Issue #467226 by litwol, markpavlitski, bmhaskar, thedavidmeister, fago,...

Issue #467226 by litwol, markpavlitski, bmhaskar, thedavidmeister, fago, CurtisTAG, catch, Jeremy: Support for per-bin key prefix

README.txt

@@ -281,9 +281,22 @@ go to 'cluster2'. All other bins go to 'default'.
 
 If you want to have multiple Drupal installations share memcached instances,
 you need to include a unique prefix for each Drupal installation in the $conf
-array of settings.php:
+array of settings.php. This can be a single string prefix, or a keyed array of
+bin => prefix pairs:
 
-$conf['memcache_key_prefix'] = 'something_unique';
+   $conf['memcache_key_prefix'] = 'something_unique';
+
+Using a per-bin prefix:
+
+   $conf['memcache_key_prefix'] = array(
+     'default' => 'something_unique',
+     'cache_page' => 'something_else_unique'
+   );
+
+In the above example, the 'something_unique' prefix will be used for all bins
+except for the 'cache_page' bin which will use the 'something_else_unique'
+prefix. Not that if using a keyed array for specifying prefix, you must specify
+the 'default' prefix.
 
 ## MAXIMUM LENGTHS ##
 

dmemcache.inc

@@ -854,8 +854,18 @@ function dmemcache_object($bin = NULL, $flush = FALSE) {
  */
 function dmemcache_key($key, $bin = 'cache') {
   $prefix = '';
-  if ($prefix = variable_get('memcache_key_prefix', '')) {
-    $prefix .= '-';
+  if ($prefixes = variable_get('memcache_key_prefix', '')) {
+    if (is_array($prefixes)) {
+      if (!empty($prefixes[$bin])) {
+        $prefix = $prefixes[$bin] . '-';
+      } // Support default prefix for site
+      elseif (!empty($prefixes['default'])) {
+        $prefix = $prefixes['default'] . '-';
+      }
+    }
+    else {
+      $prefix = $prefixes . '-';
+    }
   }
   // When simpletest is running, emulate the simpletest database prefix here
   // to avoid the child site setting cache entries in the parent site.