Running On Kubernetes

Kubernetes is a popular platform for running containers, and Cloudprober container runs on Kubernetes right out of the box. This document shows how you can run Cloudprober on kubernetes, use ConfigMap for config, and discover kubernetes targets automatically.

ConfigMap #

In Kubernetes, a convenient way to provide config to containers is to use config maps. Let’s create a config that specifies a probe to monitor “google.com”.

probe {
  name: "google-http"
  type: HTTP
  targets {
    host_names: "www.google.com"
  }
  http_probe {}
  interval_msec: 15000
  timeout_msec: 1000
}

Save this config in cloudprober.cfg, create a config map using the following command:

kubectl create configmap cloudprober-config \
  --from-file=cloudprober.cfg=cloudprober.cfg

If you change the config, you can update the config map using the following command:

kubectl create configmap cloudprober-config \
  --from-file=cloudprober.cfg=cloudprober.cfg  -o yaml --dry-run | \
  kubectl replace -f -

Deployment Map #

Now let’s add a deployment.yaml to add the config volume and cloudprober container:

apiVersion: apps/v1
kind: Deployment
metadata:
  name: cloudprober
spec:
  replicas: 1
  selector:
    matchLabels:
      app: cloudprober
  template:
    metadata:
      annotations:
        checksum/config: "${CONFIG_CHECKSUM}"
      labels:
        app: cloudprober
    spec:
      volumes:
        - name: cloudprober-config
          configMap:
            name: cloudprober-config
      containers:
        - name: cloudprober
          image: cloudprober/cloudprober
          command: ["/cloudprober"]
          args: ["--config_file", "/cfg/cloudprober.cfg"]
          volumeMounts:
            - name: cloudprober-config
              mountPath: /cfg
          ports:
            - name: http
              containerPort: 9313
---
apiVersion: v1
kind: Service
metadata:
  name: cloudprober
  labels:
    app: cloudprober
spec:
  ports:
    - port: 9313
      protocol: TCP
      targetPort: 9313
  selector:
    app: cloudprober
  type: NodePort

Note that we added an annotation to the deployment spec; this annotation allows us to update the deployment whenever cloudprober config changes. We can update this annotation based on the local cloudprober config content, and update the deployment using the following one-liner:

# Update the config checksum annotation in deployment.yaml before running
# kubectl apply.
export CONFIG_CHECKSUM=$(kubectl get cm/cloudprober-config -o yaml | sha256sum) && \
cat deployment.yaml | envsubst | kubectl apply -f -

(Note: If you use Helm for Kubernetes deployments, Helm provides a more native way to include config checksums in deployments.)

Applying the above yaml file, should create a deployment with a service at port 9313:

$ kubectl get deployment
NAME          READY   UP-TO-DATE   AVAILABLE   AGE
cloudprober   1/1     1            1           94m

$ kubectl get service cloudprober
NAME          TYPE       CLUSTER-IP      EXTERNAL-IP   PORT(S)          AGE
cloudprober   NodePort   10.31.249.108   <none>        9313:31367/TCP   94m

Now you should be able to access various cloudprober URLs (/status for status,/config for config, /metrics for prometheus-format metrics) from within the cluster. For quick verification you can also set up a port forwarder and access these URLs locally at localhost:9313:

kubectl port-forward svc/cloudprober 9313:9313

Once you’ve verified that everything is working as expected, you can go on setting up metrics collection through prometheus (or stackdriver) in usual ways.

Kubernetes Targets #

If you’re running on Kubernetes, you’d probably want to monitor Kubernetes resources (e.g. pods, endpoints, etc) as well. Cloudprober supports dynamic discovery of Kubernetes resources through the targets type k8s.

For example, the following config adds an HTTP probe for the endpoints named cloudprober (equivalent to running kubectl get ep cloudprober).

probe {
  name: "pod-to-endpoints"
  type: HTTP

  targets {
    # Equivalent to kubectl get ep cloudprober
    k8s {
      endpoints: "cloudprober"
    }
  }

  # Note that the following http_probe automatically uses target's discovered
  # port.
  http_probe {
    relative_url: "/status"
  }
}

See Kubernetes Targets for more details on Kubernetes targets.

Push Config Update #

To push new cloudprober config to the cluster:

# Update the config map
kubectl create configmap cloudprober-config \
  --from-file=cloudprober.cfg=cloudprober.cfg  -o yaml --dry-run | \
  kubectl replace -f -

# Update deployment
export CONFIG_CHECKSUM=$(kubectl get cm/cloudprober-config -o yaml | sha256sum) && \
cat deployment.yaml | envsubst | kubectl apply -f -

Cloudprober should now start monitoring cloudprober endpoints. To verify:

# Set up port fowarding such that you can access cloudprober:9313 through
# localhost:9313.
kubectl port-forward svc/cloudprober 9313:9313 &

# Check status
curl localhost:9313/status

# Check metrics (prometheus data format)
curl localhost:9313/metrics

If you’re running on GKE and have not disabled cloud logging, you’ll also see logs in Stackdriver Logging.