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  1. Spark
  2. SPARK-19185

ConcurrentModificationExceptions with CachedKafkaConsumers when Windowing

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    Details

    • Type: Bug
    • Status: Closed
    • Priority: Major
    • Resolution: Fixed
    • Affects Version/s: 2.0.2
    • Fix Version/s: 2.4.0
    • Component/s: DStreams
    • Environment:

      Spark 2.0.2
      Spark Streaming Kafka 010
      Mesos 0.28.0 - client mode

      spark.executor.cores 1
      spark.mesos.extra.cores 1

      Description

      We've been running into ConcurrentModificationExcpetions "KafkaConsumer is not safe for multi-threaded access" with the CachedKafkaConsumer. I've been working through debugging this issue and after looking through some of the spark source code I think this is a bug.

      Our set up is:
      Spark 2.0.2, running in Mesos 0.28.0-2 in client mode, using Spark-Streaming-Kafka-010
      spark.executor.cores 1
      spark.mesos.extra.cores 1

      Batch interval: 10s, window interval: 180s, and slide interval: 30s

      We would see the exception when in one executor there are two task worker threads assigned the same Topic+Partition, but a different set of offsets.

      They would both get the same CachedKafkaConsumer, and whichever task thread went first would seek and poll for all the records, and at the same time the second thread would try to seek to its offset but fail because it is unable to acquire the lock.

      Time0 E0 Task0 - TopicPartition("abc", 0) X to Y
      Time0 E0 Task1 - TopicPartition("abc", 0) Y to Z

      Time1 E0 Task0 - Seeks and starts to poll
      Time1 E0 Task1 - Attempts to seek, but fails

      Here are some relevant logs:

      17/01/06 03:10:01 Executor task launch worker-1 INFO KafkaRDD: Computing topic test-topic, partition 2 offsets 4394204414 -> 4394238058
      17/01/06 03:10:01 Executor task launch worker-0 INFO KafkaRDD: Computing topic test-topic, partition 2 offsets 4394238058 -> 4394257712
      17/01/06 03:10:01 Executor task launch worker-1 DEBUG CachedKafkaConsumer: Get spark-executor-consumer test-topic 2 nextOffset 4394204414 requested 4394204414
      17/01/06 03:10:01 Executor task launch worker-0 DEBUG CachedKafkaConsumer: Get spark-executor-consumer test-topic 2 nextOffset 4394204414 requested 4394238058
      17/01/06 03:10:01 Executor task launch worker-0 INFO CachedKafkaConsumer: Initial fetch for spark-executor-consumer test-topic 2 4394238058
      17/01/06 03:10:01 Executor task launch worker-0 DEBUG CachedKafkaConsumer: Seeking to test-topic-2 4394238058
      17/01/06 03:10:01 Executor task launch worker-0 WARN BlockManager: Putting block rdd_199_2 failed due to an exception
      17/01/06 03:10:01 Executor task launch worker-0 WARN BlockManager: Block rdd_199_2 could not be removed as it was not found on disk or in memory
      17/01/06 03:10:01 Executor task launch worker-0 ERROR Executor: Exception in task 49.0 in stage 45.0 (TID 3201)
      java.util.ConcurrentModificationException: KafkaConsumer is not safe for multi-threaded access
      	at org.apache.kafka.clients.consumer.KafkaConsumer.acquire(KafkaConsumer.java:1431)
      	at org.apache.kafka.clients.consumer.KafkaConsumer.seek(KafkaConsumer.java:1132)
      	at org.apache.spark.streaming.kafka010.CachedKafkaConsumer.seek(CachedKafkaConsumer.scala:95)
      	at org.apache.spark.streaming.kafka010.CachedKafkaConsumer.get(CachedKafkaConsumer.scala:69)
      	at org.apache.spark.streaming.kafka010.KafkaRDD$KafkaRDDIterator.next(KafkaRDD.scala:227)
      	at org.apache.spark.streaming.kafka010.KafkaRDD$KafkaRDDIterator.next(KafkaRDD.scala:193)
      	at scala.collection.Iterator$$anon$11.next(Iterator.scala:409)
      	at scala.collection.Iterator$$anon$11.next(Iterator.scala:409)
      	at scala.collection.Iterator$$anon$11.next(Iterator.scala:409)
      	at scala.collection.Iterator$$anon$13.hasNext(Iterator.scala:462)
      	at scala.collection.Iterator$$anon$11.hasNext(Iterator.scala:408)
      	at org.apache.spark.storage.memory.MemoryStore.putIteratorAsBytes(MemoryStore.scala:360)
      	at org.apache.spark.storage.BlockManager$$anonfun$doPutIterator$1.apply(BlockManager.scala:951)
      	at org.apache.spark.storage.BlockManager$$anonfun$doPutIterator$1.apply(BlockManager.scala:926)
      	at org.apache.spark.storage.BlockManager.doPut(BlockManager.scala:866)
      	at org.apache.spark.storage.BlockManager.doPutIterator(BlockManager.scala:926)
      	at org.apache.spark.storage.BlockManager.getOrElseUpdate(BlockManager.scala:670)
      	at org.apache.spark.rdd.RDD.getOrCompute(RDD.scala:330)
      	at org.apache.spark.rdd.RDD.iterator(RDD.scala:281)
      	at org.apache.spark.rdd.UnionRDD.compute(UnionRDD.scala:105)
      	at org.apache.spark.rdd.RDD.computeOrReadCheckpoint(RDD.scala:319)
      	at org.apache.spark.rdd.RDD.iterator(RDD.scala:283)
      	at org.apache.spark.scheduler.ShuffleMapTask.runTask(ShuffleMapTask.scala:79)
      	at org.apache.spark.scheduler.ShuffleMapTask.runTask(ShuffleMapTask.scala:47)
      	at org.apache.spark.scheduler.Task.run(Task.scala:86)
      	at org.apache.spark.executor.Executor$TaskRunner.run(Executor.scala:274)
      	at java.util.concurrent.ThreadPoolExecutor.runWorker(ThreadPoolExecutor.java:1142)
      	at java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:617)
      	at java.lang.Thread.run(Thread.java:745)
      17/01/06 03:10:01 Executor task launch worker-1 DEBUG CachedKafkaConsumer: Polled [test-topic-2]  8237
      17/01/06 03:10:01 Executor task launch worker-1 DEBUG CachedKafkaConsumer: Get spark-executor-consumer test-topic 2 nextOffset 4394204415 requested 4394204415
      17/01/06 03:10:01 Executor task launch worker-1 DEBUG CachedKafkaConsumer: Get spark-executor-consumer test-topic 2 nextOffset 4394204416 requested 4394204416
      ... 
      

      It looks like when WindowedDStream does the getOrCompute call its computing all the sets of of offsets it needs and tries to farm out the work in parallel. So each available worker task gets each set of offsets that need to be read.

      After realizing what was going on I tested four states:

      • spark.executor.cores 1 and spark.mesos.extra.cores 0
        • No Exceptions
      • spark.executor.cores 1 and spark.mesos.extra.cores 1
        • ConcurrentModificationException
      • spark.executor.cores 2 and spark.mesos.extra.cores 0
        • ConcurrentModificationException
      • spark.executor.cores 2 and spark.mesos.extra.cores 1
        • ConcurrentModificationException

      Minimal set of code I was able to reproduce with:
      Streaming batch interval was set to 2 seconds. This increased the rate of exceptions I saw.

      val kafkaParams = Map[String, Object](
        "bootstrap.servers" -> brokers,
        "key.deserializer" -> classOf[KafkaAvroDeserializer],
        "value.deserializer" -> classOf[KafkaAvroDeserializer],
        "enable.auto.commit" -> (false: java.lang.Boolean),
        "group.id" -> groupId,
        "schema.registry.url" -> schemaRegistryUrl,
        "auto.offset.reset" -> offset
      )
      val inputStream = KafkaUtils.createDirectStream[Object, Object](
        ssc,
        PreferConsistent,
        Subscribe[Object, Object]
          (kafkaTopic, kafkaParams)
      )
      val windowStream = inputStream.map(_.toString).window(Seconds(180), Seconds(30))
      
      windowStream.foreachRDD{
        rdd => {
          val filtered = rdd.filter(_.contains("idb"))
      
          filtered.foreach(
            message => {
              var i = 0
              if (i == 0) {
                logger.info(message)
                i = i + 1
              }
            }
          )
        }
      }
      

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              • Assignee:
                gsomogyi Gabor Somogyi
                Reporter:
                kalvinnchau Kalvin Chau
              • Votes:
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                27 Start watching this issue

                Dates

                • Created:
                  Updated:
                  Resolved: