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