Idempotent producer in Kafka - Interactive Code Practice

Practice - 5 Tasks

1fill in blank

easy

Complete the code to enable idempotence in the Kafka producer configuration.

Kafka

Properties props = new Properties();
props.put("bootstrap.servers", "localhost:9092");
props.put("key.serializer", "org.apache.kafka.common.serialization.StringSerializer");
props.put("value.serializer", "org.apache.kafka.common.serialization.StringSerializer");
props.put("[1]", "true");

Drag options to blanks, or click blank then click option'

Aretries

Backs

Cmax.in.flight.requests.per.connection

Denable.idempotence

Attempts:

3 left

💡 Hint

Common Mistakes

Using 'acks' instead of 'enable.idempotence' to enable idempotence.

Setting 'retries' to true, which is invalid.

Confusing 'max.in.flight.requests.per.connection' with the idempotence setting.

Setting 'enable.idempotence' to 'true' enables the idempotent producer feature in Kafka, ensuring exactly-once delivery.

2fill in blank

medium

Complete the code to set the maximum number of retries for the idempotent producer.

Kafka

props.put("[1]", 5);

Drag options to blanks, or click blank then click option'

Aretries

Benable.idempotence

Cacks

Dmax.in.flight.requests.per.connection

Attempts:

3 left

💡 Hint

Common Mistakes

Using 'acks' instead of 'retries' to set retry count.

Setting 'enable.idempotence' to a number instead of a boolean.

Confusing 'max.in.flight.requests.per.connection' with retry count.

The 'retries' configuration sets how many times the producer will retry sending a message if it fails.

3fill in blank

hard

Fix the error in the code to limit the number of in-flight requests for idempotent producer.

Kafka

props.put("max.in.flight.requests.per.connection", [1]);

Drag options to blanks, or click blank then click option'

A5

B"5"

C"true"

Dtrue

Attempts:

3 left

💡 Hint

Common Mistakes

Passing the number as a string instead of an integer.

Using boolean values instead of an integer.

Confusing this setting with 'enable.idempotence'.

The value for 'max.in.flight.requests.per.connection' must be an integer, not a string or boolean.

4fill in blank

hard

Fill both blanks to configure the producer for idempotent delivery with correct acknowledgments.

Kafka

props.put("[1]", "true");
props.put("[2]", "all");

Drag options to blanks, or click blank then click option'

Aenable.idempotence

Backs

Cretries

Dmax.in.flight.requests.per.connection

Attempts:

3 left

💡 Hint

Common Mistakes

Mixing 'retries' with 'acks' in these positions.

Setting 'acks' to a boolean value instead of 'all'.

Not enabling idempotence but setting 'acks' to 'all'.

To ensure idempotent delivery, 'enable.idempotence' must be true and 'acks' set to 'all' for full acknowledgment.

5fill in blank

hard

Fill all three blanks to complete the idempotent producer configuration with retries and in-flight request limits.

Kafka

props.put("[1]", "true");
props.put("[2]", 3);
props.put("[3]", 1);

Drag options to blanks, or click blank then click option'

Aenable.idempotence

Bretries

Cmax.in.flight.requests.per.connection

Dacks

Attempts:

3 left

💡 Hint

Common Mistakes

Setting 'acks' instead of 'max.in.flight.requests.per.connection' for the last blank.

Using string values for numeric settings.

Not enabling idempotence but setting retries and in-flight requests.

Enable idempotence, set retries to 3, and limit max in-flight requests to 1 for safe idempotent producer configuration.

Practice

1.

What is the main purpose of enabling enable.idempotence=true in a Kafka producer?

easy

A. To enable message encryption

B. To prevent duplicate messages from being sent to Kafka topics

C. To compress messages before sending

D. To increase the speed of message delivery

Solution

1. Step 1: Understand idempotence in Kafka producer

   Idempotence means sending the same message multiple times results in only one message stored.

2. Step 2: Identify the effect of enabling idempotence

   Setting enable.idempotence=true ensures no duplicate messages are produced even if retries happen.

3. Final Answer:

   To prevent duplicate messages from being sent to Kafka topics -> Option B

4. Quick Check:

   Idempotence prevents duplicates = D [OK]

Hint: Idempotence means no duplicates sent [OK]

Common Mistakes:

• Confusing idempotence with message speed
• Thinking it compresses messages
• Assuming it encrypts data

2.

Which of the following is the correct way to enable idempotence in Kafka producer configuration?

producerProps = new Properties();
// Which line correctly enables idempotence?

easy

A. producerProps.put("enableIdempotence", true);

B. producerProps.put("idempotent.enable", "true");

C. producerProps.put("enable.idempotence", "true");

D. producerProps.put("enable.idempotence", true);

Solution

1. Step 1: Check Kafka producer config key for idempotence

   The correct key is exactly "enable.idempotence" as a string.

2. Step 2: Check value type and syntax

   Values in Properties must be strings, so "true" as a string is correct.

3. Final Answer:

   producerProps.put("enable.idempotence", "true"); -> Option C

4. Quick Check:

   Correct key and string value = C [OK]

Hint: Use exact key "enable.idempotence" with string "true" [OK]

Common Mistakes:

• Using wrong key name like "idempotent.enable"
• Passing boolean true instead of string "true"
• Using camelCase key instead of dot notation

3.

Given the following Kafka producer configuration snippet, what will be the effect when sending messages?

props.put("enable.idempotence", "true");
props.put("acks", "all");
props.put("retries", Integer.MAX_VALUE);

Choose the best description of the behavior.

medium

A. Messages are guaranteed to be delivered exactly once without duplicates

B. Messages may be duplicated if retries happen

C. Messages will be lost if broker is down

D. Producer will not retry sending messages

Solution

1. Step 1: Analyze idempotence and acks settings

   Enabling idempotence with acks=all ensures leader and replicas confirm message receipt.

2. Step 2: Consider retries setting

   Unlimited retries mean producer will keep trying until success, avoiding message loss or duplicates.

3. Final Answer:

   Messages are guaranteed to be delivered exactly once without duplicates -> Option A

4. Quick Check:

   Idempotence + acks=all + retries = exactly once [OK]

Hint: Idempotence + acks=all + retries = no duplicates [OK]

Common Mistakes:

• Thinking duplicates still happen with idempotence
• Assuming messages can be lost with retries set
• Ignoring the importance of acks=all

4.

Identify the error in this Kafka producer configuration snippet that aims to enable idempotence:

Properties props = new Properties();
props.put("enable.idempotence", true);
props.put("acks", "all");
props.put("retries", 5);

medium

A. The value for "enable.idempotence" should be a string "true", not boolean true

B. "acks" should be set to "1" instead of "all"

C. Retries cannot be set to 5 when idempotence is enabled

D. Properties object cannot be used for Kafka configuration

Solution

1. Step 1: Check the type of value for "enable.idempotence" key

   Kafka Properties expect string values, but here boolean true is used.

2. Step 2: Understand impact of wrong value type

   Using boolean instead of string may cause config to be ignored or error.

3. Final Answer:

   The value for "enable.idempotence" should be a string "true", not boolean true -> Option A

4. Quick Check:

   Config values must be strings = A [OK]

Hint: Config values in Properties must be strings [OK]

Common Mistakes:

• Using boolean true instead of string "true"
• Changing acks to 1 which weakens guarantees
• Thinking retries=5 is invalid with idempotence

5.

You want to ensure your Kafka producer sends messages exactly once even if the network is unstable. Which combination of settings should you use?

// Choose the best configuration combination

hard

A. enable.idempotence=false, acks=1, retries=0

B. enable.idempotence=false, acks=all, retries=Integer.MAX_VALUE

C. enable.idempotence=true, acks=0, retries=3

D. enable.idempotence=true, acks=all, retries=Integer.MAX_VALUE

Solution

1. Step 1: Identify settings for exactly-once delivery

   Idempotence must be enabled to avoid duplicates on retries.

2. Step 2: Check acknowledgement and retry settings

   Setting acks=all ensures full commit, and unlimited retries prevent message loss.

3. Final Answer:

   enable.idempotence=true, acks=all, retries=Integer.MAX_VALUE -> Option D

4. Quick Check:

   Idempotence + acks=all + max retries = exactly once [OK]

Hint: Enable idempotence + acks=all + max retries for exactly once [OK]

Common Mistakes:

• Disabling idempotence but expecting no duplicates
• Using acks=0 or 1 which weakens delivery guarantees
• Setting retries to 0 causing message loss