From: Aaron Schulz <aschulz@wikimedia.org>
Date: Tue, 30 Aug 2016 19:35:08 +0000 (-0700)
Subject: Adapt the ParserOutput cache TTL when including special pages
X-Git-Tag: 1.31.0-rc.0~5819^2
X-Git-Url: http://git.cyclocoop.org/%22.%20generer_url_ecrire%28%22sites_tous%22%2C%22%22%29.%20%22?a=commitdiff_plain;h=97f004694c2688e8682d31f866d18b97653d7965;p=lhc%2Fweb%2Fwiklou.git

Adapt the ParserOutput cache TTL when including special pages

For simple pages that transclude special pages, like user pages
including Special:PrefixIndex, the TTL is allowed to drop to 15
seconds if the page parses fast enough.

Bug: T139893
Change-Id: If41885ded648d68352fe3d06336d98aa0ab53966
---

diff --git a/includes/parser/Parser.php b/includes/parser/Parser.php
index 035baacf0e..b4d9c7002b 100644
--- a/includes/parser/Parser.php
+++ b/includes/parser/Parser.php
@@ -395,7 +395,8 @@ class Parser {
 	 * @param int $revid Number to pass in {{REVISIONID}}
 	 * @return ParserOutput A ParserOutput
 	 */
-	public function parse( $text, Title $title, ParserOptions $options,
+	public function parse(
+		$text, Title $title, ParserOptions $options,
 		$linestart = true, $clearState = true, $revid = null
 	) {
 		/**
@@ -462,6 +463,10 @@ class Parser {
 			}
 		}
 
+		# Done parsing! Compute runtime adaptive expiry if set
+		$this->mOutput->finalizeAdaptiveCacheExpiry();
+
+		# Warn if too many heavyweight parser functions were used
 		if ( $this->mExpensiveFunctionCount > $this->mOptions->getExpensiveParserFunctionLimit() ) {
 			$this->limitationWarn( 'expensive-parserfunction',
 				$this->mExpensiveFunctionCount,
@@ -3144,14 +3149,17 @@ class Parser {
 						$context->setUser( User::newFromName( '127.0.0.1', false ) );
 					}
 					$context->setLanguage( $this->mOptions->getUserLangObj() );
-					$ret = SpecialPageFactory::capturePath( $title, $context, $this->getLinkRenderer() );
+					$ret = SpecialPageFactory::capturePath(
+						$title, $context, $this->getLinkRenderer() );
 					if ( $ret ) {
 						$text = $context->getOutput()->getHTML();
 						$this->mOutput->addOutputPageMetadata( $context->getOutput() );
 						$found = true;
 						$isHTML = true;
 						if ( $specialPage && $specialPage->maxIncludeCacheTime() !== false ) {
-							$this->mOutput->updateCacheExpiry( $specialPage->maxIncludeCacheTime() );
+							$this->mOutput->updateRuntimeAdaptiveExpiry(
+								$specialPage->maxIncludeCacheTime()
+							);
 						}
 					}
 				} elseif ( MWNamespace::isNonincludable( $title->getNamespace() ) ) {
diff --git a/includes/parser/ParserOutput.php b/includes/parser/ParserOutput.php
index f0528125b0..9dfa97cb5a 100644
--- a/includes/parser/ParserOutput.php
+++ b/includes/parser/ParserOutput.php
@@ -209,9 +209,21 @@ class ParserOutput extends CacheTime {
 	/** @var integer|null Assumed rev ID for {{REVISIONID}} if no revision is set */
 	private $mSpeculativeRevId;
 
+	/** @var integer Upper bound of expiry based on parse duration */
+	private $mMaxAdaptiveExpiry = INF;
+
 	const EDITSECTION_REGEX =
 		'#<(?:mw:)?editsection page="(.*?)" section="(.*?)"(?:/>|>(.*?)(</(?:mw:)?editsection>))#';
 
+	// finalizeAdaptiveCacheExpiry() uses TTL = MAX( m * PARSE_TIME + b, MIN_AR_TTL)
+	// Current values imply that m=3933.333333 and b=-333.333333
+	// See https://www.nngroup.com/articles/website-response-times/
+	const PARSE_FAST_SEC = .100; // perceived "fast" page parse
+	const PARSE_SLOW_SEC = 1.0; // perceived "slow" page parse
+	const FAST_AR_TTL = 60; // adaptive TTL for "fast" pages
+	const SLOW_AR_TTL = 3600; // adaptive TTL for "slow" pages
+	const MIN_AR_TTL = 15; // min adaptive TTL (for sanity, pool counter, and edit stashing)
+
 	public function __construct( $text = '', $languageLinks = [], $categoryLinks = [],
 		$unused = false, $titletext = ''
 	) {
@@ -1037,9 +1049,41 @@ class ParserOutput extends CacheTime {
 	}
 
 	/**
-	 * Save space for serialization by removing useless values
-	 * @return array
+	 * Lower the runtime adaptive TTL to at most this value
+	 *
+	 * @param integer $ttl
+	 * @since 1.28
+	 */
+	public function updateRuntimeAdaptiveExpiry( $ttl ) {
+		$this->mMaxAdaptiveExpiry = min( $ttl, $this->mMaxAdaptiveExpiry );
+		$this->updateCacheExpiry( $ttl );
+	}
+
+	/**
+	 * Call this when parsing is done to lower the TTL based on low parse times
+	 *
+	 * @since 1.28
 	 */
+	public function finalizeAdaptiveCacheExpiry() {
+		if ( is_infinite( $this->mMaxAdaptiveExpiry ) ) {
+			return; // not set
+		}
+
+		$runtime = $this->getTimeSinceStart( 'wall' );
+		if ( is_float( $runtime ) ) {
+			$slope = ( self::SLOW_AR_TTL - self::FAST_AR_TTL )
+				/ ( self::PARSE_SLOW_SEC - self::PARSE_FAST_SEC );
+			// SLOW_AR_TTL = PARSE_SLOW_SEC * $slope + $point
+			$point = self::SLOW_AR_TTL - self::PARSE_SLOW_SEC * $slope;
+
+			$adaptiveTTL = min(
+				max( $slope * $runtime + $point, self::MIN_AR_TTL ),
+				$this->mMaxAdaptiveExpiry
+			);
+			$this->updateCacheExpiry( $adaptiveTTL );
+		}
+	}
+
 	public function __sleep() {
 		return array_diff(
 			array_keys( get_object_vars( $this ) ),