Traffic shifting - based on header

This exercise is built and extended based on the documentation of tetratelabs.io Zero-Downtime Releases

After creating and configuring all objects the diagram will look like this.

• Traffic will arrive on AWS Classic LoadBalancer
• the call will be forwarded to tid-ingressgateway-gw pod
• the traffic will be accepted per Istio Gateway manifest
• based on hostname helloworld.tetrate.io and presence of the header blue-version: on the decision will be made:
  • no header will be send to v1 of helloworld application in green namespace
  • calls with blue-version: on header present will be forwarded to v2 of helloworld application in blue namespace

As first step we will deploy two versions of helloworld sample application instances. (you can use shell script instead of copying the command)

# create namespaces for each version 
kubectl create namespace green
kubectl create namespace blue

# enable istio-injection for each namespace
kubectl label namespace green \
    istio-injection=enabled
kubectl label namespace blue \
    istio-injection=enabled

# deploy application from upstream
kubectl apply \
    -f https://raw.githubusercontent.com/istio/istio/release-1.15/samples/helloworld/helloworld.yaml \
    -l version=v1 -n green

kubectl apply \
    -f https://raw.githubusercontent.com/istio/istio/release-1.15/samples/helloworld/helloworld.yaml \
    -l version=v2 -n blue

# also add service objects for each version
kubectl apply \
    -f https://raw.githubusercontent.com/istio/istio/release-1.15/samples/helloworld/helloworld.yaml \
    -l service=helloworld -n green

kubectl apply \
    -f https://raw.githubusercontent.com/istio/istio/release-1.15/samples/helloworld/helloworld.yaml \
    -l service=helloworld -n blue

Now lets create GW: (also this manifest can be downloaded here and applied with kubectl apply -f 6_gateway.yaml)

apiVersion: networking.istio.io/v1alpha3
kind: Gateway
metadata:
  name: tid-helloworld
  namespace: tid-ingress-ns
spec:
  selector:
    istio: tid-ingress-gw # selector needs to match one defined in previous step for Istio Gateway deployment
  servers:
  - port:
      number: 80
      name: http
      protocol: HTTP
    hosts:
    - helloworld.tetrate.io # this domain is not registered in public DNS and header needs to be supplied

And simplified version of Virtual Service from more advanced example (also this manifest can be downloaded here and applied with kubectl apply -f 6_vs.yaml)

apiVersion: networking.istio.io/v1alpha3
kind: VirtualService
metadata:
    name: helloworld-service
    namespace: tid-ingress-ns # namespace where GW was created in previous step
spec:
    gateways:
      - tid-helloworld
    hosts:
      - helloworld.tetrate.io
    http:
      - match:
        - headers:
            blue-version:  # if the request has "blue-version: on" header - requests will go to v2
              regex: '.*on.*'
        route:
          - destination:
              host: helloworld.blue.svc.cluster.local
      - route: # requests without additional header will go to v1
          - destination:
              host: helloworld.green.svc.cluster.local

To confirm the desired behavior is implemented.

• obtain the AWS LB FQDN and store in variable

  ADDR=$(kubectl -n tid-ingress-ns get service tid-ingressgateway -o=jsonpath="{.status.loadBalancer.ingress[0]['hostname','ip']}")
  

  you can confirm that address is obtained by displaying the variable

  $ ADDR=$(kubectl -n tid-ingress-ns get service tid-ingressgateway -o=jsonpath="{.status.loadBalancer.ingress[0]['hostname','ip']}")
  $ echo $ADDR
  ad33d7b9ed818419ea6a8d8b6d710742-1404212739.ap-northeast-2.elb.amazonaws.com
  

  - confirm that the blue header works and requests land on blue helloworld-v2 instance:

  $ curl $ADDR/hello -H "Host: helloworld.tetrate.io" -H "blue-version: on" 
  Hello version: v2, instance: helloworld-v2-79bf565586-p6zph
  

  - confirm that traffic without extra headed will go to green helloworld-v1 instances:

  $ curl $ADDR/hello -H "Host: helloworld.tetrate.io" 
  Hello version: v1, instance: helloworld-v1-77cb56d4b4-vzpj6
  

This example demonstrates a very flexible way to manage traffic based on the specific requirements.

Recorded video of this module is also available