Consumer poll loop in Kafka - Cheat Sheet & Quick Revision

Recall & Review

beginner

What is the purpose of the consumer poll loop in Kafka?

The consumer poll loop continuously fetches messages from Kafka topics, allowing the consumer to process new data as it arrives.

beginner

In Kafka's consumer poll loop, what does the poll() method do?

The poll() method requests records from Kafka brokers and returns any available messages for the consumer to process.

intermediate

Why should the consumer poll loop run continuously without long blocking operations?

Because Kafka expects consumers to poll regularly to maintain their group membership and avoid rebalancing or session timeouts.

intermediate

What happens if a Kafka consumer does not call poll() within the session timeout?

The consumer is considered dead, triggering a rebalance where partitions are reassigned to other consumers.

intermediate

How can you safely commit offsets in a Kafka consumer poll loop?

You can commit offsets synchronously or asynchronously after processing messages to track progress and avoid duplicate processing.

What is the main role of the poll() method in a Kafka consumer loop?

A Create new Kafka topics

B Send messages to Kafka brokers

C Delete Kafka partitions

D Fetch messages from Kafka brokers

The poll() method fetches messages from Kafka brokers for the consumer to process.

What happens if a Kafka consumer stops calling poll() for longer than the session timeout?

A Consumer automatically commits offsets

B Consumer creates new topics

C Consumer is removed from the group and partitions are reassigned

D Nothing happens

Kafka considers the consumer dead and triggers a rebalance to assign partitions to other consumers.

Which of these is a best practice inside a Kafka consumer poll loop?

A Keep the loop running continuously and call poll() regularly

B Call poll() once and then stop

C Perform long blocking operations before calling poll() again

D Close the consumer inside the loop

The consumer should call poll() regularly to maintain group membership and receive messages.

When should a Kafka consumer commit offsets in the poll loop?

A After processing the messages fetched by poll()

B Before calling poll()

C Only once when the consumer starts

D Offsets do not need to be committed

Committing offsets after processing ensures the consumer does not reprocess messages after restart.

What does a rebalance mean in the context of Kafka consumer poll loops?

A Consumer disconnects permanently

B Partitions are reassigned among consumers in the group

C Consumer creates new partitions

D Kafka deletes all messages

Rebalance redistributes partitions among consumers when group membership changes or a consumer fails.

Explain how the Kafka consumer poll loop works and why it is important.

Think about how the consumer stays connected and gets new data.

Describe what happens if a Kafka consumer does not call poll() often enough.

Consider the impact on the consumer group and message processing.