Host-based routing in Kubernetes - Mini Project: Build & Apply

Host-based routing with Kubernetes Ingress

📖 Scenario: You are managing a Kubernetes cluster that hosts multiple web applications. You want to route traffic to different services based on the hostname in the URL. This is called host-based routing.For example, requests to app1.example.com should go to the app1-service, and requests to app2.example.com should go to the app2-service.

🎯 Goal: Create a Kubernetes Ingress resource that routes traffic to two different services based on the hostname in the request.

📋 What You'll Learn

Create a basic Ingress resource with host-based rules

Route app1.example.com to app1-service

Route app2.example.com to app2-service

Use path / for both hosts

Use networking.k8s.io/v1 API version

💡 Why This Matters

🌍 Real World

Host-based routing is used in real Kubernetes clusters to serve multiple websites or apps from the same IP address, saving resources and simplifying DNS management.

💼 Career

Understanding Ingress and host-based routing is essential for Kubernetes administrators and DevOps engineers managing multi-tenant or multi-application environments.

1

Create the basic Ingress skeleton

Create a Kubernetes Ingress resource named host-routing-ingress with API version networking.k8s.io/v1 and kind Ingress. Include metadata with the name and an empty spec section.

Kubernetes

apiVersion: networking.k8s.io/v1
kind: Ingress
metadata:
  name: host-routing-ingress
spec:
  # Your code here

Hint

Start with the basic structure of an Ingress resource. Use apiVersion, kind, metadata with name, and an empty spec.

2

Add host-based routing rules

Inside the spec section, add a rules list with two entries. Each entry should have a host field and an empty http section. Use hosts app1.example.com and app2.example.com.

Kubernetes

apiVersion: networking.k8s.io/v1
kind: Ingress
metadata:
  name: host-routing-ingress
spec:
  # Add rules list with hosts and empty http below
  # Your code here

Hint

Under spec, add rules as a list. Each rule has a host and an http key. Leave http empty for now.

3

Define paths and backend services

For each host in the rules, add an http.paths list with one path. Use path: / and pathType: Prefix. Set the backend.service.name to app1-service for app1.example.com and app2-service for app2.example.com. Use backend.service.port.number: 80.

Kubernetes

apiVersion: networking.k8s.io/v1
kind: Ingress
metadata:
  name: host-routing-ingress
spec:
  rules:
  - host: app1.example.com
    http:
      # Add path and backend for app1-service
      # Your code here
  - host: app2.example.com
    http:
      # Add path and backend for app2-service
      # Your code here

Hint

Each http section needs a paths list with one path. The path is / with pathType: Prefix. The backend points to the correct service name and port 80.

4

Display the complete Ingress YAML

Print the complete Ingress YAML manifest to verify the host-based routing configuration.

Kubernetes

# Print the complete Ingress YAML below
# Your code here

Hint

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

Practice

1. What is the main purpose of host-based routing in Kubernetes Ingress?

easy

A. To encrypt all incoming traffic automatically.

B. To balance traffic evenly across all nodes in the cluster.

C. To monitor the health of backend services.

D. To send traffic to different services based on the website address (host).

Solution

1. Step 1: Understand host-based routing concept

   Host-based routing directs requests to services depending on the host name in the URL.

2. Step 2: Compare options to the concept

   Only To send traffic to different services based on the website address (host). matches this behavior; others describe different features.

3. Final Answer:

   To send traffic to different services based on the website address (host). -> Option D

4. Quick Check:

   Host-based routing = directing traffic by host [OK]

Hint: Host-based routing uses website address to choose service [OK]

Common Mistakes:

• Confusing host-based routing with load balancing
• Thinking it encrypts traffic automatically
• Assuming it monitors service health

2. Which of the following is the correct way to specify host-based routing in a Kubernetes Ingress YAML?

easy

A. spec:
host: example.com
paths:
- path: /
serviceName: my-service
servicePort: 80

B. spec:
rules:
- host: example.com
http:
paths:
- path: /
pathType: Prefix
backend:
service:
name: my-service
port:
number: 80

C. metadata:
host: example.com
spec:
service:
name: my-service
port: 80

D. spec:
rules:
- path: example.com
backend:
serviceName: my-service
servicePort: 80

Solution

1. Step 1: Review Kubernetes Ingress host-based routing syntax

   The correct syntax uses 'rules' with 'host' and 'http.paths' specifying backend service details.

2. Step 2: Match options to correct syntax

   spec: rules: - host: example.com http: paths: - path: / pathType: Prefix backend: service: name: my-service port: number: 80 matches the official Kubernetes Ingress spec format for host-based routing.

3. Final Answer:

   spec: rules: - host: example.com http: paths: - path: / pathType: Prefix backend: service: name: my-service port: number: 80 -> Option B

4. Quick Check:

   Correct Ingress host syntax = spec: rules: - host: example.com http: paths: - path: / pathType: Prefix backend: service: name: my-service port: number: 80 [OK]

Hint: Look for 'rules' with 'host' and 'http.paths' in Ingress YAML [OK]

Common Mistakes:

• Placing 'host' under metadata instead of rules
• Using deprecated 'serviceName' and 'servicePort' keys
• Confusing 'path' with 'host' field

3. Given this Ingress rule snippet, what service will receive traffic for host 'app.example.com'?

spec:
  rules:
  - host: app.example.com
    http:
      paths:
      - path: /app
        pathType: Prefix
        backend:
          service:
            name: app-service
            port:
              number: 8080
      - path: /
        pathType: Prefix
        backend:
          service:
            name: default-service
            port:
              number: 80

medium

A. Traffic to app.example.com with path starting /app goes to app-service; others go to default-service.

B. Traffic to app.example.com is rejected because of duplicate host rules.

C. Traffic to app.example.com goes only to default-service on port 80.

D. All traffic to app.example.com goes to app-service on port 8080.

Solution

1. Step 1: Analyze the Ingress rules for host 'app.example.com'

   The rule for host 'app.example.com' has two paths: '/app' and '/'.

2. Step 2: Understand path matching priority

   Requests with path starting '/app' go to 'app-service' on port 8080; all other paths go to 'default-service' on port 80.

3. Final Answer:

   Traffic to app.example.com with path starting /app goes to app-service; others go to default-service. -> Option A

4. Quick Check:

   Host + path routing = Traffic to app.example.com with path starting /app goes to app-service; others go to default-service. [OK]

Hint: Check host and path rules separately to find matching service [OK]

Common Mistakes:

• Assuming all traffic goes to first service listed
• Thinking duplicate hosts cause rejection
• Ignoring path prefixes in routing

4. You created this Ingress YAML but traffic to 'shop.example.com' is not routed correctly. What is the error?

spec:
  rules:
  - host: shop.example.com
    http:
      paths:
      - path: /shop
        backend:
          serviceName: shop-service
          servicePort: 80

medium

A. The keys 'serviceName' and 'servicePort' are deprecated; use 'service.name' and 'service.port.number'.

B. The host field is missing under metadata.

C. The path should be '/' instead of '/shop'.

D. The Ingress resource must have a selector field.

Solution

1. Step 1: Check Ingress backend service syntax

   Modern Kubernetes Ingress requires 'service.name' and 'service.port.number' keys, not 'serviceName' and 'servicePort'.

2. Step 2: Identify the error in YAML

   The YAML uses deprecated keys causing routing failure.

3. Final Answer:

   The keys 'serviceName' and 'servicePort' are deprecated; use 'service.name' and 'service.port.number'. -> Option A

4. Quick Check:

   Use correct backend service keys = The keys 'serviceName' and 'servicePort' are deprecated; use 'service.name' and 'service.port.number'. [OK]

Hint: Use 'service.name' and 'service.port.number' in Ingress backend [OK]

Common Mistakes:

• Using old 'serviceName' and 'servicePort' keys
• Adding host under metadata instead of rules
• Changing path unnecessarily

5. You want to run two websites, 'blog.example.com' and 'shop.example.com', on the same Kubernetes cluster using one Ingress. How should you configure the Ingress rules for host-based routing?

hard

A. Create one rule with host 'example.com' and use paths '/blog' and '/shop' to route to services.

B. Create separate Ingress resources for each host with identical paths.

C. Create two rules under spec.rules, each with a different host and paths pointing to their respective services.

D. Use a single rule with no host specified and rely on path prefixes only.

Solution

1. Step 1: Understand host-based routing for multiple hosts

   To route traffic by host, define separate rules for each host under spec.rules.

2. Step 2: Compare options for best practice

   Create two rules under spec.rules, each with a different host and paths pointing to their respective services. correctly uses two rules with different hosts and paths to route traffic properly.

3. Final Answer:

   Create two rules under spec.rules, each with a different host and paths pointing to their respective services. -> Option C

4. Quick Check:

   Multiple hosts need separate rules = Create two rules under spec.rules, each with a different host and paths pointing to their respective services. [OK]

Hint: Use separate rules for each host in one Ingress resource [OK]

Common Mistakes:

• Using one host with path prefixes instead of separate hosts
• Creating multiple Ingresses unnecessarily
• Not specifying hosts and relying on paths only