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KAFKA-12329; kafka-reassign-partitions command should give a better error message when a topic does not exist #10141

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Merged
dajac merged 3 commits into from
Mar 1, 2021
Merged

KAFKA-12329; kafka-reassign-partitions command should give a better error message when a topic does not exist #10141

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KAFKA-12329; kafka-reassign-partitions command should give a better e…
dajac Mar 1, 2021
72defea
remove unused import
dajac Mar 1, 2021
e71bcc1
address comment
dajac Mar 1, 2021
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47 changes: 32 additions & 15 deletions core/src/main/scala/kafka/admin/ReassignPartitionsCommand.scala
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Original file line number Diff line number Diff line change
Expand Up @@ -812,6 +812,26 @@ object ReassignPartitionsCommand extends Logging {
proposedAssignments
}

private def describeTopics(adminClient: Admin,
topics: Set[String])
: Map[String, TopicDescription] = {
adminClient.describeTopics(topics.asJava).values.asScala.map {
case (topicName, topicDescriptionFuture) =>
try {
topicName -> topicDescriptionFuture.get
}
catch {
case t: ExecutionException =>
if (classOf[UnknownTopicOrPartitionException].isInstance(t.getCause)) {

@ijuma ijuma Mar 2, 2021

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Hmm. why not write this as t.getCause.isInstanceOf[UnknownTopicOrPartitionException]?

@ijuma ijuma Mar 2, 2021

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Also, you can have the if in the case t line and then a second case for the rethrow case.

@dajac dajac Mar 3, 2021

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I initially used t.getCause != null && t.getCause.isInstanceOf[UnknownTopicOrPartitionException]. @chia7712 suggested to use classOf[UnknownTopicOrPartitionException].isInstance(t.getCause) to avoid having to do the null check as isInstance does it. That seemed reasonable to me so I went with it. Is there a reason not to use it?

I do agree with your second comment.

@ijuma ijuma Mar 8, 2021 •
edited
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Hmm, I think this is an example of code that is less readable. If cause may be nullable, it's better to write code that makes that clear rather than a non obvious alternative that could have been used for many other reasons (using Option to handle nullables is fine as a counter example since it's common usage to do that to handle nulls).

What do you think?

@ijuma ijuma Mar 8, 2021

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Oh, one more thing, did you check that the null check is actually needed? I think isInstanceOf is defined for null too.

@chia7712 chia7712 Mar 8, 2021

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I think isInstanceOf is defined for null too.

you are right. Scala does define it. https://scala-lang.org/files/archive/spec/2.13/spec.pdf

‘’’

isInstanceOf[T] always returns false.
‘’’

Good to know that :)

+1 to use ‘t.getCause.isInstanceOf[UnknownTopicOrPartitionException]‘ as it can deal with null check.

Sorry for my imprecise comment :(

@dajac dajac Mar 8, 2021

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@ijuma Yeah, I do agree with you. For the null check, I was not aware that isInstanceOf handles it. That's good to know, thanks.

I will open a small PR to fix this.

throw new ExecutionException(
new UnknownTopicOrPartitionException(s"Topic $topicName not found."))
} else {
throw t
}
}
}
}

/**
* Get the current replica assignments for some topics.
*
Expand All @@ -823,12 +843,10 @@ object ReassignPartitionsCommand extends Logging {
def getReplicaAssignmentForTopics(adminClient: Admin,
topics: Seq[String])
: Map[TopicPartition, Seq[Int]] = {
adminClient.describeTopics(topics.asJava).all().get().asScala.flatMap {
case (topicName, topicDescription) =>
topicDescription.partitions.asScala.map {
info => (new TopicPartition(topicName, info.partition),
info.replicas.asScala.map(_.id))
}
describeTopics(adminClient, topics.toSet).flatMap {
case (topicName, topicDescription) => topicDescription.partitions.asScala.map { info =>
(new TopicPartition(topicName, info.partition), info.replicas.asScala.map(_.id))
}
}
}

Expand All @@ -843,15 +861,14 @@ object ReassignPartitionsCommand extends Logging {
def getReplicaAssignmentForPartitions(adminClient: Admin,
partitions: Set[TopicPartition])
: Map[TopicPartition, Seq[Int]] = {
adminClient.describeTopics(partitions.map(_.topic).asJava).all().get().asScala.flatMap {
case (topicName, topicDescription) =>
topicDescription.partitions.asScala.flatMap {
info => if (partitions.contains(new TopicPartition(topicName, info.partition))) {
Some(new TopicPartition(topicName, info.partition()),
info.replicas.asScala.map(_.id))
} else {
None
}
describeTopics(adminClient, partitions.map(_.topic)).flatMap {
case (topicName, topicDescription) => topicDescription.partitions.asScala.flatMap { info =>
val tp = new TopicPartition(topicName, info.partition)
if (partitions.contains(tp)) {
Some(tp, info.replicas.asScala.map(_.id))
} else {
None
}
}
}
}
Expand Down
14 changes: 14 additions & 0 deletions core/src/test/scala/unit/kafka/admin/ReassignPartitionsUnitTest.scala
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Original file line number Diff line number Diff line change
Expand Up @@ -286,6 +286,20 @@ class ReassignPartitionsUnitTest {
}
}

@Test
def testGenerateAssignmentWithInvalidPartitionsFails(): Unit = {
val adminClient = new MockAdminClient.Builder().numBrokers(5).build()
try {
addTopics(adminClient)
assertStartsWith("Topic quux not found",
assertThrows(classOf[ExecutionException],
() => generateAssignment(adminClient, """{"topics":[{"topic":"foo"},{"topic":"quux"}]}""", "0,1", false),
() => "Expected generateAssignment to fail").getCause.getMessage)
} finally {
adminClient.close()
}
}

@Test
def testGenerateAssignmentWithInconsistentRacks(): Unit = {
val adminClient = new MockAdminClient.Builder().
Expand Down