Unexpected failing/rebalancing of consumers

Question

Using Apache Kafka 2.1.0 and spring-kafka 2.1.7, we are getting error messages like the following on our spring-kafka consumer-clients:

2019-01-13 23:01:34.019 consumer-1-C-1 LogContext$KafkaLogger.error SEVERE: [Consumer clientId=consumer-2, groupId=kafka-consumer-group-x] Offset commit failed on partition topic-x-16 at offset 57882: The coordinator is not aware of this member.

A few seconds before this error, we can see the following log messages on one of the kafka borkers:

[2019-01-13 23:01:17,329] INFO [GroupCoordinator 2]: Member consumer-30-13dc06ff-aed2-4e4e-a66d-2d60d79ac526 in group kafka-consumer-group-x has failed, removing it from the group (kafka.coordinator.group.GroupCoordinator)
[2019-01-13 23:01:17,330] INFO [GroupCoordinator 2]: Preparing to rebalance group kafka-consumer-group-x in state PreparingRebalance with old generation 1370 (__consumer_offsets-40) (reason: removing member consumer-30-13dc06ff-aed2-4e4e-a66d-2d60d79ac526 on heartbeat expiration) (kafka.coordinator.group.GroupCoordinator)
[2019-01-13 23:01:17,330] INFO [GroupCoordinator 2]: Member consumer-20-ba370e86-e1cc-4261-a73c-78cea1b00479 in group kafka-consumer-group-x has failed, removing it from the group (kafka.coordinator.group.GroupCoordinator)
[2019-01-13 23:01:17,335] INFO [GroupCoordinator 2]: Member consumer-32-be8807df-b88f-4cc9-bddf-bed772d1244f in group kafka-consumer-group-x has failed, removing it from the group (kafka.coordinator.group.GroupCoordinator)
[2019-01-13 23:01:17,335] INFO [GroupCoordinator 2]: Member consumer-17-3e34f026-894e-40dc-916b-d169a43da135 in group kafka-consumer-group-x has failed, removing it from the group (kafka.coordinator.group.GroupCoordinator)
[2019-01-13 23:01:17,335] INFO [GroupCoordinator 2]: Member consumer-31-4dd9cb6e-09e9-47db-9610-37e0ab5633e0 in group kafka-consumer-group-x has failed, removing it from the group (kafka.coordinator.group.GroupCoordinator)
[2019-01-13 23:01:17,335] INFO [GroupCoordinator 2]: Member consumer-18-90175650-1224-4f22-9350-246e17e75367 in group kafka-consumer-group-x has failed, removing it from the group (kafka.coordinator.group.GroupCoordinator)
[2019-01-13 23:01:18,332] INFO [GroupCoordinator 2]: Member consumer-19-663239af-9702-4e59-ad3d-f8202e9d579d in group kafka-consumer-group-x has failed, removing it from the group (kafka.coordinator.group.GroupCoordinator)
[2019-01-13 23:01:18,347] INFO [GroupCoordinator 2]: Member consumer-22-c54fb4c0-1fa1-4d9f-91fc-1da6df41b227 in group kafka-consumer-group-x has failed, removing it from the group (kafka.coordinator.group.GroupCoordinator)
[2019-01-13 23:01:18,347] INFO [GroupCoordinator 2]: Member consumer-25-3bfd915c-8bd1-454b-85e3-60212b4c568e in group kafka-consumer-group-x has failed, removing it from the group (kafka.coordinator.group.GroupCoordinator)
[2019-01-13 23:01:18,347] INFO [GroupCoordinator 2]: Member consumer-27-cbb97ebf-b5cd-4cfa-991a-5302462ddab9 in group kafka-consumer-group-x has failed, removing it from the group (kafka.coordinator.group.GroupCoordinator)
[2019-01-13 23:01:18,615] INFO [GroupCoordinator 2]: Member consumer-24-37fbcc73-e8c6-4820-ad56-580fd88f5a10 in group kafka-consumer-group-x has failed, removing it from the group (kafka.coordinator.group.GroupCoordinator)
[2019-01-13 23:01:18,618] INFO [GroupCoordinator 2]: Member consumer-21-eea1b841-202e-4ebe-bdde-007775d001dd in group kafka-consumer-group-x has failed, removing it from the group (kafka.coordinator.group.GroupCoordinator)
[2019-01-13 23:01:18,636] INFO [GroupCoordinator 2]: Member consumer-28-881da47e-87c9-4675-9f88-e3b33748cff1 in group kafka-consumer-group-x has failed, removing it from the group (kafka.coordinator.group.GroupCoordinator)
[2019-01-13 23:01:18,708] INFO [GroupCoordinator 2]: Member consumer-26-375880ee-b2a9-4ece-8eee-987d282956d8 in group kafka-consumer-group-x has failed, removing it from the group (kafka.coordinator.group.GroupCoordinator)
[2019-01-13 23:01:18,708] INFO [GroupCoordinator 2]: Member consumer-23-492417e9-f3cb-4bec-bbac-130895356907 in group kafka-consumer-group-x has failed, removing it from the group (kafka.coordinator.group.GroupCoordinator)
[2019-01-13 23:01:18,731] INFO [GroupCoordinator 2]: Member consumer-29-64732e9a-2c2b-44fb-a8a5-f606462a4201 in group kafka-consumer-group-x has failed, removing it from the group (kafka.coordinator.group.GroupCoordinator)
[2019-01-13 23:01:18,947] INFO [GroupCoordinator 2]: Member consumer-10-fdd0ca92-3604-46de-9e2b-97ca41d36150 in group kafka-consumer-group-x has failed, removing it from the group (kafka.coordinator.group.GroupCoordinator)
[2019-01-13 23:01:19,228] INFO [GroupCoordinator 2]: Member consumer-3-feb6986d-79af-4c64-a8f8-2dbb3bdb73c3 in group kafka-consumer-group-x has failed, removing it from the group (kafka.coordinator.group.GroupCoordinator)
[2019-01-13 23:01:19,257] INFO [GroupCoordinator 2]: Member consumer-2-0345e5d5-86fc-4df0-bd39-c35b75514cea in group kafka-consumer-group-x has failed, removing it from the group (kafka.coordinator.group.GroupCoordinator)
[2019-01-13 23:01:19,257] INFO [GroupCoordinator 2]: Member consumer-1-c301f59f-8a56-4bdb-a5ef-dc163232d378 in group kafka-consumer-group-x has failed, removing it from the group (kafka.coordinator.group.GroupCoordinator)
[2019-01-13 23:01:19,257] INFO [GroupCoordinator 2]: Member consumer-13-56aea64a-ecca-45e7-9474-b8f1163d01c8 in group kafka-consumer-group-x has failed, removing it from the group (kafka.coordinator.group.GroupCoordinator)
[2019-01-13 23:01:19,266] INFO [GroupCoordinator 2]: Member consumer-9-3ee76e0e-86f1-4c0c-85cc-d07721bf36b1 in group kafka-consumer-group-x has failed, removing it from the group (kafka.coordinator.group.GroupCoordinator)
[2019-01-13 23:01:19,273] INFO [GroupCoordinator 2]: Member consumer-4-9fa81414-870d-444d-b5d1-c38ce5c157a8 in group kafka-consumer-group-x has failed, removing it from the group (kafka.coordinator.group.GroupCoordinator)
[2019-01-13 23:01:19,296] INFO [GroupCoordinator 2]: Member consumer-14-8236578f-b60d-4199-b621-913d025149d1 in group kafka-consumer-group-x has failed, removing it from the group (kafka.coordinator.group.GroupCoordinator)
[2019-01-13 23:01:19,656] INFO [GroupCoordinator 2]: Member consumer-12-2921b7de-1721-460f-adbf-4fb6951cca22 in group kafka-consumer-group-x has failed, removing it from the group (kafka.coordinator.group.GroupCoordinator)
[2019-01-13 23:01:19,665] INFO [GroupCoordinator 2]: Member consumer-11-09d7015c-cc33-464e-93ac-fb270f209b3f in group kafka-consumer-group-x has failed, removing it from the group (kafka.coordinator.group.GroupCoordinator)
[2019-01-13 23:01:19,667] INFO [GroupCoordinator 2]: Member consumer-5-b3fe06ff-8ef4-4d60-8571-68b7cfee12bc in group kafka-consumer-group-x has failed, removing it from the group (kafka.coordinator.group.GroupCoordinator)
[2019-01-13 23:01:19,722] INFO [GroupCoordinator 2]: Member consumer-15-5af82ca6-0ebf-463e-b9c5-4bbde513453d in group kafka-consumer-group-x has failed, removing it from the group (kafka.coordinator.group.GroupCoordinator)
[2019-01-13 23:01:19,754] INFO [GroupCoordinator 2]: Member consumer-7-c1e2bf89-c7c5-4363-b099-191956ed1c89 in group kafka-consumer-group-x has failed, removing it from the group (kafka.coordinator.group.GroupCoordinator)
[2019-01-13 23:01:19,848] INFO [GroupCoordinator 2]: Member consumer-6-9b3be0e4-c1be-4d6a-98b1-caa9d095c403 in group kafka-consumer-group-x has failed, removing it from the group (kafka.coordinator.group.GroupCoordinator)
[2019-01-13 23:01:19,848] INFO [GroupCoordinator 2]: Member consumer-16-0f48ad44-402a-4706-9d78-9d0d5077a56d in group kafka-consumer-group-x has failed, removing it from the group (kafka.coordinator.group.GroupCoordinator)
[2019-01-13 23:01:19,848] INFO [GroupCoordinator 2]: Member consumer-8-0496aa54-79f7-41b8-8f31-7823ed72f16a in group kafka-consumer-group-x has failed, removing it from the group (kafka.coordinator.group.GroupCoordinator)
[2019-01-13 23:01:19,848] INFO [GroupCoordinator 2]: Group kafka-consumer-group-x with generation 1371 is now empty (__consumer_offsets-40) (kafka.coordinator.group.GroupCoordinator)
[2019-01-13 23:01:35,226] INFO [GroupCoordinator 2]: Preparing to rebalance group kafka-consumer-group-x in state PreparingRebalance with old generation 1371 (__consumer_offsets-40) (reason: Adding new member consumer-1-7787a334-acf2-4534-bc19-78af35371bfb) (kafka.coordinator.group.GroupCoordinator)
[2019-01-13 23:01:38,227] INFO [GroupCoordinator 2]: Stabilized group kafka-consumer-group-x generation 1372 (__consumer_offsets-40) (kafka.coordinator.group.GroupCoordinator)
[2019-01-13 23:01:38,239] INFO [GroupCoordinator 2]: Assignment received from leader for group kafka-consumer-group-x for generation 1372 (kafka.coordinator.group.GroupCoordinator)

As we don't see any errors while processing the messages or signs that the process takes to much time, we can't explain these sudden rebalancings.

Does anyone have a hint where this could come from?

The configuration for our consumer ist mostly default with enable.auto.commit=false and AckMode.RECORD.

Answer 1

Reasons to rebalance in Kafka:

1. A new consumer joins to group
2. A consumer left the group (clean shut down)
3. New partitions are added
4. A consumer seems to be dead in the view of Kafka

Reasons for 4th:

1. Consumer couldn't pool in max.poll.interval.ms (long running process)
2. Consumer couldn't send heartbeat to Kafka in session.timeout.ms

**Normally heartbeat thread is run in every heartbeat.interval.ms (default 3 sec.)

Your situtation seems like 4.2.

There can be various reasons for that. To solve the problem you can increase session.timeout.ms. (default is 10 sec.)

Another solution is to optimize your system to run heartbeat threads as expected. (avoiding high IOWait, load balancing etc.)

Answer 2

I am rather sure you are running into KAFKA-7196. You should upstep your server to 2.0.1 or later.

As a workaround, you might try to configure a random client.id every time you start up, but this can have some unwanted side effects.