Recent (February 2nd) result of Netconf cluster job had a failed test case [0] but the karaf.log [1] message suggests client should retry later. The proper status code for this situation is 503. Netconf code should communicate that to the Restconf code.

Segment from karaf.log suggests that perhaps there is an underlying issue of new Master not being elected, but currently it is not clear whether the Master would get elected later:

2017-02-02 13:16:21,748 | WARN | ult-dispatcher-3 | ReliableDeliverySupervisor | 201 - com.typesafe.akka.slf4j - 2.4.16 | Association with remote system [akka.tcp://opendaylight-cluster-data@10.29.12.204:2550] has failed, address is now gated for [5000] ms. Reason: [Association failed with [akka.tcp://opendaylight-cluster-data@10.29.12.204:2550]] Caused by: [Connection refused: /10.29.12.204:2550]
2017-02-02 13:16:23,473 | WARN | lt-dispatcher-19 | BrokerFacade | 290 - org.opendaylight.netconf.sal-rest-connector - 1.5.0.SNAPSHOT | Exception by reading CONFIGURATION via Restconf: /(urn:opendaylight:test:netconf:crud?revision=2014-10-18)cont
NetconfDocumentedException{message=RemoteDevice

:Master is down. Please try again., errorType=APPLICATION, errorTag=OPERATION_FAILED, errorSeverity=WARNING, errorInfo={}}
at org.opendaylight.netconf.topology.singleton.impl.tx.NetconfProxyDOMTransaction$1.onComplete(NetconfProxyDOMTransaction.java:70)
at akka.dispatch.OnComplete.internal(Future.scala:258)
at akka.dispatch.OnComplete.internal(Future.scala:256)
at akka.dispatch.japi$CallbackBridge.apply(Future.scala:186)
at akka.dispatch.japi$CallbackBridge.apply(Future.scala:183)
at scala.concurrent.impl.CallbackRunnable.run(Promise.scala:32)
at akka.dispatch.BatchingExecutor$AbstractBatch.processBatch(BatchingExecutor.scala:55)
at akka.dispatch.BatchingExecutor$BlockableBatch$$anonfun$run$1.apply$mcV$sp(BatchingExecutor.scala:91)
at akka.dispatch.BatchingExecutor$BlockableBatch$$anonfun$run$1.apply(BatchingExecutor.scala:91)
at akka.dispatch.BatchingExecutor$BlockableBatch$$anonfun$run$1.apply(BatchingExecutor.scala:91)
at scala.concurrent.BlockContext$.withBlockContext(BlockContext.scala:72)
at akka.dispatch.BatchingExecutor$BlockableBatch.run(BatchingExecutor.scala:90)
at akka.dispatch.TaskInvocation.run(AbstractDispatcher.scala:39)
at akka.dispatch.ForkJoinExecutorConfigurator$AkkaForkJoinTask.exec(AbstractDispatcher.scala:415)
at scala.concurrent.forkjoin.ForkJoinTask.doExec(ForkJoinTask.java:260)
at scala.concurrent.forkjoin.ForkJoinPool$WorkQueue.runTask(ForkJoinPool.java:1339)
at scala.concurrent.forkjoin.ForkJoinPool.runWorker(ForkJoinPool.java:1979)
at scala.concurrent.forkjoin.ForkJoinWorkerThread.run(ForkJoinWorkerThread.java:107)
]]
at org.opendaylight.netconf.sal.restconf.impl.BrokerFacade.handlingCallback(BrokerFacade.java:1259)[290:org.opendaylight.netconf.sal-rest-connector:1.5.0.SNAPSHOT]
at org.opendaylight.netconf.sal.restconf.impl.BrokerFacade$2.onFailure(BrokerFacade.java:537)[290:org.opendaylight.netconf.sal-rest-connector:1.5.0.SNAPSHOT]
at com.google.common.util.concurrent.Futures$6.run(Futures.java:1310)[84:com.google.guava:18.0.0]
at com.google.common.util.concurrent.MoreExecutors$DirectExecutor.execute(MoreExecutors.java:457)[84:com.google.guava:18.0.0]
at com.google.common.util.concurrent.ExecutionList.executeListener(ExecutionList.java:156)[84:com.google.guava:18.0.0]
at com.google.common.util.concurrent.ExecutionList.execute(ExecutionList.java:145)[84:com.google.guava:18.0.0]
at com.google.common.util.concurrent.AbstractFuture.setException(AbstractFuture.java:202)[84:com.google.guava:18.0.0]
at com.google.common.util.concurrent.SettableFuture.setException(SettableFuture.java:68)[84:com.google.guava:18.0.0]
at org.opendaylight.netconf.topology.singleton.impl.tx.NetconfReadOnlyTransaction$2.onComplete(NetconfReadOnlyTransaction.java:87)[320:org.opendaylight.netconf.topology-singleton:1.2.0.SNAPSHOT]
at org.opendaylight.netconf.topology.singleton.impl.tx.NetconfReadOnlyTransaction$2.onComplete(NetconfReadOnlyTransaction.java:68)[320:org.opendaylight.netconf.topology-singleton:1.2.0.SNAPSHOT]
at akka.dispatch.OnComplete.internal(Future.scala:258)[200:com.typesafe.akka.actor:2.4.16]
at akka.dispatch.OnComplete.internal(Future.scala:256)[200:com.typesafe.akka.actor:2.4.16]
at akka.dispatch.japi$CallbackBridge.apply(Future.scala:186)[200:com.typesafe.akka.actor:2.4.16]
at akka.dispatch.japi$CallbackBridge.apply(Future.scala:183)[200:com.typesafe.akka.actor:2.4.16]
at scala.concurrent.impl.CallbackRunnable.run(Promise.scala:32)[196:org.scala-lang.scala-library:2.11.8.v20160304-115712-1706a37eb8]
at akka.dispatch.BatchingExecutor$AbstractBatch.processBatch(BatchingExecutor.scala:55)[200:com.typesafe.akka.actor:2.4.16]
at akka.dispatch.BatchingExecutor$BlockableBatch$$anonfun$run$1.apply$mcV$sp(BatchingExecutor.scala:91)[200:com.typesafe.akka.actor:2.4.16]
at akka.dispatch.BatchingExecutor$BlockableBatch$$anonfun$run$1.apply(BatchingExecutor.scala:91)[200:com.typesafe.akka.actor:2.4.16]
at akka.dispatch.BatchingExecutor$BlockableBatch$$anonfun$run$1.apply(BatchingExecutor.scala:91)[200:com.typesafe.akka.actor:2.4.16]
at scala.concurrent.BlockContext$.withBlockContext(BlockContext.scala:72)[196:org.scala-lang.scala-library:2.11.8.v20160304-115712-1706a37eb8]
at akka.dispatch.BatchingExecutor$BlockableBatch.run(BatchingExecutor.scala:90)[200:com.typesafe.akka.actor:2.4.16]
at akka.dispatch.TaskInvocation.run(AbstractDispatcher.scala:39)[200:com.typesafe.akka.actor:2.4.16]
at akka.dispatch.ForkJoinExecutorConfigurator$AkkaForkJoinTask.exec(AbstractDispatcher.scala:415)[200:com.typesafe.akka.actor:2.4.16]
at scala.concurrent.forkjoin.ForkJoinTask.doExec(ForkJoinTask.java:260)[196:org.scala-lang.scala-library:2.11.8.v20160304-115712-1706a37eb8]
at scala.concurrent.forkjoin.ForkJoinPool$WorkQueue.runTask(ForkJoinPool.java:1339)[196:org.scala-lang.scala-library:2.11.8.v20160304-115712-1706a37eb8]
at scala.concurrent.forkjoin.ForkJoinPool.runWorker(ForkJoinPool.java:1979)[196:org.scala-lang.scala-library:2.11.8.v20160304-115712-1706a37eb8]
at scala.concurrent.forkjoin.ForkJoinWorkerThread.run(ForkJoinWorkerThread.java:107)[196:org.scala-lang.scala-library:2.11.8.v20160304-115712-1706a37eb8]
Caused by: NetconfDocumentedException{message=RemoteDevice

:Master is down. Please try again., errorType=APPLICATION, errorTag=OPERATION_FAILED, errorSeverity=WARNING, errorInfo={}}
at org.opendaylight.netconf.topology.singleton.impl.tx.NetconfProxyDOMTransaction$1.onComplete(NetconfProxyDOMTransaction.java:70)[320:org.opendaylight.netconf.topology-singleton:1.2.0.SNAPSHOT]
... 17 more
2017-02-02 13:16:25,632 | INFO | ult-dispatcher-3 | kka://opendaylight-cluster-data) | 201 - com.typesafe.akka.slf4j - 2.4.16 | Cluster Node [akka.tcp://opendaylight-cluster-data@10.29.12.137:2550] - Leader can currently not perform its duties, reachability status: [akka.tcp://opendaylight-cluster-data@10.29.12.137:2550 -> akka.tcp://opendaylight-cluster-data@10.29.12.204:2550: Unreachable [Unreachable] (3), akka.tcp://opendaylight-cluster-data@10.29.13.95:2550 -> akka.tcp://opendaylight-cluster-data@10.29.12.204:2550: Unreachable [Unreachable] (1)], member status: [akka.tcp://opendaylight-cluster-data@10.29.12.137:2550 Up seen=true, akka.tcp://opendaylight-cluster-data@10.29.12.204:2550 Up seen=false, akka.tcp://opendaylight-cluster-data@10.29.13.95:2550 Up seen=true]

[0] https://logs.opendaylight.org/releng/jenkins092/netconf-csit-3node-clustering-only-carbon/435/archives/log.html.gz#s1-s6-t12-k2-k1-k3-k7-k1
[1] https://logs.opendaylight.org/releng/jenkins092/netconf-csit-3node-clustering-only-carbon/435/archives/odl3_karaf.log.gz