You could acquire a coarser lock on a certain lock node for your use-case so the requests would be serialized
Or you batch your operations so that the locks are held by the same tx See maxdemarzi.com blog for several examples. Sent from mobile device Am 04.07.2014 um 13:50 schrieb ducky <[email protected]>: > Thanks Chris. > > What I meant was that a read-write lock on a node when an edge is being > created felt heavy. If thats what is required for a transactional database > like neo4j, so be it. > > I understand how I can handle this in my user code (by retrying or > structuring my data differently). > > If I know the domain of my problem well, is it possible to release the locks > manually? > > Thanks > > On Friday, 4 July 2014 09:33:36 UTC+1, Chris Vest wrote: >> >> 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. -- 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.
