I am running controller in 3 node cluster mode, and when i shutdown the leader node, and try to do some transaction on data store, it fails because of the precondition check failure in a precondition check InMemoryDataTree.java:116. This is the exception i see at the time of OOM.

opendaylight-cluster-data-akka.actor.default-dispatcher-5
at java.lang.OutOfMemoryError.<init>()V (OutOfMemoryError.java:48)
at java.util.Arrays.copyOf([CI)[C (Arrays.java:3332)
at java.lang.AbstractStringBuilder.expandCapacity(I)V (AbstractStringBuilder.java:137)
at java.lang.AbstractStringBuilder.ensureCapacityInternal(I)V (AbstractStringBuilder.java:121)
at java.lang.AbstractStringBuilder.append(Ljava/lang/String;)Ljava/lang/AbstractStringBuilder; (AbstractStringBuilder.java:421)
at java.lang.StringBuilder.append(Ljava/lang/String;)Ljava/lang/StringBuilder; (StringBuilder.java:136)
at java.lang.StringBuilder.append(Ljava/lang/Object;)Ljava/lang/StringBuilder; (StringBuilder.java:131)
at java.util.AbstractMap.toString()Ljava/lang/String; (AbstractMap.java:536)
at java.lang.String.valueOf(Ljava/lang/Object;)Ljava/lang/String; (String.java:2994)
at java.lang.StringBuilder.append(Ljava/lang/Object;)Ljava/lang/StringBuilder; (StringBuilder.java:131)
at com.google.common.base.MoreObjects$ToStringHelper.toString()Ljava/lang/String; (MoreObjects.java:359)
at org.opendaylight.yangtools.yang.data.api.schema.tree.spi.AbstractTreeNode.toString()Ljava/lang/String; (AbstractTreeNode.java:45)
at java.lang.String.valueOf(Ljava/lang/Object;)Ljava/lang/String; (String.java:2994)
at java.lang.StringBuilder.append(Ljava/lang/Object;)Ljava/lang/StringBuilder; (StringBuilder.java:131)
at java.util.AbstractMap.toString()Ljava/lang/String; (AbstractMap.java:536)
at java.lang.String.valueOf(Ljava/lang/Object;)Ljava/lang/String; (String.java:2994)
at java.lang.StringBuilder.append(Ljava/lang/Object;)Ljava/lang/StringBuilder; (StringBuilder.java:131)
at com.google.common.base.MoreObjects$ToStringHelper.toString()Ljava/lang/String; (MoreObjects.java:359)
at org.opendaylight.yangtools.yang.data.api.schema.tree.spi.AbstractTreeNode.toString()Ljava/lang/String; (AbstractTreeNode.java:45)
at java.lang.String.valueOf(Ljava/lang/Object;)Ljava/lang/String; (String.java:2994)
at java.lang.StringBuilder.append(Ljava/lang/Object;)Ljava/lang/StringBuilder; (StringBuilder.java:131)
at java.util.AbstractMap.toString()Ljava/lang/String; (AbstractMap.java:536)
at java.lang.String.valueOf(Ljava/lang/Object;)Ljava/lang/String; (String.java:2994)
at java.lang.StringBuilder.append(Ljava/lang/Object;)Ljava/lang/StringBuilder; (StringBuilder.java:131)
at com.google.common.base.MoreObjects$ToStringHelper.toString()Ljava/lang/String; (MoreObjects.java:359)
at org.opendaylight.yangtools.yang.data.api.schema.tree.spi.AbstractTreeNode.toString()Ljava/lang/String; (AbstractTreeNode.java:45)
at java.lang.String.valueOf(Ljava/lang/Object;)Ljava/lang/String; (String.java:2994)
at java.lang.StringBuilder.append(Ljava/lang/Object;)Ljava/lang/StringBuilder; (StringBuilder.java:131)
at com.google.common.base.Preconditions.format(Ljava/lang/String;[Ljava/lang/Object;)Ljava/lang/String; (Preconditions.java:422)
at com.google.common.base.Preconditions.checkState(ZLjava/lang/String;[Ljava/lang/Object;)V (Preconditions.java:197)
at org.opendaylight.yangtools.yang.data.impl.schema.tree.InMemoryDataTree.commit(Lorg/opendaylight/yangtools/yang/data/api/schema/tree/DataTreeCandidate;)V (InMemoryDataTree.java:116)
at org.opendaylight.controller.cluster.datastore.SimpleShardDataTreeCohort.commit()Lcom/google/common/util/concurrent/ListenableFuture; (SimpleShardDataTreeCohort.java:102)
at org.opendaylight.controller.cluster.datastore.ChainedCommitCohort.commit()Lcom/google/common/util/concurrent/ListenableFuture; (ChainedCommitCohort.java:32)
at org.opendaylight.controller.cluster.datastore.ShardCommitCoordinator$CohortEntry.commit()V (ShardCommitCoordinator.java:670)
at org.opendaylight.controller.cluster.datastore.Shard.finishCommit(Lakka/actor/ActorRef;Ljava/lang/String;Lorg/opendaylight/controller/cluster/datastore/ShardCommitCoordinator$CohortEntry;)V (Shard.java:348)
at org.opendaylight.controller.cluster.datastore.Shard.finishCommit(Lakka/actor/ActorRef;Ljava/lang/String;)V (Shard.java:398)
at org.opendaylight.controller.cluster.datastore.Shard.applyState(Lakka/actor/ActorRef;Ljava/lang/String;Ljava/lang/Object;)V (Shard.java:646)
at org.opendaylight.controller.cluster.raft.RaftActor.handleCommand(Ljava/lang/Object;)V (RaftActor.java:228)
at org.opendaylight.controller.cluster.common.actor.AbstractUntypedPersistentActor.onReceiveCommand(Ljava/lang/Object;)V (AbstractUntypedPersistentActor.java:36)
at org.opendaylight.controller.cluster.datastore.Shard.onReceiveCommand(Ljava/lang/Object;)V (Shard.java:273)
at akka.persistence.UntypedPersistentActor.onReceive(Ljava/lang/Object;)V (Eventsourced.scala:430)
at org.opendaylight.controller.cluster.common.actor.MeteringBehavior.apply(Ljava/lang/Object;)V (MeteringBehavior.java:97)
at akka.actor.ActorCell$$anonfun$become$1.applyOrElse(Ljava/lang/Object;Lscala/Function1;)Ljava/lang/Object; (ActorCell.scala:534)
at akka.persistence.Recovery$State$class.process(Lakka/persistence/Recovery$State;Lscala/PartialFunction;Ljava/lang/Object;)V (Recovery.scala:30)
at akka.persistence.ProcessorImpl$$anon$2.process(Lscala/PartialFunction;Ljava/lang/Object;)V (Processor.scala:103)
at akka.persistence.ProcessorImpl$$anon$2.aroundReceive(Lscala/PartialFunction;Ljava/lang/Object;)V (Processor.scala:114)
at akka.persistence.Recovery$class.aroundReceive(Lakka/persistence/Recovery;Lscala/PartialFunction;Ljava/lang/Object;)V (Recovery.scala:265)
at akka.persistence.UntypedPersistentActor.akka$persistence$Eventsourced$$super$aroundReceive(Lscala/PartialFunction;Ljava/lang/Object;)V (Eventsourced.scala:428)
at akka.persistence.Eventsourced$$anon$2.doAroundReceive(Lscala/PartialFunction;Ljava/lang/Object;)V (Eventsourced.scala:82)
at akka.persistence.Eventsourced$$anon$2.aroundReceive(Lscala/PartialFunction;Ljava/lang/Object;)V (Eventsourced.scala:78)
at akka.persistence.Eventsourced$class.aroundReceive(Lakka/persistence/Eventsourced;Lscala/PartialFunction;Ljava/lang/Object;)V (Eventsourced.scala:369)
at akka.persistence.UntypedPersistentActor.aroundReceive(Lscala/PartialFunction;Ljava/lang/Object;)V (Eventsourced.scala:428)
at akka.actor.ActorCell.receiveMessage(Ljava/lang/Object;)V (ActorCell.scala:516)
at akka.actor.ActorCell.invoke(Lakka/dispatch/Envelope;)V (ActorCell.scala:487)
at akka.dispatch.Mailbox.processMailbox(IJ)V (Mailbox.scala:238)
at akka.dispatch.Mailbox.run()V (Mailbox.scala:220)
at akka.dispatch.ForkJoinExecutorConfigurator$AkkaForkJoinTask.exec()Z (AbstractDispatcher.scala:397)
at scala.concurrent.forkjoin.ForkJoinTask.doExec()I (ForkJoinTask.java:260)
at scala.concurrent.forkjoin.ForkJoinPool$WorkQueue.runTask(Lscala/concurrent/forkjoin/ForkJoinTask;)V (ForkJoinPool.java:1339)
at scala.concurrent.forkjoin.ForkJoinPool.runWorker(Lscala/concurrent/forkjoin/ForkJoinPool$WorkQueue;)V (ForkJoinPool.java:1979)
at scala.concurrent.forkjoin.ForkJoinWorkerThread.run()V (ForkJoinWorkerThread.java:107)
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Precondition fails trying to generate the failure message and it tries to build toString() for oldRoot and currentRoot, and looks like it requires too much memory to build the toString of the thole subtree. I tried to patch it by skipping the toString() of oldRoot and currentRoot in Precondition and things looks stable.