Boink

Boink is a simple Go client application that can handle stopping and starting Kubernetes Deployments. It works by selecting Deployments based on labels. It can also remember the previous known replicas, unlike a standard kubectl scale command where you need to specify the replicas manually.

This tool can be helpful when you have certain applications which needs to be stopped during certain period of time. Pair this tool with kubernetes CronJob to automatically stop or start a Deployment

How to run the application

1. Outside of the cluster - This is a normal executable program to interact with kubernetes cluster. You can use minikube.

   Commands:

   • start - To start deployments
   • stop - To stop deployments

   Arguments:

   • --config - The location of $KUBECONFIG
   • --namespace - The namespace to use.
   • --label - Specify the selectors.

   To Stop:

   boink stop --config $KUBECONFIG --namespace test --label app=nginx
   

   To Start:

   boink start --config $KUBECONFIG --namespace test --label app=nginx
   

2. In cluster

   Make sure you have the right permission in the cluster. See samples in manifest/ folder.

   1. Create the ServiceAccount

   apiVersion: v1
   kind: ServiceAccount
   metadata:
     name: boink
     namespace: test
   

   2. Create the ClusterRole

   apiVersion: rbac.authorization.k8s.io/v1
   kind: ClusterRole
   metadata:
   name: boink
   rules:
   - apiGroups: ["extensions","apps"]
   resources: ["deployments"]
   verbs: ["get", "list", "watch", "create", "update", "patch", "delete"]
   
   

   3. Bind the Cluster role with the service account

   apiVersion: rbac.authorization.k8s.io/v1
   kind: ClusterRoleBinding
   metadata:
       name: boink        
   roleRef:
     apiGroup: rbac.authorization.k8s.io
     kind: ClusterRole
     name: boink
   subjects:
   - kind: ServiceAccount
     name: boink
     namespace: test
   

   4. Create the CronJob, Stop Deployment with label app=nginx every minute.

   apiVersion: batch/v1beta1
   kind: CronJob
   metadata:
     name: nginx-starter
     namespace: test
   spec:
     #this is in UTC  will run at 6:46 AM everyday
     schedule: "46 6 * * *"
     startingDeadlineSeconds: 10
     concurrencyPolicy: Forbid
     jobTemplate:
       spec:      
         template:
           spec:
             serviceAccountName: boink
             containers:
             - name: boink
               image: boink:1.0
               command: ["/boink"]
               args: ["--namespace","test", "--label", "app=nginx", "--action" , "start"]
             restartPolicy: OnFailure
   

Tools:

1. command line library using cobra. This library makes it easy to create a command line application in Go.

2. Uses client-go to interact with kubernetes cluster.

3. github.com/sirupsen/logrus - Standard logging mechanism for Go.

Check the go.mod to see all the dependencies.

To build and run

1. Make sure you enable $GO111MODULE to on
2. Go to the working directory $GOPATH/src/boink/.
3. Do go build .
4. Do go test ./... -cover to run unit test with code coverage.
5. Finally to run the application boink --config $KUBECONFIG --namespace test --label app=nginx [start|stop].

If you are using skaffold, there is skaffold.yaml included at the root of the project. Simply do a skaffold dev from the $GOPATH/src/boink and you are good to go.