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RelationshipCreateDeleteLockOrderingIT.java
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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();
}
}