Mirroring

 6 minute read

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: apps/v1
kind: Deployment
metadata:
  name: httpbin-v1
spec:
  replicas: 1
  selector:
    matchLabels:
      app: httpbin
      version: v1
  template:
    metadata:
      labels:
        app: httpbin
        version: v1
    spec:
      containers:
      - image: docker.io/kennethreitz/httpbin
        imagePullPolicy: IfNotPresent
        name: httpbin
        command: ["gunicorn", "--access-logfile", "-", "-b", "0.0.0.0:80", "httpbin:app"]
        ports:
        - containerPort: 80
EOF

    httpbin-v2:

    $ cat <<EOF | istioctl kube-inject -f - | kubectl create -f -
apiVersion: apps/v1
kind: Deployment
metadata:
  name: httpbin-v2
spec:
  replicas: 1
  selector:
    matchLabels:
      app: httpbin
      version: v2
  template:
    metadata:
      labels:
        app: httpbin
        version: v2
    spec:
      containers:
      - image: docker.io/kennethreitz/httpbin
        imagePullPolicy: IfNotPresent
        name: httpbin
        command: ["gunicorn", "--access-logfile", "-", "-b", "0.0.0.0:80", "httpbin:app"]
        ports:
        - containerPort: 80
EOF

    httpbin Kubernetes service:

    $ kubectl create -f - <<EOF
apiVersion: v1
kind: Service
metadata:
  name: httpbin
  labels:
    app: httpbin
spec:
  ports:
  - name: http
    port: 8000
    targetPort: 80
  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: apps/v1
kind: Deployment
metadata:
  name: sleep
spec:
  replicas: 1
  selector:
    matchLabels:
      app: sleep
  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:

    $ kubectl apply -f - <<EOF
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

    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:8000/headers' | python -m json.tool
{
  "headers": {
    "Accept": "*/*",
    "Content-Length": "0",
    "Host": "httpbin:8000",
    "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:

    $ kubectl apply -f - <<EOF
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
    mirror_percent: 100
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.

    You can use the mirror_percent field to mirror a fraction of the traffic, instead of mirroring all requests. If this field is absent, for compatibility with older versions, all traffic will be mirrored.

  2. Send in traffic:

    $ kubectl exec -it $SLEEP_POD -c sleep -- sh -c 'curl  http://httpbin:8000/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"

  3. If you want to examine traffic internals, run the following commands on another console:

    $ export SLEEP_POD=$(kubectl get pod -l app=sleep -o jsonpath={.items..metadata.name})
$ export V1_POD_IP=$(kubectl get pod -l app=httpbin -l version=v1 -o jsonpath={.items..status.podIP})
$ export V2_POD_IP=$(kubectl get pod -l app=httpbin -l version=v2 -o jsonpath={.items..status.podIP})
$ kubectl exec -it $SLEEP_POD -c istio-proxy -- sudo tcpdump -A -s 0 host $V1_POD_IP or host $V2_POD_IP
tcpdump: verbose output suppressed, use -v or -vv for full protocol decode
listening on eth0, link-type EN10MB (Ethernet), capture size 262144 bytes
05:47:50.159513 IP sleep-7b9f8bfcd-2djx5.38836 > 10-233-75-11.httpbin.default.svc.cluster.local.80: Flags [P.], seq 4039989036:4039989832, ack 3139734980, win 254, options [nop,nop,TS val 77427918 ecr 76730809], length 796: HTTP: GET /headers HTTP/1.1
E..P2.X.X.X.
.K.
.K....P..W,.$.......+.....
..t.....GET /headers HTTP/1.1
host: httpbin:8000
user-agent: curl/7.35.0
accept: */*
x-forwarded-proto: http
x-request-id: 571c0fd6-98d4-4c93-af79-6a2fe2945847
x-envoy-decorator-operation: httpbin.default.svc.cluster.local:8000/*
x-b3-traceid: 82f3e0a76dcebca2
x-b3-spanid: 82f3e0a76dcebca2
x-b3-sampled: 0
x-istio-attributes: Cj8KGGRlc3RpbmF0aW9uLnNlcnZpY2UuaG9zdBIjEiFodHRwYmluLmRlZmF1bHQuc3ZjLmNsdXN0ZXIubG9jYWwKPQoXZGVzdGluYXRpb24uc2VydmljZS51aWQSIhIgaXN0aW86Ly9kZWZhdWx0L3NlcnZpY2VzL2h0dHBiaW4KKgodZGVzdGluYXRpb24uc2VydmljZS5uYW1lc3BhY2USCRIHZGVmYXVsdAolChhkZXN0aW5hdGlvbi5zZXJ2aWNlLm5hbWUSCRIHaHR0cGJpbgo6Cgpzb3VyY2UudWlkEiwSKmt1YmVybmV0ZXM6Ly9zbGVlcC03YjlmOGJmY2QtMmRqeDUuZGVmYXVsdAo6ChNkZXN0aW5hdGlvbi5zZXJ2aWNlEiMSIWh0dHBiaW4uZGVmYXVsdC5zdmMuY2x1c3Rlci5sb2NhbA==
content-length: 0


05:47:50.159609 IP sleep-7b9f8bfcd-2djx5.49560 > 10-233-71-7.httpbin.default.svc.cluster.local.80: Flags [P.], seq 296287713:296288571, ack 4029574162, win 254, options [nop,nop,TS val 77427918 ecr 76732809], length 858: HTTP: GET /headers HTTP/1.1
E.....X.X...
.K.
.G....P......l......e.....
..t.....GET /headers HTTP/1.1
host: httpbin-shadow:8000
user-agent: curl/7.35.0
accept: */*
x-forwarded-proto: http
x-request-id: 571c0fd6-98d4-4c93-af79-6a2fe2945847
x-envoy-decorator-operation: httpbin.default.svc.cluster.local:8000/*
x-b3-traceid: 82f3e0a76dcebca2
x-b3-spanid: 82f3e0a76dcebca2
x-b3-sampled: 0
x-istio-attributes: Cj8KGGRlc3RpbmF0aW9uLnNlcnZpY2UuaG9zdBIjEiFodHRwYmluLmRlZmF1bHQuc3ZjLmNsdXN0ZXIubG9jYWwKPQoXZGVzdGluYXRpb24uc2VydmljZS51aWQSIhIgaXN0aW86Ly9kZWZhdWx0L3NlcnZpY2VzL2h0dHBiaW4KKgodZGVzdGluYXRpb24uc2VydmljZS5uYW1lc3BhY2USCRIHZGVmYXVsdAolChhkZXN0aW5hdGlvbi5zZXJ2aWNlLm5hbWUSCRIHaHR0cGJpbgo6Cgpzb3VyY2UudWlkEiwSKmt1YmVybmV0ZXM6Ly9zbGVlcC03YjlmOGJmY2QtMmRqeDUuZGVmYXVsdAo6ChNkZXN0aW5hdGlvbi5zZXJ2aWNlEiMSIWh0dHBiaW4uZGVmYXVsdC5zdmMuY2x1c3Rlci5sb2NhbA==
x-envoy-internal: true
x-forwarded-for: 10.233.75.12
content-length: 0


05:47:50.166734 IP 10-233-75-11.httpbin.default.svc.cluster.local.80 > sleep-7b9f8bfcd-2djx5.38836: Flags [P.], seq 1:472, ack 796, win 276, options [nop,nop,TS val 77427925 ecr 77427918], length 471: HTTP: HTTP/1.1 200 OK
E....3X.?...
.K.
.K..P...$....ZH...........
..t...t.HTTP/1.1 200 OK
server: envoy
date: Fri, 15 Feb 2019 05:47:50 GMT
content-type: application/json
content-length: 241
access-control-allow-origin: *
access-control-allow-credentials: true
x-envoy-upstream-service-time: 3

{
  "headers": {
    "Accept": "*/*",
    "Content-Length": "0",
    "Host": "httpbin:8000",
    "User-Agent": "curl/7.35.0",
    "X-B3-Sampled": "0",
    "X-B3-Spanid": "82f3e0a76dcebca2",
    "X-B3-Traceid": "82f3e0a76dcebca2"
  }
}

05:47:50.166789 IP sleep-7b9f8bfcd-2djx5.38836 > 10-233-75-11.httpbin.default.svc.cluster.local.80: Flags [.], ack 472, win 262, options [nop,nop,TS val 77427925 ecr 77427925], length 0
E..42.X.X.\.
.K.
.K....P..ZH.$.............
..t...t.
05:47:50.167234 IP 10-233-71-7.httpbin.default.svc.cluster.local.80 > sleep-7b9f8bfcd-2djx5.49560: Flags [P.], seq 1:512, ack 858, win 280, options [nop,nop,TS val 77429926 ecr 77427918], length 511: HTTP: HTTP/1.1 200 OK
E..3..X.>...
.G.
.K..P....l....;...........
..|...t.HTTP/1.1 200 OK
server: envoy
date: Fri, 15 Feb 2019 05:47:49 GMT
content-type: application/json
content-length: 281
access-control-allow-origin: *
access-control-allow-credentials: true
x-envoy-upstream-service-time: 3

{
  "headers": {
    "Accept": "*/*",
    "Content-Length": "0",
    "Host": "httpbin-shadow:8000",
    "User-Agent": "curl/7.35.0",
    "X-B3-Sampled": "0",
    "X-B3-Spanid": "82f3e0a76dcebca2",
    "X-B3-Traceid": "82f3e0a76dcebca2",
    "X-Envoy-Internal": "true"
  }
}

05:47:50.167253 IP sleep-7b9f8bfcd-2djx5.49560 > 10-233-71-7.httpbin.default.svc.cluster.local.80: Flags [.], ack 512, win 262, options [nop,nop,TS val 77427926 ecr 77429926], length 0
E..4..X.X...
.K.
.G....P...;..n............
..t...|.

    You can see request and response contents of the traffic.

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
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