First message (produce and consume) in Kafka - Mini Project: Build & Apply

First message (produce and consume)

📖 Scenario: You are working with Apache Kafka to send and receive messages between applications. Kafka uses topics to organize messages. In this project, you will create a simple Kafka producer to send a message and a Kafka consumer to receive it.

🎯 Goal: Build a Kafka producer that sends a message to a topic called first_topic and a Kafka consumer that reads and prints that message.

📋 What You'll Learn

Create a Kafka producer that sends the message 'Hello Kafka!' to the topic first_topic.

Create a Kafka consumer that subscribes to first_topic and reads messages.

Print the received message to the console.

💡 Why This Matters

🌍 Real World

Kafka is widely used for building real-time data pipelines and streaming apps. Sending and receiving messages is the core of Kafka's communication.

💼 Career

Understanding Kafka producers and consumers is essential for roles in data engineering, backend development, and real-time analytics.

1

Create Kafka producer and send message

Create a Kafka producer using the KafkaProducer class from kafka-python. Send the message 'Hello Kafka!' to the topic 'first_topic'. Use bootstrap_servers=['localhost:9092'] when creating the producer.

Kafka

# Your code here to create producer and send message

Hint

Use KafkaProducer to create the producer. The message must be bytes, so prefix the string with b.

2

Create Kafka consumer and subscribe to topic

Create a Kafka consumer using the KafkaConsumer class from kafka-python. Subscribe the consumer to the topic 'first_topic'. Use bootstrap_servers=['localhost:9092'] when creating the consumer.

Kafka

from kafka import KafkaConsumer

# Your code here to create consumer and subscribe to 'first_topic'

Hint

Use KafkaConsumer('first_topic', bootstrap_servers=['localhost:9092'], auto_offset_reset='earliest') to create and subscribe in one step.

3

Read message from consumer

Use a for loop to read messages from the consumer. Inside the loop, get the message value using message.value. Decode the bytes to a string using .decode('utf-8').

Kafka

# Your code here to read messages from consumer and decode them

Hint

Use a for loop to get messages. Decode the message bytes to string.

4

Print the received message

Print the decoded message stored in the variable text using print(text).

Kafka

# Your code here to print the message

Hint

Use print(text) to show the message on the screen.

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