CentralIdLookup: Add @since to factoryNonLocal()

[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 Liuggio\StatsdClient\Sender\SocketSender;
use MediaWiki\HookContainer\ProtectedHookAccessorTrait;
use MediaWiki\Logger\LoggerFactory;
use MediaWiki\MediaWikiServices;
use Psr\Log\LoggerInterface;
use Wikimedia\AtEase;
use Wikimedia\Rdbms\ChronologyProtector;
use Wikimedia\Rdbms\DBConnectionError;
use Wikimedia\Rdbms\ILBFactory;

/**
 * The MediaWiki class is the helper class for the index.php entry point.
 */
class MediaWiki {
        use ProtectedHookAccessorTrait;

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

        /** @var string Cache what action this request is */
        private $action;
        /** @var int Class DEFER_* constant; how non-blocking post-response tasks should run */
        private $postSendStrategy;

        /** @var int Use fastcgi_finish_request() */
        private const DEFER_FASTCGI_FINISH_REQUEST = 1;
        /** @var int Use ob_end_flush() after explicitly setting the Content-Length */
        private const DEFER_SET_LENGTH_AND_FLUSH = 2;

        /**
         * @param IContextSource|null $context
         */
        public function __construct( IContextSource $context = null ) {
                $this->context = $context ?: RequestContext::getMain();
                $this->config = $this->context->getConfig();
                if ( function_exists( 'fastcgi_finish_request' ) ) {
                        $this->postSendStrategy = self::DEFER_FASTCGI_FINISH_REQUEST;
                } else {
                        $this->postSendStrategy = self::DEFER_SET_LENGTH_AND_FLUSH;
                }
        }

        /**
         * 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() {
                $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 (T10054).
                        $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 ( $ret !== null && $ret->getNamespace() === NS_MEDIA ) {
                                $ret = Title::makeTitle( NS_FILE, $ret->getDBkey() );
                        }
                        $contLang = MediaWikiServices::getInstance()->getContentLanguage();
                        // Check variant links so that interwiki links don't have to worry
                        // about the possible different language variants
                        if (
                                $contLang->hasVariants() && $ret !== null && $ret->getArticleID() == 0
                        ) {
                                $contLang->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 ?: $request->getInt( 'diff' );
                        // Allow oldid to override a changed or missing title
                        if ( $oldid ) {
                                $revRecord = MediaWikiServices::getInstance()
                                        ->getRevisionLookup()
                                        ->getRevisionById( $oldid );
                                if ( $revRecord ) {
                                        $ret = Title::newFromLinkTarget(
                                                $revRecord->getPageAsLinkTarget()
                                        );
                                }
                        }
                }

                // 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() : string {
                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();
                }

                $this->getHookRunner()->onBeforeInitialize( $title, null, $output, $user, $request, $this );

                // Invalid titles. T23776: The interwikis must redirect even if the page name is empty.
                if ( $title === null || ( $title->getDBkey() == '' && !$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
                        : MediaWikiServices::getInstance()->getPermissionManager()
                                ->getPermissionErrors( 'read', $user, $title );
                if ( count( $permErrors ) ) {
                        // T34276: 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)
                        $spFactory = MediaWikiServices::getInstance()->getSpecialPageFactory();
                        if ( $title->isSpecialPage() ) {
                                $specialPage = $spFactory->getPage( $title->getDBkey() );
                                if ( $specialPage instanceof RedirectSpecialPage ) {
                                        $specialPage->setContext( $this->context );
                                        if ( $this->config->get( 'HideIdentifiableRedirects' )
                                                && $specialPage->personallyIdentifiableTarget()
                                        ) {
                                                list( , $subpage ) = $spFactory->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 ) {
                                                        if ( $target->isExternal() ) {
                                                                // Handle interwiki redirects
                                                                $target = SpecialPage::getTitleFor(
                                                                        'GoToInterwiki',
                                                                        'force/' . $target->getPrefixedDBkey()
                                                                );
                                                        }

                                                        $query = $specialPage->getRedirectQuery( $subpage ) ?: [];
                                                        $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->getLinkURL( $query ),
                                                        ] );
                                                        $output->addModules( 'mediawiki.action.view.redirect' );
                                                }
                                        }
                                }
                        }

                        // Special pages ($title may have changed since if statement above)
                        if ( $title->isSpecialPage() ) {
                                // Actions that need to be made when we have a special pages
                                $spFactory->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" );
                                }
                        }
                        $output->considerCacheSettingsFinal();
                }
        }

        /**
         * 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->getCheck( 'title' )
                                && $title->getPrefixedDBkey() == $request->getVal( 'title' ) )
                        || count( $request->getValueNames( [ 'action', 'title' ] ) )
                        || !$this->getHookRunner()->onTestCanonicalRedirect( $request, $title, $output )
                ) {
                        return false;
                }

                if ( $this->config->get( 'MainPageIsDomainRoot' ) && $request->getRequestURL() === '/' ) {
                        return false;
                }

                if ( $title->isSpecialPage() ) {
                        list( $name, $subpage ) = MediaWikiServices::getInstance()->getSpecialPageFactory()->
                                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->setCdnMaxage( 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 ( !MediaWikiServices::getInstance()
                                ->getContentHandlerFactory()
                                ->getContentHandler( $title->getContentModel() )
                                ->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;

                        $this->getHookRunner()->onInitializeArticleMaybeRedirect( $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 ?: $page->followRedirect();
                                if ( is_string( $target ) && !$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 Article $article
         * @param Title $requestTitle The original title, before any redirects were applied
         */
        private function performAction( Article $article, Title $requestTitle ) {
                $request = $this->context->getRequest();
                $output = $this->context->getOutput();
                $title = $this->context->getTitle();
                $user = $this->context->getUser();

                if ( !$this->getHookRunner()->onMediaWikiPerformAction(
                        $output, $article, $title, $user, $request, $this )
                ) {
                        return;
                }

                $act = $this->getAction();
                $action = Action::factory( $act, $article, $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( 'UseCdn' ) &&
                                in_array(
                                        // Use PROTO_INTERNAL because that's what getCdnUrls() uses
                                        wfExpandUrl( $request->getRequestURL(), PROTO_INTERNAL ),
                                        $requestTitle->getCdnUrls()
                                )
                        ) {
                                $output->setCdnMaxage( $this->config->get( 'CdnMaxAge' ) );
                        }

                        $action->show();
                        return;
                }

                // If we've not found out which action it is by now, it's unknown
                $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 ) {
                                $out = $this->context->getOutput();
                                // TODO: Should ErrorPageError::report accept a OutputPage parameter?
                                $e->report( ErrorPageError::STAGE_OUTPUT );
                                $out->considerCacheSettingsFinal();

                                // T64091: 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();
                                $out->output(); // 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( $context, HTMLFileCache::MODE_OUTAGE )
                        ) {
                                // Try to use any (even stale) file during outages...
                                $cache = new HTMLFileCache( $context->getTitle(), $action );
                                if ( $cache->isCached() ) {
                                        $cache->loadFromFileCache( $context, HTMLFileCache::MODE_OUTAGE );
                                        print MWExceptionRenderer::getHTML( $e );
                                        exit;
                                }
                        }
                        // GUI-ify and stash the page output in MediaWiki::doPreOutputCommit() while
                        // ChronologyProtector synchronizes DB positions or replicas across all datacenters.
                        MWExceptionHandler::handleException( $e, MWExceptionHandler::CAUGHT_BY_ENTRYPOINT );
                } catch ( Throwable $e ) {
                        // Type errors and such: at least handle it now and clean up the LBFactory state
                        MWExceptionHandler::handleException( $e, MWExceptionHandler::CAUGHT_BY_ENTRYPOINT );
                }

                $this->doPostOutputShutdown();
        }

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

        /**
         * If enabled, after everything specific to this request is done, occasionally run jobs
         */
        private function schedulePostSendJobs() {
                $jobRunRate = $this->config->get( 'JobRunRate' );
                if (
                        // Recursion guard
                        $this->getTitle()->isSpecial( 'RunJobs' ) ||
                        // Short circuit if there is nothing to do
                        ( $jobRunRate <= 0 || wfReadOnly() ) ||
                        // Avoid blocking the client on stock apache; see doPostOutputShutdown()
                        (
                                $this->context->getRequest()->getMethod() === 'HEAD' ||
                                $this->context->getRequest()->getHeader( 'If-Modified-Since' )
                        )
                ) {
                        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 );
                }

                // Note that DeferredUpdates will catch and log an errors (T88312)
                DeferredUpdates::addUpdate( new TransactionRoundDefiningUpdate( function () use ( $n ) {
                        $logger = LoggerFactory::getInstance( 'runJobs' );
                        if ( $this->config->get( 'RunJobsAsync' ) ) {
                                // Send an HTTP request to the job RPC entry point if possible
                                $invokedWithSuccess = $this->triggerAsyncJobs( $n, $logger );
                                if ( !$invokedWithSuccess ) {
                                        // Fall back to blocking on running the job(s)
                                        $logger->warning( "Jobs switched to blocking; Special:RunJobs disabled" );
                                        $this->triggerSyncJobs( $n );
                                }
                        } else {
                                $this->triggerSyncJobs( $n );
                        }
                }, __METHOD__ ) );
        }

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

        /**
         * This function commits all DB and session changes as needed *before* the
         * client can receive a response (in case DB commit fails) and thus also before
         * the response can trigger a subsequent related request by the client
         *
         * If there is a significant amount of content to flush, it can be done in $postCommitWork
         *
         * @param IContextSource $context
         * @param callable|null $postCommitWork [default: null]
         * @since 1.27
         */
        public static function preOutputCommit(
                IContextSource $context, callable $postCommitWork = null
        ) {
                $config = $context->getConfig();
                $request = $context->getRequest();
                $output = $context->getOutput();
                $services = MediaWikiServices::getInstance();
                $lbFactory = $services->getDBLoadBalancerFactory();

                // Try to make sure that all RDBMs, session, and other storage updates complete
                ignore_user_abort( true );

                // Commit all RDBMs changes from the main transaction round
                $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 client or affect output (this is the last chance)
                DeferredUpdates::doUpdates( 'run', DeferredUpdates::PRESEND );
                wfDebug( __METHOD__ . ': pre-send deferred updates completed' );
                // Persist the session to avoid race conditions on subsequent requests by the client
                $request->getSession()->save(); // T214471
                wfDebug( __METHOD__ . ': session changes committed' );

                // Figure out whether to wait for DB replication now or to use some method that assures
                // that subsequent requests by the client will use the DB replication positions written
                // during the shutdown() call below; the later requires working around replication lag
                // of the store containing DB replication positions (e.g. dynomite, mcrouter).
                list( $flags, $strategy ) = self::getChronProtStrategy( $lbFactory, $output );
                // Record ChronologyProtector positions for DBs affected in this request at this point
                $cpIndex = null;
                $cpClientId = null;
                $lbFactory->shutdown( $flags, $postCommitWork, $cpIndex, $cpClientId );
                wfDebug( __METHOD__ . ': LBFactory shutdown completed' );

                $allowHeaders = !( $output->isDisabled() || headers_sent() );
                if ( $cpIndex > 0 ) {
                        if ( $allowHeaders ) {
                                $now = time();
                                $expires = $now + ChronologyProtector::POSITION_COOKIE_TTL;
                                $options = [ 'prefix' => '' ];
                                $value = $lbFactory::makeCookieValueFromCPIndex( $cpIndex, $now, $cpClientId );
                                $request->response()->setCookie( 'cpPosIndex', $value, $expires, $options );
                        }

                        if ( $strategy === 'cookie+url' ) {
                                if ( $output->getRedirect() ) { // sanity
                                        $safeUrl = $lbFactory->appendShutdownCPIndexAsQuery(
                                                $output->getRedirect(),
                                                $cpIndex
                                        );
                                        $output->redirect( $safeUrl );
                                } else {
                                        MWExceptionHandler::logException(
                                                new LogicException( "No redirect; cannot append cpPosIndex parameter." ),
                                                MWExceptionHandler::CAUGHT_BY_ENTRYPOINT
                                        );
                                }
                        }
                }

                if ( $allowHeaders ) {
                        // 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 ( $services->getMessageCache()->isDisabled() ) {
                                $maxAge = $config->get( 'CdnMaxageSubstitute' );
                                $output->lowerCdnMaxage( $maxAge );
                                $request->response()->header( "X-Response-Substitute: true" );
                        }

                        if ( !$output->couldBePublicCached() || $output->haveCacheVaryCookies() ) {
                                // Autoblocks: If this user is autoblocked (and the cookie block feature is enabled
                                // for autoblocks), then set a cookie to track this block.
                                // This has to be done on all logged-in page loads (not just upon saving edits),
                                // because an autoblocked editor might not edit again from the same IP address.
                                //
                                // IP blocks: For anons, if their IP is blocked (and cookie block feature is enabled
                                // for IP blocks), we also want to set the cookie whenever it is safe to do.
                                // Basically from any url that are definitely not publicly cacheable (like viewing
                                // EditPage), or when the HTTP response is personalised for other reasons (e.g. viewing
                                // articles within the same browsing session after making an edit).
                                $user = $context->getUser();
                                $services->getBlockManager()
                                        ->trackBlockWithCookie( $user, $request->response() );
                        }
                }
        }

        /**
         * @param ILBFactory $lbFactory
         * @param OutputPage $output
         * @return array
         */
        private static function getChronProtStrategy( ILBFactory $lbFactory, OutputPage $output ) {
                // Should the client return, their request should observe the new ChronologyProtector
                // DB positions. This request might be on a foreign wiki domain, so synchronously update
                // the DB positions in all datacenters to be safe. If this output is not a redirect,
                // then OutputPage::output() will be relatively slow, meaning that running it in
                // $postCommitWork should help mask the latency of those updates.
                $flags = $lbFactory::SHUTDOWN_CHRONPROT_SYNC;
                $strategy = 'cookie+sync';

                $allowHeaders = !( $output->isDisabled() || headers_sent() );
                if ( $output->getRedirect() && $lbFactory->hasOrMadeRecentMasterChanges( INF ) ) {
                        // OutputPage::output() will be fast, so $postCommitWork is useless for masking
                        // the latency of synchronously updating the DB positions in all datacenters.
                        // Try to make use of the time the client spends following redirects instead.
                        $domainDistance = self::getUrlDomainDistance( $output->getRedirect() );
                        if ( $domainDistance === 'local' && $allowHeaders ) {
                                $flags = $lbFactory::SHUTDOWN_CHRONPROT_ASYNC;
                                $strategy = 'cookie'; // use same-domain cookie and keep the URL uncluttered
                        } elseif ( $domainDistance === 'remote' ) {
                                $flags = $lbFactory::SHUTDOWN_CHRONPROT_ASYNC;
                                $strategy = 'cookie+url'; // cross-domain cookie might not work
                        }
                }

                return [ $flags, $strategy ];
        }

        /**
         * @param string $url
         * @return string Either "local", "remote" if in the farm, "external" otherwise
         */
        private static function getUrlDomainDistance( $url ) {
                $clusterWiki = WikiMap::getWikiFromUrl( $url );
                if ( WikiMap::isCurrentWikiId( $clusterWiki ) ) {
                        return 'local'; // the current wiki
                }
                if ( $clusterWiki !== false ) {
                        return 'remote'; // another wiki in this cluster/farm
                }

                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
         *
         * @since 1.26
         */
        public function doPostOutputShutdown() {
                // Record backend request timing
                $timing = $this->context->getTiming();
                $timing->mark( 'requestShutdown' );

                // Perform the last synchronous operations...
                try {
                        // Show visible profiling data if enabled (which cannot be post-send)
                        Profiler::instance()->logDataPageOutputOnly();
                } catch ( Throwable $e ) {
                        // An error may already have been shown in run(), so just log it to be safe
                        MWExceptionHandler::logException( $e, MWExceptionHandler::CAUGHT_BY_ENTRYPOINT );
                }

                // Disable WebResponse setters for post-send processing (T191537).
                WebResponse::disableForPostSend();

                // Defer everything else if possible...
                $callback = function () {
                        try {
                                $this->restInPeace();
                        } catch ( Throwable $e ) {
                                // If this is post-send, then displaying errors can cause broken HTML
                                MWExceptionHandler::rollbackMasterChangesAndLog(
                                        $e,
                                        MWExceptionHandler::CAUGHT_BY_ENTRYPOINT
                                );
                        }
                };

                if ( $this->postSendStrategy === self::DEFER_FASTCGI_FINISH_REQUEST ) {
                        fastcgi_finish_request();
                        $callback();
                } else {
                        // Flush PHP and web server output buffers
                        if ( !$this->config->get( 'CommandLineMode' ) ) {
                                AtEase\AtEase::suppressWarnings();
                                if ( ob_get_status() ) {
                                        ob_end_flush();
                                }
                                flush();
                                AtEase\AtEase::restoreWarnings();
                        }
                        $callback();
                }
        }

        /**
         * Determine and send the response headers and body for this web request
         */
        private function main() {
                global $wgTitle;

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

                // Send Ajax requests to the Ajax dispatcher.
                if ( $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 ( $this->maybeDoHttpsRedirect() ) {
                        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 replicas across all datacenters.
                $buffer = null;
                $outputWork = function () use ( $output, &$buffer ) {
                        if ( $buffer === null ) {
                                $buffer = $output->output( true );
                        }

                        return $buffer;
                };

                // Commit any changes in the current transaction round so that:
                // a) the transaction is not rolled back after success output was already sent
                // b) error output is not jumbled together with success output in the response
                $this->doPreOutputCommit( $outputWork );
                // If needed, push a deferred update to run jobs after the output is send
                $this->schedulePostSendJobs();
                // If no exceptions occurred then send the output since it is safe now
                $this->outputResponsePayload( $outputWork() );
        }

        /**
         * Check if an HTTP->HTTPS redirect should be done. It may still be aborted
         * by a hook, so this is not the final word.
         *
         * @return bool
         */
        private function shouldDoHttpRedirect() {
                $request = $this->context->getRequest();

                // Don't redirect if we're already on HTTPS
                if ( $request->getProtocol() !== 'http' ) {
                        return false;
                }

                $force = $this->config->get( 'ForceHTTPS' );

                // Don't redirect if $wgServer is explicitly HTTP. We test for this here
                // by checking whether wfExpandUrl() is able to force HTTPS.
                if ( !preg_match( '#^https://#', wfExpandUrl( $request->getRequestURL(), PROTO_HTTPS ) ) ) {
                        if ( $force ) {
                                throw new RuntimeException( '$wgForceHTTPS is true but the server is not HTTPS' );
                        }
                        return false;
                }

                // Configured $wgForceHTTPS overrides the remaining conditions
                if ( $force ) {
                        return true;
                }

                // Check if HTTPS is required by the session or user preferences
                return $request->getSession()->shouldForceHTTPS() ||
                        // Check the cookie manually, for paranoia
                        $request->getCookie( 'forceHTTPS', '' ) ||
                        // Avoid checking the user and groups unless it's enabled.
                        (
                                $this->context->getUser()->isLoggedIn()
                                && $this->context->getUser()->requiresHTTPS()
                        );
        }

        /**
         * If the stars are suitably aligned, do an HTTP->HTTPS redirect
         *
         * Note: Do this after $wgTitle is setup, otherwise the hooks run from
         * isLoggedIn() will do all sorts of weird stuff.
         *
         * @return bool True if the redirect was done. Handling of the request
         *   should be aborted. False if no redirect was done.
         */
        private function maybeDoHttpsRedirect() {
                if ( !$this->shouldDoHttpRedirect() ) {
                        return false;
                }

                $request = $this->context->getRequest();
                $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 ( !$this->getHookRunner()->onBeforeHttpsRedirect( $this->context, $redirUrl ) ) {
                        return false;
                }

                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 = $this->context->getOutput();
                $output->addVaryHeader( 'X-Forwarded-Proto' );
                $output->redirect( $redirUrl );
                $output->output();

                return true;
        }

        /**
         * Set the actual output and attempt to flush it to the client if necessary
         *
         * No PHP buffers should be active at this point
         *
         * @param string $content
         */
        private function outputResponsePayload( $content ) {
                if (
                        $this->postSendStrategy === self::DEFER_SET_LENGTH_AND_FLUSH &&
                        DeferredUpdates::pendingUpdatesCount() &&
                        !headers_sent()
                ) {
                        $response = $this->context->getRequest()->response();
                        // Make the browser indicate the page as "loaded" as soon as it gets all the content
                        $response->header( 'Connection: close' );
                        // The client should not be blocked on "post-send" updates. If apache or ob_* decide
                        // that a response should be gzipped, the entire script will have to finish before
                        // any data can be sent. Disable compression if there are any post-send updates.
                        $response->header( 'Content-Encoding: none' );
                        AtEase\AtEase::suppressWarnings();
                        ini_set( 'zlib.output_compression', 0 );
                        if ( function_exists( 'apache_setenv' ) ) {
                                apache_setenv( 'no-gzip', '1' );
                        }
                        AtEase\AtEase::restoreWarnings();
                        // Also set the Content-Length so that apache does not block waiting on PHP to finish.
                        // If OutputPage is disabled, then either there is no body (e.g. HTTP 304) and thus no
                        // Content-Length, or it was taken care of already.
                        if ( !$this->context->getOutput()->isDisabled() ) {
                                ob_start();
                                print $content;
                                $response->header( 'Content-Length: ' . ob_get_length() );
                                ob_end_flush();
                        }
                        // @TODO: this still blocks on HEAD responses and 304 responses to GETs
                } else {
                        print $content;
                }
        }

        /**
         * Ends this task peacefully
         */
        public function restInPeace() {
                // Either all DB and deferred updates should happen or none.
                // The latter should not be cancelled due to client disconnect.
                ignore_user_abort( true );

                $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->redefineExpectations(
                        $this->context->getRequest()->hasSafeMethod()
                                ? $this->config->get( 'TrxProfilerLimits' )['PostSend-GET']
                                : $this->config->get( 'TrxProfilerLimits' )['PostSend-POST'],
                        __METHOD__
                );

                // Do any deferred jobs; preferring to run them now if a client will not wait on them
                DeferredUpdates::doUpdates( 'run' );

                // 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" );
        }

        /**
         * Send out any buffered statsd data according to sampling rules
         *
         * @param IBufferingStatsdDataFactory $stats
         * @param Config $config
         * @throws ConfigException
         * @since 1.31
         */
        public static function emitBufferedStatsdData(
                IBufferingStatsdDataFactory $stats, Config $config
        ) {
                if ( $config->get( 'StatsdServer' ) && $stats->hasData() ) {
                        try {
                                $statsdServer = explode( ':', $config->get( 'StatsdServer' ), 2 );
                                $statsdHost = $statsdServer[0];
                                $statsdPort = $statsdServer[1] ?? 8125;
                                $statsdSender = new SocketSender( $statsdHost, $statsdPort );
                                $statsdClient = new SamplingStatsdClient( $statsdSender, true, false );
                                $statsdClient->setSamplingRates( $config->get( 'StatsdSamplingRates' ) );
                                $statsdClient->send( $stats->getData() );

                                $stats->clearData(); // empty buffer for the next round
                        } catch ( Exception $e ) {
                                MWExceptionHandler::logException( $e, MWExceptionHandler::CAUGHT_BY_ENTRYPOINT );
                        }
                }
        }

        /**
         * 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.
         * @deprecated Since 1.34
         */
        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 );
                }

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

                try {
                        if ( $this->config->get( 'RunJobsAsync' ) ) {
                                // Send an HTTP request to the job RPC entry point if possible
                                $invokedWithSuccess = $this->triggerAsyncJobs( $n, $logger );
                                if ( !$invokedWithSuccess ) {
                                        // Fall back to blocking on running the job(s)
                                        $logger->warning( "Jobs switched to blocking; Special:RunJobs disabled" );
                                        $this->triggerSyncJobs( $n );
                                }
                        } else {
                                $this->triggerSyncJobs( $n );
                        }
                } catch ( JobQueueError $e ) {
                        // Do not make the site unavailable (T88312)
                        MWExceptionHandler::logException( $e, MWExceptionHandler::CAUGHT_BY_ENTRYPOINT );
                }
        }

        /**
         * @param int $n Number of jobs to try to run
         */
        private function triggerSyncJobs( $n ) {
                $trxProfiler = Profiler::instance()->getTransactionProfiler();
                $old = $trxProfiler->setSilenced( true );
                try {
                        $runner = MediaWikiServices::getInstance()->getJobRunner();
                        $runner->run( [ 'maxJobs' => $n ] );
                } finally {
                        $trxProfiler->setSilenced( $old );
                }
        }

        /**
         * @param int $n Number of jobs to try to run
         * @param LoggerInterface $runJobsLogger
         * @return bool Success
         */
        private function triggerAsyncJobs( $n, LoggerInterface $runJobsLogger ) {
                // Do not send request if there are probably no jobs
                $group = JobQueueGroup::singleton();
                if ( !$group->queuesHaveJobs( JobQueueGroup::TYPE_DEFAULT ) ) {
                        return true;
                }

                $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'];
                }

                Wikimedia\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;
                Wikimedia\restoreWarnings();

                $invokedWithSuccess = true;
                if ( $sock ) {
                        $special = MediaWikiServices::getInstance()->getSpecialPageFactory()->
                                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" );
                }

                return $invokedWithSuccess;
        }
}