Merge "Allow for dynamic TTLs in getWithSetCallback()"

[lhc/web/wiklou.git] / includes / libs / objectcache / WANObjectCache.php

diff --git a/includes/libs/objectcache/WANObjectCache.php b/includes/libs/objectcache/WANObjectCache.php
index e1f64ba..0ca0f2e 100755 (executable)
--- a/includes/libs/objectcache/WANObjectCache.php
+++ b/includes/libs/objectcache/WANObjectCache.php
@@ -307,10 +307,13 @@ class WANObjectCache {
        /**
         * Method to fetch/regenerate cache keys
         *
-        * On cache miss, the key will be set to the callback result.
+        * On cache miss, the key will be set to the callback result,
+        * unless the callback returns false. The arguments supplied are:
+        *     (current value or false, &$ttl)
         * The callback function returns the new value given the current
-        * value (false if not present). If false is returned, then nothing
-        * will be saved to cache.
+        * value (false if not present). Preemptive re-caching and $checkKeys
+        * can result in a non-false current value. The TTL of the new value
+        * can be set dynamically by altering $ttl in the callback (by reference).
         *
         * Usually, callbacks ignore the current value, but it can be used
         * to maintain "most recent X" values that come from time or sequence
@@ -333,7 +336,7 @@ class WANObjectCache {
         * @code
         *     $key = wfMemcKey( 'cat-recent-actions', $catId );
         *     // Function that derives the new key value given the old value
-        *     $callback = function( $cValue ) { ... };
+        *     $callback = function( $cValue, &$ttl ) { ... };
         *     // Get the key value from cache or from source on cache miss;
         *     // try to only let one cluster thread manage doing cache updates
         *     $opts = array( 'lockTSE' => 5, 'lowTTL' => 10 );
@@ -426,7 +429,7 @@ class WANObjectCache {
                }
 
                // Generate the new value from the callback...
-               $value = call_user_func( $callback, $cValue );
+               $value = call_user_func_array( $callback, array( $cValue, &$ttl ) );
                // When delete() is called, writes are write-holed by the tombstone,
                // so use a special stash key to pass the new value around threads.
                if ( $value !== false && ( $isHot || $isTombstone ) ) {