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

Recall & Review

beginner

What is path-based routing in Kubernetes?

Path-based routing directs incoming traffic to different backend services based on the URL path in the request. It helps split traffic by URL parts.

beginner

Which Kubernetes resource commonly uses path-based routing?

The Ingress resource uses path-based routing to route traffic to different services depending on the request path.

intermediate

How do you specify path-based routing rules in a Kubernetes Ingress?

You define rules under the 'http' section with 'paths', each having a 'path' and a 'backend' service to route to.

intermediate

What happens if no path matches in a path-based routing rule?

If no path matches, the Ingress controller usually returns a 404 error or routes to a default backend if configured.

beginner

Why is path-based routing useful in microservices?

It allows different microservices to share one domain and route requests to the right service based on URL paths, simplifying access.

In Kubernetes, which resource is primarily used for path-based routing?

A ConfigMap

B Ingress

C Pod

D ServiceAccount

Ingress is the Kubernetes resource designed to manage external access and supports path-based routing.

What does a path-based routing rule in an Ingress specify?

A The resource limits for a pod

B The container image to use

C The URL path and the backend service to route to

D The node where the pod runs

Path-based routing rules define which URL paths route to which backend services.

If a request URL path does not match any path in the Ingress rules, what usually happens?

A The request is routed to all backends

B The pod restarts

C The request is ignored silently

D The request is routed to a default backend or returns 404

Ingress controllers return 404 or use a default backend if no path matches.

Which section in an Ingress YAML defines path-based routing rules?

A spec.rules.http.paths

B metadata.labels

C spec.template.spec.containers

D status.loadBalancer

The 'spec.rules.http.paths' section contains the path and backend service definitions.

Why is path-based routing helpful in a microservices architecture?

A It allows multiple services to share one domain with different URL paths

B It increases pod memory

C It automatically scales pods

D It encrypts network traffic

Path-based routing lets different microservices be accessed via different URL paths on the same domain.

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

Think about how URLs decide which service gets the request.

Describe the structure of a path-based routing rule in a Kubernetes Ingress YAML file.

Focus on the YAML keys that define routing.

Practice

1. What does path-based routing in Kubernetes Ingress do?

easy

A. It sends traffic to different services based on URL paths.

B. It balances traffic evenly between all nodes.

C. It encrypts traffic between pods.

D. It schedules pods on specific nodes.

Solution

1. Step 1: Understand Ingress role

   Kubernetes Ingress manages external access to services, often HTTP.

2. Step 2: Identify path-based routing function

   Path-based routing directs requests to services depending on the URL path.

3. Final Answer:

   It sends traffic to different services based on URL paths. -> Option A

4. Quick Check:

   Path-based routing = directing traffic by URL path [OK]

Hint: Remember: path-based routing matches URL paths to services [OK]

Common Mistakes:

• Confusing path-based routing with load balancing
• Thinking it schedules pods
• Assuming it encrypts traffic

2. Which is the correct way to specify a path in a Kubernetes Ingress rule for path-based routing?

easy

A. url: /app
urlType: Prefix

B. route: /app
routeType: Exact

C. servicePath: /app
serviceType: Exact

D. path: /app
pathType: Prefix

Solution

1. Step 1: Recall Ingress rule syntax

   Ingress rules use path and pathType keys to define routing.

2. Step 2: Match correct keys and values

   Correct keys are path and pathType, with values like '/app' and 'Prefix'.

3. Final Answer:

   path: /app pathType: Prefix -> Option D

4. Quick Check:

   Use path and pathType keys for routing [OK]

Hint: Look for 'path' and 'pathType' keys in Ingress rules [OK]

Common Mistakes:

• Using wrong keys like 'route' or 'url'
• Mixing up pathType values
• Missing pathType field

3. Given this Ingress snippet, which service will receive traffic for URL path '/shop/cart'?

rules:
- http:
    paths:
    - path: /shop
      pathType: Prefix
      backend:
        service:
          name: shop-service
          port:
            number: 80
    - path: /blog
      pathType: Prefix
      backend:
        service:
          name: blog-service
          port:
            number: 80

medium

A. blog-service

B. shop-service

C. default backend

D. No service matches

Solution

1. Step 1: Check path matching rules

   Path '/shop/cart' starts with '/shop', matching the first path rule with pathType Prefix.

2. Step 2: Identify backend service

   The matching path routes to 'shop-service' on port 80.

3. Final Answer:

   shop-service -> Option B

4. Quick Check:

   Prefix match '/shop' routes to shop-service [OK]

Hint: Prefix path matches any URL starting with it [OK]

Common Mistakes:

• Choosing blog-service for /shop/cart
• Assuming no match for subpaths
• Confusing default backend with path rules

4. You wrote this Ingress rule but traffic to '/api' is not routed correctly:

paths:
- path: api
  pathType: Prefix
  backend:
    service:
      name: api-service
      port:
        number: 80

What is the likely error?

medium

A. Incorrect pathType value

B. Service name is invalid

C. Missing leading slash in path value

D. Port number must be a string

Solution

1. Step 1: Check path syntax

   Paths must start with a leading slash '/' to match URLs correctly.

2. Step 2: Identify missing slash

   The path is 'api' instead of '/api', so it won't match requests starting with '/api'.

3. Final Answer:

   Missing leading slash in path value -> Option C

4. Quick Check:

   Paths need leading '/' for correct matching [OK]

Hint: Always start path with '/' in Ingress rules [OK]

Common Mistakes:

• Omitting leading slash in path
• Using wrong pathType values
• Assuming port number must be string

5. You want to route traffic so that: - '/app' goes to 'app-service' - '/app/admin' goes to 'admin-service' Which Ingress path rules correctly implement this path-based routing?

hard

A. - path: /app/admin
pathType: Prefix
backend:
service:
name: admin-service
port:
number: 80
- path: /app
pathType: Prefix
backend:
service:
name: app-service
port:
number: 80

B. - path: /app
pathType: Prefix
backend:
service:
name: app-service
port:
number: 80
- path: /app/admin
pathType: Prefix
backend:
service:
name: admin-service
port:
number: 80

C. - path: /app
pathType: Exact
backend:
service:
name: app-service
port:
number: 80
- path: /app/admin
pathType: Exact
backend:
service:
name: admin-service
port:
number: 80

D. - path: /app/admin
pathType: Exact
backend:
service:
name: admin-service
port:
number: 80
- path: /app
pathType: Exact
backend:
service:
name: app-service
port:
number: 80

Solution

1. Step 1: Understand path matching order

   Ingress matches paths in order; more specific paths must come first to avoid being shadowed.

2. Step 2: Check rule order and pathType

   Placing '/app/admin' before '/app' with pathType Prefix ensures '/app/admin' routes to admin-service, others to app-service.

3. Final Answer:

   Place '/app/admin' rule before '/app' rule with Prefix pathType -> Option A

4. Quick Check:

   Order specific paths first for correct routing [OK]

Hint: List longer paths before shorter ones in Ingress rules [OK]

Common Mistakes:

• Placing general path before specific path
• Using Exact pathType causing no subpath matches
• Ignoring rule order importance