Kubernetes

Understanding Kubernetes Gateway API: A New Era of Traffic Management

Introduction

Kubernetes has revolutionized cloud-native application deployment, but managing ingress and traffic routing has always been a challenge. While the Ingress API has served well, it has limitations in extensibility and flexibility. The Gateway API is the next evolution in Kubernetes traffic management, providing a more structured, extensible, and role-oriented approach to managing network traffic.

What is Kubernetes Gateway API?

Gateway API is an open-source, Kubernetes-native API designed to standardize and enhance the way services handle external and internal traffic. It provides a more expressive, extensible, and role-based model for defining network traffic, replacing the traditional Ingress API.

It introduces Gateway, GatewayClass, Routes, and Backends as key resources, enabling better separation of concerns and interoperability across vendors.

Key Features of Gateway API

  1. Multi-protocol Support Unlike Ingress, which is limited to HTTP/HTTPS, Gateway API supports TCP, UDP, gRPC, WebSockets, and more.
  2. Improved Extensibility Uses Custom Resources (CRDs) for enhanced flexibility, allowing vendors to extend capabilities seamlessly.
  3. Separation of Concerns Different personas (platform teams, developers, security engineers) can configure different parts of the networking stack independently.
  4. Traffic Splitting & Advanced Routing Provides native support for traffic splitting, header-based routing, and weight-based distribution.
  5. Multi-Tenancy Support Enables multiple teams to share networking infrastructure without interference.

Gateway API vs. Ingress API: Key Differences

Feature Ingress API Gateway API
API Group networking.k8s.io gateway.networking.k8s.io
Routing Type HTTP/S HTTP, TCP, UDP, gRPC, WebSockets
Multi-Tenant Support Limited Strong multi-tenancy support
Traffic Splitting Requires Service Mesh Built-in with HTTPRoute
Advanced Routing Basic path/host-based More granular routing options
Extensibility Hard to extend Uses Custom Resources (CRDs) for flexibility

Key Components of Gateway API

  1. GatewayClass

    • Defines the type of Gateway infrastructure (e.g., managed by Istio, Traefik, or NGINX).
    • Similar to StorageClass in Kubernetes storage management.

  2. Gateway

    • Represents an instance of a GatewayClass.
    • Defines listeners, protocols, and ports.

  3. Routes (e.g., HTTPRoute, TCPRoute, GRPCRoute)

    • Defines traffic routing rules.
    • Attaches to a Gateway and directs traffic to Services or other Backends.

  4. Backends

    • Can be Kubernetes Services, external endpoints, or other APIs.

Use Cases for Gateway API

  1. Multi-Tenant Kubernetes Clusters

    • Enables shared infrastructure across multiple teams with strict isolation.

  2. Advanced Traffic Routing

    • Supports path-based, header-based, and weighted traffic routing, without requiring a service mesh.

  3. Hybrid and Multi-Cloud Deployments

    • Works across different cloud providers and on-premises environments using vendor-neutral API definitions.

  4. Security and Policy Enforcement

    • Fine-grained security policies with mTLS, authorization, and rate-limiting built into the API.

Getting Started with Gateway API

1. Install Gateway API CRDs

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kubectl apply -f https://github.com/kubernetes-sigs/gateway-api/releases/latest/download/standard-install.yaml

2. Create a GatewayClass

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apiVersion: gateway.networking.k8s.io/v1beta1
kind: GatewayClass
metadata:
  name: my-gateway-class
spec:
  controllerName: example.com/gateway-controller

3. Deploy a Gateway

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apiVersion: gateway.networking.k8s.io/v1beta1
kind: Gateway
metadata:
  name: my-gateway
spec:
  gatewayClassName: my-gateway-class
  listeners:
  - protocol: HTTP
    port: 80

4. Define an HTTP Route

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apiVersion: gateway.networking.k8s.io/v1beta1
kind: HTTPRoute
metadata:
  name: my-route
spec:
  parentRefs:
  - name: my-gateway
  rules:
  - matches:
    - path:
        type: Prefix
        value: /app
    backendRefs:
    - name: my-service
      port: 80

Conclusion

Gateway API represents a significant leap forward in Kubernetes traffic management. By offering multi-protocol support, enhanced extensibility, and better separation of concerns, it is poised to replace the traditional Ingress API. Organizations looking for more flexibility, security, and scalability in their Kubernetes networking should start exploring Gateway API today.

With its growing adoption and vendor support (Istio, Contour, GKE, etc.), Gateway API is the future of cloud-native networking.