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From "Giuliano Caliari (JIRA)" <j...@apache.org>
Subject [jira] [Created] (FLINK-5633) ClassCastException: X cannot be cast to X when re-submitting a job.
Date Wed, 25 Jan 2017 05:53:26 GMT
Giuliano Caliari created FLINK-5633:
---------------------------------------

             Summary: ClassCastException: X cannot be cast to X when re-submitting a job.
                 Key: FLINK-5633
                 URL: https://issues.apache.org/jira/browse/FLINK-5633
             Project: Flink
          Issue Type: Bug
          Components: Job-Submission, YARN
    Affects Versions: 1.1.4
            Reporter: Giuliano Caliari
            Priority: Minor


I’m running a job on my local cluster and the first time I submit the job everything works
but whenever I cancel and re-submit the same job it fails with:

{quote}
org.apache.flink.client.program.ProgramInvocationException: The program execution failed:
Job execution failed.

	at org.apache.flink.client.program.ClusterClient.run(ClusterClient.java:427)

	at org.apache.flink.client.program.StandaloneClusterClient.submitJob(StandaloneClusterClient.java:101)

	at org.apache.flink.client.program.ClusterClient.run(ClusterClient.java:400)

	at org.apache.flink.streaming.api.environment.StreamContextEnvironment.execute(StreamContextEnvironment.java:66)

	at org.apache.flink.streaming.api.scala.StreamExecutionEnvironment.execute(StreamExecutionEnvironment.scala:634)

	at au.com.my.package.pTraitor.OneTrait.execute(Traitor.scala:147)

	at au.com.my.package.pTraitor.TraitorAppOneTrait$.delayedEndpoint$au$com$my$package$pTraitor$TraitorAppOneTrait$1(TraitorApp.scala:22)

	at au.com.my.package.pTraitor.TraitorAppOneTrait$delayedInit$body.apply(TraitorApp.scala:21)

	at scala.Function0$class.apply$mcV$sp(Function0.scala:34)

	at scala.runtime.AbstractFunction0.apply$mcV$sp(AbstractFunction0.scala:12)

	at scala.App$$anonfun$main$1.apply(App.scala:76)

	at scala.App$$anonfun$main$1.apply(App.scala:76)

	at scala.collection.immutable.List.foreach(List.scala:381)

	at scala.collection.generic.TraversableForwarder$class.foreach(TraversableForwarder.scala:35)

	at scala.App$class.main(App.scala:76)

	at au.com.my.package.pTraitor.TraitorAppOneTrait$.main(TraitorApp.scala:21)

	at au.com.my.package.pTraitor.TraitorAppOneTrait.main(TraitorApp.scala)

	at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method)

	at sun.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:62)

	at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:43)

	at java.lang.reflect.Method.invoke(Method.java:498)

	at org.apache.flink.client.program.PackagedProgram.callMainMethod(PackagedProgram.java:528)

	at org.apache.flink.client.program.PackagedProgram.invokeInteractiveModeForExecution(PackagedProgram.java:419)

	at org.apache.flink.client.program.ClusterClient.run(ClusterClient.java:339)

	at org.apache.flink.client.CliFrontend.executeProgram(CliFrontend.java:831)

	at org.apache.flink.client.CliFrontend.run(CliFrontend.java:256)

	at org.apache.flink.client.CliFrontend.parseParameters(CliFrontend.java:1073)

	at org.apache.flink.client.CliFrontend$2.call(CliFrontend.java:1120)

	at org.apache.flink.client.CliFrontend$2.call(CliFrontend.java:1117)

	at org.apache.flink.runtime.security.NoOpSecurityContext.runSecured(NoOpSecurityContext.java:29)

	at org.apache.flink.client.CliFrontend.main(CliFrontend.java:1116)

Caused by: org.apache.flink.runtime.client.JobExecutionException: Job execution failed.

	at org.apache.flink.runtime.jobmanager.JobManager$$anonfun$handleMessage$1$$anonfun$applyOrElse$6.apply$mcV$sp(JobManager.scala:900)

	at org.apache.flink.runtime.jobmanager.JobManager$$anonfun$handleMessage$1$$anonfun$applyOrElse$6.apply(JobManager.scala:843)

	at org.apache.flink.runtime.jobmanager.JobManager$$anonfun$handleMessage$1$$anonfun$applyOrElse$6.apply(JobManager.scala:843)

	at scala.concurrent.impl.Future$PromiseCompletingRunnable.liftedTree1$1(Future.scala:24)

	at scala.concurrent.impl.Future$PromiseCompletingRunnable.run(Future.scala:24)

	at akka.dispatch.TaskInvocation.run(AbstractDispatcher.scala:40)

	at akka.dispatch.ForkJoinExecutorConfigurator$AkkaForkJoinTask.exec(AbstractDispatcher.scala:397)

	at scala.concurrent.forkjoin.ForkJoinTask.doExec(ForkJoinTask.java:260)

	at scala.concurrent.forkjoin.ForkJoinPool$WorkQueue.runTask(ForkJoinPool.java:1339)

	at scala.concurrent.forkjoin.ForkJoinPool.runWorker(ForkJoinPool.java:1979)

	at scala.concurrent.forkjoin.ForkJoinWorkerThread.run(ForkJoinWorkerThread.java:107)

Caused by: java.lang.RuntimeException: Could not forward element to next operator

	at org.apache.flink.streaming.runtime.tasks.OperatorChain$CopyingChainingOutput.collect(OperatorChain.java:415)

	at org.apache.flink.streaming.runtime.tasks.OperatorChain$CopyingChainingOutput.collect(OperatorChain.java:397)

	at org.apache.flink.streaming.api.operators.AbstractStreamOperator$CountingOutput.collect(AbstractStreamOperator.java:749)

	at org.apache.flink.streaming.api.operators.AbstractStreamOperator$CountingOutput.collect(AbstractStreamOperator.java:727)

	at org.apache.flink.streaming.api.operators.StreamSourceContexts$ManualWatermarkContext.collectWithTimestamp(StreamSourceContexts.java:272)

	at org.apache.flink.streaming.connectors.kafka.internals.AbstractFetcher.emitRecordWithTimestamp(AbstractFetcher.java:261)

	at org.apache.flink.streaming.connectors.kafka.internal.Kafka010Fetcher.emitRecord(Kafka010Fetcher.java:88)

	at org.apache.flink.streaming.connectors.kafka.internal.Kafka09Fetcher.runFetchLoop(Kafka09Fetcher.java:157)

	at org.apache.flink.streaming.connectors.kafka.FlinkKafkaConsumerBase.run(FlinkKafkaConsumerBase.java:255)

	at org.apache.flink.streaming.api.operators.StreamSource.run(StreamSource.java:78)

	at org.apache.flink.streaming.api.operators.StreamSource.run(StreamSource.java:55)

	at org.apache.flink.streaming.runtime.tasks.SourceStreamTask.run(SourceStreamTask.java:56)

	at org.apache.flink.streaming.runtime.tasks.StreamTask.invoke(StreamTask.java:269)

	at org.apache.flink.runtime.taskmanager.Task.run(Task.java:654)

	at java.lang.Thread.run(Thread.java:745)

Caused by: java.lang.ClassCastException: au.com.my.package.schema.p.WowTransaction cannot
be cast to au.com.my.package.schema.p.WowTransaction

	at au.com.my.package.pTraitor.OneTrait$$anonfun$execute$4.apply(Traitor.scala:132)

	at org.apache.flink.streaming.api.scala.DataStream$$anon$1.extractAscendingTimestamp(DataStream.scala:763)

	at org.apache.flink.streaming.api.functions.timestamps.AscendingTimestampExtractor.extractTimestamp(AscendingTimestampExtractor.java:72)

	at org.apache.flink.streaming.runtime.operators.TimestampsAndPeriodicWatermarksOperator.processElement(TimestampsAndPeriodicWatermarksOperator.java:65)

	at org.apache.flink.streaming.runtime.tasks.OperatorChain$CopyingChainingOutput.collect(OperatorChain.java:412)

	... 14 more
{quote}

This happens on versions 1.1.4 and 1.2
Here's a great description of the problem, provided by Yury Ruchin:

{quote}
In YARN setup there are several sources where classes are loaded from: Flink lib directory,
YARN lib directories, user code. The first two sources are handled by system classloader,
the last one is loaded by FlinkUserCodeClassLoader.

My streaming job parses Avro-encoded data using SpecificRecord facility. In essence, the job
looks like this: Source -> Avro parser (Map) -> Sink. Parallelism is 1. Job operates
inside a long-lived YARN session. I have a subclass of SpecificRecord, say it's name is MySpecificRecord.
From class loading perspective, Avro library classes, including the SpecificRecord, are loaded
by system class loader from YARN lib dir - such classes are shared across different Flink
tasks within task manager. On the other side, MySpecificRecord is in the job fat jar, so it
gets loaded by FlinkUserCodeClassLoader. Upon every job restart, task gets a new FlinkUserCodeClassLoader
instance, so classes from user code are confined to a task instance.

Simply put, the parsing itself looks like this:

val bean = new SpecificDatumReader[MySpecificRecord](MySpecificRecord.getClassSchema).read(...)

Now, the scenario:

1. I start my job. Parsing is initiated, so the SpecificDatumReader and SpecificData get loaded
by system classloader. A new FlinkUserCodeClassloader is instantiated, let's denote its instance
as "A". MySpecificRecord then gets loaded by A.

2. SpecificData gets a singleton SpecificData.INSTANCE that holds a cache that maps some string
key derived from Avro schema to the implementing class. So during parsing I get MySpecificRecord
(A) cached there.

3. I stop the job and re-submit it. The JVM process is the same, so all standard Avro classes,
including SpecificData, remain loaded. A new task instance is created and gets a new FlinkUserCodeClassLoader
instance, let's name it "B". A new MySpecificRecord class incarnation is loaded by B. From
JVM standpoint MySpecificRecord (B) is different from MySpecificRecord (A), even though their
bytecode is identical.

4. The job starts parsing again. SpecificDatumReader consults SpecificData.INSTANCE's cache
for any stashed classes and finds MySpecificRecord (A) there.

5. SpecificDatumReader uses the cached MySpecificRecord (A) to instantiate a bean for filling
the parsed data in.

6. SpecificDatumReader hands the filled instance of MySpecificRecord (A) back to job.

7. Job tries to cast MySpecificRecord (A) to MySpecificRecord (B).

8. ClassCastException :^(

I fixed the issue by not using the SpecificData.INSTANCE singleton (even though this is considered
a common and expected practice). I feed every parser a new instance of SpecificData. This
way the class cache is confined to a parser instance and gets recycled along with it.

{quote}

A discussion the the error can be found at:
http://apache-flink-user-mailing-list-archive.2336050.n4.nabble.com/How-to-get-help-on-ClassCastException-when-re-submitting-a-job-td10972.html



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