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kubernetes-essential-containers

Mocks the concept of essential containers from ECS in Kubernetes. Useful when the main container completes and side cars keep running.

Example - main app container exits but the connection pooler side car keeps running.

Description

This project has been bootstrapped using kube-builder framework.

The code essentially checks for container status to change from Running to Terminated and reason for termination is Completed. This filters out reasons like container crashing etc.

The controller only watches for pods with label essential-containers and treat the container mentioned in label value as essential container. Once this main container exits (with exit code 0 - success/completed), we will delete the pod (because there is no stop pod method).

Commans used for the project bootstrap

kubebuilder init --repo github.com/sumanthkumarc/kubernetes-essential-containers
kubebuilder create api --kind Pod --controller --version=v1 --group=core

Getting Started

You’ll need a Kubernetes cluster to run against. You can use KIND to get a local cluster for testing, or run against a remote cluster. Note: Your controller will automatically use the current context in your kubeconfig file (i.e. whatever cluster kubectl cluster-info shows).

Testing on local

Set the KUBECONFIG env variable to your remote cluster kubeconfig. Use the make run command to run the controller.

Running on the cluster

  1. Install Instances of Custom Resources:
kubectl apply -f config/samples/
  1. Build and push your image to the location specified by IMG:
make docker-build docker-push IMG=<some-registry>/kubernetes-essential-containers:tag
  1. Deploy the controller to the cluster with the image specified by IMG:
make deploy IMG=<some-registry>/kubernetes-essential-containers:tag

Uninstall CRDs

To delete the CRDs from the cluster:

make uninstall

Undeploy controller

UnDeploy the controller from the cluster:

make undeploy

Contributing

// TODO(user): Add detailed information on how you would like others to contribute to this project

How it works

This project aims to follow the Kubernetes Operator pattern.

It uses Controllers, which provide a reconcile function responsible for synchronizing resources until the desired state is reached on the cluster.

Test It Out

  1. Install the CRDs into the cluster:
make install
  1. Run your controller (this will run in the foreground, so switch to a new terminal if you want to leave it running):
make run

NOTE: You can also run this in one step by running: make install run

Modifying the API definitions

If you are editing the API definitions, generate the manifests such as CRs or CRDs using:

make manifests

NOTE: Run make --help for more information on all potential make targets

More information can be found via the Kubebuilder Documentation

License

Copyright 2023.

Licensed under the Apache License, Version 2.0 (the "License"); you may not use this file except in compliance with the License. You may obtain a copy of the License at

http://www.apache.org/licenses/LICENSE-2.0

Unless required by applicable law or agreed to in writing, software distributed under the License is distributed on an "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. See the License for the specific language governing permissions and limitations under the License.