[KAFKA-2674] ConsumerRebalanceListener.onPartitionsRevoked() is not called on consumer close

• Type: Bug
• Status: Resolved
• Priority: Major
• Resolution: Fixed
• Affects Version/s: 0.9.0.0
• Fix Version/s: 0.9.0.0
• Component/s: consumer
• Assignee: Jason Gustafson
• Reporter: Michal Turek
• Created: 20/Oct/15 13:47
• Updated: 09/Nov/15 19:11
• Resolved: 09/Nov/15 19:11

Description

Hi, I'm investigating and testing behavior of new consumer from the planned release 0.9 and found an inconsistency in calling of rebalance callbacks.

I noticed that ConsumerRebalanceListener.onPartitionsRevoked() is NOT called during consumer close and application shutdown. It's JavaDoc contract says:

• "This method will be called before a rebalance operation starts and after the consumer stops fetching data."
• "It is recommended that offsets should be committed in this callback to either Kafka or a custom offset store to prevent duplicate data."

I believe calling consumer.close() is a start of rebalance operation and even the local consumer that is actually closing should be notified to be able to process any rebalance logic including offsets commit (e.g. if auto-commit is disabled).

There are commented logs of current and expected behaviors.

// Application start
2015-10-20 15:14:02.208 INFO  o.a.k.common.utils.AppInfoParser    [TestConsumer-worker-0]: Kafka version : 0.9.0.0-SNAPSHOT (AppInfoParser.java:82)
2015-10-20 15:14:02.208 INFO  o.a.k.common.utils.AppInfoParser    [TestConsumer-worker-0]: Kafka commitId : 241b9ab58dcbde0c (AppInfoParser.java:83)

// Consumer started (the first one in group), rebalance callbacks are called including empty onPartitionsRevoked()
2015-10-20 15:14:02.333 INFO  c.a.e.kafka.newapi.TestConsumer     [TestConsumer-worker-0]: Rebalance callback, revoked: [] (TestConsumer.java:95)
2015-10-20 15:14:02.343 INFO  c.a.e.kafka.newapi.TestConsumer     [TestConsumer-worker-0]: Rebalance callback, assigned: [testB-1, testA-0, testB-0, testB-3, testA-2, testB-2, testA-1, testA-4, testB-4, testA-3] (TestConsumer.java:100)

// Another consumer joined the group, rebalancing
2015-10-20 15:14:17.345 INFO  o.a.k.c.c.internals.Coordinator     [TestConsumer-worker-0]: Attempt to heart beat failed since the group is rebalancing, try to re-join group. (Coordinator.java:714)
2015-10-20 15:14:17.346 INFO  c.a.e.kafka.newapi.TestConsumer     [TestConsumer-worker-0]: Rebalance callback, revoked: [testB-1, testA-0, testB-0, testB-3, testA-2, testB-2, testA-1, testA-4, testB-4, testA-3] (TestConsumer.java:95)
2015-10-20 15:14:17.349 INFO  c.a.e.kafka.newapi.TestConsumer     [TestConsumer-worker-0]: Rebalance callback, assigned: [testB-3, testA-4, testB-4, testA-3] (TestConsumer.java:100)

// Consumer started closing, there SHOULD be onPartitionsRevoked() callback to commit offsets like during standard rebalance, but it is missing
2015-10-20 15:14:39.280 INFO  c.a.e.kafka.newapi.TestConsumer     [main]: Closing instance (TestConsumer.java:42)
2015-10-20 15:14:40.264 INFO  c.a.e.kafka.newapi.TestConsumer     [TestConsumer-worker-0]: Worker thread stopped (TestConsumer.java:89)

Workaround is to call onPartitionsRevoked() explicitly and manually just before calling consumer.close() but it seems dirty and error prone for me. It can be simply forgotten be someone without such experience.