Header Based routing

When you want to isolate the behavior of clients that connect to a canary, you can simply use a different http route as explained in Advanced Deployments.

An alternative method is to use HTTP headers that distinguish which clients connect to the canary and which do not.

Using a custom header with a single route

Here is an example of a rollout that uses headers for the canary:

apiVersion: argoproj.io/v1alpha1
kind: Rollout
metadata:
  name: rollouts-demo
  namespace: default
spec:
  replicas: 5
  strategy:
    canary:
      canaryService: argo-rollouts-canary-service 
      stableService: argo-rollouts-stable-service 
      trafficRouting:
        managedRoutes:
        - name: canary-route1
        - name: canary-route2
        plugins:
          argoproj-labs/gatewayAPI:
            httpRoutes:
              - name: argo-rollouts-http-route
                useHeaderRoutes: true
            namespace: default
      steps:
      - setWeight: 10
      - setHeaderRoute:
          name: canary-route1
          match:
            - headerName: X-Canary-start
              headerValue:
                exact: ten-per-cent      
      - pause: {}      
      - setWeight: 50
      - setHeaderRoute:
          name: canary-route2
          match:
            - headerName: X-Canary-middle
              headerValue:
                exact: half-traffic      
      - pause: {}
      - setWeight: 100
      - pause: {}
  revisionHistoryLimit: 2
  selector:
    matchLabels:
      app: rollouts-demo
  template:
    metadata:
      labels:
        app: rollouts-demo
    spec:
      containers:
        - name: rollouts-demo
          image: <your-image:your-tag>
          ports:
            - name: http
              containerPort: 8080
              protocol: TCP

Notice that the route names used for headers in setHeaderRoute must also be defined in the managedRoutes block as well.

Now when the canary reaches 10% an extra route will be created that uses the X-Canary-start header with value ten-per-cent

When the canary reaches 50% a different header route will be created. At the end of the canary all header routes are discarded.

Using multiple routes with headers

It is also possible to combine multiple routes with custom headers.

Here is an example

apiVersion: argoproj.io/v1alpha1
kind: Rollout
metadata:
  name: rollouts-demo
spec:
  replicas: 4
  revisionHistoryLimit: 2
  selector:
    matchLabels:
      app: rollouts-demo
  strategy:
    canary:
      stableService: stable-service
      canaryService: canary-service
      trafficRouting:
        managedRoutes:
          - name: header-route
          - name: header-route2
        plugins:
          argoproj-labs/gatewayAPI:
            namespace: default                                  
            httpRoutes:
              - name: http-route
                useHeaderRoutes: true
              - name: http-route2
                useHeaderRoutes: true
              - name: http-route3
      steps:
      - setWeight: 20
      - pause: {duration: 10}
      - setWeight: 40
      - pause: {duration: 20}
      - setWeight: 60
      - setHeaderRoute:
          name: header-route
          match:
            - headerName: X-Test
              headerValue:
                exact: test
      - pause: {duration: 10}
      - setHeaderRoute:
          name: header-route2
          match:
            - headerName: X-Test2
              headerValue:
                exact: test
      - pause: {}
      - setWeight: 80
      - setHeaderRoute: # remove header route
          name: header-route
      - pause: {}
  template:
    metadata:
      labels:
        app: rollouts-demo
    spec:
      containers:
      - name: rollouts-demo
        image: <your-image:your-tag>
        ports:
        - name: http
          containerPort: 8080
          protocol: TCP      

With the useHeaderRoutes variable you can decide which routes will honor the custom headers.