Add sampling to unsampled event logging

Has issues:
- needs dependency injection
- needs to be DRY
- should not load mw.eventLogging when we are not in sample

Due to urgency this will be fixed in another commit.

Change-Id: I0df067a619109a7c945f82c8d33fa2e621217f0b
Mingle: https://wikimedia.mingle.thoughtworks.com/projects/multimedia/cards/619

MultimediaViewer.php

@@ -25,6 +25,17 @@ if ( !isset( $wgNetworkPerformanceSamplingFactor ) ) {
 	$wgNetworkPerformanceSamplingFactor = false;
 }
 
+if ( !isset( $wgMediaViewerSamplingFactor ) ) {
+	/**
+	 * If set, records user activity and loading times. A value of 1000 means there will be an
+	 * 1:1000 chance to enable logging on page load; for that page, either all or none of the
+	 * events will be logged.
+	 * False if unset.
+	 * @var int|bool
+	 */
+	$wgMediaViewerSamplingFactor = false;
+}
+
 if ( !isset( $wgMediaViewerIsInBeta ) ) {
 	/** @var bool: If set, Media Viewer will try to use BetaFeatures. False if unset. **/
 	$wgMediaViewerIsInBeta = false;

MultimediaViewerHooks.php

@@ -144,8 +144,8 @@ class MultimediaViewerHooks {
 	 * @return bool
 	 */
 	public static function resourceLoaderGetConfigVars( &$vars ) {
-		global $wgAPIPropModules, $wgNetworkPerformanceSamplingFactor, $wgMediaViewerIsInBeta,
+		global $wgAPIPropModules, $wgNetworkPerformanceSamplingFactor, $wgMediaViewerSamplingFactor,
-			   $wgMediaViewerUseThumbnailGuessing, $wgMediaViewerShowSurvey;
+			   $wgMediaViewerIsInBeta, $wgMediaViewerUseThumbnailGuessing, $wgMediaViewerShowSurvey;
 		$vars['wgMultimediaViewer'] = array(
 			'infoLink' => self::$infoLink,
 			'discussionLink' => self::$discussionLink,
@@ -153,6 +153,7 @@ class MultimediaViewerHooks {
 			'globalUsageAvailable' => isset( $wgAPIPropModules['globalusage'] ),
 			'useThumbnailGuessing' => (bool)$wgMediaViewerUseThumbnailGuessing,
 			'showSurvey' => (bool)$wgMediaViewerShowSurvey,
+			'samplingFactor' => $wgMediaViewerSamplingFactor,
 		);
 		$vars['wgNetworkPerformanceSamplingFactor'] = $wgNetworkPerformanceSamplingFactor;
 		$vars['wgMediaViewer'] = true;

resources/mmv/mmv.DurationLogger.js

@@ -98,7 +98,10 @@
 					e.country = self.Geo.country;
 				}
 
-				self.eventLog.logEvent( self.schema, e );
+				if ( self.isInSample() ) {
+					self.eventLog.logEvent( self.schema, e );
+				}
+
 				mw.log( message );
 			} );
 		}
@@ -138,5 +141,14 @@
 		return waitForEventLog;
 	};
 
+	L.isInSample = function () {
+		var factor = mw.config.get( 'wgMultimediaViewer' ).samplingFactor;
+
+		if ( !$.isNumeric( factor ) || factor < 1 ) {
+			return false;
+		}
+		return Math.floor( Math.random() * factor ) === 0;
+	};
+
 	mw.mmv.durationLogger = new DurationLogger();
 }( mediaWiki, jQuery ) );

resources/mmv/mmv.logger.js

@@ -75,7 +75,7 @@
 
 		mw.log( translatedAction );
 
-		if ( mw.eventLog && !skipEventLog ) {
+		if ( mw.eventLog && !skipEventLog && this.isInSample() ) {
 			return mw.eventLog.logEvent( 'MediaViewer', {
 				version: '1.1',
 				action: action
@@ -85,5 +85,14 @@
 		return $.Deferred().resolve();
 	};
 
+	L.isInSample = function () {
+		var factor = mw.config.get( 'wgMultimediaViewer' ).samplingFactor;
+
+		if ( !$.isNumeric( factor ) || factor < 1 ) {
+			return false;
+		}
+		return Math.floor( Math.random() * factor ) === 0;
+	};
+
 	mw.mmv.logger = new Logger();
 }( mediaWiki, jQuery ) );

tests/qunit/mmv/mmv.DurationLogger.test.js

@@ -2,6 +2,7 @@
 	QUnit.module( 'mmv.DurationLogger', QUnit.newMwEnvironment({
 		setup: function () {
 			this.clock = this.sandbox.useFakeTimers();
+			mw.config.get( 'wgMultimediaViewer' ).samplingFactor = 1;
 		}
 	} ) );