feat: First draft of a scheduler

[RealAnna]

Resolves: #5

edit make file and scheduler image with your own registry

make push-release-images
cd to manifest/install/charts
kubectl create -n keptn-scheduler

to run in parallel to the default scheduler
helm upgrade --install keptn-scheduler keptn-scheduler/

wait for it to be up
deploy something on the scheduler

eg.

apiVersion: apps/v1
kind: Deployment
metadata:
  name: nginx-deployment
  namespace: keptnlc
  labels:
    app: nginx
spec:
  replicas: 3
  selector:
    matchLabels:
      app: nginx
  template:
    metadata:
      labels:
        app: nginx
    spec:
     schedulerName: keptn-scheduler
     containers:
      - name: nginx
        image: nginx:1.14.2
        ports:
        - containerPort: 80

test deployment available on keptn-dev cluster

[thschue]

I would remove the as-a-second-scheduler part and make this the standard as currently the keptn scheduler won't replace another one ... Furthermore I'm not sure how many things of the boilerplate are really needed (/hack). The rest looks good like a good start 🚀

[thschue]

Shouldn't this be keptnsandbox?

[RealAnna]

do we have one or should we make it? 🤔

[RealAnna]

I commented it out for now, we will make one soon

[thschue]

I think keptnsandbox already exists ...

[thschue]

Do you think it would make sense to hook in an earlier stage? (https://kubernetes.io/docs/concepts/scheduling-eviction/scheduling-framework/)

[RealAnna]

In my mind pre-deployment checks could take a while and it would not make sense to not discover in the meantime that there are other reasons for the pod not to be scheduled e.g. filters make it impossible to find a compatible node. We discussed having prechecks and scheduling steps in parallel up to resource allocation, but maybe also pre-Score could be an option, just I could not think of a reason why we would like to interfere with the node choice. What do you think could be another approach?

[thschue]

Good point, think it makes sense to leave this in the permit-phase at the moment :-)

[thschue]

I think we should adapt the Helm-Chart readme, then we are good to go 👍

[thschue]

lgtm