[jira] [Created] (KAFKA-13468) Consumers may hang because IOException in Log# does not trigger KafkaStorageException

["Haoze Wu (Jira)" <ji...@apache.org>]

Haoze Wu created KAFKA-13468:
--------------------------------

             Summary: Consumers may hang because IOException in Log#<init> does not trigger KafkaStorageException
                 Key: KAFKA-13468
                 URL: https://issues.apache.org/jira/browse/KAFKA-13468
             Project: Kafka
          Issue Type: Bug
          Components: log
    Affects Versions: 2.8.0
            Reporter: Haoze Wu


When the Kafka Log class (`core/src/main/scala/kafka/log/Log.scala`) is initialized, it may encounter an IO exception in the locally block, e.g., when the log directory cannot be created due to permission issue or IOException in  `initializeLeaderEpochCache`, `initializePartitionMetadata`, etc.

 
{code:java}
class Log(...) {
  // ...
  locally {
    // create the log directory if it doesn't exist
    Files.createDirectories(dir.toPath)

    initializeLeaderEpochCache()
    initializePartitionMetadata()

    val nextOffset = loadSegments()
    // ...
  }
  // ...
}{code}
We found that the broker encountering the IO exception prints an KafkaApi error log like the following and proceeds. 

 
{code:java}
[2021-11-17 22:41:30,057] ERROR [KafkaApi-1] Error when handling request: clientId=1, correlationId=1, api=LEADER_AND_ISR, version=5, body=LeaderAndIsrRequestData(controllerId=1, controllerEpoch=1, brokerEpoch=4294967362, type=0, ungroupedPartitionStates=[], topicStates=[LeaderAndIsrTopicState(topicName='gray-2-0', topicId=573bAVHfRQeXApzAKevNIg, partitionStates=[LeaderAndIsrPartitionState(topicName='gray-2-0', partitionIndex=1, controllerEpoch=1, leader=1, leaderEpoch=0, isr=[1, 3], zkVersion=0, replicas=[1, 3], addingReplicas=[], removingReplicas=[], isNew=true)]), LeaderAndIsrTopicState(topicName='gray-1-0', topicId=12dW2FxLTiyKmGi41HhdZQ, partitionStates=[LeaderAndIsrPartitionState(topicName='gray-1-0', partitionIndex=1, controllerEpoch=1, leader=3, leaderEpoch=0, isr=[3, 1], zkVersion=0, replicas=[3, 1], addingReplicas=[], removingReplicas=[], isNew=true)]), LeaderAndIsrTopicState(topicName='gray-3-0', topicId=_yvmANyZSoK_PTV0e-nqCA, partitionStates=[LeaderAndIsrPartitionState(topicName='gray-3-0', partitionIndex=1, controllerEpoch=1, leader=1, leaderEpoch=0, isr=[1, 3], zkVersion=0, replicas=[1, 3], addingReplicas=[], removingReplicas=[], isNew=true)])], liveLeaders=[LeaderAndIsrLiveLeader(brokerId=1, hostName='localhost', port=9791), LeaderAndIsrLiveLeader(brokerId=3, hostName='localhost', port=9793)]) (kafka.server.RequestHandlerHelper) {code}
But all the consumers that are consuming data from the affected topics (“gray-2-0”, “gray-1-0”, “gray-3-0”) are not able to proceed. These consumers don’t have any error log related to this issue. They hang for more than 3 minutes.

 

The IOException sometimes affects multiple offset topics:

 
{code:java}
[2021-11-18 10:57:41,289] ERROR [KafkaApi-1] Error when handling request: clientId=1, correlationId=11, api=LEADER_AND_ISR, version=5, body=LeaderAndIsrRequestData(controllerId=1, controllerEpoch=1, brokerEpoch=4294967355, type=0, ungroupedPartitionStates=[], topicStates=[LeaderAndIsrTopicState(topicName='__consumer_offsets', topicId=_MiMTCViS76osIyDdxekIg, partitionStates=[LeaderAndIsrPartitionState(topicName='__consumer_offsets', partitionIndex=15, controllerEpoch=1, leader=1, leaderEpoch=0, isr=[1], zkVersion=0, replicas=[1], addingReplicas=[], removingReplicas=[], isNew=true), LeaderAndIsrPartitionState(topicName='__consumer_offsets', partitionIndex=48, controllerEpoch=1, leader=1, leaderEpoch=0, isr=[1], zkVersion=0, replicas=[1], addingReplicas=[], removingReplicas=[], isNew=true), LeaderAndIsrPartitionState(topicName='__consumer_offsets', partitionIndex=45, controllerEpoch=1, leader=1, leaderEpoch=0, isr=[1], zkVersion=0, replicas=[1], addingReplicas=[], removingReplicas=[], isNew=true), ...
addingReplicas=[], removingReplicas=[], isNew=true), LeaderAndIsrPartitionState(topicName='__consumer_offsets', partitionIndex=33, controllerEpoch=1, leader=1, leaderEpoch=0, isr=[1], zkVersion=0, replicas=[1], addingReplicas=[], removingReplicas=[], isNew=true)])], liveLeaders=[LeaderAndIsrLiveLeader(brokerId=1, hostName='localhost', port=9791)]) (kafka.server.RequestHandlerHelper) {code}
*Analysis*

 

The key stacktrace is as follows:
{code:java}
"java.lang.Thread,run,748",
"kafka.server.KafkaRequestHandler,run,74",
"kafka.server.KafkaApis,handle,236",
"kafka.server.KafkaApis,handleLeaderAndIsrRequest,258",
"kafka.server.ReplicaManager,becomeLeaderOrFollower,1411",
"kafka.server.ReplicaManager,makeLeaders,1566",
"scala.collection.mutable.HashMap,foreachEntry,499",
"scala.collection.mutable.HashMap$Node,foreachEntry,633",
"kafka.utils.Implicits$MapExtensionMethods$,$anonfun$forKeyValue$1,62",
"kafka.server.ReplicaManager,$anonfun$makeLeaders$5,1568",
"kafka.cluster.Partition,makeLeader,548",
"kafka.cluster.Partition,$anonfun$makeLeader$1,564",
"kafka.cluster.Partition,createLogIfNotExists,324",
"kafka.cluster.Partition,createLog,344",
"kafka.log.LogManager,getOrCreateLog,783",
"scala.Option,getOrElse,201",
"kafka.log.LogManager,$anonfun$getOrCreateLog$1,830",
"kafka.log.Log$,apply,2601",
"kafka.log.Log,<init>,323" {code}
Basically, the IOException is not be handled by Log but instead gets propagated all the way back to `core/src/main/scala/kafka/server/KafkaApis.scala`
{code:java}
  override def handle(request: RequestChannel.Request): Unit = {
    try {
      request.header.apiKey match {
        // ...
        case ApiKeys.LEADER_AND_ISR => handleLeaderAndIsrRequest(request)
        // ...
      }
    } catch {
      case e: FatalExitError => throw e
      case e: Throwable => requestHelper.handleError(request, e)
    } finally {
      // ...
    }
  }
{code}
I also notice the ReplicaManager in `core/src/main/scala/kafka/server/ReplicaManager.scala` has a relevant comment about “unexpected error” with a TODO.
{code:java}
  /*
   * Make the current broker to become leader for a given set of partitions by:
   *
   * 1. Stop fetchers for these partitions
   * 2. Update the partition metadata in cache
   * 3. Add these partitions to the leader partitions set
   *
   * If an unexpected error is thrown in this function, it will be propagated to KafkaApis where
   * the error message will be set on each partition since we do not know which partition caused it. Otherwise,
   * return the set of partitions that are made leader due to this method
   *
   *  TODO: the above may need to be fixed later
   */
  private def makeLeaders(...): Set[Partition] = {
    // ...
    try {
      // ...
      partitionStates.forKeyValue { (partition, partitionState) =>
        try {
          if (partition.makeLeader(partitionState, highWatermarkCheckpoints)) // line 1568
            partitionsToMakeLeaders += partition
          else
            stateChangeLogger.info(...)
        } catch {
          case e: KafkaStorageException =>
            stateChangeLogger.error(...)
            val dirOpt = getLogDir(partition.topicPartition)
            error(...)
            responseMap.put(partition.topicPartition, Errors.KAFKA_STORAGE_ERROR)
        }
      }
    } catch {
      case e: Throwable =>
        partitionStates.keys.foreach { partition =>
          stateChangeLogger.error(...)
        }
        // Re-throw the exception for it to be caught in KafkaApis
        throw e
    }
    // ...
  } {code}
*Fix*

To fix this issue, I think we should catch the potential IOException when Log is initialized, and then throw a KafkaStorageException, just like many other IOException handlers in Kafka, e.g., [https://github.com/apache/kafka/blob/ebb1d6e21cc9213071ee1c6a15ec3411fc215b81/core/src/main/scala/kafka/server/checkpoints/CheckpointFile.scala#L92-L120]

After applying this fix, the aforementioned symptoms will disappear, i.e., the consumers will not hang and proceed to finish the remaining workload.

One question is whether we should also use `logDirFailureChannel.maybeAddOfflineLogDir` to handle the IOException, like [https://github.com/apache/kafka/blob/ebb1d6e21cc9213071ee1c6a15ec3411fc215b81/core/src/main/scala/kafka/server/checkpoints/CheckpointFile.scala#L92-L120] and [https://github.com/apache/kafka/blob/ebb1d6e21cc9213071ee1c6a15ec3411fc215b81/core/src/main/scala/kafka/server/checkpoints/CheckpointFile.scala#L126-L139] . If so, `logDirFailureChannel.maybeAddOfflineLogDir` would crash the node according to the protocol in [https://github.com/apache/kafka/blob/ebb1d6e21cc9213071ee1c6a15ec3411fc215b81/core/src/main/scala/kafka/server/ReplicaManager.scala#L268-L277] and [https://github.com/apache/kafka/blob/ebb1d6e21cc9213071ee1c6a15ec3411fc215b81/core/src/main/scala/kafka/server/ReplicaManager.scala#L327-L332]

 

 

 

 



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