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https://issues.apache.org/jira/browse/FLINK-4618?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=15490153#comment-15490153
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Tzu-Li (Gordon) Tai commented on FLINK-4618:
--------------------------------------------
I'm answering your questions in SO, so that we can keep the discussion over
there ;)
> Last kafka message gets consumed twice when restarting job
> ----------------------------------------------------------
>
> Key: FLINK-4618
> URL: https://issues.apache.org/jira/browse/FLINK-4618
> Project: Flink
> Issue Type: Bug
> Components: Kafka Connector
> Affects Versions: 1.1.2
> Environment: Flink 1.1.2
> Kafka Broker 0.10.0
> Hadoop 2.7.0
> Reporter: Melmoth
>
> There seem to be an issue with the offset management in Flink. When a job is
> stopped and startet again, a message from the previous offset is read again.
> I enabled checkpoints (EXACTLY_ONCE) and FsStateBackend. I started with a new
> consumer group and emitted one record.
> You can cleary see, that the consumer waits for a new record at offset
> 4848911, which is correct. After restarting, it consumes a record at 4848910,
> causing the record to be consumed more than once.
> I checked the offset with the Kafka CMD tools, the commited offset in
> zookeeper is 4848910.
> Here is my log output:
> {code}
> 10:29:24,225 DEBUG org.apache.kafka.clients.NetworkClient
> - Initiating connection to node 2147482646 at hdp1:6667.
> 10:29:24,225 DEBUG
> org.apache.kafka.clients.consumer.internals.ConsumerCoordinator - Fetching
> committed offsets for partitions: [myTopic-0]
> 10:29:24,228 DEBUG org.apache.kafka.clients.NetworkClient
> - Completed connection to node 2147482646
> 10:29:24,234 DEBUG
> org.apache.kafka.clients.consumer.internals.ConsumerCoordinator - No
> committed offset for partition myTopic-0
> 10:29:24,238 DEBUG org.apache.kafka.clients.consumer.internals.Fetcher
> - Resetting offset for partition myTopic-0 to latest offset.
> 10:29:24,244 DEBUG org.apache.kafka.clients.consumer.internals.Fetcher
> - Fetched offset 4848910 for partition myTopic-0
> 10:29:24,245 TRACE org.apache.kafka.clients.consumer.internals.Fetcher
> - Added fetch request for partition myTopic-0 at offset 4848910
> 10:29:24,773 TRACE org.apache.kafka.clients.consumer.internals.Fetcher
> - Added fetch request for partition myTopic-0 at offset 4848910
> 10:29:25,276 TRACE org.apache.kafka.clients.consumer.internals.Fetcher
> - Added fetch request for partition myTopic-0 at offset 4848910
> -- Inserting a new event here
> 10:30:22,447 TRACE org.apache.kafka.clients.consumer.internals.Fetcher
> - Adding fetched record for partition myTopic-0 with offset 4848910 to
> buffered record list
> 10:30:22,448 TRACE org.apache.kafka.clients.consumer.internals.Fetcher
> - Returning fetched records at offset 4848910 for assigned partition
> myTopic-0 and update position to 4848911
> 10:30:22,451 TRACE org.apache.kafka.clients.consumer.internals.Fetcher
> - Added fetch request for partition myTopic-0 at offset 4848911
> 10:30:22,953 TRACE org.apache.kafka.clients.consumer.internals.Fetcher
> - Added fetch request for partition myTopic-0 at offset 4848911
> 10:30:23,456 TRACE org.apache.kafka.clients.consumer.internals.Fetcher
> - Added fetch request for partition myTopic-0 at offset 4848911
> 10:30:23,887 INFO org.apache.flink.runtime.checkpoint.CheckpointCoordinator
> - Triggering checkpoint 6 @ 1473841823887
> 10:30:23,957 TRACE org.apache.kafka.clients.consumer.internals.Fetcher
> - Added fetch request for partition myTopic-0 at offset 4848911
> 10:30:23,996 INFO org.apache.flink.runtime.checkpoint.CheckpointCoordinator
> - Completed checkpoint 6 (in 96 ms)
> 10:30:24,196 TRACE
> org.apache.kafka.clients.consumer.internals.ConsumerCoordinator - Sending
> offset-commit request with {myTopic-0=OffsetAndMetadata{offset=4848910,
> metadata=''}} to Node(2147482646, hdp1, 6667)
> 10:30:24,204 DEBUG
> org.apache.kafka.clients.consumer.internals.ConsumerCoordinator - Committed
> offset 4848910 for partition myTopic-0
> 10:30:24,460 TRACE org.apache.kafka.clients.consumer.internals.Fetcher
> - Added fetch request for partition myTopic-0 at offset 4848911
> 10:30:24,963 TRACE org.apache.kafka.clients.consumer.internals.Fetcher
> - Added fetch request for partition myTopic-0 at offset 4848911
> 10:30:48,057 INFO org.apache.flink.runtime.blob.BlobServer
> - Stopped BLOB server at 0.0.0.0:2946
> -- Restarting job
> 10:32:01,672 DEBUG org.apache.kafka.clients.NetworkClient
> - Initiating connection to node 2147482646 at hdp1:6667.
> 10:32:01,673 DEBUG
> org.apache.kafka.clients.consumer.internals.ConsumerCoordinator - Fetching
> committed offsets for partitions: [myTopic-0]
> 10:32:01,677 DEBUG org.apache.kafka.clients.NetworkClient
> - Completed connection to node 2147482646
> // See below! Shouldn't the offset be 4848911?
> 10:32:01,682 DEBUG org.apache.kafka.clients.consumer.internals.Fetcher
> - Resetting offset for partition myTopic-0 to the committed offset 4848910
> 10:32:01,683 TRACE org.apache.kafka.clients.consumer.internals.Fetcher
> - Added fetch request for partition myTopic-0 at offset 4848910
> 10:32:01,685 DEBUG org.apache.kafka.clients.NetworkClient
> - Initiating connection to node 1001 at hdp1:6667.
> 10:32:01,687 DEBUG org.apache.kafka.clients.NetworkClient
> - Completed connection to node 1001
> // Here record 4848910 gets consumed again!
> 10:32:01,707 TRACE org.apache.kafka.clients.consumer.internals.Fetcher
> - Adding fetched record for partition myTopic-0 with offset 4848910 to
> buffered record list
> 10:32:01,708 TRACE org.apache.kafka.clients.consumer.internals.Fetcher
> - Returning fetched records at offset 4848910 for assigned partition
> myTopic-0 and update position to 4848911
> 10:32:03,721 TRACE org.apache.kafka.clients.consumer.internals.Fetcher
> - Added fetch request for partition myTopic-0 at offset 4848911
> 10:32:04,224 TRACE org.apache.kafka.clients.consumer.internals.Fetcher
> - Added fetch request for partition myTopic-0 at offset 4848911
> 10:32:04,726 TRACE org.apache.kafka.clients.consumer.internals.Fetcher
> - Added fetch request for partition myTopic-0 at offset 4848911
> 10:32:04,894 INFO org.apache.flink.runtime.blob.BlobCache
> - Shutting down BlobCache
> 10:32:04,903 INFO org.apache.flink.runtime.blob.BlobServer
> - Stopped BLOB server at 0.0.0.0:3079
> {code}
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