Merge "Disable $wgServer autodetection to prevent cache poisoning attacks" into REL1_34

[lhc/web/wiklou.git] / includes / deferred / MergeableUpdate.php

diff --git a/includes/deferred/MergeableUpdate.php b/includes/deferred/MergeableUpdate.php
index 70760ce..6ae2bcc 100644 (file)
--- a/includes/deferred/MergeableUpdate.php
+++ b/includes/deferred/MergeableUpdate.php
@@ -1,12 +1,21 @@
 <?php
 
 /**
- * Interface that deferrable updates can implement. DeferredUpdates uses this to merge
- * all pending updates of PHP class into a single update by calling merge().
+ * Interface that deferrable updates can implement to signal that updates can be combined.
+ *
+ * DeferredUpdates uses this to merge all pending updates of PHP class into a single update
+ * by calling merge(). Note that upon merge(), the combined update goes to the back of the FIFO
+ * queue so that such updates occur after related non-mergeable deferred updates. For example,
+ * suppose updates that purge URLs can be merged, and the calling pattern is:
+ *   - a) DeferredUpdates::addUpdate( $purgeCdnUrlsA );
+ *   - b) DeferredUpdates::addUpdate( $deleteContentUrlsB );
+ *   - c) DeferredUpdates::addUpdate( $purgeCdnUrlsB )
+ *
+ * The purges for urls A and B will all happen after the $deleteContentUrlsB update.
  *
  * @since 1.27
  */
-interface MergeableUpdate {
+interface MergeableUpdate extends DeferrableUpdate {
        /**
         * Merge this update with $update
         *