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][git_tool]
[go][go_tool] version v1.12+.
[docker][docker_tool] version 17.03+.
- Alternatively [podman][podman_tool] v1.2.0+ or [buildah][buildah_tool] v1.7+
[kubectl][kubectl_tool] 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

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: "2019-12-18T22:35:02Z"
  generation: 1
  name: cluster
  resourceVersion: "127622"
  selfLink: /apis/operator.autoscaling.openshift.io/v1/clusterresourceoverrides/cluster
  uid: 978fc959-1717-4bd1-97d0-ae00ee111e8d
spec:
  podResourceOverride:
    spec:
      cpuRequestToLimitPercent: 25
      limitCPUToMemoryPercent: 200
      memoryRequestToLimitPercent: 50
status:
  certsRotateAt: "2020-12-15T22:52:46Z"
  conditions:
  - lastTransitionTime: "2019-12-18T23:27:03Z"
    status: "True"
    type: Available
  - lastTransitionTime: "2019-12-18T23:27:03Z"
    status: "False"
    type: InstallReadinessFailure
  hash:
    configuration: 577fe3d2b05619ac326571a3504857e3e7e70a275c941e3397aa9db5c1a1d3a4
    servingCert: bae6f72e906e9b054d0f4eb4b1540755f284373ad2febdec8454521ebfac5765
  image: docker.io/tohinkashem/clusterresourceoverride@sha256:f99ed0d7ecf197596bb34eed342ddc8a9169f68b68a457ee5a15070bc68e848a
  resources:
    configurationRef:
      apiVersion: v1
      kind: ConfigMap
      name: clusterresourceoverride-configuration
      namespace: cro
      resourceVersion: "78476"
      uid: e8a7f90e-90b1-4f2b-9b03-0064ffd33d4b
    deploymentRef:
      apiVersion: apps/v1
      kind: DaemonSet
      name: clusterresourceoverride
      namespace: cro
      resourceVersion: "78676"
      uid: 947ebfc5-c244-4621-acc3-c3117a10a97b
    mutatingWebhookConfigurationRef:
      apiVersion: admissionregistration.k8s.io/v1beta1
      kind: MutatingWebhookConfiguration
      name: clusterresourceoverrides.admission.autoscaling.openshift.io
      resourceVersion: "127621"
      uid: 98b3b8ae-d5ce-462b-8ab5-a729ea8f38f3
    serviceCAConfigMapRef:
      apiVersion: v1
      kind: ConfigMap
      name: clusterresourceoverride-service-serving
      namespace: cro
      resourceVersion: "78479"
      uid: faf27927-0fb0-453b-8656-1b05ea9a3d74
    serviceCertSecretRef:
      apiVersion: v1
      kind: Secret
      name: server-serving-cert-clusterresourceoverride
      namespace: cro
      resourceVersion: "78478"
      uid: cc6efc0e-0fce-4148-a943-6045dadaa72c
  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

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 dev-image DEV_IMAGE_REGISTRY=docker.io/{your org}/clusterresourceoverride-operator IMAGE_TAG=dev
make dev-push DEV_IMAGE_REGISTRY=docker.io/{your org}/clusterresourceoverride-operator IMAGE_TAG=dev

# deploy on local cluster
# CLUSTERRESOURCEOVERRIDE_OPERAND_IMAGE: operator image
# CLUSTERRESOURCEOVERRIDE_OPERATOR_IMAGE: operand image
make deploy-local CLUSTERRESOURCEOVERRIDE_OPERAND_IMAGE="{operand image}" CLUSTERRESOURCEOVERRIDE_OPERATOR_IMAGE="{operator image}

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.