Kubernetes Metrics Server

User guide

You can find the user guide in the official Kubernetes documentation.

Design

The detailed design of the project can be found in the following docs:

• Metrics API
• Metrics Server

For the broader view of monitoring in Kubernetes take a look into Monitoring architecture

Deployment

Compatibility matrix:

Metrics Server	Metrics API group/version	Supported Kubernetes version
0.3.x	metrics.k8s.io/v1beta1	1.8+
0.2.x	metrics.k8s.io/v1beta1	1.8+
0.1.x	metrics/v1alpha1	1.7

In order to deploy metrics-server in your cluster run the following command from the top-level directory of this repository:

# Kubernetes 1.7
$ kubectl create -f deploy/1.7/

# Kubernetes > 1.8
$ kubectl create -f deploy/1.8+/

You can also use this helm chart to deploy the metric-server in your cluster (This isn't supported by the metrics-server maintainers): https://github.com/helm/charts/tree/master/stable/metrics-server

If you want to test metric-server in a minikube cluster, please follow the steps below:

$ minikube version
minikube version: v1.2.0

# disable the metrics-server addon for minikube in case it was enabled, because it installs the metric-server@v0.2.1
$ minikube addons disable metrics-server

# now start a new minikube
$ minikube delete; minikube start --extra-config=kubelet.authentication-token-webhook=true
🔥  Deleting "minikube" from virtualbox ...
💔  The "minikube" cluster has been deleted.
😄  minikube v1.2.0 on linux (amd64)
🔥  Creating virtualbox VM (CPUs=2, Memory=2048MB, Disk=20000MB) ...
🐳  Configuring environment for Kubernetes v1.15.0 on Docker 18.09.6
    ▪ kubelet.authentication-token-webhook=true
🚜  Pulling images ...
🚀  Launching Kubernetes ...
⌛  Verifying: apiserver proxy etcd scheduler controller dns
🏄  Done! kubectl is now configured to use "minikube"

# deploy the latest metric-server
$ kubectl create -f deploy/1.8+/
clusterrole.rbac.authorization.k8s.io/system:aggregated-metrics-reader created
clusterrolebinding.rbac.authorization.k8s.io/metrics-server:system:auth-delegator created
rolebinding.rbac.authorization.k8s.io/metrics-server-auth-reader created
apiservice.apiregistration.k8s.io/v1beta1.metrics.k8s.io created
serviceaccount/metrics-server created
deployment.extensions/metrics-server created
service/metrics-server created
clusterrole.rbac.authorization.k8s.io/system:metrics-server created
clusterrolebinding.rbac.authorization.k8s.io/system:metrics-server created

# edit metric-server deployment to add the flags
# args:
# - --kubelet-insecure-tls
# - --kubelet-preferred-address-types=InternalIP,ExternalIP,Hostname
$ kubectl edit deploy -n kube-system metrics-server

Flags

Metrics Server supports all the standard Kubernetes API server flags, as well as the standard Kubernetes glog logging flags. The most commonly-used ones are:

• --logtostderr: log to standard error instead of files in the container. You generally want this on.

• --v=<X>: set log verbosity. It's generally a good idea to run a log level 1 or 2 unless you're encountering errors. At log level 10, large amounts of diagnostic information will be reported, include API request and response bodies, and raw metric results from Kubelet.

• --secure-port=<port>: set the secure port. If you're not running as root, you'll want to set this to something other than the default (port 443).

• --tls-cert-file, --tls-private-key-file: the serving certificate and key files. If not specified, self-signed certificates will be generated, but it's recommended that you use non-self-signed certificates in production.

• --kubelet-certificate-authority: the path of the CA certificate to use for validate the Kubelet's serving certificates.

Additionally, Metrics Server defines a number of flags for configuring its behavior:

• --metric-resolution=<duration>: the interval at which metrics will be scraped from Kubelets (defaults to 60s).

• --kubelet-insecure-tls: skip verifying Kubelet CA certificates. Not recommended for production usage, but can be useful in test clusters with self-signed Kubelet serving certificates.

• --kubelet-port: the port to use to connect to the Kubelet (defaults to the default secure Kubelet port, 10250).

• --kubelet-preferred-address-types: the order in which to consider different Kubelet node address types when connecting to Kubelet. Functions similarly to the flag of the same name on the API server.

Development

Runing e2e tests

Pre-requesites:

• Docker
• kubectl

Run:

make test-e2e