Dustin Cote created KAFKA-5885:
----------------------------------
Summary: NPE in ZKClient
Key: KAFKA-5885
URL: https://issues.apache.org/jira/browse/KAFKA-5885
Project: Kafka
Issue Type: Bug
Components: zkclient
Affects Versions: 0.10.2.1
Reporter: Dustin Cote
A null znode for a topic (reason how this happen isn't totally clear, but not
the focus of this issue) can currently cause controller leader election to
fail. When looking at the broker logging, you can see there is a
NullPointerException emanating from the ZKClient:
{code}
[2017-09-11 00:00:21,441] ERROR Error while electing or becoming leader on
broker 1010674 (kafka.server.ZookeeperLeaderElector)
kafka.common.KafkaException: Can't parse json string: null
at kafka.utils.Json$.liftedTree1$1(Json.scala:40)
at kafka.utils.Json$.parseFull(Json.scala:36)
at
kafka.utils.ZkUtils$$anonfun$getReplicaAssignmentForTopics$1.apply(ZkUtils.scala:704)
at
kafka.utils.ZkUtils$$anonfun$getReplicaAssignmentForTopics$1.apply(ZkUtils.scala:700)
at
scala.collection.mutable.ResizableArray$class.foreach(ResizableArray.scala:59)
at scala.collection.mutable.ArrayBuffer.foreach(ArrayBuffer.scala:48)
at kafka.utils.ZkUtils.getReplicaAssignmentForTopics(ZkUtils.scala:700)
at
kafka.controller.KafkaController.initializeControllerContext(KafkaController.scala:742)
at
kafka.controller.KafkaController.onControllerFailover(KafkaController.scala:333)
at
kafka.controller.KafkaController$$anonfun$1.apply$mcV$sp(KafkaController.scala:160)
at
kafka.server.ZookeeperLeaderElector.elect(ZookeeperLeaderElector.scala:85)
at
kafka.server.ZookeeperLeaderElector$LeaderChangeListener$$anonfun$handleDataDeleted$1.apply$mcZ$sp(ZookeeperLeaderElector.scala:154)
at
kafka.server.ZookeeperLeaderElector$LeaderChangeListener$$anonfun$handleDataDeleted$1.apply(ZookeeperLeaderElector.scala:154)
at
kafka.server.ZookeeperLeaderElector$LeaderChangeListener$$anonfun$handleDataDeleted$1.apply(ZookeeperLeaderElector.scala:154)
at kafka.utils.CoreUtils$.inLock(CoreUtils.scala:213)
at
kafka.server.ZookeeperLeaderElector$LeaderChangeListener.handleDataDeleted(ZookeeperLeaderElector.scala:153)
at org.I0Itec.zkclient.ZkClient$9.run(ZkClient.java:825)
at org.I0Itec.zkclient.ZkEventThread.run(ZkEventThread.java:72)
Caused by: java.lang.NullPointerException
{code}
Regardless of how a null topic znode ended up in ZooKeeper, we can probably
handle this better, at least by printing the path up to the problematic znode
in the log. The way this particular problem was resolved was by using the
``kafka-topics`` command and seeing it persistently fail trying to read a
particular topic with this same message. Then deleting the null znode allowed
the leader election to complete.
--
This message was sent by Atlassian JIRA
(v6.4.14#64029)
