Subscribing to topics in Kafka - Cheat Sheet & Quick Revision

Recall & Review

beginner

What does it mean to subscribe to a topic in Kafka?

Subscribing to a topic means telling the Kafka consumer which topics it should listen to for new messages. The consumer will then receive messages from those topics.

beginner

How do you subscribe to multiple topics in Kafka using the consumer API?

You provide a list of topic names to the consumer's subscribe method, like consumer.subscribe(Arrays.asList("topic1", "topic2")). This makes the consumer listen to all listed topics.

intermediate

What is the difference between subscribing to topics and assigning partitions in Kafka?

Subscribing lets Kafka manage which partitions the consumer reads from automatically. Assigning partitions means you manually tell the consumer exactly which partitions to read, giving more control but requiring manual management.

intermediate

What happens if a consumer subscribes to a topic that does not exist yet?

The consumer will keep trying to find the topic. If the topic is created later, the consumer will start receiving messages from it. This allows dynamic topic creation.

beginner

Why is it important to call consumer.poll() after subscribing to topics?

Calling consumer.poll() triggers the consumer to fetch messages from the subscribed topics. Without polling, the consumer won't receive any messages.

What method is used to subscribe a Kafka consumer to topics?

A listen()

B assign()

C subscribe()

D connect()

The subscribe() method is used to tell the consumer which topics to listen to.

If you want Kafka to automatically manage partition assignment, you should:

A Use subscribe() with topic names

B Use assign() with partitions

C Manually poll each partition

D Create topics manually

subscribe() lets Kafka handle partition assignment automatically.

What happens if you subscribe to a topic that does not exist yet?

A Consumer throws an error immediately

B Consumer subscribes to a random topic

C Consumer ignores the topic

D Consumer waits and starts receiving when topic is created

Kafka consumers wait for the topic to be created and then start receiving messages.

Which method must be called regularly to receive messages after subscribing?

A connect()

B poll()

C subscribe()

D commit()

poll() fetches messages from the subscribed topics.

To listen to multiple topics, you should:

A Pass a list of topic names to subscribe()

B Call subscribe() multiple times

C Use assign() with multiple partitions

D Create multiple consumers

You pass a list of topic names to subscribe() to listen to multiple topics.

Explain how subscribing to topics works in Kafka and why it is useful.

Think about how the consumer knows what to listen to.

Describe the difference between subscribing to topics and assigning partitions in Kafka.

Consider who manages the partitions in each case.