Custom Varnish configuration for Acquia Cloud Enterprise applications

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, contact Acquia Support. Acquia will provide you with a test environment for one week to test your new custom VCL, but coding and testing is the customer’s responsibility. For more complex changes, consider purchasing an Acquia Professional Services engagement.

Acquia Cloud Enterprise customers can contact Acquia Support to create a support ticket to request a copy of the full VCL, based on their contractual NDA. Acquia does not disclose the configuration of our Nginx servers, as the configuration is both proprietary and subject to change without notice.

Custom Varnish configuration schedule

Acquia deploys custom Varnish configurations on a weekly schedule. To deploy your custom Varnish configuration, you must meet the following weekly schedule:

  1. Request a copy of your current VCL from Acquia.

  2. Supply Acquia the list of environments in front of which you want to place the test load balancer.

  3. 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.


    VCL files on Acquia Cloud are limited to a maximum of 128KB in size.

  4. Acquia deploys a test load balancer with the new VCL no 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/hosts file on your local computer to point to the IP address of the test load balancer.

  5. If you encounter 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 to apply the revised VCL to the test load balancer.

  6. You must complete any testing and confirm your approval no later than 15:00 Eastern (North America) Time on Wednesday.

  7. Acquia performs code reviews between 15:00 Eastern (North America) Time on Wednesday and 15:00 Eastern (North America) Time on Thursday.

  8. VCL updates restart Varnish and clear Varnish cache. To minimize disruption, Acquia releases VCL files during non-peak periods, according to the following schedule:

    • Weekly Custom VCL Regional Release to APJ Datacenters (default window) (AP-SouthEast-2, AP-SouthEast-1, AP-NorthEast-1) 19:00-20:00 UTC Thursday
    • Weekly Custom VCL Regional Release to all EMEA Datacenters (EU-Central-1, EU-West-1) 04:00-05:00 UTC Friday
    • Weekly Custom VCL Regional Release to all Americas Datacenters (SA-East-1, US-East-1, CA-Central-1, US-West-2) 07:00-08:00 UTC Friday

    Customers must specify the preferred window in the ticket for the custom VCL update. Once the custom VCL has been tested and approved by the customer, it will be added to the maintenance tasks scheduled for that window.

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 (however, using .htaccess instead of custom Varnish configuration is a more flexible approach)
  • Caching 404 responses

Unsupported use cases

Acquia does not support the following types of Varnish configuration use cases:

  • Inline C in custom VCLs
  • Customer-requested Varnish VMODs

Contact supportStill need assistance? Contact Acquia Support

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