k8s-node-descale

Drains Kubernetes nodes after they reach the specified best-before age. To be used together with an autoscaler so that the node will get replaced with a fresh one when there is demand.

Installation

Building manually:

$ gem build k8s_node_descale.gemspec
$ gem install k8s_node_desacale*.gem
$ k8s-node-descale

Docker:

$ docker build -t descale --build-arg KUBE_VERSION=1.11.1 .
$ docker run -t descale

Docker Compose:

$ KUBE_VERSION=1.11.1 docker-compose run -rm

Usage

Command-line help

Usage:
    k8s-node-descale [OPTIONS]

  Drains Kubernetes nodes after they reach the specified best-before date.

Options:
    --kubectl PATH                specify path to kubectl (default: $PATH)
    --kube-config PATH            Kubernetes config path (default: $KUBECONFIG)
    --max-age DURATION            maximum age of server before draining and terminating (default: $MAX_AGE, or "3d")
    --max-nodes COUNT             drain maximum of COUNT nodes per cycle (default: $MAX_NODES_COUNT, or 1)
    --check-period SCHEDULE       run periodically, example: --every 1h (default: $CHECK_PERIOD)
    --dry-run                     perform a dry-run, doesn't drain or terminate any instances. (default: $DRY_RUN, or false)
    -h, --help                    print help

Scheduling

You can use the --check-period option to let the program do its own scheduling or deploy it as a cron job.

Configuring credentials

Kube API

The Kubernetes credentials lookup order is:

• --kube-config option or KUBECONFIG environment variable
• "in-cluster-configuration" when running on a Kubernetes node (KUBERNETES_SERVICE_HOST and KUBERNETES_SERVICE_PORT_HTTPS environment variables, /var/run/secrets/kubernetes.io/serviceaccount/ca.crt and /var/run/secrets/kubernetes.io/serviceaccount/token configuration files)

Contributing

Bug reports and pull requests are welcome on GitHub at https://github.com/kontena/k8s-node-descale