Pod Disruption Budget Controller

Hard fork of https://github.com/mikkeloscar/pdb-controller

This is a simple Kubernetes controller for adding default Pod Disruption Budgets (PDBs) for Deployments and StatefulSets in case none are defined. This is inspired by the dicussion in kubernetes/kubernetes#35318 and was created for lack of an alternative.

How it works

The controller simply gets all Pod Disruption Budgets for each namespace and compares them to Deployments and StatefulSets. For any resource with more than 1 replica and no matching Pod Disruption Budget, a default PDB will be created:

apiVersion: policy/v1beta1
kind: PodDisruptionBudget
metadata:
  name: my-app
  namespace: kube-system
  labels:
    application: my-app
    heritage: pdb-controller
    version: v1.0.0
spec:
  minAvailable: 1
  selector:
    matchLabels:
      application: my-app

The selector and labels are based on those from the related Deployment or StatefulSet. The special heritage=pdb-controller label is set by the controller and is used to find owned PDBs. Owned PDBs are removed in case replicas of the related resource is scaled to 1 or less. This is done to prevent deadlocking for clients depending on the PDBs e.g. cluster upgrade tools.

Additionally you can run the controller with the flag --non-ready-ttl=15m which means it will remove owned PDBs in case the pods of a targeted deployment or statefulset are non-ready for more than the specified ttl. This is another way to ensure broken deployments doesn't block cluster operations.

Building

To build this project you need to install Go and checkout the repository.

$ git clone https://github.com/dreamteam-gg/pdb-controller.git
$ cd pdb-controller
$ go build

GolangCI-Lint

To run code linting for this project you need to install GolangCI-Lint and checkout the repository.

$ git clone https://github.com/dreamteam-gg/pdb-controller.git
$ cd pdb-controller
$ golangci-lint run

Setup

The pdb-controller can be run as a deployment in the cluster or locally. See deployment.yaml for an in-cluster example.

Deploy it to cluster by running:

$ kubectl apply -f Docs/deployment.yaml

Or run locally for debug purposes:

$ go run pdb-controller  --kubeconfig=[path-to-kubeconfig]

This will use the current context or your local kubeconfig

TODO

• Instead of long polling, add a Watch feature.
• Helm chart.
• More logs, prettier printing.

LICENSE

See LICENSE file.