Ingress controllers (Nginx, Traefik) in Kubernetes - Step-by-Step Execution

Process Flow - Ingress controllers (Nginx, Traefik)

User sends HTTP request

↓

Ingress Controller receives request

↓

Match request to Ingress rules

↓

Route request to correct Service

↓

Service forwards to Pod

↓

Pod processes and responds

↓

Response sent back to User

The ingress controller receives user requests, matches them to rules, routes to services, and returns responses.

Execution Sample

Kubernetes

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

This Ingress resource routes requests for example.com to example-service on port 80.

Process Table

Step	Action	Ingress Controller	Request Host	Matched Rule	Service Routed	Response
1	User sends HTTP request	Nginx or Traefik listens	example.com	Check rules	None yet	None
2	Ingress Controller receives request	Receives request	example.com	Matches host example.com	None yet	None
3	Match path '/'	Matches path prefix '/'	example.com	Rule matched	example-service	None
4	Route to service	Routes request to example-service:80	example.com	Rule matched	example-service	None
5	Service forwards to Pod	Passes request to Pod	example.com	Rule matched	example-service	None
6	Pod processes request	No action	example.com	Rule matched	example-service	Response generated
7	Response sent back	Ingress Controller sends response	example.com	Rule matched	example-service	200 OK
8	End	Request complete	example.com	Rule matched	example-service	Response delivered

💡 Request processed and response sent back to user.

Status Tracker

Variable	Start	After Step 2	After Step 4	After Step 6	Final
Request Host	None	example.com	example.com	example.com	example.com
Matched Rule	None	None	Rule for example.com / matched	Rule matched	Rule matched
Service Routed	None	None	example-service	example-service	example-service
Response	None	None	None	Generated	200 OK

Key Moments - 3 Insights

How does the ingress controller know which service to send the request to?

The ingress controller checks the host and path in the request against the Ingress rules (see execution_table step 3 and 4). It matches the host 'example.com' and path '/' to route to 'example-service'.

What happens if the request host does not match any Ingress rule?

The ingress controller will not find a matching rule and will typically return a 404 error or default backend response. This is why matching rules are important (refer to execution_table step 2 where matching is checked).

Why do we need an ingress controller like Nginx or Traefik?

Ingress controllers act like traffic managers. They listen for incoming requests and route them inside the cluster based on rules. Without them, external access to services is harder to manage (see concept_flow).

Visual Quiz - 3 Questions

Look at the execution table, at which step does the ingress controller match the request path '/'?

A Step 2

B Step 3

C Step 4

D Step 5

💡 Hint

Check the 'Matched Rule' column in execution_table row for step 3.

According to the variable tracker, what is the value of 'Response' after step 6?

A Generated

B 200 OK

C None

D Rule matched

💡 Hint

Look at the 'Response' row under 'After Step 6' in variable_tracker.

If the request host was 'unknown.com', what would happen according to the flow?

A Request routed to example-service

B Pod processes request anyway

C Ingress controller returns 404 or default response

D Request ignored silently

💡 Hint

Refer to key_moments about unmatched hosts and execution_table step 2.

Concept Snapshot

Ingress controllers receive external HTTP requests.
They match requests by host and path to Ingress rules.
Then route requests to the correct Kubernetes Service.
Nginx and Traefik are popular ingress controllers.
They enable easy external access to cluster services.
Without them, managing traffic is complex.

Full Transcript

Ingress controllers like Nginx and Traefik listen for incoming HTTP requests from users. When a request arrives, the controller checks the host and path against defined Ingress rules. If a match is found, it routes the request to the appropriate Kubernetes Service, which then forwards it to the correct Pod. The Pod processes the request and sends a response back through the ingress controller to the user. If no matching rule exists, the ingress controller returns a 404 or default response. This process allows external traffic to reach internal services in a controlled way.