This page describes how to implement custom Varnish configurations, which are available only for Acquia Cloud Enterprise applications that have dedicated load balancers.
Varnish Cache is a caching reverse proxy that is installed in front of all Acquia Cloud load balancing servers. For more information, see Using Varnish. Varnish Cache is configured with its own domain-specific programming language, VCL. If you are interested in deploying a custom Varnish configuration, the first step is to contact Acquia Support. For simple configuration changes, Acquia Support can work with you to test and deploy them. For more complex changes, you may need to develop the custom VCL file yourself, or set up an Acquia Professional Services engagement.
Custom Varnish configuration schedule
The Acquia Operations team deploys custom Varnish configurations on a weekly schedule. To deploy your custom Varnish configuration, you must meet the following weekly schedule:
- Supply your new VCL file no later than 12:00 Eastern (North America) Time (find UTC equivalent) on Monday. You must supply the entire VCL file, and not only the lines that are changing.
- Acquia Operations deploys a test load balancer with the new VCL not later than 17:00 Eastern (North America) Time on Tuesday. You should then test to verify that the functionality is working as desired. To test the VCL on the test load balancer, it may be helpful to modify the
/etc/hostsfile on your local computer to point to the IP address of the test load balancer.
- If you see any issues that require a revised VCL, you must submit a revised VCL no later than 09:00 Eastern (North America) Time on Wednesday for Acquia Operations to apply the revised VCL to the test load balancer.
- You must complete any testing and confirm your approval no later than 15:00 Eastern (North America) Time on Wednesday.
- Acquia Operations performs code reviews between 15:00 Eastern (North America) Time on Wednesday and 15:00 Eastern (North America) Time on Thursday.
- Acquia Operations begins to deploy all VCLs that have been approved by the customer and by Acquia Operations starting at 15:00 Eastern (North America) Time on Thursday.
Custom Varnish configuration use cases
Here are some examples of use cases for which custom Varnish configurations can be useful:
- Changes to IP access control lists (ACLs)
- Device-based redirection (though using .htaccess instead of custom Varnish configuration is a more flexible approach)
- Caching 404 responses