Ingress resource definition in Kubernetes - Step-by-Step Execution

Process Flow - Ingress resource definition

Define Ingress YAML

↓

Apply YAML with kubectl

↓

Kubernetes creates Ingress resource

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Ingress Controller watches resource

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Ingress Controller configures routing

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External requests routed to services

The flow shows how you write an Ingress YAML, apply it, and how the Ingress Controller uses it to route external traffic to services.

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 YAML defines an Ingress that routes requests for example.com to the example-service on port 80.

Process Table

Step	Action	Resource State	Ingress Controller Reaction	Result
1	Write Ingress YAML	Ingress resource defined but not applied	No reaction	No routing configured
2	kubectl apply ingress.yaml	Ingress resource created in cluster	Ingress Controller detects new resource	Starts processing rules
3	Ingress Controller reads rules	Ingress resource with host example.com and path /	Configures routing rules in controller	Routes external traffic matching example.com to example-service:80
4	External request to example.com arrives	Ingress resource unchanged	Ingress Controller routes request	Request forwarded to example-service on port 80
5	Ingress resource deleted	Ingress resource removed	Ingress Controller removes routing rules	Traffic no longer routed through Ingress

💡 Ingress resource deleted or no longer exists, so routing stops

Status Tracker

Variable	Start	After Step 2	After Step 3	After Step 4	Final
Ingress Resource	undefined	defined in cluster	configured with rules	unchanged	deleted
Ingress Controller State	idle	detects resource	configures routing	routes traffic	removes routing

Key Moments - 3 Insights

Why doesn't the Ingress route traffic immediately after writing the YAML file?

Because the YAML file is only local until applied with kubectl (see execution_table step 1 and 2). The Ingress Controller reacts only after the resource exists in the cluster.

What happens if the Ingress resource is deleted but the service still exists?

The Ingress Controller removes routing rules (execution_table step 5), so external traffic won't reach the service via Ingress anymore.

How does the Ingress Controller know which service to route traffic to?

It reads the backend service name and port from the Ingress rules (execution_table step 3) and configures routing accordingly.

Visual Quiz - 3 Questions

Look at the execution table, at which step does the Ingress Controller start configuring routing rules?

A Step 1

B Step 2

C Step 3

D Step 4

💡 Hint

Check the 'Ingress Controller Reaction' column in execution_table rows

According to the variable tracker, what is the state of the Ingress Resource after Step 3?

A configured with rules

B defined in cluster

C undefined

D deleted

💡 Hint

Look at the 'Ingress Resource' row and 'After Step 3' column in variable_tracker

If the Ingress resource is deleted, what happens to the routing according to the execution table?

A Routing continues as before

B Routing stops because rules are removed

C Ingress Controller adds new rules

D Service is deleted automatically

💡 Hint

See the 'Result' column at Step 5 in execution_table

Concept Snapshot

Ingress resource defines rules to route external HTTP(S) traffic to Kubernetes services.
Write YAML with apiVersion, kind: Ingress, metadata, and spec.rules.
Apply with kubectl to create resource in cluster.
Ingress Controller watches resource and configures routing.
Deleting Ingress removes routing rules.
Ingress routes based on host and path to backend service and port.

Full Transcript

An Ingress resource in Kubernetes is a set of rules that tell the cluster how to route external web traffic to internal services. First, you write a YAML file defining the Ingress with host and path rules pointing to a service and port. Then you apply this YAML using kubectl, which creates the Ingress resource in the cluster. The Ingress Controller watches for these resources and configures itself to route incoming requests matching the rules to the correct service. When the Ingress resource is deleted, the controller removes the routing rules, stopping traffic from being routed through it. This flow ensures external traffic reaches the right service based on the rules you define.