James Cheng created KAFKA-4858:
----------------------------------

             Summary: Long topic names created using old kafka-topics.sh can 
prevent newer brokers from joining any ISRs
                 Key: KAFKA-4858
                 URL: https://issues.apache.org/jira/browse/KAFKA-4858
             Project: Kafka
          Issue Type: Bug
    Affects Versions: 0.10.2.0, 0.10.1.1
            Reporter: James Cheng


I ran into a variant of KAFKA-3219 that resulted in a broker being unable to 
join any ISRs the cluster.

Prior to 0.10.0.0, the maximum topic length was 255.
With 0.10.0.0 and beyond, the maximum topic length is 249.

The check on topic name length is done by kafka-topics.sh prior to topic 
creation. Thus, it is possible to use a 0.9.0.1 kafka-topics.sh script to 
create a 255 character topic on a 0.10.1.1 broker.

When this happens, you will get the following stack trace (the same one seen in 
KAFKA-3219)
{code}
$ TOPIC=$(printf 'd%.0s' {1..255} ) ; bin/kafka-topics.sh --zookeeper 127.0.0.1 
--create --topic $TOPIC --partitions 1 --replication-factor 2
Created topic 
"ddddddddddddddddddddddddddddddddddddddddddddddddddddddddddddddddddddddddddddddddddddddddddddddddddddddddddddddddddddddddddddddddddddddddddddddddddddddddddddddddddddddddddddddddddddddddddddddddddddddddddddddddddddddddddddddddddddddddddddddddddddddddddddddd".
{code}

{code}
[2017-03-06 22:01:19,011] ERROR [KafkaApi-2] Error when handling request 
{controller_id=1,controller_epoch=1,partition_states=[{topic=ddddddddddddddddddddddddddddddddddddddddddddddddddddddddddddddddddddddddddddddddddddddddddddddddddddddddddddddddddddddddddddddddddddddddddddddddddddddddddddddddddddddddddddddddddddddddddddddddddddddddddddddddddddddddddddddddddddddddddddddddddddddddddddddd,partition=0,controller_epoch=1,leader=2,leader_epoch=0,isr=[2,1],zk_version=0,replicas=[2,1]}],live_leaders=[{id=2,host=jchengmbpro15,port=9093}]}
 (kafka.server.KafkaApis)
java.lang.NullPointerException
        at 
scala.collection.mutable.ArrayOps$ofRef$.length$extension(ArrayOps.scala:192)
        at scala.collection.mutable.ArrayOps$ofRef.length(ArrayOps.scala:192)
        at 
scala.collection.IndexedSeqOptimized$class.foreach(IndexedSeqOptimized.scala:32)
        at scala.collection.mutable.ArrayOps$ofRef.foreach(ArrayOps.scala:186)
        at 
scala.collection.TraversableLike$WithFilter.foreach(TraversableLike.scala:732)
        at kafka.log.Log.loadSegments(Log.scala:155)
        at kafka.log.Log.<init>(Log.scala:108)
        at kafka.log.LogManager.createLog(LogManager.scala:362)
        at kafka.cluster.Partition.getOrCreateReplica(Partition.scala:94)
        at 
kafka.cluster.Partition$$anonfun$4$$anonfun$apply$2.apply(Partition.scala:174)
        at 
kafka.cluster.Partition$$anonfun$4$$anonfun$apply$2.apply(Partition.scala:174)
        at scala.collection.mutable.HashSet.foreach(HashSet.scala:78)
        at kafka.cluster.Partition$$anonfun$4.apply(Partition.scala:174)
        at kafka.cluster.Partition$$anonfun$4.apply(Partition.scala:168)
        at kafka.utils.CoreUtils$.inLock(CoreUtils.scala:234)
        at kafka.utils.CoreUtils$.inWriteLock(CoreUtils.scala:242)
        at kafka.cluster.Partition.makeLeader(Partition.scala:168)
        at 
kafka.server.ReplicaManager$$anonfun$makeLeaders$4.apply(ReplicaManager.scala:758)
        at 
kafka.server.ReplicaManager$$anonfun$makeLeaders$4.apply(ReplicaManager.scala:757)
        at 
scala.collection.mutable.HashMap$$anonfun$foreach$1.apply(HashMap.scala:99)
        at 
scala.collection.mutable.HashMap$$anonfun$foreach$1.apply(HashMap.scala:99)
        at 
scala.collection.mutable.HashTable$class.foreachEntry(HashTable.scala:230)
        at scala.collection.mutable.HashMap.foreachEntry(HashMap.scala:40)
        at scala.collection.mutable.HashMap.foreach(HashMap.scala:99)
        at kafka.server.ReplicaManager.makeLeaders(ReplicaManager.scala:757)
        at 
kafka.server.ReplicaManager.becomeLeaderOrFollower(ReplicaManager.scala:703)
        at kafka.server.KafkaApis.handleLeaderAndIsrRequest(KafkaApis.scala:148)
        at kafka.server.KafkaApis.handle(KafkaApis.scala:82)
        at kafka.server.KafkaRequestHandler.run(KafkaRequestHandler.scala:60)
        at java.lang.Thread.run(Thread.java:745)
{code}


The topic does not get created on disk, but the broker thinks the topic is 
ready. The broker seems functional, for other topics. I can produce/consume to 
other topics.
{code}

$ ./bin/kafka-topics.sh --zookeeper 127.0.0.1 --describe
Topic:ddddddddddddddddddddddddddddddddddddddddddddddddddddddddddddddddddddddddddddddddddddddddddddddddddddddddddddddddddddddddddddddddddddddddddddddddddddddddddddddddddddddddddddddddddddddddddddddddddddddddddddddddddddddddddddddddddddddddddddddddddddddddddddddd
   PartitionCount:1        ReplicationFactor:2     Configs:
        Topic: 
ddddddddddddddddddddddddddddddddddddddddddddddddddddddddddddddddddddddddddddddddddddddddddddddddddddddddddddddddddddddddddddddddddddddddddddddddddddddddddddddddddddddddddddddddddddddddddddddddddddddddddddddddddddddddddddddddddddddddddddddddddddddddddddddd
  Partition: 0    Leader: 2       Replicas: 2,1   Isr: 2,1
{code}


If you stop and restart the broker, it again gets that stack trace. This time, 
the broker fails to join *any* ISRs in the cluster. Notice below that broker 2 
is out of all ISRs

{code}

$ ./bin/kafka-topics.sh --zookeeper 127.0.0.1 --describe
Topic:ddddddddddddddddddddddddddddddddddddddddddddddddddddddddddddddddddddddddddddddddddddddddddddddddddddddddddddddddddddddddddddddddddddddddddddddddddddddddddddddddddddddddddddddddddddddddddddddddddddddddddddddddddddddddddddddddddddddddddddddddddddddddddddddd
   PartitionCount:1        ReplicationFactor:2     Configs:
        Topic: 
ddddddddddddddddddddddddddddddddddddddddddddddddddddddddddddddddddddddddddddddddddddddddddddddddddddddddddddddddddddddddddddddddddddddddddddddddddddddddddddddddddddddddddddddddddddddddddddddddddddddddddddddddddddddddddddddddddddddddddddddddddddddddddddddd
  Partition: 0    Leader: 1       Replicas: 2,1   Isr: 1
Topic:small     PartitionCount:5        ReplicationFactor:2     Configs:
        Topic: small    Partition: 0    Leader: 1       Replicas: 1,2   Isr: 1
        Topic: small    Partition: 1    Leader: 1       Replicas: 2,1   Isr: 1
        Topic: small    Partition: 2    Leader: 1       Replicas: 1,2   Isr: 1
        Topic: small    Partition: 3    Leader: 1       Replicas: 2,1   Isr: 1
        Topic: small    Partition: 4    Leader: 1       Replicas: 1,2   Isr: 1

{code}

So, it appears that a long topic name that sneaks into the cluster can prevent 
brokers from partipating in the cluster.

Furthermore, I'm not exactly sure how to delete the offending topic. A 
kafka-topics.sh --delete won't delete the topic because it can't talk to all 
replicas, because the replicas are not in the ISR. We ran into this at work 
today and ended up having to manually delete the topic configuration from 
zookeeper and then did a bounce of all affected brokers. Until we did that, 
those brokers weren't able to join the cluster.




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