objectcache: Fix WinCache keys longer than 150 chars

Adds MD5 hashing to the generation of keys for WinCache. This
fixes the issue of keys (e.g. sub-headings) longer than 150
characters.

Bug: T210794
Change-Id: Ieabf6b014a0660198077a23760a05564bf268535

diff --git a/includes/libs/objectcache/WinCacheBagOStuff.php b/includes/libs/objectcache/WinCacheBagOStuff.php
index 98f44d1..9c6c907 100644 (file)
--- a/includes/libs/objectcache/WinCacheBagOStuff.php
+++ b/includes/libs/objectcache/WinCacheBagOStuff.php
@@ -61,4 +61,40 @@ class WinCacheBagOStuff extends BagOStuff {
 
                return $ok;
        }
+
+       /**
+        * Construct a cache key.
+        *
+        * @since 1.27
+        * @param string $keyspace
+        * @param array $args
+        * @return string
+        */
+       public function makeKeyInternal( $keyspace, $args ) {
+               // WinCache keys have a maximum length of 150 characters. From that,
+               // subtract the number of characters we need for the keyspace and for
+               // the separator character needed for each argument. To handle some
+               // custom prefixes used by thing like WANObjectCache, limit to 125.
+               // NOTE: Same as in memcached, except the max key length there is 255.
+               $charsLeft = 125 - strlen( $keyspace ) - count( $args );
+
+               $args = array_map(
+                       function ( $arg ) use ( &$charsLeft ) {
+                               // 33 = 32 characters for the MD5 + 1 for the '#' prefix.
+                               if ( $charsLeft > 33 && strlen( $arg ) > $charsLeft ) {
+                                       $arg = '#' . md5( $arg );
+                               }
+
+                               $charsLeft -= strlen( $arg );
+                               return $arg;
+                       },
+                       $args
+               );
+
+               if ( $charsLeft < 0 ) {
+                       return $keyspace . ':BagOStuff-long-key:##' . md5( implode( ':', $args ) );
+               }
+
+               return $keyspace . ':' . implode( ':', $args );
+       }
 }