Resource requests and limits in Kubernetes - Mini Project: Build & Apply

Resource requests and limits

📖 Scenario: You are managing a Kubernetes cluster where you want to ensure that your application pods have guaranteed CPU and memory resources. This helps the cluster allocate resources efficiently and prevents pods from using too much or too little.

🎯 Goal: You will create a Kubernetes pod configuration YAML file that sets resource requests and limits for CPU and memory. This ensures your pod has the right amount of resources reserved and capped.

📋 What You'll Learn

Create a pod manifest with metadata name myapp-pod

Add a container named myapp-container using the image nginx

Set resource requests for CPU to 100m and memory to 200Mi

Set resource limits for CPU to 500m and memory to 500Mi

Print the final YAML manifest

💡 Why This Matters

🌍 Real World

Setting resource requests and limits is essential in real Kubernetes clusters to ensure fair resource distribution and stable application performance.

💼 Career

DevOps engineers and site reliability engineers often configure resource requests and limits to optimize cluster resource usage and prevent outages.

1

Create the basic pod manifest

Create a YAML manifest for a pod named myapp-pod with one container named myapp-container using the image nginx. Write the YAML starting with apiVersion: v1 and kind: Pod.

Kubernetes

# Your code here

Hint

Start with the basic pod structure and add metadata and container details.

2

Add resource requests

Add resource requests under the container spec. Set cpu to 100m and memory to 200Mi inside resources.requests.

Kubernetes

apiVersion: v1
kind: Pod
metadata:
  name: myapp-pod
spec:
  containers:
  - name: myapp-container
    image: nginx
    # Add resource requests here

Hint

Indent resource requests correctly under the container.

3

Add resource limits

Add resource limits under the container spec inside resources. Set cpu to 500m and memory to 500Mi inside resources.limits.

Kubernetes

apiVersion: v1
kind: Pod
metadata:
  name: myapp-pod
spec:
  containers:
  - name: myapp-container
    image: nginx
    resources:
      requests:
        cpu: "100m"
        memory: "200Mi"
      # Add resource limits here

Hint

Place limits at the same level as requests under resources.

4

Print the final YAML manifest

Print the complete YAML manifest for the pod with resource requests and limits exactly as created.

Kubernetes

# Your code here

Hint

Use a print statement to output the full YAML manifest as a string.

Practice

1. What does setting a resource request for a container in Kubernetes guarantee?

easy

A. The container will get at least the requested CPU and memory resources.

B. The container can never use more than the requested resources.

C. The container will be restarted if it uses more than the requested resources.

D. The container will share resources equally with all other containers.

Solution

1. Step 1: Understand resource requests in Kubernetes

   Resource requests specify the minimum CPU and memory a container needs to run properly.

2. Step 2: Clarify what is guaranteed by requests

   Kubernetes ensures the container gets at least the requested resources but does not limit usage to that amount.

3. Final Answer:

   The container will get at least the requested CPU and memory resources. -> Option A

4. Quick Check:

   Resource request = minimum guaranteed resources [OK]

Hint: Requests guarantee minimum resources, limits cap maximum [OK]

Common Mistakes:

• Confusing requests with limits
• Thinking requests cap usage
• Assuming requests cause restarts

2. Which of the following is the correct way to specify CPU and memory requests in a Kubernetes Pod YAML?

easy

A. resources:
requests:
cpu: "0.5"
memory: "256MB"

B. resources:
limits:
cpu: 500
memory: 256

C. resources:
requests:
cpu: 500m
memory: 256MiB

D. resources:
requests:
cpu: "500m"
memory: "256Mi"

Solution

1. Step 1: Review correct syntax for resource requests

   CPU requests use millicores with "m" suffix as string, memory uses Mi or Gi units as string.

2. Step 2: Identify correct option

   resources: requests: cpu: "500m" memory: "256Mi" uses "500m" for CPU and "256Mi" for memory correctly as strings.

3. Final Answer:

   resources: requests: cpu: "500m" memory: "256Mi" -> Option D

4. Quick Check:

   CPU in millicores and memory in Mi with quotes [OK]

Hint: Use quotes and correct units like "500m" and "256Mi" [OK]

Common Mistakes:

• Omitting quotes around resource values
• Using wrong units like MB instead of Mi
• Specifying CPU as plain number without m

3. Given this Pod spec snippet, what is the maximum CPU the container can use?

resources:
  requests:
    cpu: "200m"
  limits:
    cpu: "500m"

medium

A. 500 millicores

B. 200 millicores

C. 700 millicores

D. Unlimited CPU

Solution

1. Step 1: Understand CPU requests and limits

   Requests set minimum guaranteed CPU, limits set maximum allowed CPU usage.

2. Step 2: Identify maximum CPU from limits

   The limit is "500m", meaning 500 millicores is the max CPU the container can use.

3. Final Answer:

   500 millicores -> Option A

4. Quick Check:

   CPU limit = max CPU usage [OK]

Hint: Limits define max usage, requests define minimum [OK]

Common Mistakes:

• Confusing requests with limits
• Adding requests and limits incorrectly
• Assuming no max limit if requests set

4. You set a memory limit of 256Mi but forgot to set a memory request. What is the likely effect on your Pod scheduling?

medium

A. The Pod will use unlimited memory since request is missing.

B. The Pod may be scheduled with no guaranteed memory, risking eviction under pressure.

C. The Pod will be scheduled with 256Mi guaranteed memory automatically.

D. The Pod will fail to start due to missing memory request.

Solution

1. Step 1: Understand default behavior when requests are missing

   If memory request is not set, Kubernetes treats it as zero, meaning no guaranteed memory.

2. Step 2: Effect on scheduling and eviction

   Pod may be scheduled but can be evicted if node memory is low because it has no guaranteed reservation.

3. Final Answer:

   The Pod may be scheduled with no guaranteed memory, risking eviction under pressure. -> Option B

4. Quick Check:

   Missing request means no guaranteed resources [OK]

Hint: Always set requests to guarantee resources and avoid eviction [OK]

Common Mistakes:

• Assuming limits imply requests
• Thinking Pod fails without requests
• Believing missing requests mean unlimited resources

5. You want to ensure a container always has at least 100m CPU and 128Mi memory but never uses more than 300m CPU and 256Mi memory. Which is the correct resource configuration snippet?

hard

A. resources:
requests:
cpu: "300m"
memory: "256Mi"
limits:
cpu: "100m"
memory: "128Mi"

B. resources:
limits:
cpu: "100m"
memory: "128Mi"
requests:
cpu: "300m"
memory: "256Mi"

C. resources:
requests:
cpu: "100m"
memory: "128Mi"
limits:
cpu: "300m"
memory: "256Mi"

D. resources:
requests:
cpu: "100"
memory: "128"
limits:
cpu: "300"
memory: "256"

Solution

1. Step 1: Match minimum guaranteed resources to requests

   Requests must be set to 100m CPU and 128Mi memory to guarantee minimum.

2. Step 2: Match maximum allowed resources to limits

   Limits must be set to 300m CPU and 256Mi memory to cap usage.

3. Step 3: Verify correct syntax and order

   resources: requests: cpu: "100m" memory: "128Mi" limits: cpu: "300m" memory: "256Mi" correctly sets requests first, then limits with proper units and quotes.

4. Final Answer:

   resources: requests: cpu: "100m" memory: "128Mi" limits: cpu: "300m" memory: "256Mi" -> Option C

5. Quick Check:

   Requests = min, Limits = max with correct units [OK]

Hint: Requests are min, limits are max; use correct units and quotes [OK]

Common Mistakes:

• Swapping requests and limits
• Omitting units or quotes
• Using plain numbers without units