Webhook

By default, CRI Resource Manager does not see the original container resource requirements specified in the Pod Spec. It tries to calculate these for cpu and memory compute resources using the related parameters present in the CRI container creation request. The resulting estimates are normally accurate for cpu, and also for memory limits. However, it is not possible to use these parameters to estimate memory requests or any extended resources.

If you want to make sure that CRI Resource Manager uses the origin Pod Spec resource requirements, you need to duplicate these as annotations on the Pod. This is necessary if you plan using or writing a policy which needs extended resources.

This process can be fully automated using the CRI Resource Manager Annotating Webhook. Once you built the Docker* image for it using the provided Dockerfile and published it, you can set up the webhook as follows:

• Fill in the IMAGE_PLACEHOLDER in webhook-deployment.yaml to match the image.

• Create a cri-resmgr-webhook-secret that carries a key and a certificate to cri-resmgr-webhook. You can create a key, a self-signed certificate and the secret that holds them with the following commands:

  SVC=cri-resmgr-webhook NS=cri-resmgr
  openssl req -x509 -newkey rsa:2048 -sha256 -days 365 -nodes \
    -keyout cmd/cri-resmgr-webhook/server-key.pem \
    -out cmd/cri-resmgr-webhook/server-crt.pem \
    -subj "/CN=$SVC.$NS.svc" \
    -addext "subjectAltName=DNS:$SVC,DNS:$SVC.$NS,DNS:$SVC.$NS.svc"
  cat >cmd/cri-resmgr-webhook/webhook-secret.yaml <<EOF
  apiVersion: v1
  kind: Secret
  metadata:
    name: cri-resmgr-webhook-secret
    namespace: $NS
  data:
    svc.crt: $(base64 -w0 < cmd/cri-resmgr-webhook/server-crt.pem)
    svc.key: $(base64 -w0 < cmd/cri-resmgr-webhook/server-key.pem)
  type: Opaque
  EOF
  kubectl create namespace $NS
  kubectl create -f cmd/cri-resmgr-webhook/webhook-secret.yaml
  

• Fill in the CA_BUNDLE_PLACEHOLDER in mutating-webhook-config.yaml. If you created the key and the certificate with the commands above, you can do this with the following command:

  sed -e "s/CA_BUNDLE_PLACEHOLDER/$(base64 -w0 < cmd/cri-resmgr-webhook/server-crt.pem)/" \
      -i cmd/cri-resmgr-webhook/mutating-webhook-config.yaml
  

• Finally set up the webhook with these commands:

  kubectl apply -f cmd/cri-resmgr-webhook/webhook-deployment.yaml
  kubectl wait --for=condition=Available -n cri-resmgr deployments/cri-resmgr-webhook
  kubectl apply -f cmd/cri-resmgr-webhook/mutating-webhook-config.yaml