Written by sumitbhoyar

Kubernetes Ingress

A Kubernetes Ingress is a Kubernetes-managed way to route external HTTP/HTTPS traffic to the right Services inside a cluster using hostnames and URL paths.

1) What this combination is and why the components are used together

Ingress is not a single component—it’s a pattern made of a few pieces that work together:

  • Ingress (resource): a set of routing rules (e.g., api.example.com → API service, /checkout → checkout service).
  • Ingress Controller: the runtime that actually enforces those rules (commonly NGINX, HAProxy, Traefik, or a cloud provider’s controller). Without a controller, Ingress rules do nothing.
  • Service: a stable internal endpoint that points to a set of Pods (your app instances).
  • Load Balancer / Edge entry point: the “front door” that receives traffic from the internet and forwards it to the Ingress controller.
  • DNS + TLS certificates: map domain names to the front door and enable HTTPS.

They’re used together because Kubernetes needs a standard, scalable way to expose multiple services to the outside world without giving each service its own public load balancer.

2) The specific problems this combination solves

A. One “front door” for many services

Without Ingress, teams often expose each service using its own external load balancer. That’s expensive, noisy, and hard to govern. Ingress consolidates traffic through a shared entry point.

B. Routing by hostname and path

Ingress lets you route traffic based on:

  • host (e.g., api.example.com vs shop.example.com)
  • path (e.g., /api vs /static)

This is essential for microservices and for splitting a product into multiple backends cleanly.

C. Centralized HTTPS and edge policies

Ingress commonly becomes the place where you standardize:

  • TLS termination (HTTPS handling)
  • redirects, basic rate limiting, request size limits (controller-dependent)
  • consistent exposure patterns across teams

D. Cleaner separation between app teams and networking

App teams define “how to reach my service” at a high level (Ingress rules), while platform teams manage the controller and edge setup.

3) A high-level integration flow (conceptual)

Think of the flow as two parallel loops: control (how routing rules get applied) and data (how requests flow at runtime).

Control flow (deployment / change)

  1. A team creates or updates an Ingress rule (host/path → service).
  2. The Ingress Controller watches the Kubernetes API for changes.
  3. The controller updates its routing configuration automatically.
  4. The “front door” (often a cloud load balancer) continues to send traffic to the controller.

Data flow (runtime requests)

  1. A client calls https://app.example.com.
  2. DNS resolves that to the public IP/hostname of the cluster’s edge entry point.
  3. The edge forwards the request to the Ingress Controller.
  4. The controller matches host/path rules and forwards to the correct Service.
  5. The Service forwards to one of the backing Pods.
  6. The app may then call datastores/external APIs as needed.

Key point: Ingress is about HTTP/HTTPS routing into the cluster. It does not replace service-to-service routing inside the cluster (that’s usually handled by Services, and sometimes a service mesh).

4) Plain text diagram (main components and flow)

CONTROL PLANE (how rules are applied)
------------------------------------
Dev/CI updates Ingress rules
          |
          v
  Kubernetes API Server
          |
          v
  Ingress Controller (watches rules, updates routing)


DATA PLANE (how requests flow)
-----------------------------
Clients/Users
    |
    v
DNS (app.example.com)
    |
    v
Cloud Load Balancer / Edge IP
    |
    v
Ingress Controller (TLS + routing)
    |
    +----------------------+
    |                      |
    v                      v
Service: web            Service: api
    |                      |
    v                      v
Pods (web)              Pods (api)
    |
    v
Data stores / External systems (DB, cache, queues, third-party APIs)

5) When architects choose this approach—and when they avoid it

Architects choose Ingress when:

  • They need HTTP/HTTPS entry into Kubernetes for multiple services.
  • They want one shared, governed edge instead of many per-service public endpoints.
  • They want consistent TLS handling and a standard exposure pattern.
  • They have microservices and need host/path-based routing.

Architects avoid (or limit) Ingress when:

  • They need to expose non-HTTP protocols (raw TCP/UDP) at scale; Ingress is primarily for HTTP/HTTPS (some controllers can do more, but it’s not the core purpose).
  • They require very advanced edge features and prefer a dedicated API gateway or service mesh ingress pattern (policy enforcement, auth, complex routing, transformations).
  • They are running a tiny cluster with one service and prefer a simpler exposure method.
  • They let Ingress become a dumping ground for app-layer concerns (too much logic at the edge can become fragile and hard to debug).

A common overuse pattern: treating Ingress as an all-purpose traffic management system. It’s best as the cluster’s HTTP entry routing layer, not the place to implement complex product behavior.

6) Architect’s mental shortcut (when this pattern applies)

Use Ingress when you need a shared HTTP/HTTPS “front door” for Kubernetes that routes by host/path to internal Services, centralizes TLS, and reduces per-service load balancer sprawl.

If you hear: “multiple web APIs/apps, one domain strategy, consistent HTTPS, standard routing into the cluster” → Ingress is usually the right default.

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