Controller broker in Kafka - Practice Problems & Coding Challenges

Challenge - 5 Problems

🧠 Conceptual

intermediate

Role of the Controller Broker in Kafka

What is the primary responsibility of the controller broker in a Kafka cluster?

A Managing partition leader elections and cluster metadata updates

B Balancing network traffic between brokers

C Storing all topic data permanently on disk

D Serving client requests for producing and consuming messages

💡 Hint

Think about which broker coordinates cluster-wide decisions.

The controller broker is responsible for managing partition leader elections and updating cluster metadata to keep the cluster consistent.

❓ Predict Output

intermediate

Controller Broker Leader Election Output

Given the following Kafka controller election log snippet, what will be the output message indicating the new controller?

Kafka

INFO Controller 2 is now the leader for the cluster

A ERROR Controller 1 failed to become leader

B INFO Controller 2 is now the leader for the cluster

C WARN Controller 3 lost leadership

D DEBUG Controller election started

💡 Hint

Look for the message that confirms the new controller leader.

The log message confirms that broker 2 has become the new controller leader.

🔧 Debug

advanced

Identifying Controller Broker Failure Cause

Which of the following log entries indicates a controller broker failure due to session timeout?

A INFO Controller 1 successfully refreshed session

B WARN Controller 2 received heartbeat from broker 3

C ERROR Controller 1 session expired, triggering leader election

D DEBUG Controller 3 started election process

💡 Hint

Look for a message about session expiration or failure.

A session expiration error indicates the controller broker lost its leadership and triggers a new election.

📝 Syntax

advanced

Kafka Controller Broker Configuration Syntax

Which of the following is the correct syntax to configure a Kafka broker as a controller candidate in the server.properties file?

A controller.quorum.voters=1@broker1:9093,2@broker2:9093,3@broker3:9093

B controller.voters=broker1:9093,broker2:9093,broker3:9093

C controller.broker.ids=1,2,3

D controller.candidates=broker1,broker2,broker3

💡 Hint

Check the official Kafka configuration property for controller quorum voters.

The correct property is controller.quorum.voters with format id@host:port for each voter.

🚀 Application

expert

Controller Broker Failover Scenario

In a Kafka cluster with three brokers (1, 2, 3), broker 1 is the current controller. Broker 1 crashes unexpectedly. What is the expected sequence of events for controller failover?

A All brokers simultaneously try to become controller causing conflict

B Broker 3 immediately takes over without election

C Cluster stops processing until broker 1 recovers

D Broker 2 detects broker 1 failure, triggers leader election, becomes new controller

💡 Hint

Consider how Kafka handles controller failover with leader election.

When the controller broker fails, another broker detects the failure and triggers a leader election to select a new controller.