[
https://issues.apache.org/jira/browse/KAFKA-686?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=14132591#comment-14132591
]
Viktor Taranenko commented on KAFKA-686:
----------------------------------------
[~nehanarkhede], It is not 'failAsValue' what solves the problem, but wrapping
potential null value into scala Option instead if Some.
failAsValue only shortens code for catching ZkNoNodeException and returning
None of it occurs
{noformat}
failAsValue(classOf[ZkNoNodeException])(None)(Option(client.readData(path,
stat)))
{noformat}
- returns 'None' when client.readData throws ZkNoNodeException (doesn't catch
any other kind of Exception from client.readData)
- returns 'None' when client.readData returns null
- returns 'Some(value)' when client.readData returns string value
The original code had `Some(client.readData)`, which returns Some(null), so
that for example
`Some(null).map(_.length)` would throw NullPointerException
> 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: 0.8.0
> Reporter: Jay Kreps
> Labels: newbie, patch
> Fix For: 0.8.2
>
> Attachments: KAFAK-686-null-pointer-fix.patch,
> KAFKA-686-null-pointer-fix-2.patch
>
>
> 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
--
This message was sent by Atlassian JIRA
(v6.3.4#6332)
