Boost as Authcache Backend

I'm the author of the 7.x-2.x branch of authcache. Today I conducted a little experiment in order to explore the possibilities of using boost as the caching backend for authcache (instead of the drupal caching layer). At a first glance the integration seems to be relatively straight forward. The approach is heavily inspired by the stuff I found over at #629520: Cache by theme for mobile sites..

In the following I'll explain the settings and changes I've used.

.htaccess

  ### BOOST START ###

  # Authcache basic exclusion rules (see authcache.inc)
  RewriteCond %{REQUEST_METHOD} !^(GET|HEAD)$
  RewriteRule .* - [S=4]

  # Authenticated user with authcache cookie=69083ee
  RewriteCond %{HTTP_COOKIE} SESS79cbb35a3d5a3cef4d68411a1e238ad8
  RewriteCond %{HTTP_COOKIE} authcache=69083ee
  RewriteRule .* - [S=2,E=boostpath:69083ee]

  # Anonymous user
  RewriteCond %{HTTP_COOKIE} !SESS79cbb35a3d5a3cef4d68411a1e238ad8
  RewriteCond %{HTTP_COOKIE} !authcache
  RewriteRule .* - [S=1,E=boostpath:normal]

  # No match in previous conditions, skip delivery from cache
  RewriteRule .* - [S=1]

  # Deliver HTML from cache
  RewriteCond %{DOCUMENT_ROOT}/cache/%{ENV:boostpath}/localhost%{REQUEST_URI}_%{QUERY_STRING}\.html -s
  RewriteRule .* cache/%{ENV:boostpath}/localhost%{REQUEST_URI}_%{QUERY_STRING}\.html [L,T=text/html]

  ### BOOST END ###

Regarding the basic exclusion rules: Note that in authcache we follow the approach to simply avoid storing anything to the cache we do not want to deliver to the user afterwards. Therefore there are only three basic exclusion rules. Only the one given is really relevant for this POC.

I suggest checking against the session-cookie instead of relying on a custom one. The name of the session cookie can be retrieved using session_name(). Authcache basically generates a cookie-value depending on the combination of roles a user has. The cookie is not present for users which have roles which are not authcache-enabled. Therefore caching for an logged-in user is possible when a session is open and the authcache-cookie has an expected value.

On the other hand caching for anonymous users is possible when both of the cookies mentioned above are absent.

When we have some unexpected cookie-state, we give authcache a chance to fix the browser by performing a full bootstrap.

This is essentially the same thing which happens in authcache.inc

settings.php

if (isset($_SERVER['boostpath'])) {
  $conf['boost_normal_dir'] = $_SERVER['boostpath'];
}

$conf['cache_backends'][] = 'sites/all/modules/authcache/modules/authcache_ajax/authcache_ajax.inc';
$conf['cache_backends'][] = 'sites/all/modules/authcache/authcache.inc';

First we grab the value set in .htaccess and simply use that to redirect the boost-directory. Last two lines are boilerplate authcache requirements.

boost.module

diff --git a/boost.module b/boost.module
index d4825ad..a048e8f 100644
--- a/boost.module
+++ b/boost.module
@@ -322,7 +322,7 @@ function boost_exit($destination = NULL) {
     // Attach extension to filename.
     $_boost['filename'] .= '.' . $_boost['matched_header_info']['extension'];
     // Write to file.
-    boost_write_file($_boost['filename'], $data);
+    // boost_write_file($_boost['filename'], $data);
 
     // Gzip support.
     if (BOOST_GZIP && $_boost['matched_header_info']['gzip']) {

Prevent boost from actually writing cache files - quick and dirty.

authcache.inc

diff --git a/authcache.inc b/authcache.inc
index 5759b92..9c1a2ac 100644
--- a/authcache.inc
+++ b/authcache.inc
@@ -17,10 +17,10 @@
  */
 
 // Attempt to deliver the page from cache
-$delivered = authcacheinc_retrieve_cache_page();
-if ($delivered) {
-  exit;
-}
+// $delivered = authcacheinc_retrieve_cache_page();
+// if ($delivered) {
+//   exit;
+// }
 
 /**
  * Send cached page to browser, if found.

Disable delivery of cached pages from drupal core caching system.

authcache.module

diff --git a/authcache.module b/authcache.module
index 88c8ba9..f497208 100644
--- a/authcache.module
+++ b/authcache.module
@@ -761,6 +761,10 @@ function authcache_page_set_cache() {
     }
 
     if ($cache->data['body']) {
+      // BEGIN authcache-boost experiment: remember uncompressed body
+      $data = $cache->data['body'];
+      // END authcache-boost experiment
+
       if (variable_get('page_compression', TRUE) && extension_loaded('zlib')) {
         $cache->data['body'] = gzencode($cache->data['body'], 9, FORCE_GZIP);
       }
@@ -769,7 +773,36 @@ function authcache_page_set_cache() {
       drupal_alter('authcache_cache', $cache);
 
       cache_set($cache->cid, $cache->data, 'cache_page', $cache->expire);
+
+      // BEGIN authcache-boost experiment: Save page to boost cache
+      $_boost = boost_transform_url();
+
+      // Get header info.
+      $_boost['header_info'] = boost_get_header_info();
+      $_boost['matched_header_info'] = boost_match_header_attributes($_boost['header_info']);
+      if ($_boost['matched_header_info']['enabled'] === FALSE) {
+        return;
+      }
+
+      // Add note to bottom of content if possible.
+      if ($_boost['matched_header_info']['comment_start'] && $_boost['matched_header_info']['comment_end']) {
+        $expire = $_boost['matched_header_info']['lifetime_max'];
+        $cached_at = date('Y-m-d H:i:s', REQUEST_TIME);
+        $expires_at = date('Y-m-d H:i:s', REQUEST_TIME + $expire);
+        $note = "\n" . $_boost['matched_header_info']['comment_start'] . 'Page cached by Authcache-Boost @ ' . $cached_at . ', expires @ ' . $expires_at . ', lifetime ' . format_interval($expire) . $_boost['matched_header_info']['comment_end'];
+        $data .= $note;
+      }
+
+      // Write data to a file.
+      if ($_boost['filename']) {
+        // Attach extension to filename.
+        $_boost['filename'] .= '.' . $_boost['matched_header_info']['extension'];
+        // Write to file.
+        boost_write_file($_boost['filename'], $data);
+      }
+      // END authcache-boost experiment
     }
+
     return $cache;
   }
 }

Copy/paste from boost_exit into authcache_page_set_cache

Conclusion

In order to better integrate authcache and boost, I think the following things are necessary:

1. Allow to swap out the default drupal caching backend with another implementation in authcache
2. Extract the part responsible for actually writing a cached request from boost_exit into a separate function
3. Provide a way to enumerate all possible values of the authcache-cookie
4. Extend the .htaccess rules generator

I do not understand boost very well. Especially I have no idea on how the changes will affect cache expiration and crawling and stuff like that. Therefore I'd really appreciate if some boost-experts chime in and point out the relevant things. What do you think?