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Minikube and Prometheus Demo

This is a quick demo of using minikube to test Prometheus. This is meant to familiarize people with working with minikube, kubectl, prometheus, and grafana.

Prerequisites

Note: this has been developed and tested on OS X. Others should be similar.

Bootstrap

Install the prerequisites.

If using the xhyve driver for minikube, you should be able to create and start a single node, local Kubernetes cluster by running: minikube start --vm-driver=xhyve. If not using the xhyve driver, just run minikube start.

You can check that the node is up and running by running: minikube status. You should see something like:

minikubeVM: Running
localkube: Running

If you want to stop the cluster, run minikube stop. To start it, run minikube start. Note: you only need to pass the driver argument the first time you create the cluster (or if you destroy and recreate it).

You can run minikube dashboard and a browser window should open with the Kubernetes Dashboard running. You may to click around to familiarize yourself with it.

Run kubectl cluster-info and you should see something like:

kubernetes master is running at https://192.168.64.2:8443
kubernetes-dashboard is running at https://192.168.64.2:8443/api/v1/proxy/namespaces/kube-system/services/kubernetes-dashboard

To select the minikube local cluster for kubectl - useful if you are using multiple clusters - then run kubectl config use-context minikube

Monitoring Namespace

We are going to install the monitoring components into a "monitoring" namespace. While this is not necessary, it does show "best practices" in organizing applications by namespace rather than deploying everything into the default namespace.

First, create the monitoring namespace: kubectl create -f monitoring-namespace.yaml.

You can now list the namespaces by running kubectl get namespaces and you should see something similar to:

NAME          STATUS    AGE
default       Active    6d
kube-system   Active    6d
monitoring    Active    3d

Deploying Prometheus and Grafana

Let's step through deploying Prometheus. The configuration we will use is based on a blog post by CoreOS and the example configuration included with Prometheus.

Prometheus Configuration

Prometheus will get its configuration from a Kubernetes ConfigMap. This allows us to update the configuration separate from the image. Note: there is a large debate about whether this is a "good" approach or not, but for demo purposes this is fine.

Look at prometheus-config.yaml. The relevant part is in data/prometheus.yml. This is just a Prometheus configuration inlined into the Kubernetes manifest. Note that we are using the in-cluster Kubernetes service account to access the Kubernetes API.

To deploy this to the cluster run kubectl create -f prometheus-config.yaml. You can view this by running kubectl get configmap --namespace=monitoring prometheus-config -o yaml. You can also see this in the Kubernetes Dashboard.

Prometheus Pod

We will use a single Prometheus pod for this demo. Take a look at prometheus-deployment.yaml. This is a Kubernetes Deployment that describes the image to use for the pod, resources, etc. Note:

  • In the metadata section, we give the pod a label with a key of name and a value of prometheus. This will come in handy later.
  • In annotations, we set a couple of key/value pairs that will actually allow Prometheus to autodiscover and scrape itself.
  • We are using an emptyDir volume for the Prometheus data. This is basically a temporary directory that will get erased on every restart of the container. For a demo this is fine, but we'd do something more persistent for other use cases.

Deploy the deployment by running kubectl create -f prometheus-deployment.yaml. You can see this by running kubectl get deployments --namespace=monitoring.

Prometheus Service

Now that we have Prometheus deployed, we actually want to get to the UI. To do this, we will expose it using a Kubernetes Service.

In prometheus-service.yaml, there are a few things to note:

  • The label selector searches for pods that have been labeled with name: prometheus as we labeled our pod in the deployment.
  • We are exposing port 9090 of the running pods.
  • We are using a "NodePort." This means that Kubernetes will open a port on each node in our cluster. You can query the API to get this port.

Create the service by running kubectl create -f prometheus-service.yaml. You can then view it by running kubectl get services --namespace=monitoring prometheus -o yaml.

One thing to note is that you will see something like nodePort: 30827 in the output. We could access the service on that port on any node in the cluster. Minikube comes with a helper to do just that, just run minikube service --namespace=monitoring prometheus and it will open a browser window accessing the service.

From the Prometheus console, you can explore the metrics is it collecting and do some basic graphing. You can also view the configuration and the targets. Click Status->Targets and you should see the Kubernetes cluster and nodes. You should also see that Prometheus discovered itself under kubernetes-pods

Using Prometheus without Grafana

Alerts and graphs uses the same kind of queries so Prometheus should be usable without Grafana:

Do kubectl create -f testing/ to expose Prometheus locally. Sample graphs (depending on minikube service --namespace=monitoring expose-prometheus URL):

Deploying Grafana

You can deploy grafana by creating its deployment and service by running kubectl create -f grafana-deployment.yaml and kubectl create -f grafana-service.yaml. Feel free to explore via the kubectl command line and/or the Dashboard.

Go to grafana by running minikube service --namespace=monitoring grafana. Username is admin and password is also admin.

Let's add Prometheus as a datasource.

  • Click on the icon in the upper left of grafana and go to "Data Sources".
  • Click "Add data source".
  • For name, just use "prometheus"
  • Select "Prometheus" as the type
  • For the URL, we will actual use Kubernetes DNS service discovery. So, just enter http://prometheus:9090. This means that grafana will lookup the prometheus service running in the same namespace as it on port 9090.

Create a New dashboard by clicking on the upper-left icon and selecting Dashboard->New. Click the green control and add a graph panel. Under metrics, select "prometheus" as the datasource. For the query, use sum(container_memory_usage_bytes) by (kubernetes_pod_name). Click save. This graphs the memory used per pod.

Prometheus Node Explorer

We can also use Prometheus to collect metrics of the nodes themselves. We use the node exporter for this. We can also use Kubernetes to deploy this to every node. We will use a Kubernetes DaemonSet to do this.

In node-exporter-daemonset.yml you will see that it looks similar to the deployment we did earlier. Notice that we run this in privileged mode (privileged: true) as it needs access to various information about the node to perform monitoring. Also notice that we are mounting in a few node directories to monitor various things.

Run kubectl create -f node-exporter-daemonset.yml to create the daemon set. This will run an instance of this on every node. In minikube, there is only one node, but this concept scales to thousands of nodes.

You can verify that it is running by using the command line or the dash board.

After a minute or so, Prometheus will discover the node itself and begin collecting metrics from it. To create a dashboard in grafana using node metrics, follow the same procedure as before but use node_load1 as the metric query. This will be the one minute load average of the nodes.

Note: in a "real" implementation, we would label the pods in an easily queryable pattern.