Code for the Drupal ESI module
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REQUIREMENTS Use of the ESI module requires a reverse proxy with ESI support. Varnish would be a good choice. USING THE ESI MODULE The ESI module will replace blocks with ESI include tags - which look like: <esi:include src="/esi/block/....." /> The reverse-proxy will remove the ESI tags from the page, and replace each one with the appropriate block content. The proxy should be configured to cache the block content appropriately for the block-cache configuration, so that blocks which change per-user or per-role have separate caches for each context. The example VCL demonstrates how this is done with Varnish. ROLE-BASE COOKIES To support cacheing of role-based blocks, the proxy needs a way of recognising which roles a user has. On login, a cookie is set by the ESI module with a unique hash for each combination of roles; for example, all users who have no role will have hash a; users who are in role foo (and only role foo) will have hash b; users who are in role foo and role bar will have hash c; etc. The proxy has no way of interpreting which roles a user has, but can distinguish each unique combination of roles. CONFIGURATION The module stores 3 variables: - esi_seed_key_rotation_interval How often the seed key should change (in seconds). Defaults to daily. - esi_seed_key_last_changed When the seed key was last changed (unix timestamp) - esi_seed_key The current 'seed' (a 32-character string) The esi_seed_key_rotation_interval variable may be configured in settings.php. In most cases, it's best to allow the module to manage the other 2 fields automatically. VARNISH VCLs Two VCLs are provided: - docs/esi_blocks.vcl This VCL provided custom sub-routines to handle ESI-block integration. This is designed to be included from another VCL. NB: There is also a doc/esi_blocks-2_0.vcl for people that are using varnish < 2.1 - docs/default.vcl This is an example default.vcl, showing how the ESI-blocks VCL can be included.