Host-based routing in Kubernetes - Cheat Sheet & Quick Revision

Recall & Review

beginner

What is host-based routing in Kubernetes?

Host-based routing directs incoming traffic to different services based on the hostname in the request URL. It helps serve multiple websites or apps from the same IP address.

beginner

Which Kubernetes resource is commonly used to configure host-based routing?

The Ingress resource is used to define rules for host-based routing, specifying which hostnames map to which backend services.

intermediate

How does host-based routing differ from path-based routing?

Host-based routing uses the hostname (like example.com) to route traffic, while path-based routing uses the URL path (like /app1 or /app2) to decide where to send traffic.

beginner

What is a simple example of an Ingress rule for host-based routing?

An Ingress rule that sends traffic for host 'app.example.com' to service 'app-service' on port 80.

beginner

Why is host-based routing useful in real life?

It lets you run multiple websites or apps on one server or IP address, saving resources and making management easier.

Which Kubernetes resource is primarily used to implement host-based routing?

A Service

B Ingress

C Pod

D ConfigMap

Ingress defines rules for routing external traffic based on hostnames or paths.

Host-based routing directs traffic based on which part of the request?

A URL path

B IP address

C Hostname

D HTTP method

Host-based routing uses the hostname in the URL to decide where to send traffic.

What happens if no host rule matches in an Ingress configuration?

A Ingress controller crashes

B Traffic is dropped

C Traffic is routed randomly

D Traffic is routed to a default backend if configured

Ingress can have a default backend to handle unmatched requests.

Which of these is NOT a benefit of host-based routing?

A Route traffic by URL path

B Save IP addresses

C Serve multiple apps on one IP

D Simplify DNS management

Routing by URL path is path-based routing, not host-based.

In an Ingress rule, where do you specify the hostname for routing?

A spec.rules.host

B metadata.name

C spec.backend.serviceName

D spec.tls.hosts

The hostname is set under spec.rules.host in the Ingress YAML.

Explain how host-based routing works in Kubernetes and why it is useful.

Think about how websites use domain names to decide where to send visitors.

Describe the difference between host-based routing and path-based routing in Kubernetes Ingress.

Consider what part of the URL each routing method uses.

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