Consumer configuration in Kafka - Interactive Code Practice

Practice - 5 Tasks

1fill in blank

easy

Complete the code to set the consumer group ID.

Kafka

props.put("group.id", [1]);

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

A"my-group"

B"localhost"

C"auto.offset.reset"

D"enable.auto.commit"

Attempts:

3 left

💡 Hint

Common Mistakes

Using configuration keys instead of a group ID string.

Leaving the group.id unset.

The group.id property sets the consumer group identifier, which is required for consumer coordination.

2fill in blank

medium

Complete the code to configure the consumer to automatically commit offsets.

Kafka

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

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

Aenable.auto.commit

Bauto.offset.reset

Cfetch.min.bytes

Dmax.poll.records

Attempts:

3 left

💡 Hint

Common Mistakes

Confusing auto.offset.reset with enable.auto.commit.

Setting the wrong property key.

The enable.auto.commit property controls whether the consumer automatically commits offsets.

3fill in blank

hard

Fix the error in the code to set the offset reset policy to earliest.

Kafka

props.put("auto.offset.reset", [1]);

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

Atrue

Bearliest

C"latest"

D"earliest"

Attempts:

3 left

💡 Hint

Common Mistakes

Using earliest without quotes causes a syntax error.

Using boolean true instead of a string.

The value must be a string literal "earliest" to set the offset reset policy correctly.

4fill in blank

hard

Fill both blanks to configure the consumer's key and value deserializers.

Kafka

props.put("key.deserializer", [1]);
props.put("value.deserializer", [2]);

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

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

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

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

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

Attempts:

3 left

💡 Hint

Common Mistakes

Mixing different deserializer classes for key and value.

Using deserializers that don't match the data type.

Both key and value deserializers are set to StringDeserializer to read string data.

5fill in blank

hard

Fill all three blanks to create a consumer configuration that disables auto commit, sets group ID, and sets max poll records.

Kafka

props.put("enable.auto.commit", [1]);
props.put("group.id", [2]);
props.put("max.poll.records", [3]);

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

A"false"

B"consumer-group-1"

C"500"

D"true"

Attempts:

3 left

💡 Hint

Common Mistakes

Using boolean false instead of string "false".

Setting max.poll.records as a number instead of string.

Disabling auto commit requires "false", group ID is a string, and max.poll.records is a string number.

Practice

1.

What is the purpose of setting group.id in Kafka consumer configuration?

easy

A. To specify the Kafka broker address

B. To define the message deserializer class

C. To identify the consumer group for coordinating message consumption

D. To set the maximum number of messages to fetch

Solution

1. Step 1: Understand the role of group.id

   The group.id identifies the consumer group that the consumer belongs to, allowing Kafka to coordinate message consumption among multiple consumers.

2. Step 2: Differentiate from other configurations

   Other options like broker address or deserializer do not relate to consumer group coordination.

3. Final Answer:

   To identify the consumer group for coordinating message consumption -> Option C

4. Quick Check:

   group.id = consumer group ID [OK]

Hint: group.id always sets the consumer group name [OK]

Common Mistakes:

• Confusing group.id with broker address
• Thinking group.id sets deserializer
• Assuming group.id controls message fetch size

2.

Which of the following is the correct way to set the Kafka consumer's auto.offset.reset property to start reading from the earliest message?

easy

A. "auto.offset.reset" = "latest"

B. "auto.offset.reset" = "earliest"

C. "auto.offset.reset" = "none"

D. "auto.offset.reset" = "first"

Solution

1. Step 1: Recall valid values for auto.offset.reset

   The valid values are "earliest", "latest", and "none". "earliest" means start from the oldest message.

2. Step 2: Identify the value for reading from earliest

   Setting it to "earliest" makes the consumer read from the beginning if no offset is found.

3. Final Answer:

   "auto.offset.reset" = "earliest" -> Option B

4. Quick Check:

   earliest = start from oldest message [OK]

Hint: earliest means start from oldest message [OK]

Common Mistakes:

• Using "first" which is invalid
• Confusing "latest" with earliest
• Setting "none" expecting to read messages

3.

Given the following Kafka consumer configuration snippet, what will be the output behavior when consuming messages?

props.put("enable.auto.commit", "false");
props.put("auto.offset.reset", "earliest");
props.put("group.id", "my-group");

Assuming this consumer starts fresh with no committed offsets, what happens?

medium

A. Consumer reads messages from the earliest offset but does not auto-commit offsets

B. Consumer reads messages from the latest offset and auto-commits offsets

C. Consumer throws an error due to missing deserializer configuration

D. Consumer reads messages from the earliest offset and auto-commits offsets

Solution

1. Step 1: Analyze enable.auto.commit setting

   It is set to "false", so the consumer will not automatically commit offsets after reading messages.

2. Step 2: Analyze auto.offset.reset and group.id

   With "earliest" and a new group "my-group", the consumer starts reading from the earliest messages available.

3. Final Answer:

   Consumer reads messages from the earliest offset but does not auto-commit offsets -> Option A

4. Quick Check:

   enable.auto.commit=false + earliest = read earliest, no auto commit [OK]

Hint: enable.auto.commit=false means manual offset commit [OK]

Common Mistakes:

• Assuming auto-commit is enabled by default
• Confusing earliest with latest offset reset
• Expecting error without deserializer (not shown here)

4.

Identify the error in this Kafka consumer configuration snippet:

Properties props = new Properties();
props.put("bootstrap.servers", "localhost:9092");
props.put("group.id", "test-group");
props.put("enable.auto.commit", true);
props.put("key.deserializer", "org.apache.kafka.common.serialization.StringDeserializer");
props.put("value.deserializer", "org.apache.kafka.common.serialization.StringDeserializer");

medium

A. "enable.auto.commit" should be a String "true", not boolean true

B. "group.id" is missing and must be added

C. "bootstrap.servers" value is incorrect format

D. Deserializers should be set to IntegerDeserializer

Solution

1. Step 1: Check data types for properties

   Kafka consumer properties expect String values, so "enable.auto.commit" should be set as "true" (a String), not boolean true.

2. Step 2: Verify other properties

   "group.id" is present, "bootstrap.servers" format is correct, and deserializers are valid for String keys and values.

3. Final Answer:

   "enable.auto.commit" should be a String "true", not boolean true -> Option A

4. Quick Check:

   Properties values must be Strings [OK]

Hint: Property values must be strings, not booleans [OK]

Common Mistakes:

• Using boolean true instead of "true" string
• Omitting group.id property
• Incorrect bootstrap.servers format
• Wrong deserializer class for String data

5.

You want a Kafka consumer to read messages from multiple topics and manually commit offsets only after processing batches successfully. Which configuration settings should you use?

hard

A. "auto.offset.reset" = "latest" and use consumer.assign() for topics

B. "enable.auto.commit" = "true" and assign partitions manually

C. "enable.auto.commit" = "false" and set auto.offset.reset to "none"

D. "enable.auto.commit" = "false" and subscribe to multiple topics with consumer.subscribe(List.of(...))

Solution

1. Step 1: Understand manual offset commit requirement

   Setting "enable.auto.commit" to "false" disables automatic commits, allowing manual control after processing.

2. Step 2: Subscribe to multiple topics

   Using consumer.subscribe(List.of(...)) allows subscribing to multiple topics easily.

3. Step 3: Evaluate other options

   "enable.auto.commit" = "true" and assign partitions manually enables auto commit which conflicts with manual commit need; "auto.offset.reset" = "latest" and use consumer.assign() for topics uses latest offset reset which may skip old messages; "enable.auto.commit" = "false" and set auto.offset.reset to "none" sets offset reset to "none" which causes errors if no offset found.

4. Final Answer:

   "enable.auto.commit" = "false" and subscribe to multiple topics with consumer.subscribe(List.of(...)) -> Option D

5. Quick Check:

   manual commit + subscribe multiple topics = "enable.auto.commit" = "false" and subscribe to multiple topics with consumer.subscribe(List.of(...)) [OK]

Hint: Disable auto commit and subscribe to topics for manual control [OK]

Common Mistakes:

• Enabling auto commit when manual commit is needed
• Using assign() instead of subscribe() for multiple topics
• Setting auto.offset.reset to "none" causing errors