Broker nodes in Kafka - Practice Problems & Coding Challenges

Challenge - 5 Problems

🧠 Conceptual

intermediate

What is the primary role of a Kafka broker node?

In a Kafka cluster, what is the main job of a broker node?

A Receive messages from producers, store them, and serve to consumers

B Manage the cluster's Zookeeper ensemble

C Only produce messages to topics

D Handle client authentication exclusively

💡 Hint

Think about where messages are kept and how clients get them.

A Kafka broker node receives messages from producers, stores them, and serves them to consumers. It manages partitions and handles data storage and retrieval.

❓ Predict Output

intermediate

What output does this Kafka broker configuration produce?

Given this Kafka broker configuration snippet, what will be the broker's advertised listener port?

Kafka

listeners=PLAINTEXT://0.0.0.0:9092
advertised.listeners=PLAINTEXT://broker1.example.com:9094

A 9094

B 9092

C 0.0.0.0

D broker1.example.com

💡 Hint

Advertised listeners tell clients how to connect.

The advertised.listeners setting tells clients the hostname and port to use, so the port is 9094.

🔧 Debug

advanced

Why does this Kafka broker fail to start?

Examine the following Kafka broker configuration snippet. Why will the broker fail to start?

Kafka

broker.id=1
listeners=PLAINTEXT://:9092
advertised.listeners=PLAINTEXT://localhost:9092
log.dirs=/tmp/kafka-logs

A log.dirs path is invalid

B broker.id must be zero or greater

C listeners missing hostname causes startup failure

D advertised.listeners cannot use localhost

💡 Hint

Check the listeners setting format carefully.

The listeners setting requires a hostname or IP before the port. ':9092' is invalid and causes startup failure.

📝 Syntax

advanced

Which option correctly defines multiple listeners for a Kafka broker?

Choose the correct syntax to configure two listeners: one PLAINTEXT on port 9092 and one SSL on port 9093.

A listeners=PLAINTEXT://0.0.0.0:9092;SSL://0.0.0.0:9093

B listeners=PLAINTEXT://0.0.0.0:9092,SSL://0.0.0.0:9093

C listeners=[PLAINTEXT://0.0.0.0:9092, SSL://0.0.0.0:9093]

D listeners=PLAINTEXT://0.0.0.0:9092 SSL://0.0.0.0:9093

💡 Hint

Multiple listeners are separated by commas.

The correct syntax uses commas to separate listeners. Semicolons, brackets, or spaces are invalid.

🚀 Application

expert

How many partitions will broker 2 host after this assignment?

Given a Kafka cluster with 3 brokers (IDs 1, 2, 3) and a topic with 6 partitions assigned as follows:

• Partition 0: leader=1, replicas=[1,2]
• Partition 1: leader=2, replicas=[2,3]
• Partition 2: leader=3, replicas=[3,1]
• Partition 3: leader=1, replicas=[1,3]
• Partition 4: leader=2, replicas=[2,1]
• Partition 5: leader=3, replicas=[3,2]

How many partitions does broker 2 host (as leader or replica)?

A 5

B 3

C 6

D 4

💡 Hint

Count all partitions where broker 2 is either leader or in replicas.

Broker 2 is leader for partitions 1 and 4, replica for 0 and 5. Unique partitions hosted: 0, 1, 4, 5 — total 4.

Practice

1.

What is the primary role of a broker node in Kafka?

easy

A. Store and manage Kafka messages

B. Produce messages to topics

C. Consume messages from topics

D. Monitor network traffic

Solution

1. Step 1: Understand broker node function

   A broker node is a Kafka server that stores and manages messages.

2. Step 2: Differentiate roles

   Producers send messages, consumers read them, but brokers store/manage them.

3. Final Answer:

   Store and manage Kafka messages -> Option A

4. Quick Check:

   Broker = Store/manage messages [OK]

Hint: Broker nodes store messages; producers and consumers do not [OK]

Common Mistakes:

• Confusing brokers with producers or consumers
• Thinking brokers monitor network traffic
• Assuming brokers only route messages

2.

Which of the following is the correct way to specify a broker's unique ID in the Kafka server.properties file?

easy

A. broker.id=1

B. brokerID=1

C. broker-id=1

D. brokerId=1

Solution

1. Step 1: Recall Kafka broker ID syntax

   The correct property name is broker.id with a dot separator.

2. Step 2: Check options for exact match

   Only broker.id=1 matches Kafka's expected syntax.

3. Final Answer:

   broker.id=1 -> Option A

4. Quick Check:

   Broker ID property uses dot notation [OK]

Hint: Broker ID uses dot notation: broker.id [OK]

Common Mistakes:

• Using camelCase or hyphens instead of dot
• Misspelling the property name
• Confusing broker.id with other properties

3.

Given the following snippet from a Kafka server.properties file:

broker.id=2
listeners=PLAINTEXT://localhost:9093
log.dirs=/tmp/kafka-logs-2

What will be the broker's ID and listening port when Kafka starts?

medium

A. Broker ID 1, listening on port 9092

B. Broker ID 2, listening on port 9093

C. Broker ID 2, listening on port 9092

D. Broker ID 1, listening on port 9093

Solution

1. Step 1: Identify broker ID from properties

   The property broker.id=2 sets the broker ID to 2.

2. Step 2: Identify listener port

   listeners=PLAINTEXT://localhost:9093 means the broker listens on port 9093.

3. Final Answer:

   Broker ID 2, listening on port 9093 -> Option B

4. Quick Check:

   broker.id=2 and port=9093 [OK]

Hint: Broker ID and port come directly from properties file [OK]

Common Mistakes:

• Assuming default port 9092 without checking listeners
• Mixing up broker IDs
• Ignoring the listeners property

4.

Consider this server.properties snippet:

broker.id=abc
listeners=PLAINTEXT://localhost:9092

What is the issue when starting Kafka with this configuration?

medium

A. broker.id can be a string, so no issue

B. listeners property is missing a port

C. Kafka will ignore broker.id and assign default

D. broker.id must be an integer, so 'abc' causes an error

Solution

1. Step 1: Check broker.id value type

   Kafka requires broker.id to be an integer number.

2. Step 2: Identify invalid value

   Setting broker.id=abc is invalid and causes startup error.

3. Final Answer:

   broker.id must be an integer, so 'abc' causes an error -> Option D

4. Quick Check:

   broker.id integer required [OK]

Hint: broker.id must be a number, not letters [OK]

Common Mistakes:

• Assuming broker.id can be string
• Ignoring error messages on startup
• Thinking Kafka assigns default broker.id automatically

5.

You want to run three Kafka broker nodes on the same machine for testing. Which configuration change is essential for each broker to avoid conflicts?

hard

A. Use the same broker.id but different log.dirs

B. Keep listeners port same but change broker.id

C. Assign unique broker.id and different listeners ports

D. Only change log.dirs for each broker

Solution

1. Step 1: Understand broker uniqueness requirements

   Each broker must have a unique broker.id to identify it in the cluster.

2. Step 2: Avoid port conflicts

   Each broker must listen on a different port to avoid network conflicts.

3. Final Answer:

   Assign unique broker.id and different listeners ports -> Option C

4. Quick Check:

   Unique IDs and ports prevent conflicts [OK]

Hint: Unique broker.id and ports prevent conflicts [OK]

Common Mistakes:

• Using same broker.id for multiple brokers
• Using same port for multiple brokers
• Only changing log directories without ports or IDs