Transactional producer in Kafka - Interactive Code Practice

Practice - 5 Tasks

1fill in blank

easy

Complete the code to initialize the Kafka producer with transactions enabled.

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("enable.idempotence", [1]);
KafkaProducer<String, String> producer = new KafkaProducer<>(props);

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

Afalse

Btrue

C"true"

D"false"

Attempts:

3 left

💡 Hint

Common Mistakes

Using string "true" instead of boolean true

Setting 'enable.idempotence' to false

Omitting the property entirely

To enable transactions, idempotence must be enabled by setting 'enable.idempotence' to true (boolean).

2fill in blank

medium

Complete the code to initialize the transaction with a unique transactional ID.

Kafka

props.put("transactional.id", [1]);
producer.initTransactions();

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

AtransactionalId

Bmy-transactional-id

C"transactionalId"

D"my-transactional-id"

Attempts:

3 left

💡 Hint

Common Mistakes

Not using quotes around the transactional ID string

Using an invalid or empty transactional ID

The transactional ID must be a string, so it needs to be enclosed in quotes.

3fill in blank

hard

Fix the error in starting a transaction before sending messages.

Kafka

producer.[1]();
producer.send(new ProducerRecord<>("my-topic", "key", "value"));
producer.commitTransaction();

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

AbeginTransaction

BstartTransaction

CbeginTransactions

DinitTransaction

Attempts:

3 left

💡 Hint

Common Mistakes

Using 'startTransaction' which does not exist

Using plural 'beginTransactions'

Using 'initTransaction' which is incorrect

The correct method to start a transaction is 'beginTransaction()'.

4fill in blank

hard

Fill both blanks to handle exceptions properly during a transaction.

Kafka

try {
    producer.[1]();
    producer.send(new ProducerRecord<>("my-topic", "key", "value"));
    producer.commitTransaction();
} catch (ProducerFencedException e) {
    producer.close();
} catch (Exception e) {
    producer.[2]();
}

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

AbeginTransaction

BcommitTransaction

CabortTransaction

Dclose

Attempts:

3 left

💡 Hint

Common Mistakes

Calling commitTransaction() in the catch block instead of abortTransaction()

Not handling ProducerFencedException properly

You start the transaction with 'beginTransaction()' and abort it with 'abortTransaction()' on exceptions.

5fill in blank

hard

Fill all three blanks to create a transactional producer, send a message, and commit the transaction.

Kafka

Properties props = new Properties();
props.put("bootstrap.servers", "localhost:9092");
props.put("enable.idempotence", [1]);
props.put("transactional.id", [2]);
KafkaProducer<String, String> producer = new KafkaProducer<>(props);
producer.[3]();
producer.beginTransaction();
producer.send(new ProducerRecord<>("my-topic", "key", "value"));
producer.commitTransaction();

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

Atrue

B"txn-123"

CinitTransactions

DbeginTransaction

Attempts:

3 left

💡 Hint

Common Mistakes

Using 'beginTransaction()' instead of 'initTransactions()' to initialize

Not quoting the transactional ID string

Setting enable.idempotence as a string instead of boolean

Enable idempotence with true, set transactional.id as a string, and initialize transactions before use.

Practice

1.

What is the main purpose of using a transactional producer in Kafka?

easy

A. To compress messages before sending

B. To increase the speed of message delivery

C. To send multiple messages as a single atomic unit

D. To create multiple topics automatically

Solution

1. Step 1: Understand transactional producer role

   Transactional producers ensure that a group of messages are sent together as one unit, so either all succeed or none do.

2. Step 2: Compare options

   Options A, B, and D describe unrelated features like compression, speed, or topic creation, which are not the main purpose of transactions.

3. Final Answer:

   To send multiple messages as a single atomic unit -> Option C

4. Quick Check:

   Transactional producer = atomic message group [OK]

Hint: Transactional producer = all-or-nothing message send [OK]

Common Mistakes:

• Confusing transactions with message compression
• Thinking transactions speed up delivery
• Believing transactions create topics automatically

2.

Which configuration is required to enable transactions in a Kafka producer?

Properties props = new Properties();
props.put("bootstrap.servers", "localhost:9092");
// Which property below is needed for transactions?

easy

A. props.put("max.in.flight.requests.per.connection", "5");

B. props.put("acks", "0");

C. props.put("compression.type", "gzip");

D. props.put("transactional.id", "my-transactional-id");

Solution

1. Step 1: Identify transaction enabling property

   The property "transactional.id" uniquely identifies the producer's transaction and is required to enable transactions.

2. Step 2: Check other options

   Options B, C, and D configure acknowledgments, compression, and request limits, which are unrelated to enabling transactions.

3. Final Answer:

   props.put("transactional.id", "my-transactional-id"); -> Option D

4. Quick Check:

   Enable transactions = set transactional.id [OK]

Hint: Set transactional.id to enable transactions [OK]

Common Mistakes:

• Using acks=0 instead of transactional.id
• Confusing compression with transactions
• Missing transactional.id causes errors

3.

What will be the output of the following Kafka producer code snippet?

producer.initTransactions();
producer.beginTransaction();
producer.send(new ProducerRecord<>("topic", "key1", "value1"));
producer.commitTransaction();
System.out.println("Transaction committed");

Assuming no errors occur, what is printed?

medium

A. Transaction aborted

B. Transaction committed

C. Exception thrown

D. No output

Solution

1. Step 1: Follow transaction flow

   The code initializes transactions, begins one, sends a message, then commits the transaction.

2. Step 2: Check output statement

   After commitTransaction(), it prints "Transaction committed". No errors occur, so this line executes.

3. Final Answer:

   Transaction committed -> Option B

4. Quick Check:

   Commit success prints message [OK]

Hint: commitTransaction() followed by print means success message [OK]

Common Mistakes:

• Assuming commitTransaction() prints automatically
• Confusing abortTransaction() with commitTransaction()
• Expecting no output when print is present

4.

Identify the error in this Kafka transactional producer code snippet:

producer.beginTransaction();
producer.send(new ProducerRecord<>("topic", "key", "value"));
// Missing commit or abort here
producer.close();

medium

A. Missing call to commitTransaction() or abortTransaction() before close()

B. beginTransaction() should be called after send()

C. producer.close() should be called before beginTransaction()

D. ProducerRecord is missing a partition number

Solution

1. Step 1: Check transaction lifecycle

   After beginTransaction() and send(), the code must call commitTransaction() or abortTransaction() to complete the transaction.

2. Step 2: Identify missing step

   The code closes the producer without committing or aborting, which is incorrect and causes errors.

3. Final Answer:

   Missing call to commitTransaction() or abortTransaction() before close() -> Option A

4. Quick Check:

   Transaction must end before close() [OK]

Hint: Always commit or abort before closing producer [OK]

Common Mistakes:

• Skipping commitTransaction() or abortTransaction()
• Calling beginTransaction() after send()
• Ignoring transaction lifecycle rules

5.

You want to send two messages atomically to two different topics using a Kafka transactional producer. Which sequence of calls is correct?

// Assume producer is configured with transactional.id
producer.initTransactions();
// What is the correct order?

hard

A. beginTransaction(); send(topic1); send(topic2); commitTransaction();

B. send(topic1); beginTransaction(); send(topic2); commitTransaction();

C. beginTransaction(); send(topic1); commitTransaction(); send(topic2);

D. send(topic1); send(topic2); beginTransaction(); commitTransaction();

Solution

1. Step 1: Understand transaction boundaries

   beginTransaction() must be called before sending any messages to start the transaction.

2. Step 2: Send all messages within the transaction and then commit

   Both messages must be sent after beginTransaction() and before commitTransaction() to be atomic.

3. Final Answer:

   beginTransaction(); send(topic1); send(topic2); commitTransaction(); -> Option A

4. Quick Check:

   Start transaction, send all, then commit [OK]

Hint: Begin transaction before sends, commit after all sends [OK]

Common Mistakes:

• Sending messages before beginTransaction()
• Committing before all messages sent
• Starting transaction after sending messages