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krs is a command line tool for capturing and serializing Kubernetes resource statistics in OpenMetrics format. It dumps statistics about Kubernetes resources, for example the number of pods in a certain namespace, on a periodic basis to local storage. The kind of resources (pods, services, etc.) as well as the scope, that is, cluster-level or a list of namespaces, is configurable. You can use krs either on the client-side (for example, from your laptop) or in-cluster, like in a deployment. Note that krs leaves the decision where and how long-term storage is carried out up to you. More …

Index:

• Install
  • From binaries
  • From source
  • From Kubernetes
• Use
• Testing

In order to use krs you must meet the following two prerequisites:

1. kubectl must be installed.
2. Access to a Kubernetes cluster must be configured.

Here are my test environments: a v1.9 cluster via OpenShift Online, a v1.10 cluster via AKS, and a v1.11 cluster via Minikube, all with a kubectl@v1.11 client-side, on macOS.

You can download binaries for Linux, macOS, and Windows which are available via the release page. To install from binary, for example, on a macOS system, do:

$ curl -L $(curl -s https://api.github.com/repos/mhausenblas/krs/releases/latest | grep macos | grep browser_download_url | cut -d : -f 2,3 | tr -d \") -o krs
$ chmod +x krs
$ sudo mv krs /usr/local/bin

Assuming you've got Go in version 1.10 or above installed you can install krs from source like so:

$ go get -u github.com/mhausenblas/krs

You can launch krs in Kubernetes using the launch.sh script as follows. The script will dynamically create the respective permissions for the namespace and run krs as a deployment.
So, in a sense this is a self-test: create and watch a namespace krs-test and view the output like so:

$ kubectl create ns krs-test
namespace/krs-test created

$ ./launch.sh krs-test
serviceaccount/krs created
clusterrole.rbac.authorization.k8s.io/resreader configured
rolebinding.rbac.authorization.k8s.io/allowpodprobes created
deployment.apps/krs created

$ kubectl -n krs-test logs -f $(kubectl -n krs-test get po -l=run=krs --output=jsonpath={.items[*].metadata.name})
# HELP pods Number of pods in any state, for example running
# TYPE pods gauge
pods{namespace="krs-test"} 1
# HELP deployments Number of deployments
# TYPE deployments gauge
deployments{namespace="krs-test"} 1
# HELP services Number of services
# TYPE services gauge
services{namespace="krs-test"} 0
...

krs assumes that kubectl is installed and configured. It writes the OpenMetrics data to stdout which you can then redirect to a file or process further.

For example, to gathers stats of the dev42 namespace and store the OpenMetrics formatted stats in a file called /tmp/krs/2018-10-05.om as well as see the errors on screen (via stdout), do the following:

$ krs --namespace dev42 >> /tmp/krs/2018-10-05.om

If you don't provide a namespace as the first argument, krs will watch the default namespace. Also, by default, the following resources are tracked: pods, deployments, and services.

For example, an excerpt of the output of the end-to-end test looks as follows:

# HELP pods Number of pods in any state, for example running
# TYPE pods gauge
pods{namespace="krs"} 2
# HELP deployments Number of deployments
# TYPE deployments gauge
deployments{namespace="krs"} 2
# HELP services Number of services
# TYPE services gauge
services{namespace="krs"} 1
# HELP pods Number of pods in any state, for example running
# TYPE pods gauge
pods{namespace="krs"} 2
# HELP deployments Number of deployments
# TYPE deployments gauge
deployments{namespace="krs"} 2
# HELP services Number of services
# TYPE services gauge
services{namespace="krs"} 1
...

If you, for example, want to track pods, stateful sets, and persistent volumes in the namespace prod1337 you'd launch krs like so:

$ krs --namespace prod1337 --resources "pods,sts,pv,pvc"

There are two environment variables that krs understands:

• With KRS_KUBECTL_BIN you can define which kubectl binary krs will use. Note: under Windows this is required, for OpenShift, this is an option to use oc instead of kubectl.
• With KRS_VERBOSE set (for example, to true but really any value does) you can get debug-level information, down to what kubectl call has been issued.

To do:

• Improve Make file
• Complete e2e testing