[FLINK-28653] State Schema Evolution does not work - Flink defaults to Kryo serialization even for POJOs and Avro SpecificRecords

• Type: Bug
• Status: Resolved
• Priority: Major
• Resolution: Feedback Received
• Affects Version/s: 1.14.3, 1.15.0
• Component/s: API / Type Serialization System, Runtime / State Backends
• Labels: KryoSerializer State avro pojo schema-evolution

Environment

I ran the job on a Flink cluster I spun up using docker compose:
```
version: "2.2"
services:
  jobmanager:
    image: flink:latest
    ports:
      - "8081:8081"
    command: jobmanager
    environment:
      - |
        FLINK_PROPERTIES=
        jobmanager.rpc.address: jobmanager

  taskmanager:
    image: flink:latest
    depends_on:
      - jobmanager
    command: taskmanager
    scale: 1
    environment:
      - |
        FLINK_PROPERTIES=
        jobmanager.rpc.address: jobmanager
        taskmanager.numberOfTaskSlots: 2
```

 My machine is a MacBook Pro (14-inch, 2021) with the Apple M1 Pro chip.

I'm running macOS Monterey Version 12.4.

• Flags: Important

Language

English

• Assignee: Unassigned
• Reporter: Peleg Tsadok
• Created: 23/Jul/22 08:53
• Updated: 07/Sep/22 18:46
• Resolved: 07/Sep/22 18:46

Description

I am trying to do a POC of Flink State Schema Evolution. I am using Flink 1.15.0 and Java 11 but also tested on Flink 1.14.3.
I tried to create 3 data classes - one for each serialization type:
1. `io.peleg.kryo.User` - Uses `java.time.Instant` class which I know is not supported for POJO serialization in Flink.
2. `io.peleg.pojo.User` - Uses only classic wrapped primitives - `Integer`, `Long`, `String`. The getters, setters and constructors are generated using Lombok.
3. `io.peleg.avro.User` - Generated from Avro schema using Avro Maven Plugin.

For each class I wrote a stream job that uses a time window to buffer elements and turn them into a list.

For each class I tried to do the following:
1. Run a job
2. Stop with savepoint
3. Add a field to the data class
4. Submit using savepoint

For all data classes the submit with savepoint failed with this exception:

java.lang.Exception: Exception while creating StreamOperatorStateContext.
    at org.apache.flink.streaming.api.operators.StreamTaskStateInitializerImpl.streamOperatorStateContext(StreamTaskStateInitializerImpl.java:255)
    at org.apache.flink.streaming.api.operators.AbstractStreamOperator.initializeState(AbstractStreamOperator.java:268)
    at org.apache.flink.streaming.runtime.tasks.RegularOperatorChain.initializeStateAndOpenOperators(RegularOperatorChain.java:106)
    at org.apache.flink.streaming.runtime.tasks.StreamTask.restoreGates(StreamTask.java:700)
    at org.apache.flink.streaming.runtime.tasks.StreamTaskActionExecutor$1.call(StreamTaskActionExecutor.java:55)
    at org.apache.flink.streaming.runtime.tasks.StreamTask.restoreInternal(StreamTask.java:676)
    at org.apache.flink.streaming.runtime.tasks.StreamTask.restore(StreamTask.java:643)
    at org.apache.flink.runtime.taskmanager.Task.runWithSystemExitMonitoring(Task.java:948)
    at org.apache.flink.runtime.taskmanager.Task.restoreAndInvoke(Task.java:917)
    at org.apache.flink.runtime.taskmanager.Task.doRun(Task.java:741)
    at org.apache.flink.runtime.taskmanager.Task.run(Task.java:563)
    at java.base/java.lang.Thread.run(Unknown Source)
Caused by: org.apache.flink.util.FlinkException: Could not restore keyed state backend for WindowOperator_3983d6bb2f0a45b638461bc99138f22f_(2/2) from any of the 1 provided restore options.
    at org.apache.flink.streaming.api.operators.BackendRestorerProcedure.createAndRestore(BackendRestorerProcedure.java:160)
    at org.apache.flink.streaming.api.operators.StreamTaskStateInitializerImpl.keyedStatedBackend(StreamTaskStateInitializerImpl.java:346)
    at org.apache.flink.streaming.api.operators.StreamTaskStateInitializerImpl.streamOperatorStateContext(StreamTaskStateInitializerImpl.java:164)
    ... 11 more
Caused by: org.apache.flink.runtime.state.BackendBuildingException: Failed when trying to restore heap backend
    at org.apache.flink.runtime.state.heap.HeapKeyedStateBackendBuilder.restoreState(HeapKeyedStateBackendBuilder.java:172)
    at org.apache.flink.runtime.state.heap.HeapKeyedStateBackendBuilder.build(HeapKeyedStateBackendBuilder.java:106)
    at org.apache.flink.runtime.state.hashmap.HashMapStateBackend.createKeyedStateBackend(HashMapStateBackend.java:143)
    at org.apache.flink.runtime.state.hashmap.HashMapStateBackend.createKeyedStateBackend(HashMapStateBackend.java:74)
    at org.apache.flink.runtime.state.StateBackend.createKeyedStateBackend(StateBackend.java:140)
    at org.apache.flink.streaming.api.operators.StreamTaskStateInitializerImpl.lambda$keyedStatedBackend$1(StreamTaskStateInitializerImpl.java:329)
    at org.apache.flink.streaming.api.operators.BackendRestorerProcedure.attemptCreateAndRestore(BackendRestorerProcedure.java:168)
    at org.apache.flink.streaming.api.operators.BackendRestorerProcedure.createAndRestore(BackendRestorerProcedure.java:135)
    ... 13 more
Caused by: com.esotericsoftware.kryo.KryoException: java.lang.IndexOutOfBoundsException: Index 83 out of bounds for length 3
Serialization trace:
favoriteColor (io.peleg.avro.User)
    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 com.esotericsoftware.kryo.serializers.CollectionSerializer.read(CollectionSerializer.java:116)
    at com.esotericsoftware.kryo.serializers.CollectionSerializer.read(CollectionSerializer.java:22)
    at com.esotericsoftware.kryo.Kryo.readClassAndObject(Kryo.java:761)
    at org.apache.flink.api.java.typeutils.runtime.kryo.KryoSerializer.deserialize(KryoSerializer.java:402)
    at org.apache.flink.runtime.state.heap.HeapSavepointRestoreOperation.readKVStateData(HeapSavepointRestoreOperation.java:219)
    at org.apache.flink.runtime.state.heap.HeapSavepointRestoreOperation.readKeyGroupStateData(HeapSavepointRestoreOperation.java:149)
    at org.apache.flink.runtime.state.heap.HeapSavepointRestoreOperation.restore(HeapSavepointRestoreOperation.java:125)
    at org.apache.flink.runtime.state.heap.HeapSavepointRestoreOperation.restore(HeapSavepointRestoreOperation.java:57)
    at org.apache.flink.runtime.state.heap.HeapKeyedStateBackendBuilder.restoreState(HeapKeyedStateBackendBuilder.java:169)
    ... 20 more
Caused by: java.lang.IndexOutOfBoundsException: Index 83 out of bounds for length 3
    at java.base/jdk.internal.util.Preconditions.outOfBounds(Unknown Source)
    at java.base/jdk.internal.util.Preconditions.outOfBoundsCheckIndex(Unknown Source)
    at java.base/jdk.internal.util.Preconditions.checkIndex(Unknown Source)
    at java.base/java.util.Objects.checkIndex(Unknown Source)
    at java.base/java.util.ArrayList.get(Unknown Source)
    at com.esotericsoftware.kryo.util.MapReferenceResolver.getReadObject(MapReferenceResolver.java:42)
    at com.esotericsoftware.kryo.Kryo.readReferenceOrNull(Kryo.java:805)
    at com.esotericsoftware.kryo.Kryo.readObjectOrNull(Kryo.java:728)
    at com.esotericsoftware.kryo.serializers.ObjectField.read(ObjectField.java:113)
    ... 31 more

 

I expected this exception would be thrown for io.peleg.kryo.User since Flink does not support state schema evolution for Kryo serialized classes.

But it seems to me like for all classes it ended up using the Kryo serializer instead of the POJO or Avro serializers.

My entire code is public on GitHub here .

What I would like to achieve is succusfuly running a job from a savepoint of an older version of a POJO with less/more fields.