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Fix deadlock caused by different lock ordering on nodes for relations…
…hips When we create relationships we lock the nodes wrt to the node id ordering, but when we delete a relationship we were locking the start node first and the end node last. This was causing deadlock when creating and deleting relationships between the same 2 ndoes.
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112
...l/src/test/java/org/neo4j/kernel/impl/locking/RelationshipCreateDeleteLockOrderingIT.java
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| /* | ||
| * Copyright (c) 2002-2016 "Neo Technology," | ||
| * Network Engine for Objects in Lund AB [http://neotechnology.com] | ||
| * | ||
| * This file is part of Neo4j. | ||
| * | ||
| * Neo4j 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 3 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, see <http://www.gnu.org/licenses/>. | ||
| */ | ||
| package org.neo4j.kernel.impl.locking; | ||
|
|
||
| import org.junit.Rule; | ||
| import org.junit.Test; | ||
|
|
||
| import org.neo4j.graphdb.Node; | ||
| import org.neo4j.graphdb.Relationship; | ||
| import org.neo4j.graphdb.Transaction; | ||
| import org.neo4j.kernel.impl.MyRelTypes; | ||
| import org.neo4j.test.DatabaseRule; | ||
| import org.neo4j.test.ImpermanentDatabaseRule; | ||
| import org.neo4j.test.Race; | ||
| import org.neo4j.test.RandomRule; | ||
| import static org.junit.Assert.assertTrue; | ||
|
|
||
| /** | ||
| * Testing on database level that creating and deleting relationships over the the same two nodes | ||
| * doesn't create unnecessary deadlock scenarios, i.e. that locking order is predictable and symmetrical | ||
| */ | ||
| public class RelationshipCreateDeleteLockOrderingIT | ||
| { | ||
| @Rule | ||
| public final DatabaseRule db = new ImpermanentDatabaseRule(); | ||
| @Rule | ||
| public final RandomRule random = new RandomRule(); | ||
|
|
||
| @Test | ||
| public void shouldNotDeadlockWhenConcurrentCreateAndDeleteRelationships() throws Throwable | ||
| { | ||
| // GIVEN (A) -[R]-> (B) | ||
| final Node a; | ||
| final Node b; | ||
| try ( Transaction tx = db.beginTx() ) | ||
| { | ||
| (a = db.createNode()).createRelationshipTo( b = db.createNode(), MyRelTypes.TEST ); | ||
| tx.success(); | ||
| } | ||
|
|
||
| // WHEN | ||
| Race race = new Race(); | ||
| // a bunch of deleters | ||
| for ( int i = 0; i < 30; i++ ) | ||
| { | ||
| race.addContestant( new Runnable() | ||
| { | ||
| @Override | ||
| public void run() | ||
| { | ||
| try ( Transaction tx = db.beginTx() ) | ||
| { | ||
| Node node = random.nextBoolean() ? a : b; | ||
| for ( Relationship relationship : node.getRelationships() ) | ||
| { | ||
| try | ||
| { | ||
| relationship.delete(); | ||
| } | ||
| catch ( IllegalStateException e ) | ||
| { | ||
| // This is OK and expected since there are multiple threads deleting | ||
| assertTrue( e.getMessage().contains( "already deleted" ) ); | ||
| } | ||
| } | ||
| tx.success(); | ||
| } | ||
| } | ||
| } ); | ||
| } | ||
|
|
||
| // a bunch of creators | ||
| for ( int i = 0; i < 30; i++ ) | ||
| { | ||
| race.addContestant( new Runnable() | ||
| { | ||
| @Override | ||
| public void run() | ||
| { | ||
| try ( Transaction tx = db.beginTx() ) | ||
| { | ||
| boolean order = random.nextBoolean(); | ||
| Node start = order ? a : b; | ||
| Node end = order ? b : a; | ||
| start.createRelationshipTo( end, MyRelTypes.TEST ); | ||
| tx.success(); | ||
| } | ||
| } | ||
| } ); | ||
| } | ||
|
|
||
| // THEN there should be no thread throwing exception, especially DeadlockDetectedException | ||
| race.go(); | ||
| } | ||
| } |