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Blue-Green and Canary Deployments with Gateway API

Blue Green Deployment

Kubernetes Gateway API provides native, granular traffic-splitting and header-based routing via the HTTPRoute resource.

Unlike legacy Ingress controllers (which often required proprietary annotations or service-mesh sidecars for traffic weighting), Gateway API allows defining percentage-based Canary/Blue-Green deployments and Header-based test routing directly in the standard API specification.

📺 Video Walkthrough

Traffic Splitting Architecture

graph TD
    Client["Client Request"] --> GW["Gateway (external-gateway)"]
    GW --> HR["HTTPRoute (myapp-route-http)"]
    HR -- "80% Traffic (Weight: 80)" --> Blue["Service V1 (Blue - Stable)"]
    HR -- "20% Traffic (Weight: 20)" --> Green["Service V2 (Green - Canary)"]
    HR -- "Header: traffic=test" --> Red["Service V3 (QA / Preview)"]

HTTPRoute Configuration

bluegreen-httproute.yaml 

apiVersion: gateway.networking.k8s.io/v1
kind: HTTPRoute
metadata:
  name: myapp-route-http
  namespace: default
spec:
  parentRefs:
    - group: gateway.networking.k8s.io
      kind: Gateway
      name: external-gateway
      namespace: gateway
  hostnames:
    - bluegreen.vettom.online
  rules:
    # 1. Header-based routing rule (e.g. QA / Internal testers)
    - matches:
        - headers:
            - name: traffic
              type: Exact
              value: test
      backendRefs:
        - name: myapp-v3-bluegreen
          port: 8080
          weight: 1

    # 2. Percentage-based weighted traffic split (Canary / Blue-Green)
    - matches:
        - path:
            type: PathPrefix
            value: /
      backendRefs:
        - name: myapp-v1-bluegreen
          port: 8080
          weight: 80 # 80% to Blue (V1)
        - name: myapp-v2-bluegreen
          port: 8080
          weight: 20 # 20% to Green (V2)

Executing the Cutover

  1. Canary Phase: Deploy V2 and send 20% of production traffic to monitor error rates and latency.
  2. Full Cutover: Update the weights (myapp-v1-bluegreen: 0, myapp-v2-bluegreen: 100) to seamlessly transition 100% of live traffic without downtime.
  3. Rollback: If anomalies are detected in V2, instantly revert weights (V1: 100, V2: 0).