Priority classes for critical workloads in Kubernetes - Interactive Code Practice

Practice - 5 Tasks

1fill in blank

easy

Complete the code to define a PriorityClass named 'high-priority' with a value of 1000.

Kubernetes

apiVersion: scheduling.k8s.io/v1
kind: PriorityClass
metadata:
  name: high-priority
value: [1]
globalDefault: false
description: "High priority class for critical workloads"

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

A500

B100

C10

D1000

Attempts:

3 left

💡 Hint

Common Mistakes

Using a low priority value like 10 or 100 for critical workloads.

The value field sets the priority number. Higher numbers mean higher priority. Here, 1000 is used for high priority.

2fill in blank

medium

Complete the code to assign the 'high-priority' PriorityClass to a Pod spec.

Kubernetes

apiVersion: v1
kind: Pod
metadata:
  name: critical-pod
spec:
  priorityClassName: [1]
  containers:
  - name: app
    image: nginx

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

Ahigh-priority

Bdefault

Clow-priority

Dsystem-node-critical

Attempts:

3 left

💡 Hint

Common Mistakes

Using 'default' or a non-existent PriorityClass name.

The priorityClassName field assigns the pod to the specified PriorityClass. Here, 'high-priority' is used.

3fill in blank

hard

Fix the error in the PriorityClass definition by completing the missing field.

Kubernetes

apiVersion: scheduling.k8s.io/v1
kind: PriorityClass
metadata:
  name: [1]
value: 1000
globalDefault: false
description: "Critical workload priority"

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

Alow-priority

Bsystem-cluster-critical

Chigh-priority

Ddefault

Attempts:

3 left

💡 Hint

Common Mistakes

Using 'default' or unrelated names causing conflicts.

The metadata.name must be set to the PriorityClass name. Here, 'high-priority' matches the intended critical workload class.

4fill in blank

hard

Fill both blanks to create a PriorityClass with a value of 2000 and set it as the global default.

Kubernetes

apiVersion: scheduling.k8s.io/v1
kind: PriorityClass
metadata:
  name: [1]
value: [2]
globalDefault: true
description: "Default priority for critical workloads"

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

Acritical-default

B1000

C2000

Dhigh-priority

Attempts:

3 left

💡 Hint

Common Mistakes

Using a low value or forgetting to set globalDefault to true.

The name is set to 'critical-default' and value to 2000 for a very high priority. Setting globalDefault to true makes this the default PriorityClass.

5fill in blank

hard

Fill all three blanks to create a Pod spec that uses the 'critical-default' PriorityClass and runs an nginx container.

Kubernetes

apiVersion: v1
kind: Pod
metadata:
  name: [1]
spec:
  priorityClassName: [2]
  containers:
  - name: [3]
    image: nginx

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

Anginx-pod

Bcritical-default

Capp-container

Ddefault

Attempts:

3 left

💡 Hint

Common Mistakes

Using 'default' priorityClassName or mismatching container names.

The pod is named 'nginx-pod', uses the 'critical-default' PriorityClass, and runs a container named 'app-container' with the nginx image.

Practice

1. What does a higher value in a Kubernetes PriorityClass mean?

easy

A. The pod will be scheduled on nodes with more memory.

B. The pod will use less CPU resources.

C. The pod has a higher priority and is more important.

D. The pod will restart automatically on failure.

Solution

1. Step 1: Understand PriorityClass value meaning

   In Kubernetes, the value field in a PriorityClass defines the importance of the pod. Higher values mean higher priority.

2. Step 2: Relate priority to pod importance

   Pods with higher priority are considered more critical and get scheduled before lower priority pods.

3. Final Answer:

   The pod has a higher priority and is more important. -> Option C

4. Quick Check:

   Higher value = higher priority [OK]

Hint: Higher PriorityClass value means more important pod [OK]

Common Mistakes:

• Confusing priority with resource limits
• Thinking priority controls pod restart behavior
• Assuming priority affects node selection by memory

2. Which of the following is the correct YAML snippet to define a PriorityClass named high-priority with value 1000 and globalDefault: false?

easy

A. apiVersion: scheduling.k8s.io/v1
kind: PriorityClass
metadata:
name: high-priority
value: 1000
globalDefault: false
description: "High priority class"

B. apiVersion: v1
kind: PriorityClass
metadata:
name: high-priority
priority: 1000
default: false

C. apiVersion: scheduling.k8s.io/v1
kind: PriorityClass
metadata:
name: high-priority
value: 1000
globalDefault: true
description: "High priority class"

D. apiVersion: scheduling.k8s.io/v1
kind: PriorityClass
metadata:
name: high-priority
value: "1000"
globalDefault: false
description: "High priority class"

Solution

1. Step 1: Check correct apiVersion and kind

   The correct apiVersion for PriorityClass is scheduling.k8s.io/v1 and kind is PriorityClass.

2. Step 2: Verify fields and types

   The field for priority is value (integer), not priority. globalDefault is a boolean. The value must be an integer, not a string.

3. Final Answer:

   YAML with apiVersion scheduling.k8s.io/v1, kind PriorityClass, value 1000 as integer, globalDefault false -> Option A

4. Quick Check:

   Correct apiVersion and value field [OK]

Hint: Use 'value' as integer and correct apiVersion [OK]

Common Mistakes:

• Using wrong apiVersion or kind
• Using 'priority' instead of 'value'
• Setting value as string instead of integer

3. Given this PriorityClass YAML and pod spec, what priority value will the pod have?

apiVersion: scheduling.k8s.io/v1
kind: PriorityClass
metadata:
  name: critical
value: 2000
globalDefault: false
description: "Critical priority"

---

apiVersion: v1
kind: Pod
metadata:
  name: test-pod
spec:
  priorityClassName: critical
  containers:
  - name: app
    image: nginx

medium

A. 1000

B. 2000

C. 0

D. Pod will fail to schedule

Solution

1. Step 1: Identify PriorityClass used by pod

   The pod specifies priorityClassName: critical, so it uses the PriorityClass named 'critical'.

2. Step 2: Find priority value of 'critical'

   The PriorityClass 'critical' has value: 2000, so the pod's priority is 2000.

3. Final Answer:

   2000 -> Option B

4. Quick Check:

   Pod priority matches PriorityClass value [OK]

Hint: Pod priority equals PriorityClass value it references [OK]

Common Mistakes:

• Assuming default priority 0 without PriorityClass
• Confusing priorityClassName with container image
• Thinking pod fails without globalDefault

4. You created a PriorityClass with globalDefault: true but pods without priorityClassName still have priority 0. What is the likely cause?

medium

A. The PriorityClass value is set to 0.

B. globalDefault only works for DaemonSets, not pods.

C. Pods must specify priorityClassName to get any priority.

D. The PriorityClass resource was not applied correctly.

Solution

1. Step 1: Understand globalDefault behavior

   A PriorityClass with globalDefault: true sets the default priority for pods without a specified class.

2. Step 2: Check why pods have priority 0

   If pods still have priority 0, likely the PriorityClass was not created or applied properly, so Kubernetes does not see it as default.

3. Final Answer:

   The PriorityClass resource was not applied correctly. -> Option D

4. Quick Check:

   globalDefault requires correct PriorityClass creation [OK]

Hint: Check if PriorityClass resource is applied when globalDefault fails [OK]

Common Mistakes:

• Assuming pods need priorityClassName despite globalDefault
• Setting globalDefault on PriorityClass with value 0
• Believing globalDefault only applies to DaemonSets

5. You want to ensure that all pods without a specified PriorityClass get a default priority of 500, but also have a critical class with priority 2000. Which YAML snippet correctly sets this up?

hard

A. apiVersion: scheduling.k8s.io/v1
kind: PriorityClass
metadata:
name: default-priority
value: 500
globalDefault: true
description: "Default priority"
---
apiVersion: scheduling.k8s.io/v1
kind: PriorityClass
metadata:
name: critical
value: 2000
globalDefault: false
description: "Critical priority"

B. apiVersion: scheduling.k8s.io/v1
kind: PriorityClass
metadata:
name: critical
value: 2000
globalDefault: true
description: "Critical priority"
---
apiVersion: scheduling.k8s.io/v1
kind: PriorityClass
metadata:
name: default-priority
value: 500
globalDefault: false
description: "Default priority"

C. apiVersion: scheduling.k8s.io/v1
kind: PriorityClass
metadata:
name: default-priority
value: 500
globalDefault: false
description: "Default priority"
---
apiVersion: scheduling.k8s.io/v1
kind: PriorityClass
metadata:
name: critical
value: 2000
globalDefault: true
description: "Critical priority"

D. apiVersion: scheduling.k8s.io/v1
kind: PriorityClass
metadata:
name: default-priority
value: 500
globalDefault: true
description: "Default priority"
---
apiVersion: scheduling.k8s.io/v1
kind: PriorityClass
metadata:
name: critical
value: 2000
globalDefault: true
description: "Critical priority"

Solution

1. Step 1: Identify globalDefault usage

   Only one PriorityClass can have globalDefault: true. This sets the default priority for pods without a class.

2. Step 2: Assign correct priorities

   Set the default-priority class with value 500 and globalDefault true. Set critical class with value 2000 and globalDefault false.

3. Final Answer:

   Default priority 500 with globalDefault true, critical 2000 without globalDefault -> Option A

4. Quick Check:

   Only one globalDefault PriorityClass allowed [OK]

Hint: Only one PriorityClass can have globalDefault true [OK]

Common Mistakes:

• Setting globalDefault true on multiple PriorityClasses
• Confusing which class should be default
• Using same priority value for default and critical