First message (produce and consume) in Kafka - Cheat Sheet & Quick Revision

Recall & Review

beginner

What is the role of a producer in Kafka?

A producer sends messages (data) to a Kafka topic. Think of it like someone writing letters and putting them into a mailbox for others to read.

beginner

What does a consumer do in Kafka?

A consumer reads messages from a Kafka topic. It's like picking up letters from the mailbox and reading them.

beginner

Why do we need topics in Kafka?

Topics organize messages by category or type. Imagine topics as different mailboxes for different kinds of letters.

beginner

What is the first step to send a message in Kafka?

Create a producer, connect it to Kafka, and send a message to a topic.

intermediate

How does a consumer know which message to read first?

Consumers read messages in the order they were sent to the topic, starting from the earliest or latest message depending on configuration.

What is the main purpose of a Kafka producer?

A To send messages to a topic

B To read messages from a topic

C To delete messages from a topic

D To create topics

A Kafka producer's job is to send messages to a topic.

Which component reads messages from a Kafka topic?

A Producer

B Broker

C Consumer

D Zookeeper

Consumers read messages from Kafka topics.

What is a Kafka topic best compared to in real life?

A A letter

B A mailbox

C A stamp

D A postman

A topic is like a mailbox where messages are stored.

When producing the first message, what must you specify?

A The message offset

B The consumer group

C The broker address only

D The topic name

You must specify the topic name to send the message to the right place.

How does a Kafka consumer decide where to start reading messages?

A From the earliest or latest message based on config

B Randomly

C Only the newest message

D Only the oldest message

Consumers can be configured to start reading from earliest or latest messages.

Explain how to produce and consume the first message in Kafka in simple terms.

Think about sending and receiving letters using mailboxes.

Describe the roles of producer, consumer, and topic in Kafka.

Imagine a mailing system with senders, mailboxes, and readers.

Practice

1. What is the main purpose of producing a message in Kafka?

easy

A. To send data to a Kafka topic

B. To read data from a Kafka topic

C. To delete messages from a Kafka topic

D. To create a new Kafka topic

Solution

1. Step 1: Understand Kafka producing

   Producing means sending messages to a Kafka topic as bytes.

2. Step 2: Differentiate producing from consuming

   Consuming reads messages, but producing sends them.

3. Final Answer:

   To send data to a Kafka topic -> Option A

4. Quick Check:

   Producing = Sending messages [OK]

Hint: Producing means sending messages to Kafka topics [OK]

Common Mistakes:

• Confusing producing with consuming
• Thinking producing deletes messages
• Assuming producing creates topics

2. Which of the following is the correct way to create a Kafka producer in Python using the kafka-python library?

easy

A. producer = KafkaConsumer(topic='mytopic')

B. producer = KafkaConsumer(bootstrap_servers='localhost:9092')

C. producer = KafkaProducer(topic='mytopic')

D. producer = KafkaProducer(bootstrap_servers='localhost:9092')

Solution

1. Step 1: Identify Kafka producer creation syntax

   KafkaProducer is created with bootstrap_servers parameter specifying Kafka server address.

2. Step 2: Eliminate consumer and wrong parameters

   KafkaConsumer is for consuming, not producing. Topic is not a parameter for producer creation.

3. Final Answer:

   producer = KafkaProducer(bootstrap_servers='localhost:9092') -> Option D

4. Quick Check:

   Producer uses KafkaProducer with bootstrap_servers [OK]

Hint: Producer uses KafkaProducer with bootstrap_servers [OK]

Common Mistakes:

• Using KafkaConsumer instead of KafkaProducer
• Passing topic during producer creation
• Missing bootstrap_servers parameter

3. Consider this Python code snippet using kafka-python:

from kafka import KafkaProducer, KafkaConsumer

producer = KafkaProducer(bootstrap_servers='localhost:9092')
producer.send('test-topic', b'Hello Kafka')
producer.flush()

consumer = KafkaConsumer('test-topic', bootstrap_servers='localhost:9092', auto_offset_reset='earliest', consumer_timeout_ms=1000)
for msg in consumer:
    print(msg.value.decode())

What will be the output when this code runs?

medium

A. Error: topic not found

B. Hello Kafka

C. No output, consumer times out

D. b'Hello Kafka'

Solution

1. Step 1: Analyze producer sending message

   Producer sends bytes message b'Hello Kafka' to 'test-topic' and flushes to ensure delivery.

2. Step 2: Analyze consumer reading message

   Consumer reads from 'test-topic' from earliest offset and decodes bytes to string before printing.

3. Final Answer:

   Hello Kafka -> Option B

4. Quick Check:

   Consumer prints decoded message string [OK]

Hint: Consumer decodes bytes to string before printing [OK]

Common Mistakes:

• Expecting raw bytes output
• Assuming consumer misses message due to timeout
• Thinking topic does not exist

4. You wrote this code to consume messages but it raises an error:

consumer = KafkaConsumer('my-topic')
for message in consumer:
    print(message.value.decode())

What is the most likely cause of the error?

medium

A. Using decode() on message.value which is already a string

B. Not calling consumer.poll() before iterating

C. Missing bootstrap_servers parameter when creating KafkaConsumer

D. Topic name should be a list, not a string

Solution

1. Step 1: Check KafkaConsumer creation requirements

   KafkaConsumer requires bootstrap_servers parameter to connect to Kafka cluster.

2. Step 2: Validate other options

   decode() is needed because message.value is bytes; consumer.poll() is optional; topic can be string or list.

3. Final Answer:

   Missing bootstrap_servers parameter when creating KafkaConsumer -> Option C

4. Quick Check:

   KafkaConsumer needs bootstrap_servers [OK]

Hint: Always specify bootstrap_servers when creating KafkaConsumer [OK]

Common Mistakes:

• Omitting bootstrap_servers parameter
• Assuming message.value is string without decoding
• Thinking poll() is mandatory before iteration

5. You want to produce and consume the first message in a Kafka topic named 'orders'. Which sequence of steps correctly achieves this in Python using kafka-python?

hard

A. Create KafkaProducer with bootstrap_servers, send message as bytes, flush; create KafkaConsumer with bootstrap_servers and auto_offset_reset='earliest', then read and decode messages

B. Create KafkaConsumer first, then KafkaProducer; send message as string; consumer reads without decoding

C. Create KafkaProducer without bootstrap_servers, send string message; create KafkaConsumer with bootstrap_servers, read messages as bytes

D. Create KafkaProducer with topic parameter, send message; create KafkaConsumer without bootstrap_servers, read and decode messages

Solution

1. Step 1: Properly create KafkaProducer and send message

   KafkaProducer must be created with bootstrap_servers; messages sent as bytes and flushed to ensure delivery.

2. Step 2: Properly create KafkaConsumer and read messages

   KafkaConsumer needs bootstrap_servers and auto_offset_reset='earliest' to read from the first message; decode bytes to string when reading.

3. Final Answer:

   Create KafkaProducer with bootstrap_servers, send message as bytes, flush; create KafkaConsumer with bootstrap_servers and auto_offset_reset='earliest', then read and decode messages -> Option A

4. Quick Check:

   Correct producer and consumer setup with bytes and decoding [OK]

Hint: Producer sends bytes and flushes; consumer reads earliest and decodes [OK]

Common Mistakes:

• Creating producer or consumer without bootstrap_servers
• Sending string instead of bytes
• Not setting auto_offset_reset to 'earliest'
• Not decoding message bytes before printing