Kafka CLI tools overview - Practice Problems & Coding Challenges

Challenge - 5 Problems

❓ Predict Output

intermediate

What is the output of the kafka-topics.sh command?

You run the command kafka-topics.sh --list --bootstrap-server localhost:9092 on a Kafka cluster with three topics: orders, payments, and shipments. What will be the output?

Kafka

kafka-topics.sh --list --bootstrap-server localhost:9092

A Error: Topic list not found

B

orders
payments
shipments

C

Topic orders created
Topic payments created
Topic shipments created

D No topics found

💡 Hint

The --list option shows all existing topics in the cluster.

The kafka-topics.sh tool with --list option lists all topics currently in the Kafka cluster. Since there are three topics, their names are printed line by line.

❓ Predict Output

intermediate

What does kafka-console-producer.sh output after sending a message?

You run kafka-console-producer.sh --broker-list localhost:9092 --topic test and type the message Hello Kafka. What output do you see immediately after pressing Enter?

Kafka

kafka-console-producer.sh --broker-list localhost:9092 --topic test

A Error: Unable to send message

B Hello Kafka

C (No output, just a new prompt line)

D Message sent successfully

💡 Hint

The console producer does not print confirmation messages after sending.

The kafka-console-producer.sh tool sends messages to Kafka but does not print any confirmation or echo the message. It just waits for the next input.

❓ Predict Output

advanced

What is the output of kafka-consumer-groups.sh --describe?

You run kafka-consumer-groups.sh --bootstrap-server localhost:9092 --group my-group --describe and the group has one member consuming from topic orders partition 0 with lag 5. What output do you expect?

Kafka

kafka-consumer-groups.sh --bootstrap-server localhost:9092 --group my-group --describe

A GROUP my-group has no lag

B Error: Group my-group not found

C No consumers found for group my-group

D

GROUP       TOPIC   PARTITION  CURRENT-OFFSET  LOG-END-OFFSET  LAG  CONSUMER-ID  HOST  CLIENT-ID
my-group    orders  0          100             105             5    consumer-1   /127.0.0.1  client-1

💡 Hint

The --describe option shows detailed info including lag.

The kafka-consumer-groups.sh tool with --describe prints a table with group, topic, partition, offsets, lag, and consumer details. Since lag is 5, it is shown in the output.

❓ Predict Output

advanced

What error does kafka-configs.sh produce with invalid syntax?

You run kafka-configs.sh --alter --entity-type topics --entity-name my-topic --add-config retention.ms=abc --bootstrap-server localhost:9092. What error will you see?

Kafka

kafka-configs.sh --alter --entity-type topics --entity-name my-topic --add-config retention.ms=abc --bootstrap-server localhost:9092

A Error: Invalid value for retention.ms: abc

B Configuration updated successfully

C Error: Unknown entity type topics

D Syntax error: missing equals sign

💡 Hint

retention.ms expects a number in milliseconds.

The kafka-configs.sh tool validates config values. Since retention.ms expects a numeric value, passing 'abc' causes an invalid value error.

🧠 Conceptual

expert

Which Kafka CLI tool is used to reset consumer group offsets?

You want to move the offsets of a consumer group backward to reprocess messages. Which Kafka CLI tool and option do you use?

A kafka-consumer-groups.sh with --reset-offsets

B kafka-topics.sh with --alter-offsets

C kafka-configs.sh with --reset-consumer

D kafka-console-consumer.sh with --rewind

💡 Hint

Resetting offsets is done via the consumer groups tool.

The kafka-consumer-groups.sh tool supports the --reset-offsets option to change offsets for a consumer group to a specific point.

Practice

1. Which Kafka CLI tool is used to create a new topic?

easy

A. kafka-topics.sh --create

B. kafka-console-producer.sh

C. kafka-console-consumer.sh

D. kafka-configs.sh

Solution

1. Step 1: Identify the tool for topic management

   The kafka-topics.sh tool is used to manage topics including creation, deletion, and listing.

2. Step 2: Confirm the create option usage

   Using --create with kafka-topics.sh creates a new topic.

3. Final Answer:

   kafka-topics.sh --create -> Option A

4. Quick Check:

   Topic creation = kafka-topics.sh --create [OK]

Hint: Topic creation always uses kafka-topics.sh with --create [OK]

Common Mistakes:

• Confusing producer or consumer tools for topic creation
• Using kafka-configs.sh which manages configs, not topics
• Omitting --create option

2. Which of the following is the correct syntax to start a Kafka console producer connecting to a server at localhost:9092?

easy

A. kafka-console-producer.sh --connect localhost:9092 --topic mytopic

B. kafka-console-producer.sh --broker-list localhost:9092 --topic mytopic

C. kafka-console-producer.sh --server localhost:9092 --topic mytopic

D. kafka-console-producer.sh --bootstrap-server localhost:9092 --topic mytopic

Solution

1. Step 1: Identify the correct option for specifying Kafka server

   Modern Kafka CLI tools use --bootstrap-server to specify the Kafka server address.

2. Step 2: Check the full command syntax

   The correct syntax includes kafka-console-producer.sh --bootstrap-server localhost:9092 --topic mytopic.

3. Final Answer:

   kafka-console-producer.sh --bootstrap-server localhost:9092 --topic mytopic -> Option D

4. Quick Check:

   Use --bootstrap-server for server address [OK]

Hint: Always use --bootstrap-server to specify Kafka server [OK]

Common Mistakes:

• Using deprecated --broker-list instead of --bootstrap-server
• Using incorrect flags like --server or --connect
• Omitting the --topic option

3. What will be the output of this command if the topic test-topic has 3 messages: kafka-console-consumer.sh --bootstrap-server localhost:9092 --topic test-topic --from-beginning --max-messages 2?

medium

A. It will print all 3 messages from test-topic and then exit.

B. It will print the first 2 messages from test-topic and then exit.

C. It will print no messages because --max-messages is ignored.

D. It will print only the last message from test-topic.

Solution

1. Step 1: Understand the --max-messages option

   The --max-messages 2 option limits the consumer to read only 2 messages before exiting.

2. Step 2: Analyze the command behavior

   The command reads from the beginning and stops after printing 2 messages, even though the topic has 3 messages.

3. Final Answer:

   It will print the first 2 messages from test-topic and then exit. -> Option B

4. Quick Check:

   --max-messages limits output count [OK]

Hint: --max-messages limits how many messages are consumed [OK]

Common Mistakes:

• Assuming all messages will be printed ignoring --max-messages
• Thinking --max-messages prints last messages only
• Confusing --from-beginning with consuming only latest messages

4. You run this command but get an error: kafka-console-producer.sh --topic mytopic. What is missing?

medium

A. The --bootstrap-server option specifying the Kafka server address.

B. The --create option to create the topic.

C. The --from-beginning option to read messages.

D. The --max-messages option to limit output.

Solution

1. Step 1: Identify required options for kafka-console-producer.sh

   The producer needs to know which Kafka server to connect to, specified by --bootstrap-server.

2. Step 2: Check the given command

   The command lacks --bootstrap-server, so it cannot connect and throws an error.

3. Final Answer:

   The --bootstrap-server option specifying the Kafka server address. -> Option A

4. Quick Check:

   Producer needs --bootstrap-server to connect [OK]

Hint: Always include --bootstrap-server to avoid connection errors [OK]

Common Mistakes:

• Assuming topic creation is automatic without --create
• Confusing producer options with consumer options
• Adding irrelevant options like --from-beginning for producer

5. You want to list all topics on a Kafka server at localhost:9092. Which command correctly lists the topics?

hard

A. kafka-console-producer.sh --list --bootstrap-server localhost:9092

B. kafka-console-consumer.sh --list --bootstrap-server localhost:9092

C. kafka-topics.sh --list --bootstrap-server localhost:9092

D. kafka-configs.sh --list --bootstrap-server localhost:9092

Solution

1. Step 1: Identify the tool for listing topics

   The kafka-topics.sh tool manages topics and supports the --list option to show all topics.

2. Step 2: Confirm the correct command syntax

   Using --bootstrap-server localhost:9092 specifies the Kafka server to connect to.

3. Final Answer:

   kafka-topics.sh --list --bootstrap-server localhost:9092 -> Option C

4. Quick Check:

   List topics with kafka-topics.sh --list [OK]

Hint: Use kafka-topics.sh with --list to see all topics [OK]

Common Mistakes:

• Using consumer or producer tools to list topics
• Omitting --bootstrap-server causing connection failure
• Using kafka-configs.sh which lists configs, not topics