Varnish Purge Tags Override

This module solves a real-world problem that can occur when using varnish_purger module and its submodule varnish_purge_tags.
When enabled, the sub-module varnish_purge_tags adds - in some situation - the drupal cache tags to http responses in a custom http header named "Cache-Tags". In some situations, the number of cache tags for a URL can be really big, and exceed the limit supported by other systems in front of the drupal website : Apache (8k by default?), Varnish (4k by default?), Nginx...etc
When such a situation occurs, it is quite hard to identify despite the criticity, especially from the Drupal point of view. While in some situations, the maximum size of http header values can be increased for front-end servers in front of Drupal, this my not always be the possible or desired.

This module tries to solve this very specific problem without truncating the header. The idea is to replace cache tags associated to content entities by list cache tags. This only affects the HTTP header in http responses.

Features

The module allows to decide when to enable the feature :

• enable only when the size of the HTTP header "Cache-Tags" exceed a certain limit,
• restrict to some specific URLs.

The module allows to customize the action done to alter the cache tags HTTP header "Cache-Tags" :

• which content entities can be considered when replacing their associated cache tag to a list cache tag,
• whether to use bundle list cache tags or only simple list cache tags when replacing content entities cache tags.