[jira] [Issue Comment Deleted] (KAFKA-686) 0.8 Kafka broker should give a better error message when running against 0.7 zookeeper

["Phil (JIRA)" <ji...@apache.org>]

     [ https://issues.apache.org/jira/browse/KAFKA-686?page=com.atlassian.jira.plugin.system.issuetabpanels:all-tabpanel ]

Phil updated KAFKA-686:
-----------------------

    Comment: was deleted

(was: While this doesn't produce a message clarifying the error, it does prevent the error in the first place.  I am a novice at Scala, but I think there is a bug in ZkClient that was wrapping a null value in a Some instance--which caused the Json.parseFull to fail, as it received a null string to parse.

This patch attempts to detect the null from Zookeeper and return a tuple with None instead of Some(null).)
    
> 0.8 Kafka broker should give a better error message when running against 0.7 zookeeper
> --------------------------------------------------------------------------------------
>
>                 Key: KAFKA-686
>                 URL: https://issues.apache.org/jira/browse/KAFKA-686
>             Project: Kafka
>          Issue Type: Bug
>    Affects Versions: 0.8
>            Reporter: Jay Kreps
>              Labels: newbie, patch
>             Fix For: 0.8
>
>
> People will not know that the zookeeper paths are not compatible. When you try to start the 0.8 broker pointed at a 0.7 zookeeper you get a NullPointerException. We should detect this and give a more sane error.
> Error:
> kafka.common.KafkaException: Can't parse json string: null
>         at kafka.utils.Json$.liftedTree1$1(Json.scala:20)
>         at kafka.utils.Json$.parseFull(Json.scala:16)
>         at kafka.utils.ZkUtils$$anonfun$getReplicaAssignmentForTopics$2.apply(ZkUtils.scala:498)
>         at kafka.utils.ZkUtils$$anonfun$getReplicaAssignmentForTopics$2.apply(ZkUtils.scala:494)
>         at scala.collection.LinearSeqOptimized$class.foreach(LinearSeqOptimized.scala:61)
>         at scala.collection.immutable.List.foreach(List.scala:45)
>         at kafka.utils.ZkUtils$.getReplicaAssignmentForTopics(ZkUtils.scala:494)
>         at kafka.controller.KafkaController.initializeControllerContext(KafkaController.scala:446)
>         at kafka.controller.KafkaController.onControllerFailover(KafkaController.scala:220)
>         at kafka.controller.KafkaController$$anonfun$1.apply$mcV$sp(KafkaController.scala:85)
>         at kafka.server.ZookeeperLeaderElector.elect(ZookeeperLeaderElector.scala:53)
>         at kafka.server.ZookeeperLeaderElector.startup(ZookeeperLeaderElector.scala:43)
>         at kafka.controller.KafkaController.startup(KafkaController.scala:381)
>         at kafka.server.KafkaServer.startup(KafkaServer.scala:90)
>         at kafka.server.KafkaServerStartable.startup(KafkaServerStartable.scala:34)
>         at kafka.Kafka$.main(Kafka.scala:46)
>         at kafka.Kafka.main(Kafka.scala)
> Caused by: java.lang.NullPointerException
>         at scala.util.parsing.combinator.lexical.Scanners$Scanner.<init>(Scanners.scala:52)
>         at scala.util.parsing.json.JSON$.parseRaw(JSON.scala:71)
>         at scala.util.parsing.json.JSON$.parseFull(JSON.scala:85)
>         at kafka.utils.Json$.liftedTree1$1(Json.scala:17)
>         ... 16 more

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