Kafka python Consumer group session timed out

Question

I use confluent-kafka v1.3.0 and I have following problem with consumer group session timeout. My config looks like:

c['KAFKA'] = {
    'bootstrap.servers': 'host.docker.internal:9104',
    'consumer': {
        'group.id': 'consumer',
        'enable.auto.commit': True,
        'default.topic.config': {
            'auto.offset.reset': 'earliest
        },
        'heartbeat.interval.ms': 100000,
        'max.poll.interval.ms': 300000,
        'session.timeout.ms': 100000
    },
}

and logic in code like:

consumer.subscribe('database_changes')

with ThreadPoolExecutor(max_workers=500) as executor:
    while True:
        msg = consumer.poll(100)
        if msg is not None:
            executor.submit(process_message, msg)

Code in function process message waits a few ms because it's really simple logic. Everything works good but every moment I got this error:

{"asctime":"2020-04-27 08:42:25,759","levelname":"WARNING","name":"services.kafka","message":"SESSTMOUT [rdkafka#consumer-2] [thrd:main]: Consumer group session timed out (in join-state started) after 30131 ms without a successful response from the group coordinator (broker 0, last error was Success): revoking assignment and rejoining group"}

these rebalacing greatly hampers the whole process.

Does anyone have an idea of what can be wrongly set? I suspect a not working heartbeat, but I don't know how it verify or better fix.

Thanks

Answer 1

As per the confluent kafka docs, the heartbeat.interval.ms should be set no higher than 1/3 of session.timeout.ms. Since after the sessions.timeout.ms value, the consumer is assumed dead, it is recommended to wait atleast three heartbeats to assume that.