Database operators example in Kubernetes - Interactive Code Practice

Practice - 5 Tasks

1fill in blank

easy

Complete the code to create a PostgreSQL cluster using the operator.

Kubernetes

apiVersion: postgresql.k8s.enterprisedb.io/v1
kind: Cluster
metadata:
  name: my-postgres
spec:
  instances: [1]

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

A0

B3

C5

D1

Attempts:

3 left

💡 Hint

Common Mistakes

Setting instances to 0 will not create any database pods.

Using a high number like 5 without resources can cause failures.

The instances field sets the number of PostgreSQL instances. Setting it to 1 creates a single instance cluster.

2fill in blank

medium

Complete the code to expose the PostgreSQL service on port 5432.

Kubernetes

apiVersion: v1
kind: Service
metadata:
  name: postgres-service
spec:
  ports:
  - port: [1]
    targetPort: 5432

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

A3306

B5432

C80

D8080

Attempts:

3 left

💡 Hint

Common Mistakes

Using port 80 or 8080 will not connect to PostgreSQL correctly.

Port 3306 is for MySQL, not PostgreSQL.

PostgreSQL uses port 5432 by default. The service port should match this to route traffic correctly.

3fill in blank

hard

Fix the error in the container spec to use the correct image for the PostgreSQL operator.

Kubernetes

spec:
  template:
    spec:
      containers:
      - name: postgres-operator
        image: [1]

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

Ak8s.gcr.io/postgres-operator:latest

Boperator/postgres:1.0

Cpostgres-operator:latest

Dpostgres:latest

Attempts:

3 left

💡 Hint

Common Mistakes

Using the plain postgres image runs the database, not the operator.

Custom or incorrect image names cause deployment failures.

The official PostgreSQL operator image is hosted at k8s.gcr.io/postgres-operator:latest. Using this ensures the operator runs correctly.

4fill in blank

hard

Fill both blanks to define a PersistentVolumeClaim for the PostgreSQL data storage.

Kubernetes

apiVersion: v1
kind: PersistentVolumeClaim
metadata:
  name: postgres-pvc
spec:
  accessModes:
  - [1]
  resources:
    requests:
      storage: [2]

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

AReadWriteOnce

BReadOnlyMany

C10Gi

D1Gi

Attempts:

3 left

💡 Hint

Common Mistakes

Using ReadOnlyMany will prevent writing data.

Setting storage too small may cause out-of-space errors.

ReadWriteOnce allows the volume to be mounted as read-write by a single node, suitable for PostgreSQL. 10Gi sets the storage size to 10 gigabytes.

5fill in blank

hard

Fill all three blanks to create a ConfigMap with database credentials and mount it as environment variables.

Kubernetes

apiVersion: v1
kind: ConfigMap
metadata:
  name: [1]
data:
  POSTGRES_USER: [2]
  POSTGRES_PASSWORD: [3]

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

Adb-config

Badmin

Csecret123

Dpostgres-data

Attempts:

3 left

💡 Hint

Common Mistakes

Using incorrect ConfigMap names breaks environment variable references.

Leaving password empty causes authentication failures.

The ConfigMap named db-config holds the username admin and password secret123 for the PostgreSQL database environment variables.

Practice

1. What is the main purpose of a database operator in Kubernetes?

easy

A. To manually configure database settings using kubectl commands

B. To monitor network traffic between pods

C. To replace the Kubernetes API server

D. To automate database management tasks like backups and scaling

Solution

1. Step 1: Understand the role of operators

   Operators automate complex tasks for applications running in Kubernetes, such as databases.

2. Step 2: Identify database operator tasks

   Database operators handle backups, scaling, and updates automatically without manual intervention.

3. Final Answer:

   To automate database management tasks like backups and scaling -> Option D

4. Quick Check:

   Database operator purpose = automate management [OK]

Hint: Operators automate tasks, not manual configs [OK]

Common Mistakes:

• Thinking operators replace Kubernetes API
• Confusing operators with manual commands
• Assuming operators monitor network traffic

2. Which YAML field is commonly used to specify the database version in a Kubernetes operator manifest?

easy

A. spec.replicas

B. spec.version

C. status.phase

D. metadata.name

Solution

1. Step 1: Review common YAML fields in operator manifests

   Database version is usually set under the spec section to define desired state.

2. Step 2: Identify the correct field for version

   The field spec.version is used to specify which database version to deploy.

3. Final Answer:

   spec.version -> Option B

4. Quick Check:

   Database version field = spec.version [OK]

Hint: Version info is under spec, not metadata or status [OK]

Common Mistakes:

• Using metadata.name for version
• Confusing status.phase with version
• Mistaking spec.replicas for version

3. Given this snippet of a PostgreSQL operator manifest:

apiVersion: postgres-operator.crunchydata.com/v1
kind: PostgresCluster
metadata:
  name: my-postgres
spec:
  instances:
    - replicas: 3
  backups:
    pgbackrest:
      repos:
        - name: repo1
          volume:
            volumeClaimSpec:
              accessModes: ["ReadWriteOnce"]
              resources:
                requests:
                  storage: 10Gi
  version: "14"

What does the replicas: 3 setting do?

medium

A. Sets the backup frequency to 3 times per day

B. Limits the database to 3 connections

C. Creates 3 PostgreSQL instances for high availability

D. Defines 3 storage volumes for backups

Solution

1. Step 1: Understand replicas in Kubernetes

   Replicas define how many copies of a pod or instance run for availability and load balancing.

2. Step 2: Apply to PostgreSQL operator

   replicas: 3 means 3 PostgreSQL instances will run, improving availability.

3. Final Answer:

   Creates 3 PostgreSQL instances for high availability -> Option C

4. Quick Check:

   replicas = number of instances [OK]

Hint: Replicas control instance count, not connections or backups [OK]

Common Mistakes:

• Confusing replicas with connection limits
• Thinking replicas set backup frequency
• Assuming replicas define storage volumes

4. You applied a YAML manifest for a MySQL operator but the pods fail to start. The manifest includes:

spec:
  replicas: 2
  version: "8.0"
  backup:
    enabled: true
    schedule: "0 2 * * *"

What is the likely error in this manifest?

medium

A. The field 'backup' should be 'backups' to match operator schema

B. The version number must be an integer, not a string

C. Replicas cannot be set to 2 for MySQL operator

D. Schedule format is invalid; cron must have 6 fields

Solution

1. Step 1: Check operator schema for backup configuration

   Most database operators expect 'backups' (plural) as the field name, not 'backup'.

2. Step 2: Validate other fields

   Version as string is valid, replicas can be 2, and cron with 5 fields is standard.

3. Final Answer:

   The field 'backup' should be 'backups' to match operator schema -> Option A

4. Quick Check:

   Field names must match operator schema exactly [OK]

Hint: Check exact field names in operator docs [OK]

Common Mistakes:

• Changing version to integer unnecessarily
• Assuming replicas must be 1
• Misunderstanding cron schedule format

5. You want to deploy a MongoDB cluster using a Kubernetes operator that supports automatic backups and scaling. Which combination of YAML fields is essential to enable these features correctly?

hard

A. spec:
replicas: 3
version: "5.0"
backups:
enabled: true
schedule: "0 1 * * *"
autoscaling:
enabled: true
minReplicas: 2
maxReplicas: 5

B. spec:
instances: 3
version: 5
backup:
schedule: daily
scaling:
enabled: yes

C. metadata:
replicas: 3
version: "5.0"
backups:
enabled: false
autoscale:
min: 2
max: 5

D. spec:
replicas: 1
version: "latest"
backup:
enabled: true
schedule: "@daily"
autoscaling:
enabled: false

Solution

1. Step 1: Identify correct field names and types for backups and scaling

   Backups require 'backups' with enabled and schedule fields; autoscaling needs enabled, minReplicas, maxReplicas.

2. Step 2: Compare options for correctness

   spec: replicas: 3 version: "5.0" backups: enabled: true schedule: "0 1 * * *" autoscaling: enabled: true minReplicas: 2 maxReplicas: 5 uses correct field names, proper YAML structure, and valid values for version and schedule.

3. Final Answer:

   spec: replicas: 3 version: "5.0" backups: enabled: true schedule: "0 1 * * *" autoscaling: enabled: true minReplicas: 2 maxReplicas: 5 -> Option A

4. Quick Check:

   Correct fields and values enable features [OK]

Hint: Use exact field names and valid cron schedules [OK]

Common Mistakes:

• Using 'backup' instead of 'backups'
• Incorrect autoscaling field names
• Setting enabled false disables features