In CONTROLLER-1756 we're running into this from openflowplugin:

2017-08-22 17:00:50,640 | ERROR | CommitFutures-2 | ExecutionList | 65 - com.google.guava - 18.0.0 | RuntimeException while executing runnable com.google.common.util.concurrent.Futures$6@7d061282 with executor INSTANCE
java.lang.IllegalStateException: Attempted to close chain with outstanding transaction PingPongTransaction

{delegate=org.opendaylight.controller.cluster.databroker.DOMBrokerReadWriteTransaction@1947c741}

at com.google.common.base.Preconditions.checkState(Preconditions.java:197)[65:com.google.guava:18.0.0]
at org.opendaylight.controller.md.sal.dom.broker.impl.PingPongTransactionChain.close(PingPongTransactionChain.java:373)[171:org.opendaylight.controller.sal-broker-impl:1.5.2.Carbon]
at org.opendaylight.controller.md.sal.binding.impl.BindingDOMTransactionChainAdapter.close(BindingDOMTransactionChainAdapter.java:115)[173:org.opendaylight.controller.sal-binding-broker-impl:1.5.2.Carbon]
at java.util.Optional.ifPresent(Optional.java:159)[:1.8.0_141]
at org.opendaylight.openflowplugin.impl.device.TransactionChainManager.createTxChain(TransactionChainManager.java:84)[307:org.opendaylight.openflowplugin.impl:0.4.2.Carbon]
at org.opendaylight.openflowplugin.impl.device.TransactionChainManager.onTransactionChainFailed(TransactionChainManager.java:242)[307:org.opendaylight.openflowplugin.impl:0.4.2.Carbon]
at org.opendaylight.controller.md.sal.binding.impl.BindingDOMTransactionChainAdapter.failTransactionChain(BindingDOMTransactionChainAdapter.java:110)[173:org.opendaylight.controller.sal-binding-broker-impl:1.5.2.Carbon]
at org.opendaylight.controller.md.sal.binding.impl.BindingDOMTransactionChainAdapter.access$200(BindingDOMTransactionChainAdapter.java:31)[173:org.opendaylight.controller.sal-binding-broker-impl:1.5.2.Carbon]
at org.opendaylight.controller.md.sal.binding.impl.BindingDOMTransactionChainAdapter$3.onFailure(BindingDOMTransactionChainAdapter.java:91)[173:org.opendaylight.controller.sal-binding-broker-impl:1.5.2.Carbon]
at com.google.common.util.concurrent.Futures$6.run(Futures.java:1310)[65:com.google.guava:18.0.0]
at com.google.common.util.concurrent.MoreExecutors$DirectExecutor.execute(MoreExecutors.java:457)[65:com.google.guava:18.0.0]
at com.google.common.util.concurrent.ExecutionList.executeListener(ExecutionList.java:156)[65:com.google.guava:18.0.0]
at com.google.common.util.concurrent.ExecutionList.execute(ExecutionList.java:145)[65:com.google.guava:18.0.0]
at com.google.common.util.concurrent.AbstractFuture.setException(AbstractFuture.java:202)[65:com.google.guava:18.0.0]
at com.google.common.util.concurrent.SettableFuture.setException(SettableFuture.java:68)[65:com.google.guava:18.0.0]
at org.opendaylight.controller.md.sal.dom.broker.impl.PingPongTransaction.onFailure(PingPongTransaction.java:65)[171:org.opendaylight.controller.sal-broker-impl:1.5.2.Carbon]
at org.opendaylight.controller.md.sal.dom.broker.impl.PingPongTransactionChain.transactionFailed(PingPongTransactionChain.java:293)[171:org.opendaylight.controller.sal-broker-impl:1.5.2.Carbon]
at org.opendaylight.controller.md.sal.dom.broker.impl.PingPongTransactionChain$2.onFailure(PingPongTransactionChain.java:243)[171:org.opendaylight.controller.sal-broker-impl:1.5.2.Carbon]
at com.google.common.util.concurrent.Futures$6.run(Futures.java:1310)[65:com.google.guava:18.0.0]
at java.util.concurrent.ThreadPoolExecutor.runWorker(ThreadPoolExecutor.java:1149)[:1.8.0_141]
at java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:624)[:1.8.0_141]
at java.lang.Thread.run(Thread.java:748)[:1.8.0_141]

at least in some cases I see it being immediately followed in the log by this, I'm not sure how directly relevant this is:

2017-08-22 17:00:50,641 | ERROR | CommitFutures-2 | TransactionChainManager | 307 - org.opendaylight.openflowplugin.impl - 0.4.2.Carbon | Transaction commit failed.
OptimisticLockFailedException

{message=Optimistic lock failed., errorList=[RpcError [message=Optimistic lock failed., severity=ERROR, errorType=APPLICATION, tag=resource-denied, applicationTag=null, info=null, cause=org.opendaylight.yangtools.yang.data.api.schema .tree.ConflictingModificationAppliedException: Node children was modified by other transaction]]}

at org.opendaylight.controller.cluster.datastore.ShardDataTree.lambda$processNextPendingTransaction$0(ShardDataTree.java:751)[211:org.opendaylight.controller.sal-distributed-datastore:1.5.2.Carbon]
at org.opendaylight.controller.cluster.datastore.ShardDataTree.processNextPending(ShardDataTree.java:789)[211:org.opendaylight.controller.sal-distributed-datastore:1.5.2.Carbon]
at org.opendaylight.controller.cluster.datastore.ShardDataTree.processNextPendingTransaction(ShardDataTree.java:736)[211:org.opendaylight.controller.sal-distributed-datastore:1.5.2.Carbon]
at org.opendaylight.controller.cluster.datastore.ShardDataTree.startCanCommit(ShardDataTree.java:819)[211:org.opendaylight.controller.sal-distributed-datastore:1.5.2.Carbon]
at org.opendaylight.controller.cluster.datastore.SimpleShardDataTreeCohort.canCommit(SimpleShardDataTreeCohort.java:90)[211:org.opendaylight.controller.sal-distributed-datastore:1.5.2.Carbon]
at org.opendaylight.controller.cluster.datastore.CohortEntry.canCommit(CohortEntry.java:97)[211:org.opendaylight.controller.sal-distributed-datastore:1.5.2.Carbon]
at org.opendaylight.controller.cluster.datastore.ShardCommitCoordinator.handleCanCommit(ShardCommitCoordinator.java:236)[211:org.opendaylight.controller.sal-distributed-datastore:1.5.2.Carbon]
at org.opendaylight.controller.cluster.datastore.ShardCommitCoordinator.handleReadyLocalTransaction(ShardCommitCoordinator.java:200)[211:org.opendaylight.controller.sal-distributed-datastore:1.5.2.Carbon]
at org.opendaylight.controller.cluster.datastore.Shard.handleReadyLocalTransaction(Shard.java:675)[211:org.opendaylight.controller.sal-distributed-datastore:1.5.2.Carbon]
at org.opendaylight.controller.cluster.datastore.Shard.handleNonRaftCommand(Shard.java:316)[211:org.opendaylight.controller.sal-distributed-datastore:1.5.2.Carbon]
at org.opendaylight.controller.cluster.raft.RaftActor.handleCommand(RaftActor.java:270)[205:org.opendaylight.controller.sal-akka-raft:1.5.2.Carbon]
at org.opendaylight.controller.cluster.common.actor.AbstractUntypedPersistentActor.onReceiveCommand(AbstractUntypedPersistentActor.java:31)[204:org.opendaylight.controller.sal-clustering-commons:1.5.2.Carbon]
at akka.persistence.UntypedPersistentActor.onReceive(PersistentActor.scala:170)[192:com.typesafe.akka.persistence:2.4.18]
at org.opendaylight.controller.cluster.common.actor.MeteringBehavior.apply(MeteringBehavior.java:104)[204:org.opendaylight.controller.sal-clustering-commons:1.5.2.Carbon]
at akka.actor.ActorCell$$anonfun$become$1.applyOrElse(ActorCell.scala:544)[185:com.typesafe.akka.actor:2.4.18]
at akka.actor.Actor$class.aroundReceive(Actor.scala:502)[185:com.typesafe.akka.actor:2.4.18]
at akka.persistence.UntypedPersistentActor.akka$persistence$Eventsourced$$super$aroundReceive(PersistentActor.scala:168)[192:com.typesafe.akka.persistence:2.4.18]
at akka.persistence.Eventsourced$$anon$1.stateReceive(Eventsourced.scala:727)[192:com.typesafe.akka.persistence:2.4.18]
at akka.persistence.Eventsourced$class.aroundReceive(Eventsourced.scala:183)[192:com.typesafe.akka.persistence:2.4.18]
at akka.persistence.UntypedPersistentActor.aroundReceive(PersistentActor.scala:168)[192:com.typesafe.akka.persistence:2.4.18]
at akka.actor.ActorCell.receiveMessage(ActorCell.scala:526)[185:com.typesafe.akka.actor:2.4.18]
at akka.actor.ActorCell.invoke(ActorCell.scala:495)[185:com.typesafe.akka.actor:2.4.18]
at akka.dispatch.Mailbox.processMailbox(Mailbox.scala:257)[185:com.typesafe.akka.actor:2.4.18]
at akka.dispatch.Mailbox.run(Mailbox.scala:224)[185:com.typesafe.akka.actor:2.4.18]
at akka.dispatch.Mailbox.exec(Mailbox.scala:234)[185:com.typesafe.akka.actor:2.4.18]
at scala.concurrent.forkjoin.ForkJoinTask.doExec(ForkJoinTask.java:260)[181:org.scala-lang.scala-library:2.11.11.v20170413-090219-8a413ba7cc]
at scala.concurrent.forkjoin.ForkJoinPool$WorkQueue.runTask(ForkJoinPool.java:1339)[181:org.scala-lang.scala-library:2.11.11.v20170413-090219-8a413ba7cc]
at scala.concurrent.forkjoin.ForkJoinPool.runWorker(ForkJoinPool.java:1979)[181:org.scala-lang.scala-library:2.11.11.v20170413-090219-8a413ba7cc]
at scala.concurrent.forkjoin.ForkJoinWorkerThread.run(ForkJoinWorkerThread.java:107)[181:org.scala-lang.scala-library:2.11.11.v20170413-090219-8a413ba7cc]
Caused by: org.opendaylight.yangtools.yang.data.api.schema.tree.ConflictingModificationAppliedException: Node children was modified by other transaction
at org.opendaylight.yangtools.yang.data.impl.schema.tree.SchemaAwareApplyOperation.checkConflicting(SchemaAwareApplyOperation.java:78)[108:org.opendaylight.yangtools.yang-data-impl:1.1.2.Carbon]
at org.opendaylight.yangtools.yang.data.impl.schema.tree.SchemaAwareApplyOperation.checkNotConflicting(SchemaAwareApplyOperation.java:108)[108:org.opendaylight.yangtools.yang-data-impl:1.1.2.Carbon]
at org.opendaylight.yangtools.yang.data.impl.schema.tree.SchemaAwareApplyOperation.checkWriteApplicable(SchemaAwareApplyOperation.java:170)[108:org.opendaylight.yangtools.yang-data-impl:1.1.2.Carbon]
at org.opendaylight.yangtools.yang.data.impl.schema.tree.SchemaAwareApplyOperation.checkApplicable(SchemaAwareApplyOperation.java:128)[108:org.opendaylight.yangtools.yang-data-impl:1.1.2.Carbon]
at org.opendaylight.yangtools.yang.data.impl.schema.tree.AbstractNodeContainerModificationStrategy.checkChildPreconditions(AbstractNodeContainerModificationStrategy.java:305)[108:org.opendaylight.yangtools.yang-data-impl:1.1.2.Carbon]
at org.opendaylight.yangtools.yang.data.impl.schema.tree.AbstractNodeContainerModificationStrategy.checkMergeApplicable(AbstractNodeContainerModificationStrategy.java:313)[108:org.opendaylight.yangtools.yang-data-impl:1.1.2.Carbon]
at org.opendaylight.yangtools.yang.data.impl.schema.tree.SchemaAwareApplyOperation.checkApplicable(SchemaAwareApplyOperation.java:131)[108:org.opendaylight.yangtools.yang-data-impl:1.1.2.Carbon]
at org.opendaylight.yangtools.yang.data.impl.schema.tree.AbstractNodeContainerModificationStrategy.checkChildPreconditions(AbstractNodeContainerModificationStrategy.java:305)[108:org.opendaylight.yangtools.yang-data-impl:1.1.2.Carbon]
at org.opendaylight.yangtools.yang.data.impl.schema.tree.AbstractNodeContainerModificationStrategy.checkTouchApplicable(AbstractNodeContainerModificationStrategy.java:288)[108:org.opendaylight.yangtools.yang-data-impl:1.1.2.Carbon]
at org.opendaylight.yangtools.yang.data.impl.schema.tree.SchemaAwareApplyOperation.checkApplicable(SchemaAwareApplyOperation.java:125)[108:org.opendaylight.yangtools.yang-data-impl:1.1.2.Carbon]
at org.opendaylight.yangtools.yang.data.impl.schema.tree.AbstractNodeContainerModificationStrategy.checkChildPreconditions(AbstractNodeContainerModificationStrategy.java:305)[108:org.opendaylight.yangtools.yang-data-impl:1.1.2.Carbon]
at org.opendaylight.yangtools.yang.data.impl.schema.tree.AbstractNodeContainerModificationStrategy.checkTouchApplicable(AbstractNodeContainerModificationStrategy.java:288)[108:org.opendaylight.yangtools.yang-data-impl:1.1.2.Carbon]
at org.opendaylight.yangtools.yang.data.impl.schema.tree.SchemaAwareApplyOperation.checkApplicable(SchemaAwareApplyOperation.java:125)[108:org.opendaylight.yangtools.yang-data-impl:1.1.2.Carbon]
at org.opendaylight.yangtools.yang.data.impl.schema.tree.AbstractNodeContainerModificationStrategy.checkChildPreconditions(AbstractNodeContainerModificationStrategy.java:305)[108:org.opendaylight.yangtools.yang-data-impl:1.1.2.Carbon]
at org.opendaylight.yangtools.yang.data.impl.schema.tree.AbstractNodeContainerModificationStrategy.checkTouchApplicable(AbstractNodeContainerModificationStrategy.java:288)[108:org.opendaylight.yangtools.yang-data-impl:1.1.2.Carbon]
at org.opendaylight.yangtools.yang.data.impl.schema.tree.SchemaAwareApplyOperation.checkApplicable(SchemaAwareApplyOperation.java:125)[108:org.opendaylight.yangtools.yang-data-impl:1.1.2.Carbon]
at org.opendaylight.yangtools.yang.data.impl.schema.tree.AbstractNodeContainerModificationStrategy.checkChildPreconditions(AbstractNodeContainerModificationStrategy.java:305)[108:org.opendaylight.yangtools.yang-data-impl:1.1.2.Carbon]
at org.opendaylight.yangtools.yang.data.impl.schema.tree.AbstractNodeContainerModificationStrategy.checkTouchApplicable(AbstractNodeContainerModificationStrategy.java:288)[108:org.opendaylight.yangtools.yang-data-impl:1.1.2.Carbon]
at org.opendaylight.yangtools.yang.data.impl.schema.tree.SchemaAwareApplyOperation.checkApplicable(SchemaAwareApplyOperation.java:125)[108:org.opendaylight.yangtools.yang-data-impl:1.1.2.Carbon]
at org.opendaylight.yangtools.yang.data.impl.schema.tree.StructuralContainerModificationStrategy.checkApplicable(StructuralContainerModificationStrategy.java:99)[108:org.opendaylight.yangtools.yang-data-impl:1.1.2.Carbon]
at org.opendaylight.yangtools.yang.data.impl.schema.tree.AbstractNodeContainerModificationStrategy.checkChildPreconditions(AbstractNodeContainerModificationStrategy.java:305)[108:org.opendaylight.yangtools.yang-data-impl:1.1.2.Carbon]
at org.opendaylight.yangtools.yang.data.impl.schema.tree.AbstractNodeContainerModificationStrategy.checkTouchApplicable(AbstractNodeContainerModificationStrategy.java:288)[108:org.opendaylight.yangtools.yang-data-impl:1.1.2.Carbon]
at org.opendaylight.yangtools.yang.data.impl.schema.tree.SchemaAwareApplyOperation.checkApplicable(SchemaAwareApplyOperation.java:125)[108:org.opendaylight.yangtools.yang-data-impl:1.1.2.Carbon]
at org.opendaylight.yangtools.yang.data.impl.schema.tree.RootModificationApplyOperation.checkApplicable(RootModificationApplyOperation.java:72)[108:org.opendaylight.yangtools.yang-data-impl:1.1.2.Carbon]
at org.opendaylight.yangtools.yang.data.impl.schema.tree.AbstractDataTreeTip.validate(AbstractDataTreeTip.java:35)[108:org.opendaylight.yangtools.yang-data-impl:1.1.2.Carbon]
at org.opendaylight.controller.cluster.datastore.ShardDataTree.lambda$processNextPendingTransaction$0(ShardDataTree.java:743)[211:org.opendaylight.controller.sal-distributed-datastore:1.5.2.Carbon]
... 28 more