Closing consumer takes 10 second

[lyohar]

Description

I am trying to just open and close consumer. Closing takes 10 seconds.

I found on consumer code:

// Poll for rebalance events
	for {
		c.Poll(10 * 1000)
		if int(C.rd_kafka_queue_length(c.handle.rkq)) == 0 {
			break
		}
	}

Are there any parameters to force consumer fast close?
Please advise;

How to reproduce

func main() {
	cfg := &kafka.ConfigMap{
		"bootstrap.servers":     "localhost:9092",
		"group.id":              "group",
		"broker.address.family": "v4",
	}

	consumer, err := kafka.NewConsumer(cfg)
	if err != nil {
		panic(err)
	} else {
		fmt.Println("consumer opened")
	}

	startClose := time.Now()
	err = consumer.Close()
	if err != nil {
		panic(err)
	}
	fmt.Println(fmt.Sprintf("consumer closed. closing time: %v", time.Since(startClose)))
}

output: consumer closed. closing time: 10.005907343s

Checklist

Please provide the following information:

• confluent-kafka-go and librdkafka version (1.7.0):
• Apache Kafka broker version: 2.7.0
• Client configuration: &kafka.ConfigMap{"bootstrap.servers": "localhost:9092","group.id": "group","broker.address.family": "v4",}
• Operating system: macOs
• Provide client logs (with "debug": ".." as necessary)
• Provide broker log excerpts
• Critical issue

[edenhill]

@jliunyu Can you take a look at this? Haven't checked the code, but make sure Close() isn't waiting for a rebalance event if application.rebalance is not enabled.

[jliunyu]

Hi @edenhill, after checking the code, found that Close() is always waiting for rebalance event with the following code:
https://github.com/confluentinc/confluent-kafka-go/blob/master/kafka/consumer.go#L424

I will take a look how to fix it and provide a fix soon.

[KunWangV]

same problem

[alexec]

I've seen this too. Consumer always takes at least the value of x in Poll(x). I.e. if that is 10s (like the above example) then consumer.Close() takes minimum 10s. Reduce it to 5s, Close() takes 5s.

[sermojohn]

Hello, this issue seems frozen.

I had to downgrade to v1.5.2 to overcome this issue until further update.

@edenhill, @jliunyu I have a question the code pointer that causes the delay: https://github.com/confluentinc/confluent-kafka-go/blob/master/kafka/consumer.go#L438
Why is the processing of the rebalance events (assign/revoke) important when closing a consumer? Is this a requirement of Incremental Cooperative rebalance? What if processing of such event is skipped and consumer is closed without this for loop (https://github.com/confluentinc/confluent-kafka-go/blob/master/kafka/consumer.go#L437-L442)?

Additionally, this issue seems relevant to another issue: #610
If rebalance events are not triggered, then the expected event from the poll performing in the close (https://github.com/confluentinc/confluent-kafka-go/blob/master/kafka/consumer.go#L438) will never trigger, until the timeout is reached.

confluent-kafka-go version: 1.7.0
Apache Kafka broker version: 2.7.0

I would be happy to help on the resolution of this issue.

[sneko]

@jliunyu sorry I didn't see this issue before posting #728

Is any fix/improvement planned?

Thank you,

[WolfspiritM]

Same issue here. Even with poll set to 100 it takes > 5-10 seconds to Close the consumer for me

[jliunyu]

The fix for this is planned for the next release

[tzachshabtay]

@jliunyu any update on this? When's the next release due?

[jliunyu]

This is the PR for the fix: #757

[milindl]

Closing this as the PR above is merged.