Broker configuration basics in Kafka - Cheat Sheet & Quick Revision

Recall & Review

beginner

What is a Kafka broker?

A Kafka broker is a server that stores and serves Kafka topics. It handles data storage, message delivery, and client requests.

beginner

What does the broker.id configuration do?

The broker.id is a unique identifier for each Kafka broker in the cluster. It helps Kafka distinguish between brokers.

beginner

Why is log.dirs important in broker configuration?

log.dirs specifies the directory where Kafka stores its log data (messages). It must point to a valid disk location.

intermediate

What is the role of zookeeper.connect in Kafka broker config?

zookeeper.connect tells the broker how to connect to ZooKeeper, which manages cluster metadata and broker coordination.

intermediate

How does num.network.threads affect broker performance?

num.network.threads sets how many threads handle network requests. More threads can improve throughput but use more CPU.

What must each Kafka broker have to be uniquely identified in a cluster?

A zookeeper.connect

B log.dirs

C broker.id

D num.network.threads

Each broker needs a unique broker.id to be identified in the Kafka cluster.

Which configuration specifies where Kafka stores its message logs?

A broker.id

B num.network.threads

C zookeeper.connect

D log.dirs

log.dirs defines the directory path for storing Kafka logs.

What does zookeeper.connect configure?

A Connection to ZooKeeper service

B Log storage location

C Broker's unique ID

D Number of network threads

zookeeper.connect tells the broker how to connect to ZooKeeper for cluster coordination.

Increasing num.network.threads will likely:

A Improve network request handling

B Decrease CPU usage

C Change broker ID

D Modify log directory

More network threads help handle more network requests simultaneously, improving throughput.

Which of these is NOT a broker configuration?

A broker.id

B topic.name

C zookeeper.connect

D log.dirs

topic.name is not a broker configuration; it relates to topic settings.

Explain the purpose of the broker.id and why it is important in Kafka broker configuration.

Think about how Kafka knows which server is which.

Describe how log.dirs and zookeeper.connect work together in Kafka broker setup.

One handles data storage, the other handles cluster metadata.

Practice

1. What is the main purpose of Kafka broker configuration files?

easy

A. To set key=value pairs that control broker behavior

B. To write Kafka client application code

C. To store user data permanently

D. To configure the operating system settings

Solution

1. Step 1: Understand the role of broker configuration

   Broker configuration files contain settings that control how Kafka brokers behave, such as storage and network handling.

2. Step 2: Identify the correct description

   Only To set key=value pairs that control broker behavior correctly describes the purpose as setting key=value pairs for broker behavior.

3. Final Answer:

   To set key=value pairs that control broker behavior -> Option A

4. Quick Check:

   Broker config = key=value pairs [OK]

Hint: Broker config files set key=value pairs for broker control [OK]

Common Mistakes:

• Confusing broker config with client code
• Thinking config stores user data
• Mixing OS settings with Kafka broker config

2. Which of the following is the correct syntax to set the broker ID in Kafka's configuration file?

easy

A. broker_id=1

B. broker-id:1

C. broker.id=1

D. brokerId=1

Solution

1. Step 1: Recall Kafka config syntax

   Kafka uses key=value pairs with dots to separate words, like broker.id=1.

2. Step 2: Compare options

   Only broker.id=1 uses the correct dot notation and equal sign syntax.

3. Final Answer:

   broker.id=1 -> Option C

4. Quick Check:

   Correct syntax uses dot and equal sign [OK]

Hint: Kafka configs use dot notation and equal sign [OK]

Common Mistakes:

• Using underscores instead of dots
• Using colon instead of equal sign
• CamelCase keys instead of lowercase with dots

3. Given this Kafka broker configuration snippet:

log.dirs=/tmp/kafka-logs
num.network.threads=3
num.io.threads=8

What does num.network.threads=3 control?

medium

A. Number of threads for message processing

B. Number of threads writing logs to disk

C. Number of threads for client connections

D. Number of threads handling network requests

Solution

1. Step 1: Understand the meaning of num.network.threads

   This setting controls how many threads the broker uses to handle network requests from clients.

2. Step 2: Match options with setting

   Number of threads handling network requests correctly states it controls threads handling network requests; others describe unrelated functions.

3. Final Answer:

   Number of threads handling network requests -> Option D

4. Quick Check:

   num.network.threads = network threads count [OK]

Hint: network.threads means threads for network requests [OK]

Common Mistakes:

• Confusing network threads with IO threads
• Thinking it controls log writing threads
• Mixing client connections with message processing

4. You see this broker config line:

log.retention.hours 168

What is wrong with this line?

medium

A. Missing equal sign between key and value

B. Invalid value; hours must be a string

C. Key name is incorrect; should be log.retention.ms

D. No error; this line is correct

Solution

1. Step 1: Check syntax for key-value pairs

   Kafka config requires an equal sign (=) between key and value, not just a space.

2. Step 2: Identify the error in the line

   The line uses a space instead of '=', so it is a syntax error.

3. Final Answer:

   Missing equal sign between key and value -> Option A

4. Quick Check:

   Config lines need key=value format [OK]

Hint: Config lines must have key=value, not space [OK]

Common Mistakes:

• Assuming space works as separator
• Confusing retention hours with milliseconds
• Thinking the key name is wrong

5. You want to configure a Kafka broker to store logs in two directories: /data/kafka1 and /data/kafka2. Which is the correct way to set log.dirs in the broker config?

hard

A. log.dirs=/data/kafka1;/data/kafka2

B. log.dirs=/data/kafka1,/data/kafka2

C. log.dirs=/data/kafka1 /data/kafka2

D. log.dirs=[/data/kafka1,/data/kafka2]

Solution

1. Step 1: Understand log.dirs format

   Kafka expects multiple directories separated by commas without spaces or brackets.

2. Step 2: Evaluate each option

   log.dirs=/data/kafka1,/data/kafka2 uses commas correctly; B uses semicolon (wrong), C uses space (wrong), D uses brackets (wrong).

3. Final Answer:

   log.dirs=/data/kafka1,/data/kafka2 -> Option B

4. Quick Check:

   Multiple dirs separated by commas [OK]

Hint: Separate multiple log dirs with commas, no spaces [OK]

Common Mistakes:

• Using semicolons or spaces instead of commas
• Adding brackets around paths
• Including spaces between paths