I started "playing" with Apache Flink recently. I've put together a small application to start testing the framework and so on. I'm currently running into a problem when trying to serialize a usual POJO class:
@Getter
@ToString
@EqualsAndHashCode
@NoArgsConstructor
@AllArgsConstructor
public final class Species {
private String name;
private List<String> abilities;
}
Somehow, I can tell by the stacktrace that the List type cannot be serialized, but according to Flink's documentation, that shouldn't be the case. This is the stacktrace:
2021-11-20 11:52:09,195 |- WARN in org.apache.flink.runtime.taskmanager.Task:1097 [Source: Collection Source (1/1)#0] - Source: Collection Source (1/1)#0 (4073b9fb97691d505e5a5557bf7e081b) switched from RUNNING to FAILED with failure cause: java.io.IOException: Failed to deserialize an element from the source. If you are using user-defined serialization (Value and Writable types), check the serialization functions.
Serializer is org.apache.flink.api.java.typeutils.runtime.kryo.KryoSerializer@5c0e17e6
at org.apache.flink.streaming.api.functions.source.FromElementsFunction.run(FromElementsFunction.java:222)
at org.apache.flink.streaming.api.operators.StreamSource.run(StreamSource.java:116)
at org.apache.flink.streaming.api.operators.StreamSource.run(StreamSource.java:73)
at org.apache.flink.streaming.runtime.tasks.SourceStreamTask$LegacySourceFunctionThread.run(SourceStreamTask.java:323)
Caused by: com.esotericsoftware.kryo.KryoException: java.lang.UnsupportedOperationException
Serialization trace:
abilities (org.acme.domain.Species)
at com.esotericsoftware.kryo.serializers.ObjectField.read(ObjectField.java:125)
at com.esotericsoftware.kryo.serializers.FieldSerializer.read(FieldSerializer.java:528)
at com.esotericsoftware.kryo.Kryo.readClassAndObject(Kryo.java:761)
at org.apache.flink.api.java.typeutils.runtime.kryo.KryoSerializer.deserialize(KryoSerializer.java:354)
at org.apache.flink.streaming.api.functions.source.FromElementsFunction.run(FromElementsFunction.java:220)
... 3 more
Caused by: java.lang.UnsupportedOperationException
at java.base/java.util.ImmutableCollections.uoe(ImmutableCollections.java:72)
at java.base/java.util.ImmutableCollections$AbstractImmutableCollection.add(ImmutableCollections.java:76)
at com.esotericsoftware.kryo.serializers.CollectionSerializer.read(CollectionSerializer.java:109)
at com.esotericsoftware.kryo.serializers.CollectionSerializer.read(CollectionSerializer.java:22)
at com.esotericsoftware.kryo.Kryo.readObject(Kryo.java:679)
at com.esotericsoftware.kryo.serializers.ObjectField.read(ObjectField.java:106)
... 7 more
Exception in thread "main" org.apache.flink.runtime.client.JobExecutionException: Job execution failed.
at org.apache.flink.runtime.jobmaster.JobResult.toJobExecutionResult(JobResult.java:144)
at org.apache.flink.runtime.minicluster.MiniClusterJobClient.lambda$getJobExecutionResult$3(MiniClusterJobClient.java:137)
at java.base/java.util.concurrent.CompletableFuture$UniApply.tryFire(CompletableFuture.java:642)
at java.base/java.util.concurrent.CompletableFuture.postComplete(CompletableFuture.java:506)
at java.base/java.util.concurrent.CompletableFuture.complete(CompletableFuture.java:2073)
at org.apache.flink.runtime.rpc.akka.AkkaInvocationHandler.lambda$invokeRpc$0(AkkaInvocationHandler.java:250)
at java.base/java.util.concurrent.CompletableFuture.uniWhenComplete(CompletableFuture.java:859)
at java.base/java.util.concurrent.CompletableFuture$UniWhenComplete.tryFire(CompletableFuture.java:837)
at java.base/java.util.concurrent.CompletableFuture.postComplete(CompletableFuture.java:506)
at java.base/java.util.concurrent.CompletableFuture.complete(CompletableFuture.java:2073)
at org.apache.flink.util.concurrent.FutureUtils.doForward(FutureUtils.java:1389)
at org.apache.flink.runtime.concurrent.akka.ClassLoadingUtils.lambda$null$1(ClassLoadingUtils.java:93)
at org.apache.flink.runtime.concurrent.akka.ClassLoadingUtils.runWithContextClassLoader(ClassLoadingUtils.java:68)
at org.apache.flink.runtime.concurrent.akka.ClassLoadingUtils.lambda$guardCompletionWithContextClassLoader$2(ClassLoadingUtils.java:92)
at java.base/java.util.concurrent.CompletableFuture.uniWhenComplete(CompletableFuture.java:859)
at java.base/java.util.concurrent.CompletableFuture$UniWhenComplete.tryFire(CompletableFuture.java:837)
at java.base/java.util.concurrent.CompletableFuture.postComplete(CompletableFuture.java:506)
at java.base/java.util.concurrent.CompletableFuture.complete(CompletableFuture.java:2073)
at org.apache.flink.runtime.concurrent.akka.AkkaFutureUtils$1.onComplete(AkkaFutureUtils.java:47)
at akka.dispatch.OnComplete.internal(Future.scala:300)
at akka.dispatch.OnComplete.internal(Future.scala:297)
at akka.dispatch.japi$CallbackBridge.apply(Future.scala:224)
at akka.dispatch.japi$CallbackBridge.apply(Future.scala:221)
at scala.concurrent.impl.CallbackRunnable.run(Promise.scala:60)
at org.apache.flink.runtime.concurrent.akka.AkkaFutureUtils$DirectExecutionContext.execute(AkkaFutureUtils.java:65)
at scala.concurrent.impl.CallbackRunnable.executeWithValue(Promise.scala:68)
at scala.concurrent.impl.Promise$DefaultPromise.$anonfun$tryComplete$1(Promise.scala:284)
at scala.concurrent.impl.Promise$DefaultPromise.$anonfun$tryComplete$1$adapted(Promise.scala:284)
at scala.concurrent.impl.Promise$DefaultPromise.tryComplete(Promise.scala:284)
at akka.pattern.PromiseActorRef.$bang(AskSupport.scala:621)
at akka.pattern.PipeToSupport$PipeableFuture$$anonfun$pipeTo$1.applyOrElse(PipeToSupport.scala:24)
at akka.pattern.PipeToSupport$PipeableFuture$$anonfun$pipeTo$1.applyOrElse(PipeToSupport.scala:23)
at scala.concurrent.Future.$anonfun$andThen$1(Future.scala:532)
at scala.concurrent.impl.Promise.liftedTree1$1(Promise.scala:29)
at scala.concurrent.impl.Promise.$anonfun$transform$1(Promise.scala:29)
at scala.concurrent.impl.CallbackRunnable.run(Promise.scala:60)
at akka.dispatch.BatchingExecutor$AbstractBatch.processBatch(BatchingExecutor.scala:63)
at akka.dispatch.BatchingExecutor$BlockableBatch.$anonfun$run$1(BatchingExecutor.scala:100)
at scala.runtime.java8.JFunction0$mcV$sp.apply(JFunction0$mcV$sp.java:12)
at scala.concurrent.BlockContext$.withBlockContext(BlockContext.scala:81)
at akka.dispatch.BatchingExecutor$BlockableBatch.run(BatchingExecutor.scala:100)
at akka.dispatch.TaskInvocation.run(AbstractDispatcher.scala:49)
at akka.dispatch.ForkJoinExecutorConfigurator$AkkaForkJoinTask.exec(ForkJoinExecutorConfigurator.scala:48)
at java.base/java.util.concurrent.ForkJoinTask.doExec(ForkJoinTask.java:290)
at java.base/java.util.concurrent.ForkJoinPool$WorkQueue.topLevelExec(ForkJoinPool.java:1020)
at java.base/java.util.concurrent.ForkJoinPool.scan(ForkJoinPool.java:1656)
at java.base/java.util.concurrent.ForkJoinPool.runWorker(ForkJoinPool.java:1594)
at java.base/java.util.concurrent.ForkJoinWorkerThread.run(ForkJoinWorkerThread.java:183)
Caused by: org.apache.flink.runtime.JobException: Recovery is suppressed by NoRestartBackoffTimeStrategy
at org.apache.flink.runtime.executiongraph.failover.flip1.ExecutionFailureHandler.handleFailure(ExecutionFailureHandler.java:138)
at org.apache.flink.runtime.executiongraph.failover.flip1.ExecutionFailureHandler.getFailureHandlingResult(ExecutionFailureHandler.java:82)
at org.apache.flink.runtime.scheduler.DefaultScheduler.handleTaskFailure(DefaultScheduler.java:228)
at org.apache.flink.runtime.scheduler.DefaultScheduler.maybeHandleTaskFailure(DefaultScheduler.java:218)
at org.apache.flink.runtime.scheduler.DefaultScheduler.updateTaskExecutionStateInternal(DefaultScheduler.java:209)
at org.apache.flink.runtime.scheduler.SchedulerBase.updateTaskExecutionState(SchedulerBase.java:679)
at org.apache.flink.runtime.scheduler.SchedulerNG.updateTaskExecutionState(SchedulerNG.java:79)
at org.apache.flink.runtime.jobmaster.JobMaster.updateTaskExecutionState(JobMaster.java:444)
at jdk.internal.reflect.GeneratedMethodAccessor11.invoke(Unknown Source)
at java.base/jdk.internal.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:43)
at java.base/java.lang.reflect.Method.invoke(Method.java:566)
at org.apache.flink.runtime.rpc.akka.AkkaRpcActor.lambda$handleRpcInvocation$1(AkkaRpcActor.java:316)
at org.apache.flink.runtime.concurrent.akka.ClassLoadingUtils.runWithContextClassLoader(ClassLoadingUtils.java:83)
at org.apache.flink.runtime.rpc.akka.AkkaRpcActor.handleRpcInvocation(AkkaRpcActor.java:314)
at org.apache.flink.runtime.rpc.akka.AkkaRpcActor.handleRpcMessage(AkkaRpcActor.java:217)
at org.apache.flink.runtime.rpc.akka.FencedAkkaRpcActor.handleRpcMessage(FencedAkkaRpcActor.java:78)
at org.apache.flink.runtime.rpc.akka.AkkaRpcActor.handleMessage(AkkaRpcActor.java:163)
at akka.japi.pf.UnitCaseStatement.apply(CaseStatements.scala:24)
at akka.japi.pf.UnitCaseStatement.apply(CaseStatements.scala:20)
at scala.PartialFunction.applyOrElse(PartialFunction.scala:123)
at scala.PartialFunction.applyOrElse$(PartialFunction.scala:122)
at akka.japi.pf.UnitCaseStatement.applyOrElse(CaseStatements.scala:20)
at scala.PartialFunction$OrElse.applyOrElse(PartialFunction.scala:171)
at scala.PartialFunction$OrElse.applyOrElse(PartialFunction.scala:172)
at scala.PartialFunction$OrElse.applyOrElse(PartialFunction.scala:172)
at akka.actor.Actor.aroundReceive(Actor.scala:537)
at akka.actor.Actor.aroundReceive$(Actor.scala:535)
at akka.actor.AbstractActor.aroundReceive(AbstractActor.scala:220)
at akka.actor.ActorCell.receiveMessage(ActorCell.scala:580)
at akka.actor.ActorCell.invoke(ActorCell.scala:548)
at akka.dispatch.Mailbox.processMailbox(Mailbox.scala:270)
at akka.dispatch.Mailbox.run(Mailbox.scala:231)
at akka.dispatch.Mailbox.exec(Mailbox.scala:243)
... 5 more
Caused by: java.io.IOException: Failed to deserialize an element from the source. If you are using user-defined serialization (Value and Writable types), check the serialization functions.
Serializer is org.apache.flink.api.java.typeutils.runtime.kryo.KryoSerializer@5c0e17e6
at org.apache.flink.streaming.api.functions.source.FromElementsFunction.run(FromElementsFunction.java:222)
at org.apache.flink.streaming.api.operators.StreamSource.run(StreamSource.java:116)
at org.apache.flink.streaming.api.operators.StreamSource.run(StreamSource.java:73)
at org.apache.flink.streaming.runtime.tasks.SourceStreamTask$LegacySourceFunctionThread.run(SourceStreamTask.java:323)
Caused by: com.esotericsoftware.kryo.KryoException: java.lang.UnsupportedOperationException
Serialization trace:
abilities (org.acme.domain.Species)
at com.esotericsoftware.kryo.serializers.ObjectField.read(ObjectField.java:125)
at com.esotericsoftware.kryo.serializers.FieldSerializer.read(FieldSerializer.java:528)
at com.esotericsoftware.kryo.Kryo.readClassAndObject(Kryo.java:761)
at org.apache.flink.api.java.typeutils.runtime.kryo.KryoSerializer.deserialize(KryoSerializer.java:354)
at org.apache.flink.streaming.api.functions.source.FromElementsFunction.run(FromElementsFunction.java:220)
... 3 more
Caused by: java.lang.UnsupportedOperationException
at java.base/java.util.ImmutableCollections.uoe(ImmutableCollections.java:72)
at java.base/java.util.ImmutableCollections$AbstractImmutableCollection.add(ImmutableCollections.java:76)
at com.esotericsoftware.kryo.serializers.CollectionSerializer.read(CollectionSerializer.java:109)
at com.esotericsoftware.kryo.serializers.CollectionSerializer.read(CollectionSerializer.java:22)
at com.esotericsoftware.kryo.Kryo.readObject(Kryo.java:679)
at com.esotericsoftware.kryo.serializers.ObjectField.read(ObjectField.java:106)
... 7 more
Process finished with exit code 1
I've tried adding enableForceKyro to StreamExecutionEnvironment.getExecutionEnvironment().getCOnfig, but didn't change anything.
What am I missing here? I'm using Apache Flink 1.14.0 with Java (Eclipse Temurin) 11.x.
Since the issue is with Kryo serialization, you can register your own custom Kryo serializers. But in my experience this hasn't worked all that well for reasons I don't completely understand (not always used). Plus Kryo serialization is going to be much slower than creating a POJO that Flink can serialize using built-in support. So add setters for every field, verify nothing gets logged about class Species missing something that qualifies it for fast serialization, and you should be all set.