Kafka on Kubernetes (Strimzi) - Practice Problems & Coding Challenges

Challenge - 5 Problems

🧠 Conceptual

intermediate

Understanding Strimzi Kafka Cluster Custom Resource

Which field in the Strimzi Kafka custom resource defines the number of Kafka broker replicas?

A spec.kafka.brokers.count

B spec.zookeeper.replicas

C metadata.replicas

D spec.kafka.replicas

💡 Hint

Think about where the Kafka broker count is configured inside the Kafka resource spec.

The spec.kafka.replicas field sets how many Kafka broker pods will run. The spec.zookeeper.replicas controls Zookeeper nodes, and metadata.replicas is not a valid field here.

💻 Command Output

intermediate

Output of Kafka Topic List Command in Strimzi

What is the output of this command when run inside a Kafka pod managed by Strimzi?

bin/kafka-topics.sh --bootstrap-server localhost:9092 --list

A No topics found

B Error: Could not connect to bootstrap server

C

my-topic
another-topic

D Usage: kafka-topics.sh [options]

💡 Hint

Assume the Kafka cluster has two topics named 'my-topic' and 'another-topic'.

The command lists all topics in the Kafka cluster. If topics exist, their names are printed line by line.

❓ Configuration

advanced

Correct YAML for Kafka User Authentication with TLS

Which YAML snippet correctly configures a KafkaUser resource with TLS authentication in Strimzi?

A

apiVersion: kafka.strimzi.io/v1beta2
kind: KafkaUser
metadata:
  name: my-user
spec:
  authentication:
    type: tls

B

apiVersion: kafka.strimzi.io/v1beta2
kind: KafkaUser
metadata:
  name: my-user
spec:
  auth:
    type: tls

C

apiVersion: kafka.strimzi.io/v1beta2
kind: KafkaUser
metadata:
  name: my-user
spec:
  authentication:
    tls: true

D

apiVersion: kafka.strimzi.io/v1beta2
kind: KafkaUser
metadata:
  name: my-user
spec:
  authentication:
    type: scram-sha-512

💡 Hint

Look for the correct field names and values for TLS authentication.

The authentication.type field must be set to tls to enable TLS authentication. Option A uses an invalid field auth, B uses invalid tls: true, and D configures SCRAM instead of TLS.

❓ Troubleshoot

advanced

Troubleshooting Kafka Broker CrashLoopBackOff in Strimzi

You see a Kafka broker pod stuck in CrashLoopBackOff after deploying Strimzi Kafka cluster. Which of these is the most likely cause?

A Incorrect TLS certificates or missing secrets for broker authentication

B Zookeeper pods are running normally

C KafkaUser resource is missing

D Kafka topics are empty

💡 Hint

Think about what can cause Kafka broker pods to fail starting repeatedly.

Kafka brokers require valid TLS certificates and secrets to start properly. Missing or invalid certificates cause startup failures and CrashLoopBackOff. Zookeeper running normally or empty topics do not cause broker pod crashes. Missing KafkaUser affects clients, not brokers.

🔀 Workflow

expert

Order of Steps to Upgrade Kafka Cluster with Strimzi

Arrange the correct order of steps to safely upgrade a Kafka cluster managed by Strimzi without downtime.

A 1,3,4,2

B 4,1,2,3

C 4,2,1,3

D 1,4,2,3

💡 Hint

Think about what must be done before changing the cluster and what to verify after.

First, backup data and configs to prevent data loss. Then update the Kafka resource to trigger upgrade. Next, verify new pods are ready. Finally, check cluster health and topic availability to confirm success.

Practice

1. What is the main purpose of Strimzi when running Kafka on Kubernetes?

easy

A. To simplify and automate Kafka cluster management on Kubernetes

B. To replace Kubernetes with a new container orchestration system

C. To provide a graphical user interface for Kafka topics

D. To convert Kafka messages into SQL queries automatically

Solution

1. Step 1: Understand Strimzi's role

   Strimzi is designed to help run Kafka on Kubernetes by managing Kafka clusters easily.

2. Step 2: Identify the correct purpose

   It automates pod management, storage, and recovery, simplifying Kafka operations on Kubernetes.

3. Final Answer:

   To simplify and automate Kafka cluster management on Kubernetes -> Option A

4. Quick Check:

   Strimzi = Kafka automation on Kubernetes [OK]

Hint: Strimzi automates Kafka on Kubernetes, not replaces or adds UI [OK]

Common Mistakes:

• Thinking Strimzi replaces Kubernetes
• Confusing Strimzi with Kafka UI tools
• Assuming Strimzi converts Kafka messages to SQL

2. Which of the following is the correct command to apply a Kafka cluster YAML file named kafka-cluster.yaml using Strimzi on Kubernetes?

easy

A. kubectl run kafka-cluster.yaml

B. strimzi create kafka-cluster.yaml

C. kubectl apply -f kafka-cluster.yaml

D. kafka apply kafka-cluster.yaml

Solution

1. Step 1: Recall how Kubernetes applies YAML files

   Kubernetes uses kubectl apply -f filename.yaml to create or update resources.

2. Step 2: Match the command to Strimzi usage

   Strimzi uses Kubernetes resources, so applying the Kafka cluster YAML is done with kubectl apply -f.

3. Final Answer:

   kubectl apply -f kafka-cluster.yaml -> Option C

4. Quick Check:

   Apply YAML with kubectl apply -f [OK]

Hint: Use kubectl apply -f for YAML files on Kubernetes [OK]

Common Mistakes:

• Using non-existent 'strimzi create' command
• Confusing kubectl run with apply
• Trying to use kafka CLI for Kubernetes YAML

3. Given the following YAML snippet for a Kafka cluster managed by Strimzi:

apiVersion: kafka.strimzi.io/v1beta2
kind: Kafka
metadata:
  name: my-cluster
spec:
  kafka:
    replicas: 3
    storage:
      type: ephemeral
  zookeeper:
    replicas: 3
    storage:
      type: ephemeral

What will be the number of Kafka broker pods created in the Kubernetes cluster?

medium

A. 3

B. 0

C. 6

D. 1

Solution

1. Step 1: Identify Kafka replicas in YAML

   The replicas field under kafka is set to 3, meaning 3 Kafka broker pods.

2. Step 2: Understand pod creation

   Strimzi creates one pod per replica, so 3 Kafka broker pods will be created.

3. Final Answer:

   3 -> Option A

4. Quick Check:

   Kafka replicas = 3 pods [OK]

Hint: Kafka replicas number = Kafka pods count [OK]

Common Mistakes:

• Adding Kafka and Zookeeper replicas together
• Confusing ephemeral storage with pod count
• Assuming default pod count if replicas missing

4. You applied a Kafka cluster YAML with 3 replicas, but only 1 Kafka pod is running. Which of the following is the most likely cause?

medium

A. Kafka storage type is set to ephemeral

B. The YAML file has replicas: 1 under Kafka section

C. Zookeeper replicas are set to 1

D. Strimzi operator is not installed or running

Solution

1. Step 1: Check Kafka replicas in YAML

   If YAML specifies 3 replicas, pod count should be 3, so replicas: 1 is unlikely.

2. Step 2: Consider Strimzi operator role

   Strimzi operator manages Kafka pods. If it is missing or not running, pods won't be created properly.

3. Final Answer:

   Strimzi operator is not installed or running -> Option D

4. Quick Check:

   Operator missing = pods not managed [OK]

Hint: Check Strimzi operator status if pods don't match replicas [OK]

Common Mistakes:

• Blaming Zookeeper replicas for Kafka pod count
• Thinking ephemeral storage stops pod creation
• Assuming YAML replicas value is always correct

5. You want to update your Kafka cluster managed by Strimzi to use persistent storage instead of ephemeral. Which YAML snippet correctly changes the Kafka storage to persistent with 10Gi volume size?

hard

A. storage:
type: persistent-claim
size: 10Gi

B. storage:
type: persistent-claim
volumeClaimTemplate:
spec:
resources:
requests:
storage: 10Gi

C. storage:
type: persistent
size: 10Gi

D. storage:
persistentVolume:
size: 10Gi

Solution

1. Step 1: Understand Strimzi persistent storage syntax

   Strimzi uses persistent-claim type with a volumeClaimTemplate to define PVC size.

2. Step 2: Identify correct YAML structure

   storage: type: persistent-claim volumeClaimTemplate: spec: resources: requests: storage: 10Gi correctly uses volumeClaimTemplate.spec.resources.requests.storage: 10Gi to request 10Gi persistent volume.

3. Final Answer:

   storage: type: persistent-claim volumeClaimTemplate: spec: resources: requests: storage: 10Gi -> Option B

4. Quick Check:

   Persistent storage needs volumeClaimTemplate with size [OK]

Hint: Use volumeClaimTemplate for persistent storage size in Strimzi [OK]

Common Mistakes:

• Using 'size' directly under storage without volumeClaimTemplate
• Using wrong storage type like 'persistent'
• Confusing persistentVolume with persistent-claim