HTTP probe configuration in Kubernetes - Mini Project: Build & Apply

HTTP Probe Configuration in Kubernetes

📖 Scenario: You are deploying a web application in Kubernetes. To ensure your app is running and healthy, you need to configure an HTTP readiness probe. This probe will check if the app is ready to serve traffic by sending HTTP requests to a specific path.

🎯 Goal: Configure an HTTP readiness probe in a Kubernetes Pod manifest that checks the /health endpoint on port 8080.

📋 What You'll Learn

Create a Pod manifest with a container named webapp using the image nginx:latest.

Add an HTTP readiness probe to the container that sends requests to /health on port 8080.

Set the probe's initial delay to 5 seconds and period to 10 seconds.

Print the final Pod manifest YAML.

💡 Why This Matters

🌍 Real World

HTTP probes help Kubernetes know when your app is ready to receive traffic and when it needs restarting, improving reliability.

💼 Career

Configuring readiness and liveness probes is a common task for DevOps engineers and site reliability engineers managing Kubernetes workloads.

1

Create the basic Pod manifest

Create a Kubernetes Pod manifest named pod.yaml with a spec that includes one container named webapp using the image nginx:latest. Do not add any probes yet.

Kubernetes

apiVersion: v1
kind: Pod
metadata:
  name: webapp-pod
spec:
  containers:
  - name: webapp
    image: nginx:latest
    # Your code here

Hint

Start with the basic Pod structure and add one container named webapp with the nginx:latest image.

2

Add the HTTP readiness probe configuration

Add a readinessProbe section under the webapp container. Configure it to use an httpGet action that targets path: /health and port: 8080.

Kubernetes

apiVersion: v1
kind: Pod
metadata:
  name: webapp-pod
spec:
  containers:
  - name: webapp
    image: nginx:latest
    # Add readinessProbe with httpGet to /health on port 8080
    # Your code here

Hint

Use readinessProbe with httpGet specifying the path and port.

3

Set initial delay and period for the readiness probe

Under the readinessProbe, add initialDelaySeconds: 5 and periodSeconds: 10 to control when the probe starts and how often it runs.

Kubernetes

apiVersion: v1
kind: Pod
metadata:
  name: webapp-pod
spec:
  containers:
  - name: webapp
    image: nginx:latest
    readinessProbe:
      httpGet:
        path: /health
        port: 8080
      # Add initialDelaySeconds and periodSeconds
      # Your code here

Hint

These settings tell Kubernetes to wait 5 seconds before the first probe and then check every 10 seconds.

4

Print the final Pod manifest

Print the complete Pod manifest YAML to verify your HTTP readiness probe configuration.

Kubernetes

# Print the Pod manifest YAML
# Your code here

Hint

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

Practice

1. What is the main purpose of an HTTP probe in Kubernetes?

easy

A. To deploy new versions of the application automatically

B. To store application logs for debugging

C. To check if the application is running and responding to HTTP requests

D. To manage network traffic between pods

Solution

1. Step 1: Understand the role of HTTP probes

   HTTP probes send HTTP requests to the app to check if it is alive and ready.

2. Step 2: Identify the correct purpose

   Only To check if the application is running and responding to HTTP requests describes checking app health via HTTP requests.

3. Final Answer:

   To check if the application is running and responding to HTTP requests -> Option C

4. Quick Check:

   HTTP probe purpose = health check [OK]

Hint: HTTP probes test app health by sending HTTP requests [OK]

Common Mistakes:

• Confusing probes with deployment or logging
• Thinking probes manage network traffic
• Assuming probes store logs

2. Which of the following is the correct syntax to define an HTTP liveness probe in a Kubernetes pod spec?

easy

A. livenessProbe:
exec:
command: ["curl", "/healthz"]
initialDelaySeconds: 5
periodSeconds: 10

B. livenessProbe:
httpGet:
path: /healthz
port: 8080
initialDelaySeconds: 5
periodSeconds: 10

C. livenessProbe:
tcpSocket:
port: 8080
initialDelaySeconds: 5
periodSeconds: 10

D. livenessProbe:
httpGet:
url: http://localhost:8080/healthz
initialDelaySeconds: 5
periodSeconds: 10

Solution

1. Step 1: Review HTTP probe syntax

   The correct HTTP probe uses httpGet with path and port keys.

2. Step 2: Identify the correct YAML structure

   livenessProbe: httpGet: path: /healthz port: 8080 initialDelaySeconds: 5 periodSeconds: 10 correctly uses httpGet with path and port. livenessProbe: httpGet: url: http://localhost:8080/healthz initialDelaySeconds: 5 periodSeconds: 10 is invalid because url is not a valid key.

3. Final Answer:

   Correct HTTP liveness probe syntax with httpGet, path, and port -> Option B

4. Quick Check:

   httpGet uses path and port keys [OK]

Hint: Use httpGet with path and port, not url [OK]

Common Mistakes:

• Using 'url' instead of 'path' in httpGet
• Confusing exec or tcpSocket probes with httpGet
• Wrong indentation or missing keys

3. Given this probe configuration snippet in a pod spec:

livenessProbe:
  httpGet:
    path: /status
    port: 8080
  initialDelaySeconds: 10
  periodSeconds: 5

What will Kubernetes do after the pod starts?

medium

A. Send an HTTP GET to /status only once after 10 seconds

B. Send an HTTP GET to /status immediately, then every 10 seconds

C. Wait 5 seconds, then send an HTTP GET to /status every 10 seconds

D. Wait 10 seconds, then send an HTTP GET to /status every 5 seconds

Solution

1. Step 1: Understand initialDelaySeconds

   This value tells Kubernetes to wait 10 seconds after pod start before first probe.

2. Step 2: Understand periodSeconds

   This value sets the interval between probes, here every 5 seconds.

3. Final Answer:

   Wait 10 seconds, then send an HTTP GET to /status every 5 seconds -> Option D

4. Quick Check:

   initialDelaySeconds = wait, periodSeconds = repeat interval [OK]

Hint: initialDelaySeconds = wait before first probe, periodSeconds = probe interval [OK]

Common Mistakes:

• Confusing initialDelaySeconds with periodSeconds
• Assuming immediate probe on pod start
• Mixing up timing values

4. You configured this HTTP readiness probe:

readinessProbe:
  httpGet:
    path: /ready
    port: 80
  initialDelaySeconds: 5
  periodSeconds: 10
  timeoutSeconds: 2

But Kubernetes marks the pod as not ready even though the app is healthy. What is the likely problem?

medium

A. The probe path /ready is incorrect or not handled by the app

B. initialDelaySeconds is too high, delaying readiness

C. timeoutSeconds is too long, causing probe to fail

D. periodSeconds is too short, causing probe overload

Solution

1. Step 1: Check probe path correctness

   If the app does not respond correctly to /ready, probe fails and pod is not ready.

2. Step 2: Evaluate timing parameters

   initialDelaySeconds of 5 is reasonable; timeoutSeconds of 2 is short but typical; periodSeconds of 10 is normal.

3. Final Answer:

   The probe path /ready is incorrect or not handled by the app -> Option A

4. Quick Check:

   Probe path must match app endpoint [OK]

Hint: Check if probe path matches app endpoint exactly [OK]

Common Mistakes:

• Ignoring probe path correctness
• Changing timing values unnecessarily
• Assuming timeoutSeconds causes readiness failure

5. You want to configure a Kubernetes HTTP readiness probe that waits 15 seconds after container start, then checks the path /health every 3 seconds, but fails the pod if no response within 1 second. Which is the correct probe configuration snippet?

hard

A. readinessProbe:
httpGet:
path: /health
port: 8080
initialDelaySeconds: 15
periodSeconds: 3
timeoutSeconds: 1

B. readinessProbe:
httpGet:
path: /health
port: 8080
initialDelaySeconds: 3
periodSeconds: 15
timeoutSeconds: 1

C. readinessProbe:
httpGet:
path: /health
port: 8080
initialDelaySeconds: 15
periodSeconds: 1
timeoutSeconds: 3

D. readinessProbe:
httpGet:
path: /health
port: 8080
initialDelaySeconds: 1
periodSeconds: 15
timeoutSeconds: 3

Solution

1. Step 1: Match initialDelaySeconds to 15 seconds

   The probe must wait 15 seconds before first check, so initialDelaySeconds: 15.

2. Step 2: Set periodSeconds to 3 seconds and timeoutSeconds to 1 second

   Checks happen every 3 seconds, and timeout is 1 second as required.

3. Final Answer:

   Correct probe with initialDelaySeconds 15, periodSeconds 3, timeoutSeconds 1 -> Option A

4. Quick Check:

   initialDelay=15, period=3, timeout=1 matches requirements [OK]

Hint: Match timing values exactly to requirements [OK]

Common Mistakes:

• Swapping initialDelaySeconds and periodSeconds
• Setting timeoutSeconds longer than periodSeconds
• Using wrong path or port