Java consumer client in Kafka - Cheat Sheet & Quick Revision

Recall & Review

beginner

What is the main role of a Java Kafka consumer client?

A Java Kafka consumer client reads messages from Kafka topics, allowing applications to process data streams in real time.

beginner

Which method in the KafkaConsumer class is used to subscribe to topics?

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

beginner

What does the poll() method do in a Kafka consumer?

The poll() method fetches records from the subscribed topics. It waits for new data and returns a batch of records.

intermediate

Why is it important to commit offsets in a Kafka consumer?

Committing offsets tells Kafka which messages have been processed, so the consumer can resume from the right place after a restart.

beginner

What configuration property sets the Kafka server address in a Java consumer client?

The bootstrap.servers property specifies the Kafka broker addresses the consumer connects to.

Which method do you use to start receiving messages from Kafka topics in a Java consumer?

A poll()

B send()

C connect()

D subscribe()

The poll() method fetches messages from Kafka topics. subscribe() only tells the consumer which topics to listen to.

What does the group.id configuration property define in a Kafka consumer?

A The consumer group the client belongs to

B The topic name

C The Kafka broker address

D The message key

group.id defines the consumer group, which allows multiple consumers to share the work of reading from topics.

How does a Kafka consumer know where to resume reading after a restart?

A By remembering the last message content

B By reconnecting to the broker

C By subscribing again

D By committing offsets

Committing offsets saves the position of the last processed message so the consumer can resume correctly.

Which of these is NOT a valid Kafka consumer configuration property?

A bootstrap.servers

B key.deserializer

C poll.interval

D value.deserializer

poll.interval is not a standard Kafka consumer config. The others are required to connect and deserialize messages.

What type of object does the poll() method return in a Kafka consumer?

A List of strings

B ConsumerRecords object

C String

D Map of topics

poll() returns a ConsumerRecords object containing the fetched messages.

Explain the basic steps to create and run a Java Kafka consumer client.

Think about how the consumer connects, listens, and remembers progress.

Describe why committing offsets is important in Kafka consumer clients and how it affects message processing.

Consider what happens if the consumer crashes and restarts.