Priority classes for critical workloads in Kubernetes - Practice Problems & Coding Challenges

Challenge - 5 Problems

🧠 Conceptual

intermediate

Understanding PriorityClass purpose

What is the main purpose of defining a PriorityClass in Kubernetes?

A To configure persistent storage classes for pods

B To assign a priority value to pods that influences scheduling and eviction order

C To specify resource limits like CPU and memory for pods

D To define network policies for pod communication

💡 Hint

Think about how Kubernetes decides which pods to keep or evict under resource pressure.

PriorityClass assigns a priority number to pods. Higher priority pods are scheduled first and evicted last during resource shortages.

💻 Command Output

intermediate

Output of kubectl get priorityclass

What is the output of the command kubectl get priorityclass if you have two priority classes named high-priority with value 1000 and low-priority with value 100?

A

NAME           VALUE   GLOBAL-DEFAULT   DESCRIPTION
high-priority  1000    false            High priority class
low-priority   100     false            Low priority class

B

NAME           VALUE   GLOBAL-DEFAULT   DESCRIPTION
high-priority  100     false            High priority class
low-priority   1000    false            Low priority class

C

NAME           VALUE   GLOBAL-DEFAULT   DESCRIPTION
low-priority   100     false            Low priority class
high-priority  1000    false            High priority class

D Error: priorityclass not found

💡 Hint

Check the order and values of priority classes as listed by kubectl.

The output lists priority classes by name alphabetically with their correct values and descriptions.

❓ Configuration

advanced

Correct PriorityClass YAML for critical workload

Which YAML snippet correctly defines a PriorityClass named critical with a value of 100000 and sets it as the global default?

A

apiVersion: scheduling.k8s.io/v1
kind: PriorityClass
metadata:
  name: critical
value: 100000
globalDefault: false
description: "Critical priority class"

B

apiVersion: scheduling.k8s.io/v1
kind: PriorityClass
metadata:
  name: critical
spec:
  value: 100000
globalDefault: true
description: "Critical priority class"

C

apiVersion: scheduling.k8s.io/v1
kind: PriorityClass
metadata:
  name: critical
value: "100000"
globalDefault: true
description: "Critical priority class"

D

apiVersion: scheduling.k8s.io/v1
kind: PriorityClass
metadata:
  name: critical
value: 100000
globalDefault: true
description: "Critical priority class"

💡 Hint

Remember that value is a top-level field, not under spec, and globalDefault must be true to set default.

The PriorityClass resource requires value and globalDefault as top-level fields. The value must be an integer, and setting globalDefault: true makes it the default priority.

❓ Troubleshoot

advanced

Pod scheduling failure due to PriorityClass

A pod with PriorityClass critical is stuck in Pending state. The cluster has resource pressure and other pods with lower priority are running. What is the most likely cause?

A The pod's PriorityClass value is lower than other pods running

B The pod's container image is missing

C The PriorityClass <code>critical</code> is not defined in the cluster

D The pod has resource requests higher than node capacity

💡 Hint

Check if the PriorityClass exists and is spelled correctly.

If the PriorityClass is not defined, the pod cannot be scheduled because Kubernetes cannot assign the priority, causing it to remain pending.

✅ Best Practice

expert

Choosing PriorityClass values for critical workloads

When assigning PriorityClass values for critical workloads, which practice is best to ensure proper scheduling and eviction behavior?

A Assign very high values (e.g., 1000000) to critical workloads and low values (e.g., 10) to others, ensuring clear priority separation

B Use the same PriorityClass value for all workloads to avoid scheduling conflicts

C Assign random values to PriorityClass to distribute scheduling evenly

D Set all PriorityClass values to zero and rely on resource requests for scheduling

💡 Hint

Think about how Kubernetes uses priority values to decide which pods to evict first.

Using clearly separated priority values helps Kubernetes decide which pods to evict under resource pressure, protecting critical workloads effectively.