Host-based routing in Kubernetes - Practice Problems & Coding Challenges

Challenge - 5 Problems

🧠 Conceptual

intermediate

Understanding Host-based Routing in Kubernetes Ingress

What is the primary purpose of host-based routing in a Kubernetes Ingress resource?

A To route traffic to different backend services based on the requested hostname

B To route traffic based on the client IP address

C To route traffic to services based on the container port number

D To route traffic only to services running on the same node as the Ingress controller

💡 Hint

Think about how Ingress directs requests to different services depending on the URL host.

Host-based routing allows the Ingress controller to send requests to different backend services depending on the hostname in the HTTP request. This enables multiple domains to be served from the same Ingress.

❓ Configuration

intermediate

Identify the Correct Host-based Routing Ingress YAML Snippet

Which Ingress YAML snippet correctly routes traffic to service-a when the host is app.example.com?

A

apiVersion: networking.k8s.io/v1
kind: Ingress
metadata:
  name: example-ingress
spec:
  rules:
  - host: example.com
    http:
      paths:
      - path: /
        pathType: Prefix
        backend:
          service:
            name: service-a
            port:
              number: 80

B

apiVersion: networking.k8s.io/v1
kind: Ingress
metadata:
  name: example-ingress
spec:
  rules:
  - host: app.example.com
    http:
      paths:
      - path: /app
        pathType: Prefix
        backend:
          service:
            name: service-b
            port:
              number: 80

C

apiVersion: networking.k8s.io/v1
kind: Ingress
metadata:
  name: example-ingress
spec:
  rules:
  - host: app.example.com
    http:
      paths:
      - path: /
        pathType: Prefix
        backend:
          service:
            name: service-a
            port:
              number: 80

D

apiVersion: networking.k8s.io/v1
kind: Ingress
metadata:
  name: example-ingress
spec:
  rules:
  - host: app.example.com
    http:
      paths:
      - path: /
        pathType: Exact
        backend:
          service:
            name: service-a
            port:
              number: 8080

💡 Hint

Check the host, path, and port values carefully.

Option C correctly sets the host to app.example.com, the path to / with prefix matching, and routes to service-a on port 80.

💻 Command Output

advanced

Output of kubectl get ingress with Multiple Hosts

Given an Ingress resource with two host rules: app1.example.com routing to service1 and app2.example.com routing to service2, what is the output of kubectl get ingress my-ingress?

Kubernetes

kubectl get ingress my-ingress

A Error from server (NotFound): ingresses.networking.k8s.io "my-ingress" not found

B

NAME         CLASS    HOSTS                       ADDRESS        PORTS   AGE
my-ingress   <none>   app1.example.com              192.168.1.10   80      10m

C

NAME         CLASS    HOSTS                       ADDRESS        PORTS   AGE
my-ingress   <none>   app2.example.com              192.168.1.10   80      10m

D

NAME         CLASS    HOSTS                       ADDRESS        PORTS   AGE
my-ingress   <none>   app1.example.com,app2.example.com   192.168.1.10   80      10m

💡 Hint

Remember that multiple hosts appear comma-separated in the HOSTS column.

The kubectl get ingress command lists all hosts configured in the Ingress resource separated by commas in the HOSTS column.

❓ Troubleshoot

advanced

Troubleshooting Host-based Routing Failure

You have an Ingress configured with host app.example.com routing to service-a. Requests to app.example.com return 404 errors. Which is the most likely cause?

A The service <code>service-a</code> is exposing the wrong port number

B The Ingress controller is not running or not configured properly

C The DNS for <code>app.example.com</code> is not pointing to the Ingress controller's IP

D The pod labels do not match the service selector

💡 Hint

Consider what happens if the Ingress controller is missing or misconfigured.

If the Ingress controller is not running or misconfigured, it cannot route requests, causing 404 errors even if the Ingress resource is correct.

🔀 Workflow

expert

Correct Order to Deploy Host-based Routing Ingress

Arrange the steps in the correct order to deploy host-based routing using Kubernetes Ingress.

A 1,2,3,4

B 3,2,1,4

C 1,3,2,4

D 2,1,3,4

💡 Hint

Think about what must exist before the Ingress can route traffic.

You must first create backend services and deployments, then deploy the Ingress controller, then create the Ingress resource, and finally verify DNS settings.

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