MirrorMaker 2 concept in Kafka - Practice Problems & Coding Challenges

Challenge - 5 Problems

🧠 Conceptual

intermediate

What is the primary role of MirrorMaker 2 in Kafka?

MirrorMaker 2 is a tool used in Kafka ecosystems. What is its main purpose?

A To manage Kafka topic configurations automatically

B To compress Kafka messages to save storage space

C To monitor Kafka cluster health and performance metrics

D To replicate data between Kafka clusters for disaster recovery and geo-replication

💡 Hint

Think about data movement between clusters.

MirrorMaker 2 is designed to replicate topics between Kafka clusters, enabling disaster recovery and geo-replication.

❓ Predict Output

intermediate

What output does this MirrorMaker 2 configuration produce?

Given this MirrorMaker 2 configuration snippet, what will be the effect?

Kafka

clusters = {
  'primary': {
    'bootstrap.servers': 'primary.kafka:9092'
  },
  'secondary': {
    'bootstrap.servers': 'secondary.kafka:9092'
  }
}

tasks.max = 2

replication.policy.class = org.apache.kafka.connect.mirror.DefaultReplicationPolicy

# Replicate all topics from primary to secondary
source.cluster = primary
target.cluster = secondary

A No topics will be replicated because tasks.max is too low

B Only topics starting with 'primary' will be replicated

C All topics from the primary cluster will be replicated to the secondary cluster

D Topics will be replicated from secondary to primary cluster

💡 Hint

Look at source and target cluster settings.

The configuration sets the source as primary and target as secondary, replicating all topics by default.

🔧 Debug

advanced

Why does this MirrorMaker 2 setup fail to replicate topics?

This MirrorMaker 2 config does not replicate any topics. Identify the cause.

Kafka

clusters = {
  'clusterA': {
    'bootstrap.servers': 'clusterA.kafka:9092'
  },
  'clusterB': {
    'bootstrap.servers': 'clusterB.kafka:9092'
  }
}

tasks.max = 1

replication.policy.class = org.apache.kafka.connect.mirror.DefaultReplicationPolicy

source.cluster = clusterA
target.cluster = clusterB

# Missing topics whitelist filter

A Because no topics are specified in the whitelist, no topics are replicated

B Because tasks.max is set to 1, replication is disabled

C Because replication.policy.class is incorrect, replication fails

D Because source and target clusters are reversed, replication fails

💡 Hint

Check if topics are selected for replication.

MirrorMaker 2 requires a topics whitelist or pattern to know which topics to replicate; without it, no topics are replicated.

📝 Syntax

advanced

Which MirrorMaker 2 configuration snippet is syntactically correct?

Select the configuration snippet that is valid for MirrorMaker 2.

A

clusters = { 'src' => { 'bootstrap.servers' => 'src.kafka:9092' }, 'dest' => { 'bootstrap.servers' => 'dest.kafka:9092' } }
tasks.max=3
source.cluster=src
target.cluster=dest

B

clusters = { 'src': { 'bootstrap.servers': 'src.kafka:9092' }, 'dest': { 'bootstrap.servers': 'dest.kafka:9092' } }
tasks.max=3
source.cluster=src
target.cluster=dest

C

clusters = [ 'src': { 'bootstrap.servers': 'src.kafka:9092' }, 'dest': { 'bootstrap.servers': 'dest.kafka:9092' } ]
tasks.max=3
source.cluster=src
target.cluster=dest

D

clusters = { 'src': { 'bootstrap.servers': 'src.kafka:9092' }, 'dest': { 'bootstrap.servers': 'dest.kafka:9092' } }
tasks.max=three
source.cluster=src
target.cluster=dest

💡 Hint

Look for correct data structure and value types.

Option B uses correct dictionary syntax and numeric value for tasks.max; others have syntax errors or invalid values.

🚀 Application

expert

How does MirrorMaker 2 handle topic offsets during replication?

When MirrorMaker 2 replicates topics between clusters, how does it manage consumer offsets to ensure consumers can continue seamlessly?

A It replicates consumer offsets to the target cluster's __consumer_offsets topic to maintain consumer group state

B It resets all consumer offsets to zero on the target cluster after replication

C It does not replicate offsets; consumers must manually reset offsets on the target cluster

D It stores offsets externally in a separate database outside Kafka

💡 Hint

Think about how consumer groups keep track of their position.

MirrorMaker 2 replicates the __consumer_offsets topic so that consumer groups can continue consuming from the correct position on the target cluster.

Practice

1. What is the main purpose of Kafka MirrorMaker 2?

easy

A. To copy data between Kafka clusters for backup and availability

B. To create new Kafka topics automatically

C. To monitor Kafka cluster health

D. To compress Kafka messages for storage

Solution

1. Step 1: Understand MirrorMaker 2 role

   MirrorMaker 2 is designed to replicate data from one Kafka cluster to another to ensure data safety and availability.

2. Step 2: Compare options with MirrorMaker 2 function

   Only To copy data between Kafka clusters for backup and availability describes copying data between clusters, which matches MirrorMaker 2's purpose.

3. Final Answer:

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

4. Quick Check:

   MirrorMaker 2 purpose = Data replication [OK]

Hint: MirrorMaker 2 copies data between clusters for safety [OK]

Common Mistakes:

• Confusing MirrorMaker 2 with monitoring tools
• Thinking it creates topics automatically
• Assuming it compresses messages

2. Which configuration is required to specify the source Kafka cluster in MirrorMaker 2?

easy

A. producer.bootstrap.servers

B. replica.bootstrap.servers

C. mirror.bootstrap.servers

D. consumer.bootstrap.servers

Solution

1. Step 1: Identify source cluster connection

   MirrorMaker 2 uses consumer configs to read from the source Kafka cluster.

2. Step 2: Match config key to source cluster

   The correct config key for source cluster is consumer.bootstrap.servers, which tells MirrorMaker 2 where to consume data from.

3. Final Answer:

   consumer.bootstrap.servers -> Option D

4. Quick Check:

   Source cluster = consumer.bootstrap.servers [OK]

Hint: Source cluster uses consumer.bootstrap.servers config [OK]

Common Mistakes:

• Using producer.bootstrap.servers for source cluster
• Confusing config keys with mirror.bootstrap.servers
• Assuming replica.bootstrap.servers is valid

3. Given this MirrorMaker 2 config snippet:

{
  "source.cluster.bootstrap.servers": "source:9092",
  "target.cluster.bootstrap.servers": "target:9092",
  "topics": "topicA,topicB",
  "num.streams": 3
}

How many parallel streams will MirrorMaker 2 use to copy data?

medium

A. 3

B. 2

C. 1

D. 4

Solution

1. Step 1: Locate num.streams setting

   The config sets "num.streams" to 3, which controls how many parallel streams MirrorMaker 2 uses.

2. Step 2: Understand effect of num.streams

   More streams mean more parallelism in copying data, so MirrorMaker 2 will use 3 streams here.

3. Final Answer:

   3 -> Option A

4. Quick Check:

   num.streams = 3 [OK]

Hint: Check num.streams value for parallelism count [OK]

Common Mistakes:

• Assuming default 1 stream if not read carefully
• Confusing topics count with streams count
• Ignoring num.streams config

4. You configured MirrorMaker 2 with:

topics = "topic1,topic2"
num.streams = 0

What is the problem with this configuration?

medium

A. topics must be a single topic, not multiple

B. num.streams cannot be zero; it must be at least 1

C. topics should be configured as a list, not a string

D. num.streams must be an even number

Solution

1. Step 1: Check num.streams value validity

   num.streams controls parallel streams and must be at least 1 to work properly.

2. Step 2: Identify error in config

   Setting num.streams to 0 disables streams, causing MirrorMaker 2 to fail or not copy data.

3. Final Answer:

   num.streams cannot be zero; it must be at least 1 -> Option B

4. Quick Check:

   num.streams ≥ 1 required [OK]

Hint: num.streams must be ≥ 1, zero disables copying [OK]

Common Mistakes:

• Thinking topics must be single only
• Assuming num.streams can be zero
• Believing num.streams must be even

5. You want MirrorMaker 2 to replicate only topics starting with "logs-" from source to target cluster. Which config setting achieves this?

hard

A. "topics": "logs-*"

B. "topics": "logs-"

C. "topics.regex": "logs-.*"

D. "topics.regex": "^logs$"

Solution

1. Step 1: Understand topic filtering in MirrorMaker 2

   MirrorMaker 2 supports filtering topics by regex using the "topics.regex" config.

2. Step 2: Match regex to desired pattern

   To match all topics starting with "logs-", the regex "logs-.*" correctly matches any topic beginning with "logs-".

3. Step 3: Compare options

   "topics": "logs-*" uses "topics" with wildcard which is not supported; "topics": "logs-" matches exact topic name; "topics.regex": "^logs$" matches only "logs" exactly.

4. Final Answer:

   "topics.regex": "logs-.*" -> Option C

5. Quick Check:

   Use topics.regex with proper regex for filtering [OK]

Hint: Use topics.regex with regex pattern to filter topics [OK]

Common Mistakes:

• Using wildcard * in topics instead of regex
• Confusing exact match with regex match
• Using incorrect regex that matches wrong topics