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** This tutorial was originally published on Datawire.io in 2017. As a result, some of the tools mentioned may no longer be actively maintained. Please join our Slack if you have any questions.

Monitoring Envoy and Ambassador on Kubernetes with the Prometheus Operator

In the Kubernetes ecosystem, one of the emerging themes is how applications can best take advantage of the various capabilities of Kubernetes. The Kubernetes community has also introduced new concepts such as Custom Resources to make it easier to build Kubernetes-native software.

In late 2016, CoreOS introduced the Operator pattern and released the Prometheus Operator as a working example of the pattern. The Prometheus Operator automatically creates and manages Prometheus monitoring instances.

The operator model is especially powerful for cloud-native organizations deploying multiple services. In this model, each team can deploy their own Prometheus instance as necessary, instead of relying on a central SRE team to implement monitoring.

Envoy, Ambassador, and Prometheus

In this tutorial, we'll show how the Prometheus Operator can be used to monitor an Envoy proxy deployed at the edge. Envoy is an open source L7 proxy. One of the (many) reasons for Envoy's growing popularity is its emphasis on observability. Envoy uses statsd as its output format.

Instead of using Envoy directly, we'll use Ambassador. Ambassador is a Kubernetes-native API Gateway built on Envoy. Similar to the Prometheus Operator, Ambassador configures and manages Envoy instances in Kubernetes, so that the end user doesn't need to do that work directly.

Prerequisites

This tutorial assumes you're running Kubernetes 1.8 or later, with RBAC enabled.

Note: If you're running on Google Kubernetes Engine, you'll need to grant cluster-admin privileges to the account that will be installing Prometheus and Ambassador. You can do this with the commands below:

$ gcloud info | grep Account
Account: [username@example.org]
$ kubectl create clusterrolebinding my-cluster-admin-binding --clusterrole=cluster-admin --user=username@example.org

Deploy the Prometheus Operator

The Prometheus Operator is configured as a Kubernetes deployment. We'll first deploy the Prometheus operator.

apiVersion: rbac.authorization.k8s.io/v1beta1
kind: ClusterRoleBinding
metadata:
  name: prometheus-operator
roleRef:
  apiGroup: rbac.authorization.k8s.io
  kind: ClusterRole
  name: prometheus-operator
subjects:
- kind: ServiceAccount
  name: prometheus-operator
  namespace: default
---
apiVersion: rbac.authorization.k8s.io/v1beta1
kind: ClusterRole
metadata:
  name: prometheus-operator
rules:
- apiGroups:
  - extensions
  resources:
  - thirdpartyresources
  verbs:
  - "*"
- apiGroups:
  - apiextensions.k8s.io
  resources:
  - customresourcedefinitions
  verbs:
  - "*"
- apiGroups:
  - monitoring.coreos.com
  resources:
  - alertmanagers
  - prometheuses
  - servicemonitors
  verbs:
  - "*"
- apiGroups:
  - apps
  resources:
  - statefulsets
  verbs: ["*"]
- apiGroups: [""]
  resources:
  - configmaps
  - secrets
  verbs: ["*"]
- apiGroups: [""]
  resources:
  - pods
  verbs: ["list", "delete"]
- apiGroups: [""]
  resources:
  - services
  - endpoints
  verbs: ["get", "create", "update"]
- apiGroups: [""]
  resources:
  - nodes
  verbs: ["list", "watch"]
- apiGroups: [""]
  resources:
  - namespaces
  verbs: ["list"]
---
apiVersion: v1
kind: ServiceAccount
metadata:
  name: prometheus-operator
---
apiVersion: extensions/v1beta1
kind: Deployment
metadata:
  labels:
    k8s-app: prometheus-operator
  name: prometheus-operator
spec:
  replicas: 1
  template:
    metadata:
      labels:
        k8s-app: prometheus-operator
    spec:
      containers:
      - args:
        - --kubelet-service=kube-system/kubelet
        - --config-reloader-image=quay.io/coreos/configmap-reload:v0.0.1
        image: quay.io/coreos/prometheus-operator:v0.15.0
        name: prometheus-operator
        ports:
        - containerPort: 8080
          name: http
        resources:
          limits:
            cpu: 200m
            memory: 100Mi
          requests:
            cpu: 100m
            memory: 50Mi
      serviceAccountName: prometheus-operator

kubectl apply -f prom-operator.yaml

We'll also want to create an additional ServiceAccounts for the actual Prometheus instances.

apiVersion: v1
kind: ServiceAccount
metadata:
  name: prometheus
---
apiVersion: rbac.authorization.k8s.io/v1beta1
kind: ClusterRole
metadata:
  name: prometheus
rules:
- apiGroups: [""]
  resources:
  - nodes
  - services
  - endpoints
  - pods
  verbs: ["get", "list", "watch"]
- apiGroups: [""]
  resources:
  - configmaps
  verbs: ["get"]
- nonResourceURLs: ["/metrics"]
  verbs: ["get"]
---
apiVersion: rbac.authorization.k8s.io/v1beta1
kind: ClusterRoleBinding
metadata:
  name: prometheus
roleRef:
  apiGroup: rbac.authorization.k8s.io
  kind: ClusterRole
  name: prometheus
subjects:
- kind: ServiceAccount
  name: prometheus
  namespace: default

kubectl apply -f prom-rbac.yaml

The Operator functions as your virtual SRE. At all times, the Prometheus operator insures that you have a set of Prometheus servers running with the appropriate configuration.

Deploy Ambassador

Ambassador also functions as your virtual SRE. At all times, Ambassador insures that you have a set of Envoy proxies running the appropriate configuration.

We're going to deploy Ambassador into Kubernetes. On each Ambassador pod, we'll also deploy an additional container that runs the Prometheus statsd exporter. The exporter will collect the statsd metrics emitted by Envoy over UDP, and proxy them to Prometheus over TCP in Prometheus metrics format.

---
apiVersion: v1
kind: Service
metadata:
  labels:
    service: ambassador-admin
  name: ambassador-admin
spec:
  type: NodePort
  ports:
  - name: ambassador-admin
    port: 8877
    targetPort: 8877
  selector:
    service: ambassador
---
apiVersion: rbac.authorization.k8s.io/v1beta1
kind: ClusterRole
metadata:
  name: ambassador
rules:
- apiGroups: [""]
  resources:
  - services
  verbs: ["get", "list", "watch"]
- apiGroups: [""]
  resources:
  - configmaps
  verbs: ["create", "update", "patch", "get", "list", "watch"]
- apiGroups: [""]
  resources:
  - secrets
  verbs: ["get", "list", "watch"]
---
apiVersion: v1
kind: ServiceAccount
metadata:
  name: ambassador
---
apiVersion: rbac.authorization.k8s.io/v1beta1
kind: ClusterRoleBinding
metadata:
  name: ambassador
roleRef:
  apiGroup: rbac.authorization.k8s.io
  kind: ClusterRole
  name: ambassador
subjects:
- kind: ServiceAccount
  name: ambassador
  namespace: default
---
apiVersion: extensions/v1beta1
kind: Deployment
metadata:
  name: ambassador
spec:
  replicas: 1
  template:
    metadata:
      labels:
        service: ambassador
    spec:
      serviceAccountName: ambassador
      containers:
      - name: ambassador
        image: datawire/ambassador:0.21.0
        imagePullPolicy: Always
        resources:
          limits:
            cpu: 1
            memory: 400Mi
          requests:
            cpu: 200m
            memory: 100Mi
        env:
        - name: AMBASSADOR_NAMESPACE
          valueFrom:
            fieldRef:
              fieldPath: metadata.namespace
        livenessProbe:
          httpGet:
            path: /ambassador/v0/check_alive
            port: 8877
          initialDelaySeconds: 3
          periodSeconds: 3
        readinessProbe:
          httpGet:
            path: /ambassador/v0/check_ready
            port: 8877
          initialDelaySeconds: 3
          periodSeconds: 3
      - name: statsd-sink
        image: datawire/prom-statsd-exporter:0.6.0
      restartPolicy: Always

kubectl apply -f ambassador-rbac.yaml

Ambassador is typically deployed as an API Gateway at the edge of your network. We'll deploy a service to map to the Ambassador deployment. Note: if you're not on AWS or GKE, you'll need to update the service below to be a NodePort instead of a LoadBalancer.

---
apiVersion: v1
kind: Service
metadata:
  labels:
    service: ambassador
  name: ambassador
spec:
  type: LoadBalancer
  ports:
  - name: ambassador
    port: 80
    targetPort: 80
  selector:
    service: ambassador

kubectl apply -f ambassador.yaml

You should now have a working Ambassador and StatsD/Prometheus exporter that is accessible from outside your cluster.

Configure Prometheus

We now have Ambassador/Envoy running, along with the Prometheus Operator. How do we hook this all together? Logically, all the metrics data flows from Envoy to Prometheus in the following way:

So far, we've deployed Envoy and the StatsD exporter, so now it's time to deploy the other components of this flow.

We'll first create a Kubernetes service that points to the StatsD exporter. We'll then create a ServiceMonitor that tells Prometheus to add the service as a target.

---
apiVersion: v1
kind: Service
metadata:
  name: ambassador-monitor
  labels:
    service: ambassador-monitor
spec:
  selector:
    service: ambassador
  type: ClusterIP
  clusterIP: None
  ports:
  - name: prometheus-metrics
    port: 9102
    targetPort: 9102
    protocol: TCP
---
apiVersion: monitoring.coreos.com/v1
kind: ServiceMonitor
metadata:
  name: ambassador-monitor
  labels:
    ambassador: monitoring
spec:
  selector:
    matchLabels:
      service: ambassador-monitor
  endpoints:
  - port: prometheus-metrics

kubectl apply -f statsd-sink-svc.yaml

Next, we need to tell the Prometheus Operator to create a Prometheus cluster for us. The Prometheus cluster is configured to collect data from any ServiceMonitor with the ambassador:monitoring label.

apiVersion: monitoring.coreos.com/v1
kind: Prometheus
metadata:
  name: prometheus
spec:
  serviceAccountName: prometheus
  serviceMonitorSelector:
    matchLabels:
      ambassador: monitoring
  resources:
    requests:
      memory: 400Mi

kubectl apply -f prometheus.yaml

Finally, we can create a service to expose Prometheus to the rest of the world. Again, if you're not on AWS or GKE, you'll want to use a NodePort instead.

apiVersion: v1
kind: Service
metadata:
  name: prometheus
spec:
  type: NodePort
  ports:
  - name: web
    port: 9090
    protocol: TCP
    targetPort: web
  selector:
    prometheus: prometheus

kubectl apply -f prom-svc.yaml

Testing

We've now configured Prometheus to monitor Envoy, so now let's test this out. Get the external IP address for Prometheus.

$ kubectl get services
NAME                  CLUSTER-IP      EXTERNAL-IP      PORT(S)          AGE
ambassador            10.11.255.93    35.221.115.102   80:32079/TCP     3h
ambassador-admin      10.11.246.117   <nodes>          8877:30366/TCP   3h
ambassador-monitor    None            <none>           9102/TCP         3h
kubernetes            10.11.240.1     <none>           443/TCP          3h
prometheus            10.11.254.180   35.191.39.173    9090:32134/TCP   3h
prometheus-operated   None            <none>           9090/TCP         3h

In the example above, this is 35.191.39.173. Now, go to http://$PROM_IP:9090 to see the Prometheus UI. You should see a number of metrics automatically populate in Prometheus.

Troubleshooting

If the above doesn't work, there are a few things to investigate:

  • Make sure all your pods are running (kubectl get pods)
  • Check the logs on the Prometheus cluster (kubectl logs $PROM_POD prometheus)
  • Check Ambassador diagnostics to verify Ambassador is working correctly

Get a service running in Envoy

The metrics so far haven't been very interesting, since we haven't routed any traffic through Envoy. We'll use Ambassador to set up a route from Envoy to the httpbin service. Ambassador is configured using Kubernetes annotations, so we'll do that here.

apiVersion: v1
kind: Service
metadata:
  name: httpbin
  annotations:
    getambassador.io/config: |
      ---
      apiVersion: ambassador/v0
      kind:  Mapping
      name:  httpbin_mapping
      prefix: /httpbin/
      service: httpbin.org:80
      host_rewrite: httpbin.org
spec:
  ports:
  - port: 80

kubectl apply -f httpbin.yaml

Now, if we get the external IP address of Ambassador, we can route requests through Ambassador to the httpbin service:

$ kubectl get services
NAME                  CLUSTER-IP      EXTERNAL-IP      PORT(S)          AGE
ambassador            10.11.255.93    35.221.115.102   80:32079/TCP     3h
ambassador-admin      10.11.246.117   <nodes>          8877:30366/TCP   3h
ambassador-monitor    None            <none>           9102/TCP         3h
kubernetes            10.11.240.1     <none>           443/TCP          3h
prometheus            10.11.254.180   35.191.39.173    9090:32134/TCP   3h
prometheus-operated   None            <none>           9090/TCP         3h
$ curl http://35.221.115.102/httpbin/ip
{
  "origin": "35.214.10.110"
}

Run a curl command a few times, as shown above. Going back to the Prometheus dashboard, you'll see that a bevy of new metrics that contain httpbin have appeared. Pick any of these metrics to explore further. For more information on Envoy stats, Matt Klein has written a detailed overview of Envoy's stats architecture. If you are interested in setting up a Grafana dashboard, Alex Gervais has published a sample Grafana/Ambassador dashboard.

Conclusion

Microservices, as you know, are distributed systems. The key to scaling distributed systems is creating loose coupling between each of the components. In a microservices architecture, the most painful source of coupling is actually organizational and not architectural. Design patterns such as the Prometheus Operator enable teams to be more self-sufficient, and reduce organizational coupling, enabling teams to code faster.

Next Steps