isabella232 / ht-k8s-action-plugin

Hollowtrees plugin used to interact with Kubernetes on specific event triggers

Kubernetes Hollowtrees action plugin

This is an action plugin for the Hollowtrees project. It interacts with the Kubernetes API to handle different Hollowtrees events in a K8S cluster.

When started it is listening on a gRPC interface and accepts Hollowtrees events.

Quick start

The project can be build with make. To create the binary locally, run:

make build

It creates the binary in the ./bin directory.

To create a docker image that can be run on Kubernetes run:

make docker-build

It creates a docker image with the name banzaicloud/ht-k8s-action-plugin:$(GIT_REVISION)

Configuration

The following options can be configured when starting the action plugin. Configuration is done through a plugin-config.toml file that can be placed in conf/ or near the binary:

[log]
    format = "text"
    level = "debug"

[plugin]
    port = "8887"

Instead of using a configuration file, environment variables can be used as well with the prefix HTPLUGIN. For example to configure the port where the application will listen, use the environment variable HTPLUGIN_PLUGIN_PORT.

The project is using an in-cluster config to interact with Kubernetes so it must be deployed accordingly.

To run:

kubectl run ht-k8s-action-plugin --image=banzaicloud/ht-k8s-action-plugin:$GITREV  --port=8887

Event types that the plugin can understand:

prometheus.server.alert.SpotTerminationNotice - Prepares a node for termination by draining it similarily to kubectl drain. It cordons the Kubernetes node by making it unschedulable (node.Spec.Unschedulable = true) and evicts or deletes the pods on the node that will be terminated.

Default Hollowtrees plugins

There are a few default Hollowtrees action plugins available:

• Kubernetes action plugin to execute k8s operations (e.g. graceful drain)
• AWS autoscaling group plugin to replace instances with a better cost or stability characteristics