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.

Istio supports the Kubernetes Gateway API and intends to make it the default API for traffic management in the future. The following instructions allow you to choose to use either the Gateway API or the Istio configuration API when configuring traffic management in the mesh. Follow instructions under either the Gateway API or Istio APIs tab, according to your preference.

Note that the Kubernetes Gateway API CRDs do not come installed by default on most Kubernetes clusters, so make sure they are installed before using the Gateway API:

  1. $ kubectl get crd gateways.gateway.networking.k8s.io &> /dev/null || \
  2.   { kubectl apply -f https://github.com/kubernetes-sigs/gateway-api/releases/download/v1.2.0/standard-install.yaml; }

Before you begin

  1. Set up Istio by following the Installation guide.

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

    1. Deploy httpbin-v1:

      1. $ kubectl create -f - <<EOF
      2. apiVersion: apps/v1
      3. kind: Deployment
      4. metadata:
      5.   name: httpbin-v1
      6. spec:
      7.   replicas: 1
      8.   selector:
      9.     matchLabels:
      10.       app: httpbin
      11.       version: v1
      12.   template:
      13.     metadata:
      14.       labels:
      15.         app: httpbin
      16.         version: v1
      17.     spec:
      18.       containers:
      19.       - image: docker.io/kennethreitz/httpbin
      20.         imagePullPolicy: IfNotPresent
      21.         name: httpbin
      22.         command: ["gunicorn", "--access-logfile", "-", "-b", "0.0.0.0:80", "httpbin:app"]
      23.         ports:
      24.         - containerPort: 80
      25. EOF

    2. Deploy httpbin-v2:

      1. $ kubectl create -f - <<EOF
      2. apiVersion: apps/v1
      3. kind: Deployment
      4. metadata:
      5.   name: httpbin-v2
      6. spec:
      7.   replicas: 1
      8.   selector:
      9.     matchLabels:
      10.       app: httpbin
      11.       version: v2
      12.   template:
      13.     metadata:
      14.       labels:
      15.         app: httpbin
      16.         version: v2
      17.     spec:
      18.       containers:
      19.       - image: docker.io/kennethreitz/httpbin
      20.         imagePullPolicy: IfNotPresent
      21.         name: httpbin
      22.         command: ["gunicorn", "--access-logfile", "-", "-b", "0.0.0.0:80", "httpbin:app"]
      23.         ports:
      24.         - containerPort: 80
      25. EOF

    3. Deploy the httpbin Kubernetes service:

      1. $ kubectl create -f - <<EOF
      2. apiVersion: v1
      3. kind: Service
      4. metadata:
      5.   name: httpbin
      6.   labels:
      7.     app: httpbin
      8. spec:
      9.   ports:
      10.   - name: http
      11.     port: 8000
      12.     targetPort: 80
      13.   selector:
      14.     app: httpbin
      15. EOF

  3. Deploy the curl workload you’ll use to send requests to the httpbin service:

    1. $ cat <<EOF | kubectl create -f -
    2. apiVersion: apps/v1
    3. kind: Deployment
    4. metadata:
    5.   name: curl
    6. spec:
    7.   replicas: 1
    8.   selector:
    9.     matchLabels:
    10.       app: curl
    11.   template:
    12.     metadata:
    13.       labels:
    14.         app: curl
    15.     spec:
    16.       containers:
    17.       - name: curl
    18.         image: curlimages/curl
    19.         command: ["/bin/sleep","3650d"]
    20.         imagePullPolicy: IfNotPresent
    21. 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:

    1. $ kubectl apply -f - <<EOF
    2. apiVersion: networking.istio.io/v1
    3. kind: VirtualService
    4. metadata:
    5.   name: httpbin
    6. spec:
    7.   hosts:
    8. - httpbin
    9.   http:
    10.   - route:
    11. - destination:
    12.     host: httpbin
    13.     subset: v1
    14.   weight: 100
    15. ---
    16. apiVersion: networking.istio.io/v1
    17. kind: DestinationRule
    18. metadata:
    19.   name: httpbin
    20. spec:
    21.   host: httpbin
    22.   subsets:
    23.   - name: v1
    24. labels:
    25.   version: v1
    26.   - name: v2
    27. labels:
    28.   version: v2
    29. EOF
    1. $ kubectl apply -f - <<EOF
    2. apiVersion: v1
    3. kind: Service
    4. metadata:
    5.   name: httpbin-v1
    6. spec:
    7.   ports:
    8.   - port: 80
    9. name: http
    10.   selector:
    11. app: httpbin
    12. version: v1
    13. ---
    14. apiVersion: v1
    15. kind: Service
    16. metadata:
    17.   name: httpbin-v2
    18. spec:
    19.   ports:
    20.   - port: 80
    21. name: http
    22.   selector:
    23. app: httpbin
    24. version: v2
    25. ---
    26. apiVersion: gateway.networking.k8s.io/v1
    27. kind: HTTPRoute
    28. metadata:
    29.   name: httpbin
    30. spec:
    31.   parentRefs:
    32.   - group: ""
    33. kind: Service
    34. name: httpbin
    35. port: 8000
    36.   rules:
    37.   - backendRefs:
    38. - name: httpbin-v1
    39.   port: 80
    40. EOF

  2. Now, with all traffic directed to httpbin:v1, send a request to the service:

    1. $ kubectl exec deploy/curl -c curl -- curl -sS http://httpbin:8000/headers
    2. {
    3.   "headers": {
    4.     "Accept": "*/*",
    5.     "Content-Length": "0",
    6.     "Host": "httpbin:8000",
    7.     "User-Agent": "curl/7.35.0",
    8.     "X-B3-Parentspanid": "57784f8bff90ae0b",
    9.     "X-B3-Sampled": "1",
    10.     "X-B3-Spanid": "3289ae7257c3f159",
    11.     "X-B3-Traceid": "b56eebd279a76f0b57784f8bff90ae0b",
    12.     "X-Envoy-Attempt-Count": "1",
    13.     "X-Forwarded-Client-Cert": "By=spiffe://cluster.local/ns/default/sa/default;Hash=20afebed6da091c850264cc751b8c9306abac02993f80bdb76282237422bd098;Subject=\"\";URI=spiffe://cluster.local/ns/default/sa/default"
    14.   }
    15. }

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

    1. $ kubectl logs deploy/httpbin-v1 -c httpbin
    2. 127.0.0.1 - - [07/Mar/2018:19:02:43 +0000] "GET /headers HTTP/1.1" 200 321 "-" "curl/7.35.0"
    1. $ kubectl logs deploy/httpbin-v2 -c httpbin
    2. <none>

Mirroring traffic to httpbin-v2

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

    1. $ kubectl apply -f - <<EOF
    2. apiVersion: networking.istio.io/v1
    3. kind: VirtualService
    4. metadata:
    5.   name: httpbin
    6. spec:
    7.   hosts:
    8. - httpbin
    9.   http:
    10.   - route:
    11. - destination:
    12.     host: httpbin
    13.     subset: v1
    14.   weight: 100
    15. mirror:
    16.   host: httpbin
    17.   subset: v2
    18. mirrorPercentage:
    19.   value: 100.0
    20. EOF

    This route rule sends 100% of the traffic to v1. The last stanza specifies that you want to mirror (i.e., also send) 100% of the same traffic 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.

    You can use the value field under the mirrorPercentage field to mirror a fraction of the traffic, instead of mirroring all requests. If this field is absent, all traffic will be mirrored.

    1. $ kubectl apply -f - <<EOF
    2. apiVersion: gateway.networking.k8s.io/v1
    3. kind: HTTPRoute
    4. metadata:
    5.   name: httpbin
    6. spec:
    7.   parentRefs:
    8.   - group: ""
    9. kind: Service
    10. name: httpbin
    11. port: 8000
    12.   rules:
    13.   - filters:
    14. - type: RequestMirror
    15.   requestMirror:
    16.     backendRef:
    17.       name: httpbin-v2
    18.       port: 80
    19. backendRefs:
    20. - name: httpbin-v1
    21.   port: 80
    22. EOF

    This route rule sends 100% of the traffic to v1. The RequestMirror filter specifies that you want to mirror (i.e., also send) 100% of the same traffic 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 the traffic:

    1. $ kubectl exec deploy/curl -c curl -- curl -sS http://httpbin:8000/headers

    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.

    1. $ kubectl logs deploy/httpbin-v1 -c httpbin
    2. 127.0.0.1 - - [07/Mar/2018:19:02:43 +0000] "GET /headers HTTP/1.1" 200 321 "-" "curl/7.35.0"
    3. 127.0.0.1 - - [07/Mar/2018:19:26:44 +0000] "GET /headers HTTP/1.1" 200 321 "-" "curl/7.35.0"
    1. $ kubectl logs deploy/httpbin-v2 -c httpbin
    2. 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:

    1. $ kubectl delete virtualservice httpbin
    2. $ kubectl delete destinationrule httpbin
    1. $ kubectl delete httproute httpbin
    2. $ kubectl delete svc httpbin-v1 httpbin-v2

  2. Delete httpbin and curl deployments and httpbin service:

    1. $ kubectl delete deploy httpbin-v1 httpbin-v2 curl
    2. $ kubectl delete svc httpbin