CPU requests and limits in Kubernetes - Interactive Code Practice

Practice - 5 Tasks

1fill in blank

easy

Complete the code to set a CPU request of 500m in the container spec.

Kubernetes

resources:
  requests:
    cpu: [1]

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

A500

B0.5

C1

D500m

Attempts:

3 left

💡 Hint

Common Mistakes

Using '0.5' instead of '500m' (equivalent, but task expects millicores notation).

Using '500' means 500 cores, which is too large.

CPU requests can be specified in millicores, so 500m means 0.5 CPU cores. Note: 0.5 is equivalent.

2fill in blank

medium

Complete the code to set a CPU limit of 1 core in the container spec.

Kubernetes

resources:
  limits:
    cpu: [1]

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

A1

B1000m

C1m

D0.1

Attempts:

3 left

💡 Hint

Common Mistakes

Using '1m' means 0.001 CPU, which is too low.

Using '0.1' is valid but not the requested 1 core.

The CPU limit can be set as 1 to mean 1 full CPU core. Note: 1000m is equivalent.

3fill in blank

hard

Fix the error in the CPU request value to be valid.

Kubernetes

resources:
  requests:
    cpu: [1]

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

A500

B500m

C0.5

Dfive hundred

Attempts:

3 left

💡 Hint

Common Mistakes

Using '500' means 500 cores, which is too large.

Using words like 'five hundred' is invalid.

CPU requests can be specified in cores or millicores like 500m (0.5 cores). Plain numbers like '500' are valid but mean 500 cores, usually too large. Note: 0.5 is equivalent to 500m.

4fill in blank

hard

Fill both blanks to set CPU request to 250m and CPU limit to 500m.

Kubernetes

resources:
  requests:
    cpu: [1]
  limits:
    cpu: [2]

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

A250m

B500m

C1

D100m

Attempts:

3 left

💡 Hint

Common Mistakes

Swapping request and limit values.

Using whole numbers instead of millicores.

CPU request is set to 250m (0.25 cores) and limit to 500m (0.5 cores).

5fill in blank

hard

Fill all three blanks to set CPU request to 100m, CPU limit to 200m, and memory limit to 512Mi.

Kubernetes

resources:
  requests:
    cpu: [1]
  limits:
    cpu: [2]
    memory: [3]

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

A100m

B200m

C512Mi

D1Gi

Attempts:

3 left

💡 Hint

Common Mistakes

Using '512M' instead of '512Mi' for memory.

Mixing CPU and memory units.

CPU request is 100m, CPU limit is 200m, and memory limit is 512Mi.

Practice

1. What does setting a cpu request in a Kubernetes pod specification do?

easy

A. It guarantees a minimum amount of CPU for the container.

B. It limits the maximum CPU the container can use.

C. It sets the CPU priority for the container.

D. It reserves memory for the container.

Solution

1. Step 1: Understand CPU request meaning

   CPU request is the minimum CPU resource Kubernetes guarantees to a container.

2. Step 2: Differentiate from CPU limit

   CPU limit sets the maximum CPU usage, not the minimum guaranteed.

3. Final Answer:

   It guarantees a minimum amount of CPU for the container. -> Option A

4. Quick Check:

   CPU request = minimum CPU guaranteed [OK]

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

Common Mistakes:

• Confusing CPU request with CPU limit
• Thinking requests set maximum CPU
• Mixing CPU with memory resource

2. Which of the following is the correct way to specify CPU requests and limits in a pod YAML?

easy

A. resources:
cpu:
request: 500m
limit: 1

B. resources:
requests:
cpu: 500
limits:
cpu: 1000

C. resources:
requests:
cpu: "500m"
limits:
cpu: "1"

D. resources:
requests:
cpu: "1.0"
limits:
cpu: "0.5"

Solution

1. Step 1: Check correct YAML structure for resources

   The correct keys are requests and limits under resources, with CPU values as strings with units like "500m" or "1".

2. Step 2: Validate resources: requests: cpu: "500m" limits: cpu: "1" format

   resources: requests: cpu: "500m" limits: cpu: "1" uses correct keys and units: "500m" means 0.5 CPU, "1" means 1 CPU core.

3. Final Answer:

   resources: requests: cpu: "500m" limits: cpu: "1" -> Option C

4. Quick Check:

   Correct YAML keys and CPU units = resources: requests: cpu: "500m" limits: cpu: "1" [OK]

Hint: Use 'requests' and 'limits' keys with CPU as string with units [OK]

Common Mistakes:

• Using 'request' instead of 'requests'
• Specifying CPU as numbers without quotes or units
• Mixing up 'cpu' and 'memory' keys

3. Given this pod spec snippet:

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

What happens if the container tries to use 600m CPU?

medium

A. The container will be killed immediately.

B. The container will be throttled to 500m CPU.

C. The container will be allowed to use 600m CPU.

D. The container will be throttled to 200m CPU.

Solution

1. Step 1: Understand CPU limit effect

   The CPU limit is the maximum CPU the container can use. Here it is 500m (0.5 CPU).

2. Step 2: Predict container behavior when exceeding limit

   If the container tries to use 600m CPU, Kubernetes throttles it to the limit, 500m CPU.

3. Final Answer:

   The container will be throttled to 500m CPU. -> Option B

4. Quick Check:

   CPU limit caps usage = throttled to 500m [OK]

Hint: CPU usage above limit gets throttled to limit [OK]

Common Mistakes:

• Thinking container can exceed CPU limit
• Confusing throttling with killing container
• Assuming CPU request is the max limit

4. You wrote this pod spec:

resources:
  requests:
    cpu: "100m"
  limits:
    cpu: "50m"

What is wrong with this configuration?

medium

A. CPU requests and limits cannot be set together.

B. CPU request is less than CPU limit, which is invalid.

C. CPU values must be integers, not strings.

D. CPU limit is less than CPU request, which is invalid.

Solution

1. Step 1: Compare CPU request and limit values

   CPU request is 100m (0.1 CPU), CPU limit is 50m (0.05 CPU).

2. Step 2: Validate Kubernetes rules for requests and limits

   CPU limit must be equal or greater than CPU request. Here limit < request, which is invalid.

3. Final Answer:

   CPU limit is less than CPU request, which is invalid. -> Option D

4. Quick Check:

   Limit >= Request rule violated = CPU limit is less than CPU request, which is invalid. [OK]

Hint: Limit must be >= request, else config is invalid [OK]

Common Mistakes:

• Setting limit less than request
• Thinking CPU values must be integers
• Believing requests and limits can't coexist

5. You want to ensure a container always gets at least 250m CPU but never uses more than 750m CPU. Which YAML snippet correctly sets this with CPU requests and limits?

hard

A. resources:
requests:
cpu: "250m"
limits:
cpu: "750m"

B. resources:
requests:
cpu: "750m"
limits:
cpu: "250m"

C. resources:
requests:
cpu: 0.25
limits:
cpu: 0.75

D. resources:
requests:
cpu: "0.75"
limits:
cpu: "0.25"

Solution

1. Step 1: Identify correct CPU units and values

   CPU values can be specified as millicores with 'm' suffix, e.g., "250m" for 0.25 CPU.

2. Step 2: Check request and limit order

   Request must be less than or equal to limit. resources: requests: cpu: "250m" limits: cpu: "750m" sets request to 250m and limit to 750m correctly.

3. Final Answer:

   resources: requests: cpu: "250m" limits: cpu: "750m" -> Option A

4. Quick Check:

   Request 250m ≤ Limit 750m with correct units = resources: requests: cpu: "250m" limits: cpu: "750m" [OK]

Hint: Use millicores with 'm' and keep request ≤ limit [OK]

Common Mistakes:

• Swapping request and limit values
• Using decimal numbers without quotes
• Not using millicores for fractional CPU