Overview

This operator manages OpenShift ClusterResourceOverride Admission Webhook Server.

Scheduling is based on resources requested, while quota and hard limits refer to resource limits, which can be set higher than requested resources. The difference between request and limit determines the level of overcommit; for instance, if a container is given a memory request of 1Gi and a memory limit of 2Gi, it is scheduled based on the 1Gi request being available on the node, but could use up to 2Gi; so it is 200% overcommitted.

If OpenShift Container Platform administrators would like to control the level of overcommit and manage container density on nodes, ClusterResourceOverride Admission Webhook can be configured to override the ratio between request and limit set on developer containers. In conjunction with a per-project LimitRange specifying limits and defaults, this adjusts the container limit and request to achieve the desired level of overcommit.

ClusterResourceOverride Admission Webhook Server is located at cluster-resource-override-admission.

Prerequisites

• git
• go version v1.22+
• podman version 17.03+
  • Alternatively docker v1.2.0+ or buildah v1.7+
• kubectl version v1.11.3+
• Access to a OpenShift v4.x cluster.

Getting Started

A quick way to test your changes is to build the operator binary and run it directly from the command line.

# change to the root folder of the repo

# build the operator binary
make build

# the operator owns a CRD, so register the CRD
kubectl apply -f artifacts/olm/manifests/clusterresourceoverride/1.0.0/clusterresourceoverride.crd.yaml 

# make sure you have a cluster up and running
# create a namespace where the operator binary will manage its resource(s)
kubectl create ns cro

# before you run the operator binary, make sure you have the following
# OPERAND_IMAGE: this points to the image of ClusterResourceOverride admission webhook server.
# OPERAND_VERSION: the version of the operand.

# run the operator binary
OPERAND_IMAGE=quay.io/{openshift}/clusterresourceoverride@sha256:{image digest} OPERAND_VERSION=1.0.0 \
bin/cluster-resource-override-admission-operator start --namespace=cro --kubeconfig=${KUBECONFIG} --v=4

Now, if you want to install the ClusterResourceOverride admission webhook server then simply create a custom resource of ClusterResourceOverride type.

apiVersion: operator.autoscaling.openshift.io/v1
kind: ClusterResourceOverride
metadata:
  name: cluster
spec:
  podResourceOverride:
    spec:
      memoryRequestToLimitPercent: 50
      cpuRequestToLimitPercent: 25
      limitCPUToMemoryPercent: 200

This repo ships with an example CR, you can directly apply the YAML resource as well.

kubectl apply -f artifacts/example/clusterresourceoverride-cr.yaml
# or 
# make create-cro-cr

The operator watches for the custom resource(s) of ClusterResourceOverride type and will ensure that the ClusterResourceOverride admission webhook server is installed into the same namespace as the operator. You can check the current state of the admission webhook by checking the status of the cluster custom resource

kubectl get clusterresourceoverride cluster -o yaml

apiVersion: operator.autoscaling.openshift.io/v1
kind: ClusterResourceOverride
metadata:
  annotations:
    kubectl.kubernetes.io/last-applied-configuration: |
      {"apiVersion":"operator.autoscaling.openshift.io/v1","kind":"ClusterResourceOverride","metadata":{"annotations":{},"name":"cluster"},"spec":{"podResourceOverride":{"spec":{"cpuRequestToLimitPercent":25,"limitCPUToMemoryPercent":200,"memoryRequestToLimitPercent":50}}}}
  creationTimestamp: "2024-07-24T17:49:53Z"
  generation: 1
  name: cluster
  resourceVersion: "61017"
  uid: f75c6946-a556-429f-a1f6-99fe31368cb8
spec:
  podResourceOverride:
    spec:
      cpuRequestToLimitPercent: 25
      limitCPUToMemoryPercent: 200
      memoryRequestToLimitPercent: 50
status:
  certsRotateAt: null
  conditions:
  - lastTransitionTime: "2024-07-24T17:50:03Z"
    status: "True"
    type: Available
  - lastTransitionTime: "2024-07-24T17:50:02Z"
    status: "False"
    type: InstallReadinessFailure
  hash:
    configuration: 577fe3d2b05619ac326571a3504857e3e7e70a275c941e3397aa9db5c1a1d3a4
  image: quay.io/macao/clusterresourceoverride:dev
  resources:
    apiServiceRef:
      apiVersion: apiregistration.k8s.io/v1
      kind: APIService
      name: v1.admission.autoscaling.openshift.io
      resourceVersion: "60981"
      uid: 79385b4e-43bb-4b14-b145-d50399db4ad8
    configurationRef:
      apiVersion: v1
      kind: ConfigMap
      name: clusterresourceoverride-configuration
      namespace: clusterresourceoverride-operator
      resourceVersion: "60858"
      uid: a50a2095-bab9-4834-8be3-633028c35f9e
    deploymentRef:
      apiVersion: apps/v1
      kind: Deployment
      name: clusterresourceoverride
      namespace: clusterresourceoverride-operator
      resourceVersion: "61013"
      uid: 4f21e033-e806-48e0-b053-0bbb9d6f688d
    mutatingWebhookConfigurationRef:
      apiVersion: admissionregistration.k8s.io/v1
      kind: MutatingWebhookConfiguration
      name: clusterresourceoverrides.admission.autoscaling.openshift.io
      resourceVersion: "61016"
      uid: 4fd5e040-9445-48de-9ea6-0d7028e5ab5c
    serviceRef:
      apiVersion: v1
      kind: Service
      name: clusterresourceoverride
      namespace: clusterresourceoverride-operator
      resourceVersion: "60876"
      uid: 1e343ec2-8c71-4cbc-a236-8c9c3a791db2
  version: 1.0.0

Test Pod Resource Override

The ClusterResourceOverride admission webhook enforces an opt-in approach, object(s) belonging to a namespace that has the following label are admitted, all other objects are ignored.

apiVersion: v1
kind: Namespace
metadata:
  name: test
  labels:
    clusterresourceoverrides.admission.autoscaling.openshift.io/enabled: "true"

• Create a namespace with the appropriate label.
• Create a Pod in the above namespace. The requests and limits of the Pod's resources are overridden according to the configuration of the webhook server.

kubectl apply -f artifacts/example/test-namespace.yaml
kubectl apply -f artifacts/example/test-pod.yaml
# or
# make create-test-pod

The original request of the Pod has the following resources section.

spec:
  containers:
    - name: hello-openshift
      image: openshift/hello-openshift
      resources:
        limits:
          memory: "512Mi"
          cpu: "2000m"

The Admission webhook intercepts the original Pod request and overrides the resources according to the configuration.

spec:
  containers:
  - image: openshift/hello-openshift
    name: hello-openshift
    resources:
      limits:
        cpu: "1"
        memory: 512Mi
      requests:
        cpu: 250m
        memory: 256Mi

Deploy

You can also deploy the operator on an OpenShift cluster:

• Build the operator binary
• Build and push operator image
• Apply kubernetes manifests

# change to the root folder of the repo

# build operator binary
make build

# build and push operator image
make local-image LOCAL_OPERATOR_IMAGE="{operator image}"
make local-push LOCAL_OPERATOR_IMAGE="{operator image}"

# deploy on local cluster
# LOCAL_OPERAND_IMAGE: operand image
# LOCAL_OPERATOR_IMAGE: operator image
make deploy-local LOCAL_OPERAND_IMAGE="{operand image}" LOCAL_OPERATOR_IMAGE="{operator image}"

Delete the operator and its resources.

make undeploy-local

Deploy via OLM

There are three steps:

• Package the OLM manifests into an operator registry bundle image and push it to an image registry
• Make the above operator catalog source available to your OpenShift cluster.
• Deploy the operator via OLM.

Before you package the OLM manifests, make sure the CSV file artifacts/olm/manifests/clusterresourceoverride/1.0.0/clusterresourceoverride.v1.csv.yamlpoints to the right operator and operand image.

# build and push the image
make operator-registry OLM_IMAGE_REGISTRY=docker.io/{your org}/clusterresourceoverride-registry IMAGE_TAG=dev

# make your catalog source available to the cluster
kubectl apply -f artifacts/olm/catalog-source.yaml

# wait for the CatalogSource object to be in 'READY' state.
# one way to make sure is to check the 'status' block of the CatalogSource object
kubectl -n clusterresourceoverride-operator get catalogsource clusterresourceoverride-catalog -o yaml

# or, you can query to check if your operator has been registered
kubectl -n clusterresourceoverride-operator get packagemanifests | grep clusterresourceoverride 

# at this point, you can install the operator from OperatorHub UI.
# if you want to do it from the command line, then execute the following:

# create an `OperatorGroup` object to associated with the operator namespace
# and the create a Subscription object.
kubectl apply -f artifacts/olm/operator-group.yaml
kubectl apply -f artifacts/olm/subscription.yaml

# install the ClusterResourceOverride admission webhook server by creating a custom resource
kubectl apply -f artifacts/example/clusterresourceoverride-cr.yaml 

E2E Tests

To run local E2E tests, you need to have a running OpenShift cluster and the following environment variables set:

• KUBECONFIG: path to the kubeconfig file.
• LOCAL_OPERATOR_IMAGE: operator image.
• LOCAL_OPERAND_IMAGE: operand image.

make e2e-local KUBECONFIG={path to kubeconfig} LOCAL_OPERATOR_IMAGE={operator image} LOCAL_OPERAND_IMAGE={operand image}