Cross-datacenter replication in Kafka - Mini Project: Build & Apply

Cross-datacenter replication with Kafka

📖 Scenario: You work for a company that has two data centers in different cities. They want to keep data synchronized between these centers using Kafka. This helps keep data safe and available even if one center has problems.

🎯 Goal: You will set up a simple Kafka topic and configure cross-datacenter replication so messages sent in one data center appear in the other.

📋 What You'll Learn

Create a Kafka topic named orders with replication factor 2

Set up a variable source_cluster with the source Kafka cluster address

Write a command to start MirrorMaker to replicate orders from source_cluster

Print the MirrorMaker command to verify the setup

💡 Why This Matters

🌍 Real World

Cross-datacenter replication keeps data safe and available by copying Kafka topics between data centers automatically.

💼 Career

Kafka administrators and DevOps engineers use these skills to ensure reliable data replication and disaster recovery.

1

Create Kafka topic orders

Create a Kafka topic called orders with replication-factor set to 2 and partitions set to 3. Use the command kafka-topics --create with these exact options.

Kafka

# Your code here

Hint

Use the kafka-topics command with --create and specify --topic orders, --partitions 3, and --replication-factor 2.

2

Set source cluster address

Create a variable called source_cluster and set it to the string localhost:9092 which is the address of the source Kafka cluster.

Kafka

kafka-topics --create --topic orders --partitions 3 --replication-factor 2 --bootstrap-server localhost:9092

# Your code here

Hint

Assign the string "localhost:9092" to the variable source_cluster.

3

Write MirrorMaker command for replication

Write a command string called mirror_command that uses kafka-mirror-maker to replicate the orders topic from the source_cluster. Use --consumer.config and --producer.config files named consumer.properties and producer.properties respectively. The command should include --whitelist orders to replicate only the orders topic.

Kafka

kafka-topics --create --topic orders --partitions 3 --replication-factor 2 --bootstrap-server localhost:9092

source_cluster = "localhost:9092"

# Your code here

Hint

Create a string variable mirror_command with the full MirrorMaker command including --consumer.config consumer.properties, --producer.config producer.properties, and --whitelist orders.

4

Print the MirrorMaker command

Print the variable mirror_command to display the full MirrorMaker replication command.

Kafka

kafka-topics --create --topic orders --partitions 3 --replication-factor 2 --bootstrap-server localhost:9092

source_cluster = "localhost:9092"

mirror_command = f"kafka-mirror-maker --consumer.config consumer.properties --producer.config producer.properties --whitelist orders"

# Your code here

Hint

Use print(mirror_command) to show the command.

Practice

1.

What is the main purpose of cross-datacenter replication in Kafka?

easy

A. To copy Kafka topics between clusters for data safety and availability

B. To compress Kafka messages for faster transmission

C. To encrypt Kafka topics for security

D. To delete old Kafka topics automatically

Solution

1. Step 1: Understand the concept of cross-datacenter replication

   Cross-datacenter replication means copying data from one Kafka cluster to another in a different location.

2. Step 2: Identify the main goal of this replication

   The goal is to keep data safe and available even if one cluster fails.

3. Final Answer:

   To copy Kafka topics between clusters for data safety and availability -> Option A

4. Quick Check:

   Replication = Data safety and availability [OK]

Hint: Replication means copying data across clusters for safety [OK]

Common Mistakes:

• Confusing replication with compression
• Thinking replication encrypts data
• Assuming replication deletes data

2.

Which of the following is the correct way to specify the source cluster's bootstrap servers in Kafka MirrorMaker configuration?

consumer.bootstrap.servers = ?

easy

A. "source.kafka.cluster:9092"

B. "target.kafka.cluster:9092"

C. "localhost:2181"

D. "mirror.kafka.cluster:2181"

Solution

1. Step 1: Identify the role of consumer.bootstrap.servers

   This property tells MirrorMaker where to read data from, so it must point to the source Kafka cluster.

2. Step 2: Choose the correct server address for the source cluster

   The source cluster's Kafka broker address is usually in the form host:port, like "source.kafka.cluster:9092".

3. Final Answer:

   "source.kafka.cluster:9092" -> Option A

4. Quick Check:

   consumer.bootstrap.servers = source cluster address [OK]

Hint: Consumer connects to source cluster bootstrap servers [OK]

Common Mistakes:

• Using target cluster address for consumer.bootstrap.servers
• Using ZooKeeper address instead of Kafka broker
• Confusing consumer and producer properties

3.

Given the following MirrorMaker configuration snippet, what will be the value of producer.bootstrap.servers?

consumer.bootstrap.servers=source1.kafka:9092,source2.kafka:9092
producer.bootstrap.servers=target.kafka:9092

medium

A. "source1.kafka:9092,source2.kafka:9092"

B. "target.kafka:9092"

C. "source1.kafka:9092"

D. "localhost:9092"

Solution

1. Step 1: Read the configuration lines carefully

   The snippet shows two properties: consumer.bootstrap.servers and producer.bootstrap.servers with their values.

2. Step 2: Identify the value assigned to producer.bootstrap.servers

   It is explicitly set to "target.kafka:9092" in the second line.

3. Final Answer:

   "target.kafka:9092" -> Option B

4. Quick Check:

   producer.bootstrap.servers = target cluster address [OK]

Hint: Producer connects to target cluster bootstrap servers [OK]

Common Mistakes:

• Mixing consumer and producer server addresses
• Assuming producer uses source cluster address
• Ignoring explicit configuration values

4.

Identify the error in this MirrorMaker consumer configuration:

consumer.bootstrap.servers=target.kafka:9092
consumer.group.id=mirror-group

medium

A. consumer.bootstrap.servers should use port 2181

B. consumer.group.id is missing

C. consumer.bootstrap.servers should point to the source cluster, not target

D. consumer.group.id should be unique per topic

Solution

1. Step 1: Understand the role of consumer.bootstrap.servers

   This property must point to the source Kafka cluster to read data for replication.

2. Step 2: Check the given value

   It incorrectly points to "target.kafka:9092", which is the destination cluster, not the source.

3. Final Answer:

   consumer.bootstrap.servers should point to the source cluster, not target -> Option C

4. Quick Check:

   Consumer connects to source cluster [OK]

Hint: Consumer must connect to source cluster, not target [OK]

Common Mistakes:

• Using target cluster address for consumer.bootstrap.servers
• Confusing ZooKeeper port with Kafka broker port
• Assuming group.id is missing when it is present

5.

You want to replicate only topics starting with logs- from the source cluster to the target cluster using MirrorMaker. Which configuration property should you set to filter these topics?

hard

A. consumer.topic.filter=logs-*

B. producer.topic.filter=logs-*

C. mirror.topic.prefix=logs-

D. consumer.topic.whitelist=logs-*

Solution

1. Step 1: Identify the property to filter topics in MirrorMaker

   MirrorMaker uses consumer.topic.whitelist to specify which topics to consume from the source cluster.

2. Step 2: Match the pattern for topics starting with 'logs-'

   The pattern "logs-*" matches all topics starting with "logs-".

3. Final Answer:

   consumer.topic.whitelist=logs-* -> Option D

4. Quick Check:

   Use consumer.topic.whitelist to filter topics [OK]

Hint: Use consumer.topic.whitelist to select topics by pattern [OK]

Common Mistakes:

• Using producer.topic.filter which does not exist
• Confusing mirror.topic.prefix with filtering
• Using consumer.topic.filter instead of whitelist