Description

The get_watermark_offsets ignores the timeout and blocks forever when the kafka broker for a selected partition is down. Once the broker is back up, the function returns. I suspect this is a bug in rdkafka, but I'm posting it here first in case it's an issue with the python bindings.

How to reproduce

Create a topic with one partition. Run the below example. Once the example has consumed a few messages, kill the broker hosting the partition. The call to get_watermark_offsets will block until the broker comes back up.

import time
import sys
import confluent_kafka
from confluent_kafka import Consumer, KafkaError
from uuid import uuid4

if __name__ == '__main__':
    debug_thread = threading.Thread(target=debug_thread_func)
    debug_thread.start()

    client = Consumer({'bootstrap.servers': 'gateway:9092', 'group.id': str(uuid4()),
              'default.topic.config': {'auto.offset.reset': 'smallest'}})

    def assigned(consumer, partitions):
        print("Assigned:", partitions)
        

    client.subscribe(['ibbot'], on_assign=assigned)

    while True:
        msg = client.poll(timeout=1)
        for partition in client.assignment():
            print(client.get_watermark_offsets(partition, timeout=1))

        if msg is not None:
            if msg.error():
                print("Error: ", msg.error())
            else:
                print("Data")

    client.close()
   

Note that this example is probably dependent on a bug in rdkafka, so it may not be reproducible 100% of the time. You can also reproduce this with a multi-partition and broker setup. In this case, the function only blocks for as long as it takes for a new leader to be elected.

Checklist

Please provide the following information:

• confluent-kafka-python and librdkafka version (confluent_kafka.version() and confluent_kafka.libversion()): kafka-python: ('0.11.4', 721920) rdkafka: ('0.11.4', 722175)
• Apache Kafka broker version: 0.11.0.2
• Client configuration: {'bootstrap.servers': 'gateway:9092', 'group.id': str(uuid4()), 'default.topic.config': {'auto.offset.reset': 'smallest'}}
• Operating system: RHEL 7
• Provide client logs (with 'debug': '..' as necessary)
• Provide broker log excerpts
• Critical issue