From: Aaron Schulz <aschulz@wikimedia.org>
Date: Thu, 18 Jul 2019 19:27:07 +0000 (-0700)
Subject: Clean up DeferredUpdates transaction handling
X-Git-Tag: 1.34.0-rc.0~951^2
X-Git-Url: https://git.cyclocoop.org/%7B%24www_url%7Dadmin/compta/exercices/journal.php?a=commitdiff_plain;h=b39f8289ff56e50213129abee91f3791bc6ffeb5;p=lhc%2Fweb%2Fwiklou.git

Clean up DeferredUpdates transaction handling

Bail out in attemptUpdate() if the transaction state is dirty rather
that failing at some later point. Also, flush implicit transaction
rounds before calling DeferrableUpdate::doUpdate() for fresher data.

Bug: T225103
Change-Id: I4f5d2f9814a562069619f05e003663fcedbd3f64
---

diff --git a/includes/deferred/DeferredUpdates.php b/includes/deferred/DeferredUpdates.php
index c754cff685..d43ffbc975 100644
--- a/includes/deferred/DeferredUpdates.php
+++ b/includes/deferred/DeferredUpdates.php
@@ -28,6 +28,7 @@ use MediaWiki\MediaWikiServices;
 use Wikimedia\Rdbms\LBFactory;
 use Wikimedia\Rdbms\ILBFactory;
 use Wikimedia\Rdbms\LoadBalancer;
+use Wikimedia\Rdbms\DBTransactionError;
 
 /**
  * Class for managing the deferred updates
@@ -352,28 +353,30 @@ class DeferredUpdates {
 	 * @since 1.34
 	 */
 	public static function attemptUpdate( DeferrableUpdate $update, ILBFactory $lbFactory ) {
+		$ticket = $lbFactory->getEmptyTransactionTicket( __METHOD__ );
+		if ( !$ticket || $lbFactory->hasTransactionRound() ) {
+			throw new DBTransactionError( null, "A database transaction round is pending." );
+		}
+
 		if ( $update instanceof DataUpdate ) {
-			$update->setTransactionTicket( $lbFactory->getEmptyTransactionTicket( __METHOD__ ) );
+			$update->setTransactionTicket( $ticket );
 		}
 
-		if (
+		$fnameTrxOwner = get_class( $update ) . '::doUpdate';
+		$useExplicitTrxRound = !(
 			$update instanceof TransactionRoundAwareUpdate &&
 			$update->getTransactionRoundRequirement() == $update::TRX_ROUND_ABSENT
-		) {
-			$fnameTrxOwner = null;
+		);
+		// Flush any pending changes left over from an implicit transaction round
+		if ( $useExplicitTrxRound ) {
+			$lbFactory->beginMasterChanges( $fnameTrxOwner ); // new explicit round
 		} else {
-			$fnameTrxOwner = get_class( $update ) . '::doUpdate';
+			$lbFactory->commitMasterChanges( $fnameTrxOwner ); // new implicit round
 		}
-
-		if ( $fnameTrxOwner !== null ) {
-			$lbFactory->beginMasterChanges( $fnameTrxOwner );
-		}
-
+		// Run the update after any stale master view snapshots have been flushed
 		$update->doUpdate();
-
-		if ( $fnameTrxOwner !== null ) {
-			$lbFactory->commitMasterChanges( $fnameTrxOwner );
-		}
+		// Commit any pending changes from the explicit or implicit transaction round
+		$lbFactory->commitMasterChanges( $fnameTrxOwner );
 	}
 
 	/**