[FLINK-4618] FlinkKafkaConsumer09 should start from the next record on startup from offsets in Kafka

• Type: Bug
• Status: Resolved
• Priority: Major
• Resolution: Fixed
• Affects Version/s: 1.1.2
• Fix Version/s: 1.1.3, 1.2.0
• Component/s: Connectors / Kafka

Environment

Flink 1.1.2
Kafka Broker 0.10.0
Hadoop 2.7.0

• Assignee: Unassigned
• Reporter: static-max
• Created: 14/Sep/16 09:01
• Updated: 01/Oct/16 10:24
• Resolved: 01/Oct/16 10:24

Description

*Original reported ticket title: Last kafka message gets consumed twice when restarting job*

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:

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

Issue Links

• links to: GitHub Pull Request #2579