Hi, This is expected behaviour for transactional databases with pessimistic concurrency control. You usually handle this in user-code by retrying the transaction, making sure that external side-effects, such as sending emails and processing payments, only happen after the transaction has committed, or as participants in a distributed transaction, e.g. two-phase commit.
-- Chris Vest System Engineer, Neo Technology [ skype: mr.chrisvest, twitter: chvest ] On 04 Jul 2014, at 09:53, ducky <[email protected]> wrote: > Hi Chris, > i) I do create more than 1 relationship per transaction. > ii) As you suggest, the nodes b, c are involved in creating other > relationships but not between each other. > > This is a real bummer. So in my case, creating locks on the nodes when > creating relationships and the locks only being released at the end of the > transaction is the source of the problem. > > This seems quite heavy to me and I am guessing that this has the potential > for effecting the unmanaged extensions and even the REST API based > transactions pretty badly in a multiprocessing environment. Is it worth > raising on the github? > > Thanks a lot for your help! > > On Thursday, 3 July 2014 22:14:02 UTC+1, Chris Vest wrote: > Do you create more than one relationship per transaction? Both the start and > the end node have to be lock to create a relationship between them, and locks > are not released until the transaction commits. It could also be that you > have some other transaction that happens to work with the start and end nodes. > > > -- > Chris Vest > System Engineer, Neo Technology > [ skype: mr.chrisvest, twitter: chvest ] > > > On 03 Jul 2014, at 18:13, ducky <[email protected]> wrote: > >> Hi, >> I am using Neo4j 2.1.2 and I have an unmanaged extension in which I am >> trying to create the following relationships in separate concurrent >> transactions: >> >> 1) (b)-[:REL]->(a) >> 2) (c)-[:REL]->(a) >> >> I am never deleting any relationship and I am getting this error: >> >> org.neo4j.kernel.DeadlockDetectedException: LockClient[118] can't wait on >> resource RWLock[NODE(429288), hash=1375407138] since => LockClient[118] >> <-[:HELD_BY]- RWLock[NODE(429304), hash=1035143818] <-[:WAITING_FOR]- >> LockClient[119] <-[:HELD_BY]- RWLock[NODE(429288), hash=1375407138] >> at >> org.neo4j.kernel.impl.locking.community.RagManager.checkWaitOnRecursive(RagManager.java:211) >> at >> org.neo4j.kernel.impl.locking.community.RagManager.checkWaitOnRecursive(RagManager.java:238) >> at >> org.neo4j.kernel.impl.locking.community.RagManager.checkWaitOn(RagManager.java:178) >> at >> org.neo4j.kernel.impl.locking.community.RWLock.deadlockGuardedWait(RWLock.java:547) >> at >> org.neo4j.kernel.impl.locking.community.RWLock.acquireWriteLock(RWLock.java:319) >> at >> org.neo4j.kernel.impl.locking.community.LockManagerImpl.getWriteLock(LockManagerImpl.java:68) >> at >> org.neo4j.kernel.impl.locking.community.CommunityLockClient.acquireExclusive(CommunityLockClient.java:73) >> at >> org.neo4j.kernel.impl.api.LockingStatementOperations.relationshipCreate(LockingStatementOperations.java:215) >> at >> org.neo4j.kernel.impl.api.OperationsFacade.relationshipCreate(OperationsFacade.java:515) >> at >> org.neo4j.kernel.impl.core.NodeProxy.createRelationshipTo(NodeProxy.java:455) >> .......(snipped)....... >> >> I've read the section called Deadlocks in the documentation but I don't >> think what I am doing should lead to the deadlock. >> >> Any help would be appreciated. >> >> Thanks! >> >> -- >> You received this message because you are subscribed to the Google Groups >> "Neo4j" group. >> To unsubscribe from this group and stop receiving emails from it, send an >> email to [email protected]. >> For more options, visit https://groups.google.com/d/optout. > > > -- > You received this message because you are subscribed to the Google Groups > "Neo4j" group. > To unsubscribe from this group and stop receiving emails from it, send an > email to [email protected]. > For more options, visit https://groups.google.com/d/optout. -- You received this message because you are subscribed to the Google Groups "Neo4j" group. To unsubscribe from this group and stop receiving emails from it, send an email to [email protected]. For more options, visit https://groups.google.com/d/optout.
