Don't call localisation functions when initializing pageset

Language::commaList() gets called even though in 99% of cases it's not
description that's needed but other parameter information, resulting in
0.6% of overall cluster CPU time being wasted per
https://performance.wikimedia.org/xenon/svgs/daily/2015-01-02.svgz

Change-Id: Ic77e4a03d1bbd1aa5f86dc250d9f903d7eb25618

diff --git a/autoload.php b/autoload.php
index a1ac905..f2b0554 100644 (file)
--- a/autoload.php
+++ b/autoload.php
@@ -291,6 +291,7 @@ $wgAutoloadLocalClasses = array(
        'DateFormatter' => __DIR__ . '/includes/parser/DateFormatter.php',
        'DeadendPagesPage' => __DIR__ . '/includes/specials/SpecialDeadendpages.php',
        'DeferrableUpdate' => __DIR__ . '/includes/deferred/DeferredUpdates.php',
+       'DeferredStringifier' => __DIR__ . '/includes/DeferredStringifier.php',
        'DeferredUpdates' => __DIR__ . '/includes/deferred/DeferredUpdates.php',
        'DeleteAction' => __DIR__ . '/includes/actions/DeleteAction.php',
        'DeleteArchivedFiles' => __DIR__ . '/maintenance/deleteArchivedFiles.php',

diff --git a/includes/DeferredStringifier.php b/includes/DeferredStringifier.php
new file mode 100644 (file)
index 0000000..bd32949
--- /dev/null
+++ b/includes/DeferredStringifier.php
@@ -0,0 +1,55 @@
+<?php
+/**
+ * Class that defers a slow string generation until the string is actually needed.
+ *
+ * This program is free software; you can redistribute it and/or modify
+ * it under the terms of the GNU General Public License as published by
+ * the Free Software Foundation; either version 2 of the License, or
+ * (at your option) any later version.
+ *
+ * This program is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
+ * GNU General Public License for more details.
+ *
+ * You should have received a copy of the GNU General Public License along
+ * with this program; if not, write to the Free Software Foundation, Inc.,
+ * 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301, USA.
+ * http://www.gnu.org/copyleft/gpl.html
+ *
+ * @file
+ */
+
+/**
+ * @since 1.25
+ */
+class DeferredStringifier {
+       /** @var callable Callback used for result string generation */
+       private $callback;
+       /** @var array */
+       private $params;
+       /** @var string */
+       private $result;
+
+       /**
+        * @param callable $callback Callback that gets called by __toString
+        * @param mixed $param,... Parameters to the callback
+        */
+       public function __construct( $callback /*...*/ ) {
+               $this->params = func_get_args();
+               array_shift( $this->params );
+               $this->callback = $callback;
+       }
+
+       /**
+        * Returns a string generated by callback
+        *
+        * @return string
+        */
+       public function __toString() {
+               if ( $this->result === null ) {
+                       $this->result = call_user_func_array( $this->callback, $this->params );
+               }
+               return $this->result;
+       }
+}

diff --git a/includes/api/ApiPageSet.php b/includes/api/ApiPageSet.php
index 1417ef7..c7147cb 100644 (file)
--- a/includes/api/ApiPageSet.php
+++ b/includes/api/ApiPageSet.php
@@ -1326,7 +1326,13 @@ class ApiPageSet extends ApiBase {
                                ApiBase::PARAM_DFLT => false,
                                ApiBase::PARAM_HELP_MSG => array(
                                        'api-pageset-param-converttitles',
-                                       $this->getLanguage()->commaList( LanguageConverter::$languagesWithVariants ),
+                                       new DeferredStringifier(
+                                               function ( IContextSource $context ) {
+                                                       return $context->getLanguage()
+                                                               ->commaList( LanguageConverter::$languagesWithVariants );
+                                               },
+                                               $this
+                                       )
                                ),
                        ),
                );