I see this exception in the logs a lot when doing load testing. I haven't noticed any ill effect. Presumably related to the delete topic stuff?
[2014-02-18 15:16:58,569] ERROR Error handling event ZkEvent[Children of /admin/delete_topics changed sent to kafka.controller.PartitionStateMachine$DeleteTopicsListener@39abdac9] (org.I0Itec.zkclient.ZkEventThread) java.lang.NullPointerException at scala.collection.JavaConversions$JListWrapper.iterator(JavaConversions.scala:524) at scala.collection.IterableLike$class.foreach(IterableLike.scala:79) at scala.collection.JavaConversions$JListWrapper.foreach(JavaConversions.scala:521) at scala.collection.TraversableOnce$class.foldLeft(TraversableOnce.scala:176) at scala.collection.JavaConversions$JListWrapper.foldLeft(JavaConversions.scala:521) at scala.collection.TraversableOnce$class.$div$colon(TraversableOnce.scala:139) at scala.collection.JavaConversions$JListWrapper.$div$colon(JavaConversions.scala:521) at scala.collection.generic.Addable$class.$plus$plus(Addable.scala:54) at scala.collection.immutable.Set$EmptySet$.$plus$plus(Set.scala:47) at scala.collection.TraversableOnce$class.toSet(TraversableOnce.scala:436) at scala.collection.JavaConversions$JListWrapper.toSet(JavaConversions.scala:521) at kafka.controller.PartitionStateMachine$DeleteTopicsListener$$anonfun$handleChildChange$2.apply$mcV$sp(PartitionStateMachine.scala:448) at kafka.controller.PartitionStateMachine$DeleteTopicsListener$$anonfun$handleChildChange$2.apply(PartitionStateMachine.scala:445) at kafka.controller.PartitionStateMachine$DeleteTopicsListener$$anonfun$handleChildChange$2.apply(PartitionStateMachine.scala:445) at kafka.utils.Utils$.inLock(Utils.scala:538) at kafka.controller.PartitionStateMachine$DeleteTopicsListener.handleChildChange(PartitionStateMachine.scala:445) at org.I0Itec.zkclient.ZkClient$7.run(ZkClient.java:570) at org.I0Itec.zkclient.ZkEventThread.run(ZkEventThread.java:71) [2014-02-18 15:16:58,609] ERROR Error handling event ZkEvent[Data of /controller changed sent to kafka.server.ZookeeperLeaderElector$LeaderChangeListener@69f94884] (org.I0Itec.zkclient.ZkEventThread) java.lang.IllegalStateException: Kafka scheduler has not been started at kafka.utils.KafkaScheduler.ensureStarted(KafkaScheduler.scala:116) at kafka.utils.KafkaScheduler.shutdown(KafkaScheduler.scala:86) at kafka.controller.KafkaController$$anonfun$onControllerResignation$1.apply$mcV$sp(KafkaController.scala:338) at kafka.controller.KafkaController$$anonfun$onControllerResignation$1.apply(KafkaController.scala:337) at kafka.controller.KafkaController$$anonfun$onControllerResignation$1.apply(KafkaController.scala:337) at kafka.utils.Utils$.inLock(Utils.scala:538) at kafka.controller.KafkaController.onControllerResignation(KafkaController.scala:337) at kafka.controller.KafkaController$$anonfun$2.apply$mcV$sp(KafkaController.scala:162) at kafka.server.ZookeeperLeaderElector$LeaderChangeListener$$anonfun$handleDataDeleted$1.apply$mcZ$sp(ZookeeperLeaderElector.scala:122) at kafka.server.ZookeeperLeaderElector$LeaderChangeListener$$anonfun$handleDataDeleted$1.apply(ZookeeperLeaderElector.scala:118) at kafka.server.ZookeeperLeaderElector$LeaderChangeListener$$anonfun$handleDataDeleted$1.apply(ZookeeperLeaderElector.scala:118) at kafka.utils.Utils$.inLock(Utils.scala:538) at kafka.server.ZookeeperLeaderElector$LeaderChangeListener.handleDataDeleted(ZookeeperLeaderElector.scala:118) at org.I0Itec.zkclient.ZkClient$6.run(ZkClient.java:549) at org.I0Itec.zkclient.ZkEventThread.run(ZkEventThread.java:71)
