[
https://issues.apache.org/jira/browse/FLINK-8005?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=16245630#comment-16245630
]
ASF GitHub Bot commented on FLINK-8005:
---------------------------------------
Github user GJL commented on the issue:
https://github.com/apache/flink/pull/4980
There is only one thread dispatching the calls:
```
executor = Executors.newSingleThreadExecutor(
new
DispatcherThreadFactory(TASK_THREADS_GROUP, "Async calls on " +
taskNameWithSubtask));
this.asyncCallDispatcher = executor;
```
The tasks cannot overtake each other. I could make the test more strict and
wait additionally on `triggerLatch` in case somebody decides to have multiple
threads.
> Snapshotting FlinkKafkaProducer011 fails due to ClassLoader issues
> ------------------------------------------------------------------
>
> Key: FLINK-8005
> URL: https://issues.apache.org/jira/browse/FLINK-8005
> Project: Flink
> Issue Type: Bug
> Components: Core, Kafka Connector, State Backends, Checkpointing
> Affects Versions: 1.4.0
> Reporter: Gary Yao
> Assignee: Gary Yao
> Priority: Blocker
> Fix For: 1.4.0
>
>
> *Problem Description*
> Classes in the user code jar cannot be loaded by the snapshot thread’s
> context class loader ({{AppClassLoader}}).
> For example, when creating instances of {{KafkaProducer}}, Strings are
> resolved to class objects by Kafka.
> Find below an extract from {{ConfigDef.java}}:
> {code}
> case CLASS:
> if (value instanceof Class)
> return value;
> else if (value instanceof String)
> return Class.forName(trimmed, true,
> Utils.getContextOrKafkaClassLoader());
> else
> throw new ConfigException(name, value, "Expected a Class instance or
> class name.");
> {code}
> *Exception/Stacktrace*
> {noformat}
> Caused by: java.lang.Exception: Could not complete snapshot 1 for operator
> Source: Collection Source -> Sink: kafka-sink-1510048188383 (1/1).
> at
> org.apache.flink.streaming.api.operators.AbstractStreamOperator.snapshotState(AbstractStreamOperator.java:379)
> at
> org.apache.flink.streaming.runtime.tasks.StreamTask$CheckpointingOperation.checkpointStreamOperator(StreamTask.java:1077)
> at
> org.apache.flink.streaming.runtime.tasks.StreamTask$CheckpointingOperation.executeCheckpointing(StreamTask.java:1026)
> at
> org.apache.flink.streaming.runtime.tasks.StreamTask.checkpointState(StreamTask.java:659)
> at
> org.apache.flink.streaming.runtime.tasks.StreamTask.performCheckpoint(StreamTask.java:595)
> at
> org.apache.flink.streaming.runtime.tasks.StreamTask.triggerCheckpoint(StreamTask.java:526)
> ... 7 more
> Caused by: org.apache.kafka.common.config.ConfigException: Invalid value
> org.apache.kafka.common.serialization.ByteArraySerializer for configuration
> key.serializer: Class
> org.apache.kafka.common.serialization.ByteArraySerializer could not be found.
> at
> org.apache.kafka.common.config.ConfigDef.parseType(ConfigDef.java:715)
> at
> org.apache.kafka.common.config.ConfigDef.parseValue(ConfigDef.java:460)
> at org.apache.kafka.common.config.ConfigDef.parse(ConfigDef.java:453)
> at
> org.apache.kafka.common.config.AbstractConfig.<init>(AbstractConfig.java:62)
> at
> org.apache.kafka.common.config.AbstractConfig.<init>(AbstractConfig.java:75)
> at
> org.apache.kafka.clients.producer.ProducerConfig.<init>(ProducerConfig.java:360)
> at
> org.apache.kafka.clients.producer.KafkaProducer.<init>(KafkaProducer.java:288)
> at
> org.apache.flink.streaming.connectors.kafka.internal.FlinkKafkaProducer.<init>(FlinkKafkaProducer.java:114)
> at
> org.apache.flink.streaming.connectors.kafka.FlinkKafkaProducer011.initProducer(FlinkKafkaProducer011.java:913)
> at
> org.apache.flink.streaming.connectors.kafka.FlinkKafkaProducer011.initTransactionalProducer(FlinkKafkaProducer011.java:904)
> at
> org.apache.flink.streaming.connectors.kafka.FlinkKafkaProducer011.createOrGetProducerFromPool(FlinkKafkaProducer011.java:637)
> at
> org.apache.flink.streaming.connectors.kafka.FlinkKafkaProducer011.beginTransaction(FlinkKafkaProducer011.java:613)
> at
> org.apache.flink.streaming.connectors.kafka.FlinkKafkaProducer011.beginTransaction(FlinkKafkaProducer011.java:94)
> at
> org.apache.flink.streaming.api.functions.sink.TwoPhaseCommitSinkFunction.beginTransactionInternal(TwoPhaseCommitSinkFunction.java:359)
> at
> org.apache.flink.streaming.api.functions.sink.TwoPhaseCommitSinkFunction.snapshotState(TwoPhaseCommitSinkFunction.java:294)
> at
> org.apache.flink.streaming.connectors.kafka.FlinkKafkaProducer011.snapshotState(FlinkKafkaProducer011.java:756)
> at
> org.apache.flink.streaming.util.functions.StreamingFunctionUtils.trySnapshotFunctionState(StreamingFunctionUtils.java:118)
> at
> org.apache.flink.streaming.util.functions.StreamingFunctionUtils.snapshotFunctionState(StreamingFunctionUtils.java:99)
> at
> org.apache.flink.streaming.api.operators.AbstractUdfStreamOperator.snapshotState(AbstractUdfStreamOperator.java:90)
> at
> org.apache.flink.streaming.api.operators.AbstractStreamOperator.snapshotState(AbstractStreamOperator.java:357)
> ... 12 more
> {noformat}
> *How to reproduce*
> Note that the problem only appears when a job is deployed on a cluster.
> # Build Flink 1.4
> # Build test job https://github.com/GJL/flink-kafka011-producer-test with
> {{mvn -o clean install -Pbuild-jar}}
> # Start job:
> {noformat}
> bin/flink run -c com.garyyao.StreamingJob
> /pathto/flink-kafka011-producer/target/flink-kafka011-producer-1.0-SNAPSHOT.jar
> {noformat}
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