First message (produce and consume) in Kafka - Practice Problems & Coding Challenges

Challenge - 5 Problems

❓ Predict Output

intermediate

What is the output of this Kafka producer code?

Consider this Kafka producer code snippet in Python using confluent_kafka. What will it print?

Kafka

from confluent_kafka import Producer

conf = {'bootstrap.servers': 'localhost:9092'}
producer = Producer(conf)

producer.produce('test-topic', key='key1', value='Hello Kafka!')
producer.flush()

print('Message sent')

A TimeoutError

B Message sent

C KeyError

D Hello Kafka!

💡 Hint

The produce method queues the message, and flush sends it. The print statement runs after sending.

The code prints 'Message sent' because the print statement executes after the message is sent. The message itself is sent to Kafka but not printed.

❓ Predict Output

intermediate

What does this Kafka consumer print after consuming one message?

Given this Kafka consumer code in Python, what will it print after receiving one message?

Kafka

from confluent_kafka import Consumer

conf = {
    'bootstrap.servers': 'localhost:9092',
    'group.id': 'mygroup',
    'auto.offset.reset': 'earliest'
}
consumer = Consumer(conf)
consumer.subscribe(['test-topic'])

msg = consumer.poll(1.0)
if msg is None:
    print('No message received')
elif msg.error():
    print(f'Error: {msg.error()}')
else:
    print(f'Received: {msg.value().decode("utf-8")}')
consumer.close()

A Error: KafkaError{code=_TIMED_OUT}

B No message received

C Received: key1

D Received: Hello Kafka!

💡 Hint

The consumer reads the message value, decoding bytes to string.

The consumer prints the message value 'Hello Kafka!' because it consumes the message sent to 'test-topic'.

🔧 Debug

advanced

Why does this Kafka consumer code raise an error?

This Kafka consumer code raises an exception. What is the cause?

Kafka

from confluent_kafka import Consumer

conf = {
    'bootstrap.servers': 'localhost:9092',
    'group.id': 'mygroup'
}
consumer = Consumer(conf)
consumer.subscribe(['test-topic'])

msg = consumer.poll(1.0)
print(msg.value().decode('utf-8'))
consumer.close()

A TimeoutError because poll timeout is too short

B KeyError because 'auto.offset.reset' is missing

C AttributeError because msg is None and msg.value() is called

D TypeError because decode is called on a string

💡 Hint

Check what happens if poll returns None.

If no message is received, poll returns None. Calling msg.value() on None causes an AttributeError.

📝 Syntax

advanced

Which option correctly produces a message with key and value in Kafka?

Which of these Python code snippets correctly produces a Kafka message with key 'user1' and value 'data'?

A producer.produce('topic', key='user1', value='data')

B producer.produce('topic', 'user1', 'data')

C producer.produce(topic='topic', key='user1', value='data')

D producer.produce('topic', key=user1, value=data)

💡 Hint

Remember that key and value must be strings or bytes, and keyword arguments are required.

Option A uses correct keyword arguments with string literals. Option A passes positional arguments incorrectly. Option A uses an invalid keyword argument 'topic'. Option A uses undefined variables.

🚀 Application

expert

How many messages will be consumed by this Kafka consumer loop?

Given this Kafka consumer code, how many messages will it consume before stopping?

Kafka

from confluent_kafka import Consumer

conf = {
    'bootstrap.servers': 'localhost:9092',
    'group.id': 'mygroup',
    'auto.offset.reset': 'earliest'
}
consumer = Consumer(conf)
consumer.subscribe(['test-topic'])

count = 0
while True:
    msg = consumer.poll(0.5)
    if msg is None:
        break
    if msg.error():
        break
    count += 1
consumer.close()
print(count)

A Number of messages currently in 'test-topic' partition(s)

B 0 because poll timeout is too short

C Infinite loop because break conditions are wrong

D 1 because it stops after first message

💡 Hint

The loop stops when poll returns None, which means no more messages are available.

The code counts all available messages in 'test-topic' partitions at the time of consumption. It stops when no more messages are returned.