use MediaWiki\Logger\LoggerFactory;
use Psr\Log\LoggerInterface;
use MediaWiki\MediaWikiServices;
+use Wikimedia\Rdbms\ILBFactory;
use Wikimedia\Rdbms\ChronologyProtector;
-use Wikimedia\Rdbms\LBFactory;
use Wikimedia\Rdbms\DBConnectionError;
use Liuggio\StatsdClient\Sender\SocketSender;
public static function preOutputCommit(
IContextSource $context, callable $postCommitWork = null
) {
- // Either all DBs should commit or none
- ignore_user_abort( true );
-
$config = $context->getConfig();
$request = $context->getRequest();
$output = $context->getOutput();
$lbFactory = MediaWikiServices::getInstance()->getDBLoadBalancerFactory();
- // Commit all changes
+ // 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
);
wfDebug( __METHOD__ . ': primary transaction round committed' );
- // Run updates that need to block the user or affect output (this is the last chance)
+ // 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' );
- // T214471: persist the session to avoid race conditions on subsequent requests
- $request->getSession()->save();
-
- // 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
- }
- }
-
+ // 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 );
+ $value = $lbFactory::makeCookieValueFromCPIndex( $cpIndex, $now, $cpClientId );
$request->response()->setCookie( 'cpPosIndex', $value, $expires, $options );
}
}
}
- // 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 );
- }
+ 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 letting a few seconds of replica DB lag cause a month of stale data. This logic is
- // also intimately related to the value of $wgCdnReboundPurgeDelay.
- if ( $lbFactory->laggedReplicaUsed() ) {
- $maxAge = $config->get( 'CdnMaxageLagged' );
- $output->lowerCdnMaxage( $maxAge );
- $request->response()->header( "X-Database-Lagged: true" );
- wfDebugLog( 'replication', "Lagged DB used; CDN cache TTL limited to $maxAge seconds" );
+ // Avoid long-term cache pollution due to message cache rebuild timeouts (T133069)
+ if ( MessageCache::singleton()->isDisabled() ) {
+ $maxAge = $config->get( 'CdnMaxageSubstitute' );
+ $output->lowerCdnMaxage( $maxAge );
+ $request->response()->header( "X-Response-Substitute: true" );
+ }
}
+ }
+
+ /**
+ * @param 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';
- // Avoid long-term cache pollution due to message cache rebuild timeouts (T133069)
- if ( MessageCache::singleton()->isDisabled() ) {
- $maxAge = $config->get( 'CdnMaxageSubstitute' );
- $output->lowerCdnMaxage( $maxAge );
- $request->response()->header( "X-Response-Substitute: true" );
+ $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 ];
}
/**
// Commit and close up!
$lbFactory->commitMasterChanges( __METHOD__ );
- $lbFactory->shutdown( LBFactory::SHUTDOWN_NO_CHRONPROT );
+ $lbFactory->shutdown( $lbFactory::SHUTDOWN_NO_CHRONPROT );
wfDebug( "Request ended normally\n" );
}