Mirroring

This task demonstrates the traffic mirroring capabilities of Istio.

Traffic mirroring, also called shadowing, is a powerful concept that allows feature teams to bring changes to production with as little risk as possible. Mirroring sends a copy of live traffic to a mirrored service. The mirrored traffic happens out of band of the critical request path for the primary service.

In this task, you will first force all traffic to v1 of a test service. Then, you will apply a rule to mirror a portion of traffic to v2.

Before you begin

• Set up Istio by following the instructions in the Installation guide.

• Start by deploying two versions of the httpbin service that have access logging enabled:

  httpbin-v1:

  cat <<EOF | istioctl kube-inject -f - | kubectl create -f -
  apiVersion: extensions/v1beta1
  kind: Deployment
  metadata:
    name: httpbin-v1
  spec:
    replicas: 1
    template:
      metadata:
        labels:
          app: httpbin
          version: v1
      spec:
        containers:
        - image: docker.io/kennethreitz/httpbin
          imagePullPolicy: IfNotPresent
          name: httpbin
          command: ["gunicorn", "--access-logfile", "-", "-b", "0.0.0.0:8080", "httpbin:app"]
          ports:
          - containerPort: 8080
  EOF

  httpbin-v2:

  cat <<EOF | istioctl kube-inject -f - | kubectl create -f -
  apiVersion: extensions/v1beta1
  kind: Deployment
  metadata:
    name: httpbin-v2
  spec:
    replicas: 1
    template:
      metadata:
        labels:
          app: httpbin
          version: v2
      spec:
        containers:
        - image: docker.io/kennethreitz/httpbin
          imagePullPolicy: IfNotPresent
          name: httpbin
          command: ["gunicorn", "--access-logfile", "-", "-b", "0.0.0.0:8080", "httpbin:app"]
          ports:
          - containerPort: 8080
  EOF

  httpbin Kubernetes service:

  cat <<EOF | kubectl create -f -
  apiVersion: v1
  kind: Service
  metadata:
    name: httpbin
    labels:
      app: httpbin
  spec:
    ports:
    - name: http
      port: 8080
    selector:
      app: httpbin
  EOF

• Start the sleep service so you can use curl to provide load:

  sleep service:

  cat <<EOF | istioctl kube-inject -f - | kubectl create -f -
  apiVersion: extensions/v1beta1
  kind: Deployment
  metadata:
    name: sleep
  spec:
    replicas: 1
    template:
      metadata:
        labels:
          app: sleep
      spec:
        containers:
        - name: sleep
          image: tutum/curl
          command: ["/bin/sleep","infinity"]
          imagePullPolicy: IfNotPresent
  EOF

Creating a default routing policy

By default Kubernetes load balances across both versions of the httpbin service. In this step, you will change that behavior so that all traffic goes to v1.

1. Create a default route rule to route all traffic to v1 of the service:

   cat <<EOF | kubectl apply -f -
   apiVersion: networking.istio.io/v1alpha3
   kind: VirtualService
   metadata:
     name: httpbin
   spec:
     hosts:
       - httpbin
     http:
     - route:
       - destination:
           host: httpbin
           subset: v1
         weight: 100
   ---
   apiVersion: networking.istio.io/v1alpha3
   kind: DestinationRule
   metadata:
     name: httpbin
   spec:
     host: httpbin
     subsets:
     - name: v1
       labels:
         version: v1
     - name: v2
       labels:
         version: v2
   EOF

   NOTE: If you installed/configured Istio with mutual TLS Authentication enabled, you must add the TLSSettings.TLSmode, mode: ISTIO_MUTUAL as noted in the TLSSettings reference.

   Now all traffic goes to the httpbin v1 service.

2. Send some traffic to the service:

   $ export SLEEP_POD=$(kubectl get pod -l app=sleep -o jsonpath={.items..metadata.name})
   $ kubectl exec -it $SLEEP_POD -c sleep -- sh -c 'curl  http://httpbin:8080/headers' | python -m json.tool
   {
     "headers": {
       "Accept": "*/*",
       "Content-Length": "0",
       "Host": "httpbin:8080",
       "User-Agent": "curl/7.35.0",
       "X-B3-Sampled": "1",
       "X-B3-Spanid": "eca3d7ed8f2e6a0a",
       "X-B3-Traceid": "eca3d7ed8f2e6a0a",
       "X-Ot-Span-Context": "eca3d7ed8f2e6a0a;eca3d7ed8f2e6a0a;0000000000000000"
     }
   }

3. Check the logs for v1 and v2 of the httpbin pods. You should see access log entries for v1 and none for v2:

   $ export V1_POD=$(kubectl get pod -l app=httpbin,version=v1 -o jsonpath={.items..metadata.name})
   $ kubectl logs -f $V1_POD -c httpbin
   127.0.0.1 - - [07/Mar/2018:19:02:43 +0000] "GET /headers HTTP/1.1" 200 321 "-" "curl/7.35.0"

   $ export V2_POD=$(kubectl get pod -l app=httpbin,version=v2 -o jsonpath={.items..metadata.name})
   $ kubectl logs -f $V2_POD -c httpbin
   <none>

Mirroring traffic to v2

1. Change the route rule to mirror traffic to v2:

   cat <<EOF | kubectl apply -f -
   apiVersion: networking.istio.io/v1alpha3
   kind: VirtualService
   metadata:
     name: httpbin
   spec:
     hosts:
       - httpbin
     http:
     - route:
       - destination:
           host: httpbin
           subset: v1
         weight: 100
       mirror:
         host: httpbin
         subset: v2
   EOF

   This route rule sends 100% of the traffic to v1. The last stanza specifies that you want to mirror to the httpbin v2 service. When traffic gets mirrored, the requests are sent to the mirrored service with their Host/Authority headers appended with -shadow. For example, cluster-1 becomes cluster-1-shadow.

   Also, it is important to note that these requests are mirrored as “fire and forget”, which means that the responses are discarded.

2. Send in traffic:

   $ kubectl exec -it $SLEEP_POD -c sleep -- sh -c 'curl  http://httpbin:8080/headers' | python -m json.tool

   Now, you should see access logging for both v1 and v2. The access logs created in v2 are the mirrored requests that are actually going to v1.

   $ kubectl logs -f $V1_POD -c httpbin
   127.0.0.1 - - [07/Mar/2018:19:02:43 +0000] "GET /headers HTTP/1.1" 200 321 "-" "curl/7.35.0"
   127.0.0.1 - - [07/Mar/2018:19:26:44 +0000] "GET /headers HTTP/1.1" 200 321 "-" "curl/7.35.0"

   $ kubectl logs -f $V2_POD -c httpbin
   127.0.0.1 - - [07/Mar/2018:19:26:44 +0000] "GET /headers HTTP/1.1" 200 361 "-" "curl/7.35.0"

Cleaning up

1. Remove the rules:

   $ kubectl delete virtualservice httpbin
   $ kubectl delete destinationrule httpbin

2. Shutdown the httpbin service and client:

   $ kubectl delete deploy httpbin-v1 httpbin-v2 sleep
   $ kubectl delete svc httpbin

3. If you are not planning to explore any follow-on tasks, refer to the Bookinfo cleanup instructions to shutdown the application.

See also