Producer API basics in Kafka - Interactive Code Practice

Practice - 5 Tasks

1fill in blank

easy

Complete the code to create a Kafka producer.

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

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

A"org.apache.kafka.common.serialization.StringSerializer"

B"org.apache.kafka.common.serialization.IntegerSerializer"

C"org.apache.kafka.common.serialization.ByteArraySerializer"

D"org.apache.kafka.common.serialization.LongSerializer"

Attempts:

3 left

💡 Hint

Common Mistakes

Using IntegerSerializer when sending strings.

Forgetting to set value.serializer property.

The value.serializer must be set to StringSerializer to send string messages.

2fill in blank

medium

Complete the code to send a message to topic "my-topic".

Kafka

ProducerRecord<String, String> record = new ProducerRecord<>("my-topic", [1], "Hello Kafka");
producer.send(record);

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

A"key1"

Bnull

C"value1"

D"my-key"

Attempts:

3 left

💡 Hint

Common Mistakes

Using a value instead of a key in the ProducerRecord constructor.

Passing an undefined variable as key.

You can send a message without a key by passing null.

3fill in blank

hard

Fix the error in the code to properly close the producer.

Kafka

producer.[1]();

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

Aclose

Bstop

Cflush

Dshutdown

Attempts:

3 left

💡 Hint

Common Mistakes

Using flush() instead of close(), which does not close the producer.

Using shutdown() or stop(), which are not valid methods.

The close() method properly closes the producer and releases resources.

4fill in blank

hard

Fill both blanks to create a ProducerRecord with a key and value.

Kafka

ProducerRecord<String, String> record = new ProducerRecord<>("my-topic", [1], [2]);

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

A"user1"

B"Hello"

C"World"

D"key1"

Attempts:

3 left

💡 Hint

Common Mistakes

Swapping key and value positions.

Using invalid strings for key or value.

The first blank is the key "user1", the second blank is the value "World".

5fill in blank

hard

Fill all three blanks to send a message and flush the producer.

Kafka

ProducerRecord<String, String> record = new ProducerRecord<>("my-topic", [1], [2]);
producer.send(record);
producer.[3]();

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

A"key123"

B"Kafka Rocks"

Cflush

Dclose

Attempts:

3 left

💡 Hint

Common Mistakes

Using close() instead of flush() before sending more messages.

Mixing up key and value positions.

The key is "key123", the value is "Kafka Rocks", and flush() sends all buffered records.

Practice

1. What is the main purpose of the Kafka Producer API?

easy

A. To send messages to Kafka topics

B. To read messages from Kafka topics

C. To manage Kafka cluster configurations

D. To monitor Kafka broker health

Solution

1. Step 1: Understand Kafka Producer role

   The Producer API is designed to send data to Kafka topics, acting as the message sender.

2. Step 2: Differentiate from other Kafka APIs

   Reading messages is done by the Consumer API, not the Producer API.

3. Final Answer:

   To send messages to Kafka topics -> Option A

4. Quick Check:

   Producer API = send messages [OK]

Hint: Producer API sends data; Consumer API reads data [OK]

Common Mistakes:

• Confusing Producer with Consumer API
• Thinking Producer manages cluster
• Assuming Producer monitors brokers

2. Which of the following is the correct way to create a Kafka Producer in Java?

easy

A. Producer<String> producer = new Producer(props);

B. KafkaProducer producer = new KafkaProducer<>(props);

C. KafkaProducer producer = new KafkaProducer();

D. KafkaProducer producer = KafkaProducer.create(props);

Solution

1. Step 1: Recall KafkaProducer constructor usage

   The KafkaProducer class requires properties and type parameters for key and value types.

2. Step 2: Check each option's syntax

   KafkaProducer producer = new KafkaProducer<>(props); correctly uses generics and constructor with properties. Others miss generics, constructor, or use invalid methods.

3. Final Answer:

   KafkaProducer producer = new KafkaProducer<>(props); -> Option B

4. Quick Check:

   Correct constructor with generics = KafkaProducer producer = new KafkaProducer<>(props); [OK]

Hint: Use new KafkaProducer<>(props) with key and value types [OK]

Common Mistakes:

• Omitting generics for key and value
• Using wrong constructor or method
• Not passing properties object

3. What will be the output of the following Java code snippet?

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");
KafkaProducer producer = new KafkaProducer<>(props);
ProducerRecord record = new ProducerRecord<>("my-topic", "key1", "value1");
producer.send(record);
System.out.println("Message sent");
producer.close();

medium

A. No output

B. Compilation error

C. Message sent

D. Runtime exception due to missing topic

Solution

1. Step 1: Analyze producer setup and send call

   The code sets up properties correctly, creates a producer, and sends a message to "my-topic" with key and value.

2. Step 2: Check output statement and close

   After sending, it prints "Message sent" and closes the producer. No errors expected if Kafka broker is running.

3. Final Answer:

   Message sent -> Option C

4. Quick Check:

   Successful send prints message [OK]

Hint: If send() succeeds, print statement runs [OK]

Common Mistakes:

• Assuming send() is synchronous and blocks
• Thinking missing topic causes error here
• Ignoring need for running Kafka broker

4. Identify the error in this Kafka Producer code snippet:

Properties props = new Properties();
props.put("bootstrap.servers", "localhost:9092");
props.put("key.serializer", "StringSerializer");
props.put("value.serializer", "StringSerializer");
KafkaProducer producer = new KafkaProducer<>(props);
ProducerRecord record = new ProducerRecord<>("topic", "key", "value");
producer.send(record);
producer.close();

medium

A. Missing topic name in ProducerRecord

B. Properties object not initialized

C. Producer not closed properly

D. Incorrect serializer class names

Solution

1. Step 1: Check serializer class names in properties

   The serializer values must be full class names like "org.apache.kafka.common.serialization.StringSerializer".

2. Step 2: Verify other code parts

   Topic name is present, producer is closed properly, and properties object is initialized correctly.

3. Final Answer:

   Incorrect serializer class names -> Option D

4. Quick Check:

   Serializer class names must be full package names [OK]

Hint: Use full serializer class names with package [OK]

Common Mistakes:

• Using short class names without package
• Forgetting to close producer
• Leaving topic name empty

5. You want to send messages with keys to ensure ordering per key in Kafka. Which ProducerRecord constructor should you use?

hard

A. ProducerRecord(String topic, K key, V value)

B. ProducerRecord(String topic, V value)

C. ProducerRecord(K key, V value)

D. ProducerRecord(String topic)

Solution

1. Step 1: Understand ordering by key in Kafka

   Kafka guarantees ordering within a partition, and keys determine partition assignment.

2. Step 2: Identify correct ProducerRecord constructor

   To send with a key, use the constructor that includes topic, key, and value.

3. Final Answer:

   ProducerRecord(String topic, K key, V value) -> Option A

4. Quick Check:

   Use constructor with topic, key, and value for ordering [OK]

Hint: Include key in ProducerRecord to maintain order [OK]

Common Mistakes:

• Using constructor without key loses ordering
• Omitting topic causes errors
• Confusing key and value parameters