[jira] [Commented] (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:comment-tabpanel&focusedCommentId=13598869#comment-13598869 ] 

Phil commented on KAFKA-686:
----------------------------

Patch here using git diff

diff --git a/core/src/main/scala/kafka/utils/ZkUtils.scala b/core/src/main/scala/kafka/utils/ZkUtils.scala
index c6119d9..90ee2d0 100644
--- a/core/src/main/scala/kafka/utils/ZkUtils.scala
+++ b/core/src/main/scala/kafka/utils/ZkUtils.scala
@@ -419,7 +419,12 @@ object ZkUtils extends Logging {
   def readDataMaybeNull(client: ZkClient, path: String): (Option[String], Stat) = {
     val stat: Stat = new Stat()
     val dataAndStat = try {
-                        (Some(client.readData(path, stat)), stat)
+                                               val data: String = client.readData(path,stat)
+                                               if(data != null) {
+                                                 (Some(client.readData(path, stat)), stat)
+                                               } else {
+                                                 (None,stat)
+                                               }
                       } catch {
                         case e: ZkNoNodeException =>
                           (None, stat)

                
> 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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