Hi All, I am hosting kafka consumers inside microservice hosted as kubernetes pods, 3 consumers in a consumer group. There is a requirement to add auto-scaling where there will be a single pod which will be auto-scaled out or scaled-in based on the load on microservice. So, 1 pod can be scaled out to 2 or 3 pods, and similarly 3 pods can be scaled down to 2 or 1 pod.
Currently, I am using enabled.auto.commit set to 'true' in the consumers and during scale out or scale-in, i want to commit offset of polled and processed records so duplicates won't occur. I have narrowed the problem to 2 scenarios: 1. During scale-down operation, I am adding a shutdown hook to the Java Runtime, and calling close on the consumer. As per kafka docs, close provides 30 sec to commit current offsets if auto.commit is enabled: so, i assume that it will process the current batch of polled records within 30 sec timeout before committing offsets and then close the consumer. Is my understanding correct? public void close() Close the consumer, waiting for up to the default timeout of 30 seconds for any needed cleanup. If auto-commit is enabled, this will commit the current offsets if possible within the default timeout. See close(Duration) <https://kafka.apache.org/25/javadoc/org/apache/kafka/clients/consumer/KafkaConsumer.html#close-java.time.Duration-> for details. Note that wakeup() <https://kafka.apache.org/25/javadoc/org/apache/kafka/clients/consumer/KafkaConsumer.html#wakeup--> cannot be used to interrupt close. 2. During scale out operation, new pod (consumer) will be added to the consumer group, so partitions of existing consumers will be rebalanced to new consumer. In this case, I want to ensure that the current batch of records polled and being processed by the consumer is processed and offsets are committed before partition rebalance happens to new consumer. How can I ensure this with auto-commit enabled?
