, Unix & Linux, or Stack Overflow

Supported tags and respective Dockerfile links

• fresh, latest, 9.1.0-2, 9.1.0, 9.1, 9

• old, 9.0.4-5, 9.0.4, 9.0

• stable, 6.0.18-1, 6.0.18, 6.0, 6

Quick reference (cont.)

• Where to file issues:
  https://github.com/varnish/docker-varnish/issues

• Supported architectures: (more info)
  amd64, arm64v8

• Published image artifact details:
  repo-info repo's repos/varnish/ directory (history)
  (image metadata, transfer size, etc)

• Image updates:
  official-images repo's library/varnish label
  official-images repo's library/varnish file (history)

• Source of this description:
  docs repo's varnish/ directory (history)

What is Varnish?

Varnish is an HTTP accelerator designed for content-heavy dynamic web sites as well as APIs. In contrast to other web accelerators, such as Squid, which began life as a client-side cache, or Apache and nginx, which are primarily origin servers, Varnish was designed as an HTTP accelerator. Varnish is focused exclusively on HTTP, unlike other proxy servers that often support FTP, SMTP and other network protocols.

wikipedia.org/wiki/Varnish_(software)

How to use this image.

$ docker run -p 8080:80 --ulimit memlock=-1:-1 --tmpfs /var/lib/varnish/varnishd:exec varnish

You can then visit http://localhost:8080 with your browser and be greeted by the default landing page.

Note: while the --ulimit and --tmpfs options aren't necessary, they are greatly recommended. More details are available at the end of this page.

Basic usage

Simple cache

The default Varnish configuration will read the VARNISH_BACKEND_HOST environment variable which should be an HTTP or HTTPS URL, for example:

$ docker run \
	--ulimit memlock=-1:-1 \
	--tmpfs /var/lib/varnish/varnishd:exec \
	-p 8080:80 \
	-e VARNISH_BACKEND_HOST=https://example.com/ \
	varnish

By default, Varnish is extremely careful regarding what it can and cannot cache by looking at the client request and at the backend response.

Notably, Varnish will not cache if:

• the request is not a GET or HEAD
• the request contains an Authorization or Cookie header
• the response status is not cacheable (i.e., not a 2xx or 4xx response)
• the response contains a Set-Cookie header
• the response contains headers indicating it is uncacheable

These rules can, of course, be overridden by providing your own VCL file, as explained in the next section.

Custom caching logic

If you already have a VCL file, you can directly mount it as /etc/varnish/default.vcl:

$ docker run \
	--ulimit memlock=-1:-1 \
	--tmpfs /var/lib/varnish/varnishd:exec \
	-p 8080:80 \
	-v /path/to/default.vcl:/etc/varnish/default.vcl:ro \
	varnish

Alternatively, a simple Dockerfile can be used to generate a new image that includes the necessary default.vcl:

FROM varnish

COPY default.vcl /etc/varnish/

Place this file in the same directory as your default.vcl, run docker build -t my-varnish ., then start your container:

$ docker \
	--ulimit memlock=-1:-1 \
	--tmpfs /var/lib/varnish/varnishd:exec \
	-p 8080:80 \
	my-varnish

Reloading the configuration

The images all ship with varnishreload which allows you to easily update the running configuration without restarting the container (and therefore losing your cache). At its most basic, you just need this:

# update the default.vcl in your container
docker cp new_default.vcl running_container:/etc/varnish/default.vcl
# run varnishreload
docker exec running_container varnishreload

Note that varnishreload also supports reloading other files (it doesn't have to be default.vcl), labels (-l), and garbage collection of old labels (-m), among others. To learn more, run

$ docker run --rm varnish varnishreload -h

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