Acknowledgment modes (acks=0, 1, all) in Kafka - Practice Problems & Coding Challenges

Challenge - 5 Problems

❓ Predict Output

intermediate

What is the output when using acks=0?

Consider a Kafka producer configured with acks=0. What is the expected behavior when sending a message?

Kafka

producer.send('topic', b'message')
print('Message sent')

A The producer waits for the broker to confirm the message before printing 'Message sent'.

B The producer retries sending the message until it receives an acknowledgment.

C The producer sends the message and immediately prints 'Message sent' without waiting for any acknowledgment.

D The producer raises an error because acks=0 is invalid.

💡 Hint

Think about what it means to not wait for any acknowledgment from the broker.

With acks=0, the producer does not wait for any acknowledgment from the broker. It sends the message and immediately continues, so 'Message sent' prints right away.

❓ Predict Output

intermediate

What happens with acks=1 when broker is slow?

A Kafka producer is set with acks=1. The broker is slow to respond. What will the producer do?

Kafka

producer.send('topic', b'message')
print('Message sent')

A The producer waits for the leader broker to acknowledge before printing 'Message sent'.

B The producer raises a timeout error immediately.

C The producer waits for all replicas to acknowledge before printing 'Message sent'.

D The producer does not wait and prints 'Message sent' immediately.

💡 Hint

Recall what acks=1 means about waiting for acknowledgments.

With acks=1, the producer waits for the leader broker to confirm the message before continuing. If the broker is slow, the producer waits until it receives the acknowledgment or times out.

❓ Predict Output

advanced

What is the effect of acks=all on message durability?

When a Kafka producer uses acks=all, what is the effect on message durability?

A The message is considered durable after all in-sync replicas have acknowledged it.

B The message is sent without waiting for any acknowledgment, so durability is not guaranteed.

C The message is considered durable only after the leader broker writes it to its local log.

D The message is durable only if the producer retries sending it multiple times.

💡 Hint

Think about what all means in the context of acknowledgments.

With acks=all, the producer waits for all in-sync replicas to confirm the message, ensuring the highest durability.

🧠 Conceptual

advanced

Which acknowledgment mode risks message loss on broker failure?

Among acks=0, acks=1, and acks=all, which mode has the highest risk of message loss if the broker crashes immediately after receiving the message?

A <code>acks=1</code> because it waits only for the leader broker's acknowledgment.

B <code>acks=0</code> because it does not wait for any acknowledgment.

C All modes have the same risk of message loss.

D <code>acks=all</code> because it waits for all replicas and can lose messages if replicas are slow.

💡 Hint

Consider what happens if the producer does not wait for any confirmation.

acks=0 does not wait for any acknowledgment, so if the broker crashes before writing the message, the message is lost.

🔧 Debug

expert

Why does this Kafka producer hang with acks=all?

A Kafka producer is configured with acks=all and sends a message. The program hangs indefinitely. What is the most likely cause?

Kafka

producer = KafkaProducer(acks='all')
producer.send('topic', b'message')
producer.flush()

A The topic does not exist, so the producer immediately raises an error.

B The producer is missing the <code>flush()</code> call, so messages are not sent.

C The <code>acks</code> parameter is invalid and causes a configuration error.

D There are no in-sync replicas available, so the producer waits forever for acknowledgments.

💡 Hint

Think about what acks=all requires from the cluster.

If there are no in-sync replicas available, the producer waits indefinitely for acknowledgments that never come, causing the hang.