Group coordinator in Kafka - Practice Problems & Coding Challenges

Challenge - 5 Problems

❓ Predict Output

intermediate

What is the output of this Kafka group coordinator state transition?

Consider a Kafka consumer group coordinator handling a rebalance. What will be the final state of the coordinator after the following sequence of events?

Kafka

States: INITIALIZING -> PREPARING_REBALANCE -> COMPLETING_REBALANCE -> STABLE
Events: Start -> Prepare -> Complete

Transition:
INITIALIZING --Start--> PREPARING_REBALANCE
PREPARING_REBALANCE --Prepare--> COMPLETING_REBALANCE
COMPLETING_REBALANCE --Complete--> STABLE

A PREPARING_REBALANCE

B STABLE

C INITIALIZING

D COMPLETING_REBALANCE

💡 Hint

Follow the event sequence step-by-step through the state transitions.

The coordinator moves through each state in order: INITIALIZING to PREPARING_REBALANCE on Start, then to COMPLETING_REBALANCE on Prepare, and finally to STABLE on Complete.

🧠 Conceptual

intermediate

Which component is responsible for managing group membership in Kafka?

In Kafka's group coordinator architecture, which component manages the membership and heartbeat of consumers in a group?

A Group Coordinator Broker

B Kafka Producer

C Zookeeper

D Kafka Topic Partition

💡 Hint

Think about which broker handles consumer group coordination.

The Group Coordinator Broker manages group membership, heartbeats, and rebalances for consumer groups.

🔧 Debug

advanced

What error occurs when a consumer fails to send heartbeats to the group coordinator?

Given a Kafka consumer that stops sending heartbeats, what error will the group coordinator raise?

A GroupInstanceIdNotFoundException

B CommitFailedException

C GroupCoordinatorNotAvailableException

D GroupRebalanceInProgressException

💡 Hint

Missing heartbeats cause the coordinator to trigger a rebalance.

If a consumer misses heartbeats, the coordinator triggers a rebalance and raises GroupRebalanceInProgressException.

📝 Syntax

advanced

Which option correctly initializes a Kafka group coordinator client in Java?

Select the correct Java code snippet to create a Kafka consumer with a group coordinator configuration.

Kafka

Properties props = new Properties();
props.put("bootstrap.servers", "localhost:9092");
props.put("group.id", "my-group");
props.put("key.deserializer", "org.apache.kafka.common.serialization.StringDeserializer");
props.put("value.deserializer", "org.apache.kafka.common.serialization.StringDeserializer");

KafkaConsumer<String, String> consumer = ???;

A new KafkaConsumer<>(props);

B new KafkaConsumer(props);

C new KafkaConsumer<String, String>(props);

D KafkaConsumer<String, String> consumer = KafkaConsumer(props);

💡 Hint

Remember to specify generic types when creating the consumer.

The correct syntax requires specifying generic types and passing the properties object to the constructor.

🚀 Application

expert

How many partitions can a Kafka consumer group coordinator assign if the group has 3 consumers and the topic has 10 partitions?

Given a Kafka topic with 10 partitions and a consumer group with 3 consumers, how many partitions will each consumer be assigned if the coordinator uses the default range assignor?

A Consumer 1: 4, Consumer 2: 3, Consumer 3: 3

B Consumer 1: 3, Consumer 2: 3, Consumer 3: 4

C Consumer 1: 3, Consumer 2: 4, Consumer 3: 3

D Consumer 1: 3, Consumer 2: 3, Consumer 3: 3

💡 Hint

The default range assignor distributes partitions as evenly as possible, assigning extra partitions to the first consumers.

With 10 partitions and 3 consumers, the first consumer gets 4 partitions, the others get 3 each.