我试图优雅地关闭一个kafka消费者，但是脚本阻止了心跳线程的停止。我如何才能优雅地关闭消费者与Kafkapython的sigterm。这就是我所做的

import logger as logging
import time
import sys
from kafka import KafkaConsumer
import numpy as np
import signal
log = logging.getLogger(__name__)
class Cons:
    def __init__(self):
        signal.signal(signal.SIGINT, self.sigterm_handler)
        signal.signal(signal.SIGTERM, self.sigterm_handler)
        self.consumer = KafkaConsumer('dummy-topic', group_id='poll-test', bootstrap_servers=['b1'])
    def sigterm_handler(self, signum, frame):
        log.info("Sigterm handler")
        self.consumer.close(autocommit=False)
        sys.exit(0)
    def consume(self):
        try:
            while True:
                records = self.consumer.poll(timeout_ms=500, max_records=500)
                for topic_partition, consumer_records in records.items():
                    for record in consumer_records:
                        log.info("Got Record - {}".format(record))
                    #code to manually commit
        except ValueError as e:
            log.exception("exception")
if __name__ == '__main__':
    c=Cons()
    c.consume()

启用调试日志后，这就是我得到的输出，代码在此日志上被阻止。

^C2020-04-28 07:18:33,050 - MainThread - __main__ - INFO - Sigterm handler
2020-04-28 07:18:33,050 - MainThread - kafka.consumer.group - DEBUG - Closing the KafkaConsumer.
2020-04-28 07:18:33,051 - MainThread - kafka.coordinator - INFO - Stopping heartbeat thread

这背后的原因是什么？什么是关闭sigterm或sigint消费者的正确方法？