Special case opus mime detction

[mediawiki.git] / includes / MediaWiki.php

<?php
/**
 * Helper class for the index.php entry point.
 *
 * 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
 */

use MediaWiki\Logger\LoggerFactory;
use MediaWiki\MediaWikiServices;

/**
 * The MediaWiki class is the helper class for the index.php entry point.
 */
class MediaWiki {
        /**
         * @var IContextSource
         */
        private $context;

        /**
         * @var Config
         */
        private $config;

        /**
         * @var String Cache what action this request is
         */
        private $action;

        /**
         * @param IContextSource|null $context
         */
        public function __construct( IContextSource $context = null ) {
                if ( !$context ) {
                        $context = RequestContext::getMain();
                }

                $this->context = $context;
                $this->config = $context->getConfig();
        }

        /**
         * Parse the request to get the Title object
         *
         * @throws MalformedTitleException If a title has been provided by the user, but is invalid.
         * @return Title Title object to be $wgTitle
         */
        private function parseTitle() {
                global $wgContLang;

                $request = $this->context->getRequest();
                $curid = $request->getInt( 'curid' );
                $title = $request->getVal( 'title' );
                $action = $request->getVal( 'action' );

                if ( $request->getCheck( 'search' ) ) {
                        // Compatibility with old search URLs which didn't use Special:Search
                        // Just check for presence here, so blank requests still
                        // show the search page when using ugly URLs (bug 8054).
                        $ret = SpecialPage::getTitleFor( 'Search' );
                } elseif ( $curid ) {
                        // URLs like this are generated by RC, because rc_title isn't always accurate
                        $ret = Title::newFromID( $curid );
                } else {
                        $ret = Title::newFromURL( $title );
                        // Alias NS_MEDIA page URLs to NS_FILE...we only use NS_MEDIA
                        // in wikitext links to tell Parser to make a direct file link
                        if ( !is_null( $ret ) && $ret->getNamespace() == NS_MEDIA ) {
                                $ret = Title::makeTitle( NS_FILE, $ret->getDBkey() );
                        }
                        // Check variant links so that interwiki links don't have to worry
                        // about the possible different language variants
                        if ( count( $wgContLang->getVariants() ) > 1
                                && !is_null( $ret ) && $ret->getArticleID() == 0
                        ) {
                                $wgContLang->findVariantLink( $title, $ret );
                        }
                }

                // If title is not provided, always allow oldid and diff to set the title.
                // If title is provided, allow oldid and diff to override the title, unless
                // we are talking about a special page which might use these parameters for
                // other purposes.
                if ( $ret === null || !$ret->isSpecialPage() ) {
                        // We can have urls with just ?diff=,?oldid= or even just ?diff=
                        $oldid = $request->getInt( 'oldid' );
                        $oldid = $oldid ? $oldid : $request->getInt( 'diff' );
                        // Allow oldid to override a changed or missing title
                        if ( $oldid ) {
                                $rev = Revision::newFromId( $oldid );
                                $ret = $rev ? $rev->getTitle() : $ret;
                        }
                }

                // Use the main page as default title if nothing else has been provided
                if ( $ret === null
                        && strval( $title ) === ''
                        && !$request->getCheck( 'curid' )
                        && $action !== 'delete'
                ) {
                        $ret = Title::newMainPage();
                }

                if ( $ret === null || ( $ret->getDBkey() == '' && !$ret->isExternal() ) ) {
                        // If we get here, we definitely don't have a valid title; throw an exception.
                        // Try to get detailed invalid title exception first, fall back to MalformedTitleException.
                        Title::newFromTextThrow( $title );
                        throw new MalformedTitleException( 'badtitletext', $title );
                }

                return $ret;
        }

        /**
         * Get the Title object that we'll be acting on, as specified in the WebRequest
         * @return Title
         */
        public function getTitle() {
                if ( !$this->context->hasTitle() ) {
                        try {
                                $this->context->setTitle( $this->parseTitle() );
                        } catch ( MalformedTitleException $ex ) {
                                $this->context->setTitle( SpecialPage::getTitleFor( 'Badtitle' ) );
                        }
                }
                return $this->context->getTitle();
        }

        /**
         * Returns the name of the action that will be executed.
         *
         * @return string Action
         */
        public function getAction() {
                if ( $this->action === null ) {
                        $this->action = Action::getActionName( $this->context );
                }

                return $this->action;
        }

        /**
         * Performs the request.
         * - bad titles
         * - read restriction
         * - local interwiki redirects
         * - redirect loop
         * - special pages
         * - normal pages
         *
         * @throws MWException|PermissionsError|BadTitleError|HttpError
         * @return void
         */
        private function performRequest() {
                global $wgTitle;

                $request = $this->context->getRequest();
                $requestTitle = $title = $this->context->getTitle();
                $output = $this->context->getOutput();
                $user = $this->context->getUser();

                if ( $request->getVal( 'printable' ) === 'yes' ) {
                        $output->setPrintable();
                }

                $unused = null; // To pass it by reference
                Hooks::run( 'BeforeInitialize', [ &$title, &$unused, &$output, &$user, $request, $this ] );

                // Invalid titles. Bug 21776: The interwikis must redirect even if the page name is empty.
                if ( is_null( $title ) || ( $title->getDBkey() == '' && !$title->isExternal() )
                        || $title->isSpecial( 'Badtitle' )
                ) {
                        $this->context->setTitle( SpecialPage::getTitleFor( 'Badtitle' ) );
                        try {
                                $this->parseTitle();
                        } catch ( MalformedTitleException $ex ) {
                                throw new BadTitleError( $ex );
                        }
                        throw new BadTitleError();
                }

                // Check user's permissions to read this page.
                // We have to check here to catch special pages etc.
                // We will check again in Article::view().
                $permErrors = $title->isSpecial( 'RunJobs' )
                        ? [] // relies on HMAC key signature alone
                        : $title->getUserPermissionsErrors( 'read', $user );
                if ( count( $permErrors ) ) {
                        // Bug 32276: allowing the skin to generate output with $wgTitle or
                        // $this->context->title set to the input title would allow anonymous users to
                        // determine whether a page exists, potentially leaking private data. In fact, the
                        // curid and oldid request  parameters would allow page titles to be enumerated even
                        // when they are not guessable. So we reset the title to Special:Badtitle before the
                        // permissions error is displayed.

                        // The skin mostly uses $this->context->getTitle() these days, but some extensions
                        // still use $wgTitle.
                        $badTitle = SpecialPage::getTitleFor( 'Badtitle' );
                        $this->context->setTitle( $badTitle );
                        $wgTitle = $badTitle;

                        throw new PermissionsError( 'read', $permErrors );
                }

                // Interwiki redirects
                if ( $title->isExternal() ) {
                        $rdfrom = $request->getVal( 'rdfrom' );
                        if ( $rdfrom ) {
                                $url = $title->getFullURL( [ 'rdfrom' => $rdfrom ] );
                        } else {
                                $query = $request->getValues();
                                unset( $query['title'] );
                                $url = $title->getFullURL( $query );
                        }
                        // Check for a redirect loop
                        if ( !preg_match( '/^' . preg_quote( $this->config->get( 'Server' ), '/' ) . '/', $url )
                                && $title->isLocal()
                        ) {
                                // 301 so google et al report the target as the actual url.
                                $output->redirect( $url, 301 );
                        } else {
                                $this->context->setTitle( SpecialPage::getTitleFor( 'Badtitle' ) );
                                try {
                                        $this->parseTitle();
                                } catch ( MalformedTitleException $ex ) {
                                        throw new BadTitleError( $ex );
                                }
                                throw new BadTitleError();
                        }
                // Handle any other redirects.
                // Redirect loops, titleless URL, $wgUsePathInfo URLs, and URLs with a variant
                } elseif ( !$this->tryNormaliseRedirect( $title ) ) {
                        // Prevent information leak via Special:MyPage et al (T109724)
                        if ( $title->isSpecialPage() ) {
                                $specialPage = SpecialPageFactory::getPage( $title->getDBkey() );
                                if ( $specialPage instanceof RedirectSpecialPage ) {
                                        $specialPage->setContext( $this->context );
                                        if ( $this->config->get( 'HideIdentifiableRedirects' )
                                                && $specialPage->personallyIdentifiableTarget()
                                        ) {
                                                list( , $subpage ) = SpecialPageFactory::resolveAlias( $title->getDBkey() );
                                                $target = $specialPage->getRedirect( $subpage );
                                                // target can also be true. We let that case fall through to normal processing.
                                                if ( $target instanceof Title ) {
                                                        $query = $specialPage->getRedirectQuery() ?: [];
                                                        $request = new DerivativeRequest( $this->context->getRequest(), $query );
                                                        $request->setRequestURL( $this->context->getRequest()->getRequestURL() );
                                                        $this->context->setRequest( $request );
                                                        // Do not varnish cache these. May vary even for anons
                                                        $this->context->getOutput()->lowerCdnMaxage( 0 );
                                                        $this->context->setTitle( $target );
                                                        $wgTitle = $target;
                                                        // Reset action type cache. (Special pages have only view)
                                                        $this->action = null;
                                                        $title = $target;
                                                        $output->addJsConfigVars( [
                                                                'wgInternalRedirectTargetUrl' => $target->getFullURL( $query ),
                                                        ] );
                                                        $output->addModules( 'mediawiki.action.view.redirect' );
                                                }
                                        }
                                }
                        }

                        // Special pages ($title may have changed since if statement above)
                        if ( NS_SPECIAL == $title->getNamespace() ) {
                                // Actions that need to be made when we have a special pages
                                SpecialPageFactory::executePath( $title, $this->context );
                        } else {
                                // ...otherwise treat it as an article view. The article
                                // may still be a wikipage redirect to another article or URL.
                                $article = $this->initializeArticle();
                                if ( is_object( $article ) ) {
                                        $this->performAction( $article, $requestTitle );
                                } elseif ( is_string( $article ) ) {
                                        $output->redirect( $article );
                                } else {
                                        throw new MWException( "Shouldn't happen: MediaWiki::initializeArticle()"
                                                . " returned neither an object nor a URL" );
                                }
                        }
                }
        }

        /**
         * Handle redirects for uncanonical title requests.
         *
         * Handles:
         * - Redirect loops.
         * - No title in URL.
         * - $wgUsePathInfo URLs.
         * - URLs with a variant.
         * - Other non-standard URLs (as long as they have no extra query parameters).
         *
         * Behaviour:
         * - Normalise title values:
         *   /wiki/Foo%20Bar -> /wiki/Foo_Bar
         * - Normalise empty title:
         *   /wiki/ -> /wiki/Main
         *   /w/index.php?title= -> /wiki/Main
         * - Don't redirect anything with query parameters other than 'title' or 'action=view'.
         *
         * @param Title $title
         * @return bool True if a redirect was set.
         * @throws HttpError
         */
        private function tryNormaliseRedirect( Title $title ) {
                $request = $this->context->getRequest();
                $output = $this->context->getOutput();

                if ( $request->getVal( 'action', 'view' ) != 'view'
                        || $request->wasPosted()
                        || ( $request->getVal( 'title' ) !== null
                                && $title->getPrefixedDBkey() == $request->getVal( 'title' ) )
                        || count( $request->getValueNames( [ 'action', 'title' ] ) )
                        || !Hooks::run( 'TestCanonicalRedirect', [ $request, $title, $output ] )
                ) {
                        return false;
                }

                if ( $title->isSpecialPage() ) {
                        list( $name, $subpage ) = SpecialPageFactory::resolveAlias( $title->getDBkey() );
                        if ( $name ) {
                                $title = SpecialPage::getTitleFor( $name, $subpage );
                        }
                }
                // Redirect to canonical url, make it a 301 to allow caching
                $targetUrl = wfExpandUrl( $title->getFullURL(), PROTO_CURRENT );
                if ( $targetUrl == $request->getFullRequestURL() ) {
                        $message = "Redirect loop detected!\n\n" .
                                "This means the wiki got confused about what page was " .
                                "requested; this sometimes happens when moving a wiki " .
                                "to a new server or changing the server configuration.\n\n";

                        if ( $this->config->get( 'UsePathInfo' ) ) {
                                $message .= "The wiki is trying to interpret the page " .
                                        "title from the URL path portion (PATH_INFO), which " .
                                        "sometimes fails depending on the web server. Try " .
                                        "setting \"\$wgUsePathInfo = false;\" in your " .
                                        "LocalSettings.php, or check that \$wgArticlePath " .
                                        "is correct.";
                        } else {
                                $message .= "Your web server was detected as possibly not " .
                                        "supporting URL path components (PATH_INFO) correctly; " .
                                        "check your LocalSettings.php for a customized " .
                                        "\$wgArticlePath setting and/or toggle \$wgUsePathInfo " .
                                        "to true.";
                        }
                        throw new HttpError( 500, $message );
                }
                $output->setSquidMaxage( 1200 );
                $output->redirect( $targetUrl, '301' );
                return true;
        }

        /**
         * Initialize the main Article object for "standard" actions (view, etc)
         * Create an Article object for the page, following redirects if needed.
         *
         * @return Article|string An Article, or a string to redirect to another URL
         */
        private function initializeArticle() {
                $title = $this->context->getTitle();
                if ( $this->context->canUseWikiPage() ) {
                        // Try to use request context wiki page, as there
                        // is already data from db saved in per process
                        // cache there from this->getAction() call.
                        $page = $this->context->getWikiPage();
                } else {
                        // This case should not happen, but just in case.
                        // @TODO: remove this or use an exception
                        $page = WikiPage::factory( $title );
                        $this->context->setWikiPage( $page );
                        wfWarn( "RequestContext::canUseWikiPage() returned false" );
                }

                // Make GUI wrapper for the WikiPage
                $article = Article::newFromWikiPage( $page, $this->context );

                // Skip some unnecessary code if the content model doesn't support redirects
                if ( !ContentHandler::getForTitle( $title )->supportsRedirects() ) {
                        return $article;
                }

                $request = $this->context->getRequest();

                // Namespace might change when using redirects
                // Check for redirects ...
                $action = $request->getVal( 'action', 'view' );
                $file = ( $page instanceof WikiFilePage ) ? $page->getFile() : null;
                if ( ( $action == 'view' || $action == 'render' ) // ... for actions that show content
                        && !$request->getVal( 'oldid' ) // ... and are not old revisions
                        && !$request->getVal( 'diff' ) // ... and not when showing diff
                        && $request->getVal( 'redirect' ) != 'no' // ... unless explicitly told not to
                        // ... and the article is not a non-redirect image page with associated file
                        && !( is_object( $file ) && $file->exists() && !$file->getRedirected() )
                ) {
                        // Give extensions a change to ignore/handle redirects as needed
                        $ignoreRedirect = $target = false;

                        Hooks::run( 'InitializeArticleMaybeRedirect',
                                [ &$title, &$request, &$ignoreRedirect, &$target, &$article ] );
                        $page = $article->getPage(); // reflect any hook changes

                        // Follow redirects only for... redirects.
                        // If $target is set, then a hook wanted to redirect.
                        if ( !$ignoreRedirect && ( $target || $page->isRedirect() ) ) {
                                // Is the target already set by an extension?
                                $target = $target ? $target : $page->followRedirect();
                                if ( is_string( $target ) ) {
                                        if ( !$this->config->get( 'DisableHardRedirects' ) ) {
                                                // we'll need to redirect
                                                return $target;
                                        }
                                }
                                if ( is_object( $target ) ) {
                                        // Rewrite environment to redirected article
                                        $rpage = WikiPage::factory( $target );
                                        $rpage->loadPageData();
                                        if ( $rpage->exists() || ( is_object( $file ) && !$file->isLocal() ) ) {
                                                $rarticle = Article::newFromWikiPage( $rpage, $this->context );
                                                $rarticle->setRedirectedFrom( $title );

                                                $article = $rarticle;
                                                $this->context->setTitle( $target );
                                                $this->context->setWikiPage( $article->getPage() );
                                        }
                                }
                        } else {
                                // Article may have been changed by hook
                                $this->context->setTitle( $article->getTitle() );
                                $this->context->setWikiPage( $article->getPage() );
                        }
                }

                return $article;
        }

        /**
         * Perform one of the "standard" actions
         *
         * @param Page $page
         * @param Title $requestTitle The original title, before any redirects were applied
         */
        private function performAction( Page $page, Title $requestTitle ) {
                $request = $this->context->getRequest();
                $output = $this->context->getOutput();
                $title = $this->context->getTitle();
                $user = $this->context->getUser();

                if ( !Hooks::run( 'MediaWikiPerformAction',
                                [ $output, $page, $title, $user, $request, $this ] )
                ) {
                        return;
                }

                $act = $this->getAction();
                $action = Action::factory( $act, $page, $this->context );

                if ( $action instanceof Action ) {
                        // Narrow DB query expectations for this HTTP request
                        $trxLimits = $this->config->get( 'TrxProfilerLimits' );
                        $trxProfiler = Profiler::instance()->getTransactionProfiler();
                        if ( $request->wasPosted() && !$action->doesWrites() ) {
                                $trxProfiler->setExpectations( $trxLimits['POST-nonwrite'], __METHOD__ );
                                $request->markAsSafeRequest();
                        }

                        # Let CDN cache things if we can purge them.
                        if ( $this->config->get( 'UseSquid' ) &&
                                in_array(
                                        // Use PROTO_INTERNAL because that's what getCdnUrls() uses
                                        wfExpandUrl( $request->getRequestURL(), PROTO_INTERNAL ),
                                        $requestTitle->getCdnUrls()
                                )
                        ) {
                                $output->setCdnMaxage( $this->config->get( 'SquidMaxage' ) );
                        }

                        $action->show();
                        return;
                }
                // NOTE: deprecated hook. Add to $wgActions instead
                if ( Hooks::run(
                        'UnknownAction',
                        [
                                $request->getVal( 'action', 'view' ),
                                $page
                        ],
                        '1.19'
                ) ) {
                        $output->setStatusCode( 404 );
                        $output->showErrorPage( 'nosuchaction', 'nosuchactiontext' );
                }
        }

        /**
         * Run the current MediaWiki instance; index.php just calls this
         */
        public function run() {
                try {
                        $this->setDBProfilingAgent();
                        try {
                                $this->main();
                        } catch ( ErrorPageError $e ) {
                                // Bug 62091: while exceptions are convenient to bubble up GUI errors,
                                // they are not internal application faults. As with normal requests, this
                                // should commit, print the output, do deferred updates, jobs, and profiling.
                                $this->doPreOutputCommit();
                                $e->report(); // display the GUI error
                        }
                } catch ( Exception $e ) {
                        $context = $this->context;
                        $action = $context->getRequest()->getVal( 'action', 'view' );
                        if (
                                $e instanceof DBConnectionError &&
                                $context->hasTitle() &&
                                $context->getTitle()->canExist() &&
                                in_array( $action, [ 'view', 'history' ], true ) &&
                                HTMLFileCache::useFileCache( $this->context, HTMLFileCache::MODE_OUTAGE )
                        ) {
                                // Try to use any (even stale) file during outages...
                                $cache = new HTMLFileCache( $context->getTitle(), 'view' );
                                if ( $cache->isCached() ) {
                                        $cache->loadFromFileCache( $context, HTMLFileCache::MODE_OUTAGE );
                                        print MWExceptionRenderer::getHTML( $e );
                                        exit;
                                }

                        }

                        MWExceptionHandler::handleException( $e );
                }

                $this->doPostOutputShutdown( 'normal' );
        }

        private function setDBProfilingAgent() {
                $services = MediaWikiServices::getInstance();
                // Add a comment for easy SHOW PROCESSLIST interpretation
                $name = $this->context->getUser()->getName();
                $services->getDBLoadBalancerFactory()->setAgentName(
                        mb_strlen( $name ) > 15 ? mb_substr( $name, 0, 15 ) . '...' : $name
                );
        }

        /**
         * @see MediaWiki::preOutputCommit()
         * @param callable $postCommitWork [default: null]
         * @since 1.26
         */
        public function doPreOutputCommit( callable $postCommitWork = null ) {
                self::preOutputCommit( $this->context, $postCommitWork );
        }

        /**
         * This function commits all DB changes as needed before
         * the user can receive a response (in case commit fails)
         *
         * @param IContextSource $context
         * @param callable $postCommitWork [default: null]
         * @since 1.27
         */
        public static function preOutputCommit(
                IContextSource $context, callable $postCommitWork = null
        ) {
                // Either all DBs should commit or none
                ignore_user_abort( true );

                $config = $context->getConfig();
                $request = $context->getRequest();
                $output = $context->getOutput();
                $lbFactory = MediaWikiServices::getInstance()->getDBLoadBalancerFactory();

                // Commit all changes
                $lbFactory->commitMasterChanges(
                        __METHOD__,
                        // Abort if any transaction was too big
                        [ 'maxWriteDuration' => $config->get( 'MaxUserDBWriteDuration' ) ]
                );
                wfDebug( __METHOD__ . ': primary transaction round committed' );

                // Run updates that need to block the user or affect output (this is the last chance)
                DeferredUpdates::doUpdates( 'enqueue', DeferredUpdates::PRESEND );
                wfDebug( __METHOD__ . ': pre-send deferred updates completed' );

                // Decide when clients block on ChronologyProtector DB position writes
                $urlDomainDistance = (
                        $request->wasPosted() &&
                        $output->getRedirect() &&
                        $lbFactory->hasOrMadeRecentMasterChanges( INF )
                ) ? self::getUrlDomainDistance( $output->getRedirect(), $context ) : false;

                if ( $urlDomainDistance === 'local' || $urlDomainDistance === 'remote' ) {
                        // OutputPage::output() will be fast; $postCommitWork will not be useful for
                        // masking the latency of syncing DB positions accross all datacenters synchronously.
                        // Instead, make use of the RTT time of the client follow redirects.
                        $flags = $lbFactory::SHUTDOWN_CHRONPROT_ASYNC;
                        $cpPosTime = microtime( true );
                        // Client's next request should see 1+ positions with this DBMasterPos::asOf() time
                        if ( $urlDomainDistance === 'local' ) {
                                // Client will stay on this domain, so set an unobtrusive cookie
                                $expires = time() + ChronologyProtector::POSITION_TTL;
                                $options = [ 'prefix' => '' ];
                                $request->response()->setCookie( 'cpPosTime', $cpPosTime, $expires, $options );
                        } else {
                                // Cookies may not work across wiki domains, so use a URL parameter
                                $safeUrl = $lbFactory->appendPreShutdownTimeAsQuery(
                                        $output->getRedirect(),
                                        $cpPosTime
                                );
                                $output->redirect( $safeUrl );
                        }
                } else {
                        // OutputPage::output() is fairly slow; run it in $postCommitWork to mask
                        // the latency of syncing DB positions accross all datacenters synchronously
                        $flags = $lbFactory::SHUTDOWN_CHRONPROT_SYNC;
                        if ( $lbFactory->hasOrMadeRecentMasterChanges( INF ) ) {
                                $cpPosTime = microtime( true );
                                // Set a cookie in case the DB position store cannot sync accross datacenters.
                                // This will at least cover the common case of the user staying on the domain.
                                $expires = time() + ChronologyProtector::POSITION_TTL;
                                $options = [ 'prefix' => '' ];
                                $request->response()->setCookie( 'cpPosTime', $cpPosTime, $expires, $options );
                        }
                }
                // Record ChronologyProtector positions for DBs affected in this request at this point
                $lbFactory->shutdown( $flags, $postCommitWork );
                wfDebug( __METHOD__ . ': LBFactory shutdown completed' );

                // Set a cookie to tell all CDN edge nodes to "stick" the user to the DC that handles this
                // POST request (e.g. the "master" data center). Also have the user briefly bypass CDN so
                // ChronologyProtector works for cacheable URLs.
                if ( $request->wasPosted() && $lbFactory->hasOrMadeRecentMasterChanges() ) {
                        $expires = time() + $config->get( 'DataCenterUpdateStickTTL' );
                        $options = [ 'prefix' => '' ];
                        $request->response()->setCookie( 'UseDC', 'master', $expires, $options );
                        $request->response()->setCookie( 'UseCDNCache', 'false', $expires, $options );
                }

                // Avoid letting a few seconds of replica DB lag cause a month of stale data. This logic is
                // also intimately related to the value of $wgCdnReboundPurgeDelay.
                if ( $lbFactory->laggedReplicaUsed() ) {
                        $maxAge = $config->get( 'CdnMaxageLagged' );
                        $output->lowerCdnMaxage( $maxAge );
                        $request->response()->header( "X-Database-Lagged: true" );
                        wfDebugLog( 'replication', "Lagged DB used; CDN cache TTL limited to $maxAge seconds" );
                }

                // Avoid long-term cache pollution due to message cache rebuild timeouts (T133069)
                if ( MessageCache::singleton()->isDisabled() ) {
                        $maxAge = $config->get( 'CdnMaxageSubstitute' );
                        $output->lowerCdnMaxage( $maxAge );
                        $request->response()->header( "X-Response-Substitute: true" );
                }
        }

        /**
         * @param string $url
         * @param IContextSource $context
         * @return string Either "local", "remote" if in the farm, "external" otherwise
         */
        private static function getUrlDomainDistance( $url, IContextSource $context ) {
                static $relevantKeys = [ 'host' => true, 'port' => true ];

                $infoCandidate = wfParseUrl( $url );
                if ( $infoCandidate === false ) {
                        return 'external';
                }

                $infoCandidate = array_intersect_key( $infoCandidate, $relevantKeys );
                $clusterHosts = array_merge(
                        // Local wiki host (the most common case)
                        [ $context->getConfig()->get( 'CanonicalServer' ) ],
                        // Any local/remote wiki virtual hosts for this wiki farm
                        $context->getConfig()->get( 'LocalVirtualHosts' )
                );

                foreach ( $clusterHosts as $i => $clusterHost ) {
                        $parseUrl = wfParseUrl( $clusterHost );
                        if ( !$parseUrl ) {
                                continue;
                        }
                        $infoHost = array_intersect_key( $parseUrl, $relevantKeys );
                        if ( $infoCandidate === $infoHost ) {
                                return ( $i === 0 ) ? 'local' : 'remote';
                        }
                }

                return 'external';
        }

        /**
         * This function does work that can be done *after* the
         * user gets the HTTP response so they don't block on it
         *
         * This manages deferred updates, job insertion,
         * final commit, and the logging of profiling data
         *
         * @param string $mode Use 'fast' to always skip job running
         * @since 1.26
         */
        public function doPostOutputShutdown( $mode = 'normal' ) {
                $timing = $this->context->getTiming();
                $timing->mark( 'requestShutdown' );

                // Show visible profiling data if enabled (which cannot be post-send)
                Profiler::instance()->logDataPageOutputOnly();

                $callback = function () use ( $mode ) {
                        try {
                                $this->restInPeace( $mode );
                        } catch ( Exception $e ) {
                                MWExceptionHandler::handleException( $e );
                        }
                };

                // Defer everything else...
                if ( function_exists( 'register_postsend_function' ) ) {
                        // https://github.com/facebook/hhvm/issues/1230
                        register_postsend_function( $callback );
                } else {
                        if ( function_exists( 'fastcgi_finish_request' ) ) {
                                fastcgi_finish_request();
                        } else {
                                // Either all DB and deferred updates should happen or none.
                                // The latter should not be cancelled due to client disconnect.
                                ignore_user_abort( true );
                        }

                        $callback();
                }
        }

        private function main() {
                global $wgTitle;

                $output = $this->context->getOutput();
                $request = $this->context->getRequest();

                // Send Ajax requests to the Ajax dispatcher.
                if ( $this->config->get( 'UseAjax' ) && $request->getVal( 'action' ) === 'ajax' ) {
                        // Set a dummy title, because $wgTitle == null might break things
                        $title = Title::makeTitle( NS_SPECIAL, 'Badtitle/performing an AJAX call in '
                                . __METHOD__
                        );
                        $this->context->setTitle( $title );
                        $wgTitle = $title;

                        $dispatcher = new AjaxDispatcher( $this->config );
                        $dispatcher->performAction( $this->context->getUser() );

                        return;
                }

                // Get title from request parameters,
                // is set on the fly by parseTitle the first time.
                $title = $this->getTitle();
                $action = $this->getAction();
                $wgTitle = $title;

                // Set DB query expectations for this HTTP request
                $trxLimits = $this->config->get( 'TrxProfilerLimits' );
                $trxProfiler = Profiler::instance()->getTransactionProfiler();
                $trxProfiler->setLogger( LoggerFactory::getInstance( 'DBPerformance' ) );
                if ( $request->hasSafeMethod() ) {
                        $trxProfiler->setExpectations( $trxLimits['GET'], __METHOD__ );
                } else {
                        $trxProfiler->setExpectations( $trxLimits['POST'], __METHOD__ );
                }

                // If the user has forceHTTPS set to true, or if the user
                // is in a group requiring HTTPS, or if they have the HTTPS
                // preference set, redirect them to HTTPS.
                // Note: Do this after $wgTitle is setup, otherwise the hooks run from
                // isLoggedIn() will do all sorts of weird stuff.
                if (
                        $request->getProtocol() == 'http' &&
                        // switch to HTTPS only when supported by the server
                        preg_match( '#^https://#', wfExpandUrl( $request->getRequestURL(), PROTO_HTTPS ) ) &&
                        (
                                $request->getSession()->shouldForceHTTPS() ||
                                // Check the cookie manually, for paranoia
                                $request->getCookie( 'forceHTTPS', '' ) ||
                                // check for prefixed version that was used for a time in older MW versions
                                $request->getCookie( 'forceHTTPS' ) ||
                                // Avoid checking the user and groups unless it's enabled.
                                (
                                        $this->context->getUser()->isLoggedIn()
                                        && $this->context->getUser()->requiresHTTPS()
                                )
                        )
                ) {
                        $oldUrl = $request->getFullRequestURL();
                        $redirUrl = preg_replace( '#^http://#', 'https://', $oldUrl );

                        // ATTENTION: This hook is likely to be removed soon due to overall design of the system.
                        if ( Hooks::run( 'BeforeHttpsRedirect', [ $this->context, &$redirUrl ] ) ) {

                                if ( $request->wasPosted() ) {
                                        // This is weird and we'd hope it almost never happens. This
                                        // means that a POST came in via HTTP and policy requires us
                                        // redirecting to HTTPS. It's likely such a request is going
                                        // to fail due to post data being lost, but let's try anyway
                                        // and just log the instance.

                                        // @todo FIXME: See if we could issue a 307 or 308 here, need
                                        // to see how clients (automated & browser) behave when we do
                                        wfDebugLog( 'RedirectedPosts', "Redirected from HTTP to HTTPS: $oldUrl" );
                                }
                                // Setup dummy Title, otherwise OutputPage::redirect will fail
                                $title = Title::newFromText( 'REDIR', NS_MAIN );
                                $this->context->setTitle( $title );
                                // Since we only do this redir to change proto, always send a vary header
                                $output->addVaryHeader( 'X-Forwarded-Proto' );
                                $output->redirect( $redirUrl );
                                $output->output();

                                return;
                        }
                }

                if ( $title->canExist() && HTMLFileCache::useFileCache( $this->context ) ) {
                        // Try low-level file cache hit
                        $cache = new HTMLFileCache( $title, $action );
                        if ( $cache->isCacheGood( /* Assume up to date */ ) ) {
                                // Check incoming headers to see if client has this cached
                                $timestamp = $cache->cacheTimestamp();
                                if ( !$output->checkLastModified( $timestamp ) ) {
                                        $cache->loadFromFileCache( $this->context );
                                }
                                // Do any stats increment/watchlist stuff, assuming user is viewing the
                                // latest revision (which should always be the case for file cache)
                                $this->context->getWikiPage()->doViewUpdates( $this->context->getUser() );
                                // Tell OutputPage that output is taken care of
                                $output->disable();

                                return;
                        }
                }

                // Actually do the work of the request and build up any output
                $this->performRequest();

                // GUI-ify and stash the page output in MediaWiki::doPreOutputCommit() while
                // ChronologyProtector synchronizes DB positions or slaves accross all datacenters.
                $buffer = null;
                $outputWork = function () use ( $output, &$buffer ) {
                        if ( $buffer === null ) {
                                $buffer = $output->output( true );
                        }

                        return $buffer;
                };

                // Now commit any transactions, so that unreported errors after
                // output() don't roll back the whole DB transaction and so that
                // we avoid having both success and error text in the response
                $this->doPreOutputCommit( $outputWork );

                // Now send the actual output
                print $outputWork();
        }

        /**
         * Ends this task peacefully
         * @param string $mode Use 'fast' to always skip job running
         */
        public function restInPeace( $mode = 'fast' ) {
                $lbFactory = MediaWikiServices::getInstance()->getDBLoadBalancerFactory();
                // Assure deferred updates are not in the main transaction
                $lbFactory->commitMasterChanges( __METHOD__ );

                // Loosen DB query expectations since the HTTP client is unblocked
                $trxProfiler = Profiler::instance()->getTransactionProfiler();
                $trxProfiler->resetExpectations();
                $trxProfiler->setExpectations(
                        $this->config->get( 'TrxProfilerLimits' )['PostSend'],
                        __METHOD__
                );

                // Do any deferred jobs
                DeferredUpdates::doUpdates( 'enqueue' );
                DeferredUpdates::setImmediateMode( true );

                // Make sure any lazy jobs are pushed
                JobQueueGroup::pushLazyJobs();

                // Now that everything specific to this request is done,
                // try to occasionally run jobs (if enabled) from the queues
                if ( $mode === 'normal' ) {
                        $this->triggerJobs();
                }

                // Log profiling data, e.g. in the database or UDP
                wfLogProfilingData();

                // Commit and close up!
                $lbFactory->commitMasterChanges( __METHOD__ );
                $lbFactory->shutdown( LBFactory::SHUTDOWN_NO_CHRONPROT );

                wfDebug( "Request ended normally\n" );
        }

        /**
         * Potentially open a socket and sent an HTTP request back to the server
         * to run a specified number of jobs. This registers a callback to cleanup
         * the socket once it's done.
         */
        public function triggerJobs() {
                $jobRunRate = $this->config->get( 'JobRunRate' );
                if ( $this->getTitle()->isSpecial( 'RunJobs' ) ) {
                        return; // recursion guard
                } elseif ( $jobRunRate <= 0 || wfReadOnly() ) {
                        return;
                }

                if ( $jobRunRate < 1 ) {
                        $max = mt_getrandmax();
                        if ( mt_rand( 0, $max ) > $max * $jobRunRate ) {
                                return; // the higher the job run rate, the less likely we return here
                        }
                        $n = 1;
                } else {
                        $n = intval( $jobRunRate );
                }

                $runJobsLogger = LoggerFactory::getInstance( 'runJobs' );

                // Fall back to running the job(s) while the user waits if needed
                if ( !$this->config->get( 'RunJobsAsync' ) ) {
                        $runner = new JobRunner( $runJobsLogger );
                        $runner->run( [ 'maxJobs' => $n ] );
                        return;
                }

                // Do not send request if there are probably no jobs
                try {
                        $group = JobQueueGroup::singleton();
                        if ( !$group->queuesHaveJobs( JobQueueGroup::TYPE_DEFAULT ) ) {
                                return;
                        }
                } catch ( JobQueueError $e ) {
                        MWExceptionHandler::logException( $e );
                        return; // do not make the site unavailable
                }

                $query = [ 'title' => 'Special:RunJobs',
                        'tasks' => 'jobs', 'maxjobs' => $n, 'sigexpiry' => time() + 5 ];
                $query['signature'] = SpecialRunJobs::getQuerySignature(
                        $query, $this->config->get( 'SecretKey' ) );

                $errno = $errstr = null;
                $info = wfParseUrl( $this->config->get( 'CanonicalServer' ) );
                $host = $info ? $info['host'] : null;
                $port = 80;
                if ( isset( $info['scheme'] ) && $info['scheme'] == 'https' ) {
                        $host = "tls://" . $host;
                        $port = 443;
                }
                if ( isset( $info['port'] ) ) {
                        $port = $info['port'];
                }

                MediaWiki\suppressWarnings();
                $sock = $host ? fsockopen(
                        $host,
                        $port,
                        $errno,
                        $errstr,
                        // If it takes more than 100ms to connect to ourselves there is a problem...
                        0.100
                ) : false;
                MediaWiki\restoreWarnings();

                $invokedWithSuccess = true;
                if ( $sock ) {
                        $special = SpecialPageFactory::getPage( 'RunJobs' );
                        $url = $special->getPageTitle()->getCanonicalURL( $query );
                        $req = (
                                "POST $url HTTP/1.1\r\n" .
                                "Host: {$info['host']}\r\n" .
                                "Connection: Close\r\n" .
                                "Content-Length: 0\r\n\r\n"
                        );

                        $runJobsLogger->info( "Running $n job(s) via '$url'" );
                        // Send a cron API request to be performed in the background.
                        // Give up if this takes too long to send (which should be rare).
                        stream_set_timeout( $sock, 2 );
                        $bytes = fwrite( $sock, $req );
                        if ( $bytes !== strlen( $req ) ) {
                                $invokedWithSuccess = false;
                                $runJobsLogger->error( "Failed to start cron API (socket write error)" );
                        } else {
                                // Do not wait for the response (the script should handle client aborts).
                                // Make sure that we don't close before that script reaches ignore_user_abort().
                                $start = microtime( true );
                                $status = fgets( $sock );
                                $sec = microtime( true ) - $start;
                                if ( !preg_match( '#^HTTP/\d\.\d 202 #', $status ) ) {
                                        $invokedWithSuccess = false;
                                        $runJobsLogger->error( "Failed to start cron API: received '$status' ($sec)" );
                                }
                        }
                        fclose( $sock );
                } else {
                        $invokedWithSuccess = false;
                        $runJobsLogger->error( "Failed to start cron API (socket error $errno): $errstr" );
                }

                // Fall back to running the job(s) while the user waits if needed
                if ( !$invokedWithSuccess ) {
                        $runJobsLogger->warning( "Jobs switched to blocking; Special:RunJobs disabled" );

                        $runner = new JobRunner( $runJobsLogger );
                        $runner->run( [ 'maxJobs'  => $n ] );
                }
        }
}