Traffic mirroring is also referred to as traffic shadowing. You can send a copy of live traffic to a mirrored service before you deploy your updates to production. This way, you can reduce risks when upgrading your apps by testing out the changes first.

For more information, see the following resources.

Before you begin

  1. Complete the multicluster getting started guide to set up the following testing environment.

    • Three clusters along with environment variables for the clusters and their Kubernetes contexts.
    • The Gloo meshctl CLI, along with other CLI tools such as kubectl and istioctl.
    • The Gloo management server in the management cluster, and the Gloo agents in the workload clusters.
    • Istio installed in the workload clusters.
    • A simple Gloo workspace setup.
  2. Install Bookinfo and other sample apps.

  3. In order to see the traffic mirroring, you must enable access logging on the remote reviews-v3 service in cluster2.

Configure mirror policies

You can apply a mirror policy at the route level. For more information, see Applying policies.

Review the following sample configuration file.

  apiVersion: trafficcontrol.policy.gloo.solo.io/v2
kind: MirrorPolicy
metadata:
  annotations:
    cluster.solo.io/cluster: ""
  name: mirror-policy
  namespace: bookinfo
spec:
  applyToRoutes:
  - route:
      labels:
        route: reviews-federated
  config:
    destination:
      port:
        number: 9080
      ref:
        cluster: cluster-1
        name: reviews
        namespace: bookinfo

Review the following table to understand this configuration. For more information, see the API docs.

SettingDescription
spec.applyToRoutesUse labels to configure which routes to apply the policy to. This example label matches the app and route from the example route table that you apply separately. If omitted and you do not have another selector such as applyToDestinations, the policy applies to all routes in the workspace.
spec.config.destination.portSpecify the port number in the service to mirror traffic to.
spec.config.destination.refSet the cluster, name, and namespace details for the service that you want to mirror traffic to.
spec.config.percentageSpecify the percentage of requests that you want to mirror to the service. The default is 100 to mirror all requests.

Verify mirror policies

Verify a mirror policy by checking for mirrored logs.

  1. Apply the example mirror policy in the cluster with the Bookinfo workspace in your example setup.

      kubectl apply --context ${REMOTE_CONTEXT1} -f - << EOF
apiVersion: trafficcontrol.policy.gloo.solo.io/v2
kind: MirrorPolicy
metadata:
  annotations:
    cluster.solo.io/cluster: ""
  name: mirror-policy
  namespace: bookinfo
spec:
  applyToRoutes:
  - route:
      labels:
        route: reviews-federated
  config:
    destination:
      port:
        number: 9080
      ref:
        cluster: cluster-1
        name: reviews
        namespace: bookinfo
EOF

  2. Create a route table for the reviews app. Because mirror policies apply at the route level, Gloo checks for the route in a route table resource.

      kubectl apply --context ${REMOTE_CONTEXT1} -f - << EOF
apiVersion: networking.gloo.solo.io/v2
kind: RouteTable
metadata:
  name: reviews-rt
  namespace: bookinfo
spec:
  hosts:
  - reviews
  http:
  - forwardTo:
      destinations:
      - ref:
          name: reviews
          namespace: bookinfo
          cluster: ${REMOTE_CLUSTER1}
    labels:
      route: reviews-federated
  workloadSelectors:
  - {}
EOF

    Review the following table to understand this configuration. For more information, see the API docs.

    SettingDescription
    hostsThe host that the route table routes traffic for. In this example, the ratings host matches the ratings service within the mesh.
    http.forwardTo.destinationsThe destination to forward requests that come in along the host route. In this example, the ratings service is selected.
    http.labelsThe label for the route. This label must match the label that the policy selects.
    workloadSelectorsThe source workloads within the mesh that this route table routes traffic for. In the example, all workloads are selected. This way, the curl container that you create in subsequent steps can send a request along the ratings route.

  3. Send a request to the reviews-v1 app. Create a temporary curl pod in the bookinfo namespace, so that you can test the app setup. You can also use this method in Kubernetes 1.23 or later, but an ephemeral container might be simpler.

    1. Create the curl pod.
        kubectl run -it -n bookinfo --context $REMOTE_CONTEXT1 curl \
   --image=curlimages/curl:7.73.0 --rm  -- sh
    2. Send a request to the ratings app.
        curl -v http://reviews:9080/reviews/1
    3. Exit the temporary pod. The pod deletes itself.
        exit

    In the output, notice that no stars are included. Reviews v1 does not include stars in the reviews, whereas reviews v2 includes black stars.

      {"id": "1","podname": "reviews-v2-858f99c99-dll8j","clustername": "null","reviews": [{  "reviewer": "Reviewer1",  "text": "An extremely entertaining play by Shakespeare. The slapstick humour is refreshing!", "rating": {"error": "Ratings service is currently unavailable"}},{  "reviewer": "Reviewer2",  "text": "Absolutely fun and entertaining. The play lacks thematic depth when compared to other plays by Shakespeare.", "rating": {"error": "Ratings service is currently unavailable"}}]}

  4. Check the pod logs for the reviews v2 app. The access logs are for the mirrored requests that are actually served by the reviews v1 app.

      kubectl logs deploy/reviews-v2 -c istio-proxy -n bookinfo --context $REMOTE_CONTEXT1

    Example output:

       {
  "x_forwarded_for": null,
  "duration": 1611,
  "downstream_remote_address": "10.244.2.47:43102",
  "authority": "reviews:9080",
  "bytes_received": 0,
  "bytes_sent": 487,
  "upstream_cluster": "inbound|9080||",
  "path": "/reviews/1",
  "requested_server_name": "outbound_.9080_._.reviews.bookinfo.svc.cluster.local",
  "protocol": "HTTP/1.1",
  "upstream_host": "10.244.1.16:9080",
  "method": "GET",
  "route_name": "default",
  "upstream_service_time": "1609",
  "response_code": 200,
  "response_code_details": "via_upstream",
  "upstream_transport_failure_reason": null,
  "connection_termination_details": null,
  "start_time": "2022-09-06T16:08:00.510Z",
  "downstream_local_address": "10.244.1.16:9080",
  "user_agent": "curl/7.73.0-DEV",
  "response_flags": "-",
  "upstream_local_address": "127.0.0.6:45009",
  "request_id": "b6e1f09c-b029-49e0-95fe-8affaaf2f542"
}

Cleanup

You can optionally remove the resources that you set up as part of this guide.
  kubectl --context $REMOTE_CONTEXT1 -n bookinfo delete RouteTable reviews-rt
kubectl --context $REMOTE_CONTEXT1 -n bookinfo delete MirrorPolicy mirror-policy