[jira] [Commented] (FLINK-11987) Kafka producer occasionally throws NullpointerException

["Stephan Ewen (JIRA)" <ji...@apache.org>]

    [ https://issues.apache.org/jira/browse/FLINK-11987?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=16832335#comment-16832335 ] 

Stephan Ewen commented on FLINK-11987:
--------------------------------------

I think there is a deeper issue here, with {{StateDescriptors}} and the way they hold {{Serializers}}.

The easiest fix for now might be to remove the line that nulls out the {{TypeInformation}} in the {{StateDescriptor}} class.

> Kafka producer occasionally throws NullpointerException
> -------------------------------------------------------
>
>                 Key: FLINK-11987
>                 URL: https://issues.apache.org/jira/browse/FLINK-11987
>             Project: Flink
>          Issue Type: Bug
>          Components: Connectors / Kafka
>    Affects Versions: 1.6.3, 1.6.4, 1.7.2
>         Environment: Flink 1.6.2 (Standalone Cluster)
> Oracle JDK 1.8u151
> Centos 7.4
>            Reporter: LIU Xiao
>            Priority: Major
>              Labels: pull-request-available
>          Time Spent: 10m
>  Remaining Estimate: 0h
>
> We are using Flink 1.6.2 in our production environment, and kafka producer occasionally throws NullpointerException.
> We found in line 175 of flink/flink-connectors/flink-connector-kafka-0.11/src/main/java/org/apache/flink/streaming/connectors/kafka/FlinkKafkaProducer011.java, NEXT_TRANSACTIONAL_ID_HINT_DESCRIPTOR was created as a static variable.
> Then in line 837, "context.getOperatorStateStore().getUnionListState(NEXT_TRANSACTIONAL_ID_HINT_DESCRIPTOR);" was called, and that leads to line 734 of 
>  flink/flink-runtime/src/main/java/org/apache/flink/runtime/state/DefaultOperatorStateBackend.java: "stateDescriptor.initializeSerializerUnlessSet(getExecutionConfig());"
> In function initializeSerializerUnlessSet(line 283 of flink/flink-core/src/main/java/org/apache/flink/api/common/state/StateDescriptor.java):
> if (serializer == null) {
>   checkState(typeInfo != null, "no serializer and no type info");
>   // instantiate the serializer
>   serializer = typeInfo.createSerializer(executionConfig);
>   // we can drop the type info now, no longer needed
>   typeInfo  = null;
> }
> "serializer = typeInfo.createSerializer(executionConfig);" is the line which throws the exception.
> We think that's because multiple subtasks of the same producer in a same TaskManager share a same NEXT_TRANSACTIONAL_ID_HINT_DESCRIPTOR.



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