How exactly Kafka's consumer communicate to server?

Question

1. Does Kafka consumer keep checking the health of the broker(Kafka Server) or vice versa?
2. Let's say by anyhow, Consumers and brokers know each other's health so how exactly the consumer will read from the partition?
3. Let's say I have 48 partitions for a topic and have two consumer groups for the topic, so how many threads will be consuming the data from all partitions?

Answer 1

1. Consumers send out healthchecks so that the broker knows if the consumers are healthy. Brokers' health is controlled by Controller, which is a Kafka service that runs on every broker in a Kafka cluster, but only one can be active (elected) at any point in time.
2. See this video for detailed description. In a nutshell, first consumer in the group is a leader and decided on the assignments for the rest of the consumers in the same group. This data is send to the broker and distributed across consumers.
3. Thread management is your own responsibility. Both KafkaProducer and KafkaConsumer are single-threaded components.