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 035baac..b4d9c70 100644 (file)
--- 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 f052812..9dfa97c 100644 (file)
--- 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 ) ),