Configure and use Varnish

Overview of the Varnish solution

Varnish Cache is an open source web application accelerator (also referred to as an HTTP accelerator or caching HTTP reverse proxy). Varnish stores (or caches) files or fragments of files in memory; this enables Varnish to reduce the response time and network bandwidth consumption on future, equivalent requests. Unlike web servers like Apache and nginx, Varnish was designed for use exclusively with the HTTP protocol.

Magento 2 supports versions 3.0.5 or later or any Varnish 4.x version.

For more information about Varnish, see:

• wikipedia
• The Big Varnish Picture
• Varnish startup options
• Varnish and Website Performance

Varnish topology diagram

The following figure shows a basic view of Varnish in your Magento topology.

In the preceding figure, users’ HTTP requests over the internet result in numerous requests for CSS, HTML, JavaScript, and images (referred to collectively as assets). Varnish sits in front of the web server and proxies these requests to the web server.

As the web server returns assets, cacheable assets are stored in Varnish. Any subsequent requests for those assets are fulfilled by Varnish (meaning, the requests don’t reach the web server). Varnish returns cached content extremely quickly. The results are faster response times to return the content to users and a reduced number of requests that must be fulfilled by Magento.

Assets cached by Varnish expire at a configurable interval or are replaced by newer versions of the same assets. You can also clear the cache manually either using the Magento Admin or the magento cache:clean command.

Process overview

This topic discusses how to initially install Varnish with a minimal set of parameters and test that it works. Then you’ll export a Varnish configuration from the Magento Admin and test it again.

The process can be summarized as follows:

1. Install Varnish and test it by accessing any Magento page to see if you’re getting HTTP response headers that indicate Varnish is working.
2. Install the Magento software and use the Magento Admin to create a Varnish configuration file.
3. Replace your existing Varnish configuration file with the one generated by the Admin.

4. Test everything again.

   If there is nothing in your <your Magento install dir>/var/page_cache directory, you’ve successfully configured Varnish with Magento!

Known issues

We know of the following issues with Varnish:

• Varnish does not support SSL

  As an alternative, use SSL termination or an SSL termination proxy.

• If you manually delete the contents of the <your Magento install dir>/var/cache directory, you must restart Varnish.

• Possible error installing Magento:

  Error 503 Service Unavailable
  Service Unavailable
  XID: 303394517
  Varnish cache server
  

  If you experience this error, edit default.vcl and add a timeout to the backend stanza as follows:

  backend default {
    .host = "127.0.0.1";
    .port = "8080";
    .first_byte_timeout = 600s;
  }
  

Next step

Install Varnish