In-sync replicas (ISR) in Kafka - Mini Project: Build & Apply

In-sync Replicas (ISR) in Kafka

📖 Scenario: You are managing a Kafka cluster that replicates messages across multiple brokers to keep data safe. You want to understand which replicas are currently in-sync with the leader to ensure data reliability.

🎯 Goal: Build a simple Kafka script that lists the in-sync replicas (ISR) for a given topic partition.

📋 What You'll Learn

Create a dictionary called topic_partitions with one entry: key 'my_topic-0' and value {'replicas': [1, 2, 3], 'leader': 1, 'isr': [1, 2]}

Create a variable called partition_key and set it to 'my_topic-0'

Use a for loop with variable replica to iterate over the replicas and check if each is in the ISR list

Create a list called replica_status that stores strings like 'Replica 1 is in-sync' or 'Replica 3 is out-of-sync'

Print each string in replica_status on a new line

💡 Why This Matters

🌍 Real World

Kafka uses in-sync replicas to ensure data is safely replicated across brokers. Monitoring ISR helps maintain data durability and availability.

💼 Career

Understanding ISR is important for roles like Kafka administrators, DevOps engineers, and backend developers working with distributed systems.

1

Create the topic partition data

Create a dictionary called topic_partitions with one entry: key 'my_topic-0' and value {'replicas': [1, 2, 3], 'leader': 1, 'isr': [1, 2]}

Kafka

# Create the topic_partitions dictionary with the given key and value
# Your code here

Need a hint?

Think of topic_partitions as a map where the key is the topic and partition, and the value is another map with replica info.

2

Set the partition key

Create a variable called partition_key and set it to 'my_topic-0'

Kafka

topic_partitions = {'my_topic-0': {'replicas': [1, 2, 3], 'leader': 1, 'isr': [1, 2]}}
# Create the partition_key variable and assign 'my_topic-0'
# Your code here

Need a hint?

This variable will help us access the data for the specific partition.

3

Check which replicas are in-sync

Use a for loop with variable replica to iterate over the replicas in topic_partitions[partition_key]['replicas'] and check if each replica is in topic_partitions[partition_key]['isr']. Create a list called replica_status that stores strings like 'Replica 1 is in-sync' or 'Replica 3 is out-of-sync'

Kafka

topic_partitions = {'my_topic-0': {'replicas': [1, 2, 3], 'leader': 1, 'isr': [1, 2]}}
partition_key = 'my_topic-0'
# Create replica_status list and fill it by checking each replica's sync status
# Your code here

Need a hint?

Loop over each replica and check if it is in the ISR list. Use an f-string to create the status message.

4

Print the replica sync status

Print each string in the replica_status list on a new line using a for loop

Kafka

topic_partitions = {'my_topic-0': {'replicas': [1, 2, 3], 'leader': 1, 'isr': [1, 2]}}
partition_key = 'my_topic-0'
replica_status = []
for replica in topic_partitions[partition_key]['replicas']:
    in_sync = replica in topic_partitions[partition_key]['isr']
    status = f"Replica {replica} is {'in-sync' if in_sync else 'out-of-sync'}"
    replica_status.append(status)
# Print each replica status on a new line
# Your code here

Need a hint?

Use a simple for loop to print each message in the list.