Replace cpPosTime cookie/parameter with cpPosIndex

[lhc/web/wiklou.git] / includes / MediaWiki.php

diff --git a/includes/MediaWiki.php b/includes/MediaWiki.php
index beb9de5..b1b1a7a 100644 (file)
--- a/includes/MediaWiki.php
+++ b/includes/MediaWiki.php
@@ -603,50 +603,54 @@ class MediaWiki {
                DeferredUpdates::doUpdates( 'enqueue', DeferredUpdates::PRESEND );
                wfDebug( __METHOD__ . ': pre-send deferred updates completed' );
 
-               // Decide when clients block on ChronologyProtector DB position writes
-               $urlDomainDistance = (
-                       $request->wasPosted() &&
-                       $output->getRedirect() &&
-                       $lbFactory->hasOrMadeRecentMasterChanges( INF )
-               ) ? self::getUrlDomainDistance( $output->getRedirect() ) : false;
+               // 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 ( $urlDomainDistance === 'local' || $urlDomainDistance === 'remote' ) {
-                       // OutputPage::output() will be fast; $postCommitWork will not be useful for
-                       // masking the latency of syncing DB positions accross all datacenters synchronously.
-                       // Instead, make use of the RTT time of the client follow redirects.
-                       $flags = $lbFactory::SHUTDOWN_CHRONPROT_ASYNC;
-                       $cpPosTime = microtime( true );
-                       // Client's next request should see 1+ positions with this DBMasterPos::asOf() time
-                       if ( $urlDomainDistance === 'local' && $allowHeaders ) {
-                               // Client will stay on this domain, so set an unobtrusive cookie
-                               $expires = time() + ChronologyProtector::POSITION_TTL;
-                               $options = [ 'prefix' => '' ];
-                               $request->response()->setCookie( 'cpPosTime', $cpPosTime, $expires, $options );
-                       } else {
-                               // Cookies may not work across wiki domains, so use a URL parameter
-                               $safeUrl = $lbFactory->appendPreShutdownTimeAsQuery(
-                                       $output->getRedirect(),
-                                       $cpPosTime
-                               );
-                               $output->redirect( $safeUrl );
+               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
                        }
-               } else {
-                       // OutputPage::output() is fairly slow; run it in $postCommitWork to mask
-                       // the latency of syncing DB positions accross all datacenters synchronously
-                       $flags = $lbFactory::SHUTDOWN_CHRONPROT_SYNC;
-                       if ( $lbFactory->hasOrMadeRecentMasterChanges( INF ) && $allowHeaders ) {
-                               $cpPosTime = microtime( true );
-                               // Set a cookie in case the DB position store cannot sync accross datacenters.
-                               // This will at least cover the common case of the user staying on the domain.
+               }
+
+               // Record ChronologyProtector positions for DBs affected in this request at this point
+               $cpIndex = null;
+               $lbFactory->shutdown( $flags, $postCommitWork, $cpIndex );
+               wfDebug( __METHOD__ . ': LBFactory shutdown completed' );
+
+               if ( $cpIndex > 0 ) {
+                       if ( $allowHeaders ) {
                                $expires = time() + ChronologyProtector::POSITION_TTL;
                                $options = [ 'prefix' => '' ];
-                               $request->response()->setCookie( 'cpPosTime', $cpPosTime, $expires, $options );
+                               $request->response()->setCookie( 'cpPosIndex', $cpIndex, $expires, $options );
+                       }
+
+                       if ( $strategy === 'cookie+url' ) {
+                               if ( $output->getRedirect() ) { // sanity
+                                       $safeUrl = $lbFactory->appendShutdownCPIndexAsQuery(
+                                               $output->getRedirect(),
+                                               $cpIndex
+                                       );
+                                       $output->redirect( $safeUrl );
+                               } else {
+                                       $e = new LogicException( "No redirect; cannot append cpPosIndex parameter." );
+                                       MWExceptionHandler::logException( $e );
+                               }
                        }
                }
-               // Record ChronologyProtector positions for DBs affected in this request at this point
-               $lbFactory->shutdown( $flags, $postCommitWork );
-               wfDebug( __METHOD__ . ': LBFactory shutdown completed' );
 
                // Set a cookie to tell all CDN edge nodes to "stick" the user to the DC that handles this
                // POST request (e.g. the "master" data center). Also have the user briefly bypass CDN so