Remove unused variable in ProfilerMwprof

[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
 */

/**
 * The MediaWiki class is the helper class for the index.php entry point.
 *
 * @internal documentation reviewed 15 Mar 2010
 */
class MediaWiki {
        /**
         * @var IContextSource
         */
        private $context;

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

        /**
         * @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
         *
         * @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', 'view' );

                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() ) ) {
                        $ret = SpecialPage::getTitleFor( 'Badtitle' );
                }

                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() ) {
                        $this->context->setTitle( $this->parseTitle() );
                }
                return $this->context->getTitle();
        }

        /**
         * Returns the name of the action that will be executed.
         *
         * @return string Action
         */
        public function getAction() {
                static $action = null;

                if ( $action === null ) {
                        $action = Action::getActionName( $this->context );
                }

                return $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;

                wfProfileIn( __METHOD__ );

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

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

                $unused = null; // To pass it by reference
                wfRunHooks( 'BeforeInitialize', array( &$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' ) );
                        wfProfileOut( __METHOD__ );
                        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' )
                        ? array() // 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;

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

                $pageView = false; // was an article or special page viewed?

                // Interwiki redirects
                if ( $title->isExternal() ) {
                        $rdfrom = $request->getVal( 'rdfrom' );
                        if ( $rdfrom ) {
                                $url = $title->getFullURL( array( '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' ) );
                                wfProfileOut( __METHOD__ );
                                throw new BadTitleError();
                        }
                // Redirect loops, no title in URL, $wgUsePathInfo URLs, and URLs with a variant
                } elseif ( $request->getVal( 'action', 'view' ) == 'view' && !$request->wasPosted()
                        && ( $request->getVal( 'title' ) === null
                                || $title->getPrefixedDBkey() != $request->getVal( 'title' ) )
                        && !count( $request->getValueNames( array( 'action', 'title' ) ) )
                        && wfRunHooks( 'TestCanonicalRedirect', array( $request, $title, $output ) )
                ) {
                        if ( $title->isSpecialPage() ) {
                                list( $name, $subpage ) = SpecialPageFactory::resolveAlias( $title->getDBkey() );
                                if ( $name ) {
                                        $title = SpecialPage::getTitleFor( $name, $subpage );
                                }
                        }
                        $targetUrl = wfExpandUrl( $title->getFullURL(), PROTO_CURRENT );
                        // Redirect to canonical url, make it a 301 to allow caching
                        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 );
                        } else {
                                $output->setSquidMaxage( 1200 );
                                $output->redirect( $targetUrl, '301' );
                        }
                // Special pages
                } elseif ( NS_SPECIAL == $title->getNamespace() ) {
                        $pageView = true;
                        // 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 be a redirect to another article or URL.
                        $article = $this->initializeArticle();
                        if ( is_object( $article ) ) {
                                $pageView = true;
                                $this->performAction( $article, $requestTitle );
                        } elseif ( is_string( $article ) ) {
                                $output->redirect( $article );
                        } else {
                                wfProfileOut( __METHOD__ );
                                throw new MWException( "Shouldn't happen: MediaWiki::initializeArticle()"
                                        . " returned neither an object nor a URL" );
                        }
                }

                if ( $pageView ) {
                        // Promote user to any groups they meet the criteria for
                        $user->addAutopromoteOnceGroups( 'onView' );
                }

                wfProfileOut( __METHOD__ );
        }

        /**
         * Initialize the main Article object for "standard" actions (view, etc)
         * Create an Article object for the page, following redirects if needed.
         *
         * @return mixed An Article, or a string to redirect to another URL
         */
        private function initializeArticle() {
                wfProfileIn( __METHOD__ );

                $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();
                        $article = Article::newFromWikiPage( $page, $this->context );
                } else {
                        // This case should not happen, but just in case.
                        $article = Article::newFromTitle( $title, $this->context );
                        $this->context->setWikiPage( $article->getPage() );
                }

                // NS_MEDIAWIKI has no redirects.
                // It is also used for CSS/JS, so performance matters here...
                if ( $title->getNamespace() == NS_MEDIAWIKI ) {
                        wfProfileOut( __METHOD__ );
                        return $article;
                }

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

                // Namespace might change when using redirects
                // Check for redirects ...
                $action = $request->getVal( 'action', 'view' );
                $file = ( $title->getNamespace() == NS_FILE ) ? $article->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;

                        wfRunHooks( 'InitializeArticleMaybeRedirect',
                                array( &$title, &$request, &$ignoreRedirect, &$target, &$article ) );

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

                wfProfileOut( __METHOD__ );
                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 ) {
                wfProfileIn( __METHOD__ );

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

                if ( !wfRunHooks( 'MediaWikiPerformAction',
                                array( $output, $page, $title, $user, $request, $this ) )
                ) {
                        wfProfileOut( __METHOD__ );
                        return;
                }

                $act = $this->getAction();

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

                if ( $action instanceof Action ) {
                        # Let Squid cache things if we can purge them.
                        if ( $this->config->get( 'UseSquid' ) &&
                                in_array( $request->getFullRequestURL(), $requestTitle->getSquidURLs() )
                        ) {
                                $output->setSquidMaxage( $this->config->get( 'SquidMaxage' ) );
                        }

                        $action->show();
                        wfProfileOut( __METHOD__ );
                        return;
                }

                if ( wfRunHooks( 'UnknownAction', array( $request->getVal( 'action', 'view' ), $page ) ) ) {
                        $output->setStatusCode( 404 );
                        $output->showErrorPage( 'nosuchaction', 'nosuchactiontext' );
                }

                wfProfileOut( __METHOD__ );
        }

        /**
         * Run the current MediaWiki instance
         * index.php just calls this
         */
        public function run() {
                try {
                        $this->checkMaxLag();
                        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.
                                wfGetLBFactory()->commitMasterChanges();
                                $e->report(); // display the GUI error
                        }
                        if ( function_exists( 'fastcgi_finish_request' ) ) {
                                fastcgi_finish_request();
                        }
                        $this->triggerJobs();
                        $this->restInPeace();
                } catch ( Exception $e ) {
                        MWExceptionHandler::handle( $e );
                }
        }

        /**
         * Checks if the request should abort due to a lagged server,
         * for given maxlag parameter.
         * @return bool
         */
        private function checkMaxLag() {
                wfProfileIn( __METHOD__ );
                $maxLag = $this->context->getRequest()->getVal( 'maxlag' );
                if ( !is_null( $maxLag ) ) {
                        list( $host, $lag ) = wfGetLB()->getMaxLag();
                        if ( $lag > $maxLag ) {
                                $resp = $this->context->getRequest()->response();
                                $resp->header( 'HTTP/1.1 503 Service Unavailable' );
                                $resp->header( 'Retry-After: ' . max( intval( $maxLag ), 5 ) );
                                $resp->header( 'X-Database-Lag: ' . intval( $lag ) );
                                $resp->header( 'Content-Type: text/plain' );
                                if ( $this->config->get( 'ShowHostnames' ) ) {
                                        echo "Waiting for $host: $lag seconds lagged\n";
                                } else {
                                        echo "Waiting for a database server: $lag seconds lagged\n";
                                }

                                wfProfileOut( __METHOD__ );

                                exit;
                        }
                }
                wfProfileOut( __METHOD__ );
                return true;
        }

        private function main() {
                global $wgTitle;

                wfProfileIn( __METHOD__ );

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

                // Send Ajax requests to the Ajax dispatcher.
                if ( $this->config->get( 'UseAjax' ) && $request->getVal( 'action', 'view' ) == 'ajax' ) {

                        // Set a dummy title, because $wgTitle == null might break things
                        $title = Title::makeTitle( NS_MAIN, 'AJAX' );
                        $this->context->setTitle( $title );
                        $wgTitle = $title;

                        $dispatcher = new AjaxDispatcher( $this->config );
                        $dispatcher->performAction( $this->context->getUser() );
                        wfProfileOut( __METHOD__ );
                        return;
                }

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

                // 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' &&
                        (
                                $request->getCookie( 'forceHTTPS', '' ) ||
                                // check for prefixed version for currently logged in users
                                $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 ( wfRunHooks( 'BeforeHttpsRedirect', array( $this->context, &$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( NS_MAIN, 'REDIR' );
                                $this->context->setTitle( $title );
                                $output = $this->context->getOutput();
                                // Since we only do this redir to change proto, always send a vary header
                                $output->addVaryHeader( 'X-Forwarded-Proto' );
                                $output->redirect( $redirUrl );
                                $output->output();
                                wfProfileOut( __METHOD__ );
                                return;
                        }
                }

                if ( $this->config->get( 'UseFileCache' ) && $title->getNamespace() >= 0 ) {
                        wfProfileIn( 'main-try-filecache' );
                        if ( 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 = $cache->cacheTimestamp();
                                        if ( !$this->context->getOutput()->checkLastModified( $timestamp ) ) {
                                                $cache->loadFromFileCache( $this->context );
                                        }
                                        // Do any stats increment/watchlist stuff
                                        // Assume we're viewing the latest revision (this should always be the case with file cache)
                                        $this->context->getWikiPage()->doViewUpdates( $this->context->getUser() );
                                        // Tell OutputPage that output is taken care of
                                        $this->context->getOutput()->disable();
                                        wfProfileOut( 'main-try-filecache' );
                                        wfProfileOut( __METHOD__ );
                                        return;
                                }
                        }
                        wfProfileOut( 'main-try-filecache' );
                }

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

                // Either all DB and deferred updates should happen or none.
                // The later should not be cancelled due to client disconnect.
                ignore_user_abort( true );
                // Now commit any transactions, so that unreported errors after
                // output() don't roll back the whole DB transaction
                wfGetLBFactory()->commitMasterChanges();

                // Output everything!
                $this->context->getOutput()->output();

                wfProfileOut( __METHOD__ );
        }

        /**
         * Ends this task peacefully
         */
        public function restInPeace() {
                // Do any deferred jobs
                DeferredUpdates::doUpdates( 'commit' );

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

                // Commit and close up!
                $factory = wfGetLBFactory();
                $factory->commitMasterChanges();
                $factory->shutdown();

                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.
         */
        protected function triggerJobs() {
                $jobRunRate = $this->config->get( 'JobRunRate' );
                if ( $jobRunRate <= 0 || wfReadOnly() ) {
                        return;
                } elseif ( $this->getTitle()->isSpecial( 'RunJobs' ) ) {
                        return; // recursion guard
                }

                $section = new ProfileSection( __METHOD__ );

                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 );
                }

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

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

                $query = array( '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( 'Server' ) );
                wfSuppressWarnings();
                $sock = fsockopen(
                        $info['host'],
                        isset( $info['port'] ) ? $info['port'] : 80,
                        $errno,
                        $errstr,
                        // If it takes more than 100ms to connect to ourselves there
                        // is a problem elsewhere.
                        0.1
                );
                wfRestoreWarnings();
                if ( !$sock ) {
                        wfDebugLog( 'runJobs', "Failed to start cron API (socket error $errno): $errstr\n" );
                        // Fall back to running the job here while the user waits
                        $runner = new JobRunner();
                        $runner->run( array( 'maxJobs'  => $n ) );
                        return;
                }

                $url = wfAppendQuery( wfScript( 'index' ), $query );
                $req = "POST $url HTTP/1.1\r\nHost: {$info['host']}\r\nConnection: Close\r\n\r\n";

                wfDebugLog( 'runJobs', "Running $n job(s) via '$url'\n" );
                // 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, 1 );
                $bytes = fwrite( $sock, $req );
                if ( $bytes !== strlen( $req ) ) {
                        wfDebugLog( 'runJobs', "Failed to start cron API (socket write error)\n" );
                } 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().
                        $status = fgets( $sock );
                        if ( !preg_match( '#^HTTP/\d\.\d 202 #', $status ) ) {
                                wfDebugLog( 'runJobs', "Failed to start cron API: received '$status'\n" );
                        }
                }
                fclose( $sock );
        }
}