How does a consumer know it is no longer listed in the Kafka cluster? - apache-kafka

Question

We have this issue that when Kafka brokers must be taken offline, no consumer service has any idea about that and keeps running.
We tried listing consumers in the new Kafka instance, and saw no existing consumer listed there. All consumers listed are those newly created.
We had to manually terminate all existing consumer services which is not convenient every time we hit this issue.
Question - How does a consumer know it is no longer listed in the Kafka cluster so it should terminate itself?
P.S. We use Spring Kafka.

Answer 1

1 -- To Check Clusters & Replica status ?
Check Kafka cluster all broker status
$ zookeeper-shell.sh localhost:9001 ls /brokers/ids
Check Kafka cluster Specific broker status
$ zookeeper-shell.sh localhost:9001 get /brokers/ids/<id>
specific to replica_unavailability check
$ kafka-check --cluster-type=sample_type replica_unavailability
For first broker check
$ kafka-check --cluster-type=sample_type --broker-id 3 replica_unavailability --first-broker-only
Any partitions replicas not available
$ kafka-check --cluster-type=sample_type replica_unavailability
Checking offline partitions
$ kafka-check --cluster-type=sample_type offline
2 -- Code sample to send/auto-shutdown
2 custom options to do handle the shutdown using a kill-message,
do it gracefully by sending a kill-message before taking down
brokers or topics.
Option 1: Consider an in-band message/signal - i.e. send a “kill” message pertaining to topics/brokers consumer is listening to as it follows the offset order on the topic-partition
Option 2: make the consumer listen to 2 topics for e.g. “topic” and “topic_kill”
The difference between the 2 options above, is that the first version is comes in the the order it was sent, consider that there maybe blocking messages maybe waiting, depending on your implementation, to be consumed before that “kill message”.
While, the second version allows kill-signal to arrive independently without being blocked out of band, this is a nicer & reusable architectural pattern, with a clear separation between data topic and signaling.
Code Sample a) producer sending the kill-message & b) consumer to recieve and handle the shutdown
// Producer -- modify and adapt as needed
import json
from kafka import KafkaProducer
producer = KafkaProducer(bootstrap_servers=['0.0.0.0:<my port number>'],
key_serializer=lambda m: m.encode('utf8'),
value_serializer=lambda m: json.dumps(m).encode('utf8'))
def send_kill(topic: str, partitions: [int]):
for p in partitions:
producer.send(topic, key='kill', partition=p)
producer.flush()
// Consumer to accept a kill-message -- please modify and adapt as needed
import json
from kafka import KafkaConsumer
from kafka.structs import OffsetAndMetadata, TopicPartition
consumer = KafkaConsumer(bootstrap_servers=['0.0.0.0:<my port number>'],
key_deserializer=lambda m: m.decode('utf8'),
value_deserializer=lambda m: json.loads(m.decode('utf8')),
auto_offset_reset="earliest",
group_id='1')
consumer.subscribe(['topic'])
for msg in consumer:
tp = TopicPartition(msg.topic, msg.partition)
offsets = {tp: OffsetAndMetadata(msg.offset, None)}
if msg.key == "kill":
consumer.commit(offsets=offsets)
consumer.unsuscribe()
exit(0)
# do your work...
consumer.commit(offsets=offsets)