From: Gilles Dubuc <gilles@wikimedia.org>
Date: Wed, 3 Apr 2019 07:06:38 +0000 (+0200)
Subject: Make the ratio of requests getting Priority Hints configurable
X-Git-Tag: 1.34.0-rc.0~1903
X-Git-Url: http://git.cyclocoop.org/%27.%28%24current%20%3E%202?a=commitdiff_plain;h=7433fa97f6ef1aa19114e111f3568c60080c262b;p=lhc%2Fweb%2Fwiklou.git

Make the ratio of requests getting Priority Hints configurable

This will allow to create 2 separate populations in
order to verify the effect of the hint.

It's fine if it's not exactly balanced in practice,
what matters is getting a significant amount of
traffic for both scenarios (origin trial is enabled +
an image is given high prio/origin trial is enabled +
no image is given special treatment).

Bug: T216499
Change-Id: I373960b2bed8437c2e97e6d729d43aff6901046c
---

diff --git a/includes/DefaultSettings.php b/includes/DefaultSettings.php
index af830fde42..8b51c59bab 100644
--- a/includes/DefaultSettings.php
+++ b/includes/DefaultSettings.php
@@ -9024,6 +9024,16 @@ $wgOriginTrials = [];
  */
 $wgPriorityHints = false;
 
+/**
+ * Ratio of requests that should get Priority Hints when the feature is enabled.
+ *
+ * @warning EXPERIMENTAL!
+ *
+ * @since 1.34
+ * @var float
+ */
+$wgPriorityHintsRatio = 1.0;
+
 /**
  * Enable Element Timing.
  *
diff --git a/includes/media/ThumbnailImage.php b/includes/media/ThumbnailImage.php
index 36cf4228e5..7ee6dcbee3 100644
--- a/includes/media/ThumbnailImage.php
+++ b/includes/media/ThumbnailImage.php
@@ -110,7 +110,7 @@ class ThumbnailImage extends MediaTransformOutput {
 	 * @return string
 	 */
 	function toHtml( $options = [] ) {
-		global $wgPriorityHints, $wgElementTiming;
+		global $wgPriorityHints, $wgPriorityHintsRatio, $wgElementTiming;
 
 		if ( func_num_args() == 2 ) {
 			throw new MWException( __METHOD__ . ' called in the old style' );
@@ -133,8 +133,16 @@ class ThumbnailImage extends MediaTransformOutput {
 			&& $this->width * $this->height > 100 * 100 ) {
 			self::$firstNonIconImageRendered = true;
 
-			$attribs['importance'] = 'high';
-			$elementTimingName = 'thumbnail-high';
+			// Generate a random number between 0.01 and 1.0, included
+			$random = rand( 1, 100 ) / 100.0;
+
+			if ( $random <= $wgPriorityHintsRatio ) {
+				$attribs['importance'] = 'high';
+				$elementTimingName = 'thumbnail-high';
+			} else {
+				// This lets us track that the thumbnail *would* have gotten high priority but didn't.
+				$elementTimingName = 'thumbnail-top';
+			}
 		}
 
 		if ( $wgElementTiming ) {