intel-device-plugins-for-kubernetes/cmd/fpga_admissionwebhook

Intel FPGA admission controller for Kubernetes

Table of Contents

• Introduction
• Dependencies
• Installation
  • Getting the source code
  • Deploying via the script
    • Pre-requisites
    • Build the webhook image
    • Deploying via the script
• Mappings
• Next steps

Introduction

The FPGA admission controller is one of the components used to add support for Intel FPGA devices to Kubernetes.

The FPGA admission controller webhook is responsible for performing mapping from user-friendly function IDs to the Interface ID and Bitstream ID that are required for FPGA programming by the FPGA CRI-O hook.

Mappings are stored in namespaced custom resource definition (CRD) objects, therefore the admission controller also performs access control, determining which bitstream can be used for which namespace. More details can be found in the Mappings section.

The admission controller also keeps the user from bypassing namespaced mapping restrictions, by denying admission of any pods that are trying to use internal knowledge of InterfaceID or Bitstream ID environment variables used by the prestart hook.

Dependencies

This component is one of a set of components that work together. You may also want to install the following:

• FPGA device plugin
• FPGA prestart CRI-O hook

All components have the same basic dependencies as the generic plugin framework dependencies

Installation

The following sections detail how to obtain, build and deploy the admission controller webhook plugin.

Getting the source code

$ mkdir -p $(go env GOPATH)/src/github.com/intel
$ git clone https://github.com/intel/intel-device-plugins-for-kubernetes $(go env GOPATH)/src/github.com/intel/intel-device-plugins-for-kubernetes

Deploying via the script

Deploying the webhook admission controller consists of a number of components, and actions, including:

• Certificates (secrets)
• CRDs
• Deployment
• Service
• Registration

A script is provided to make the whole process easier.

Pre-requisites

The script has some pre-requisite tools that must be installed on your system:

• jq
• cfssl

Build the webhook image

Before the webhook can be deployed, its container image needs to be built:

$ cd $(go env GOPATH)/src/github.com/intel/intel-device-plugins-for-kubernetes
$ make intel-fpga-admissionwebhook
...
Successfully tagged intel/intel-fpga-admissionwebhook:devel

Deploying via the script

To deploy the webhook, run the scripts/webhook-deploy.sh script:

$ cd $(go env GOPATH)/src/github.com/intel/intel-device-plugins-for-kubernetes
$ ./scripts/webhook-deploy.sh
Create secret including signed key/cert pair for the webhook
...
Create FPGA CRDs
customresourcedefinition.apiextensions.k8s.io/acceleratorfunctions.fpga.intel.com created
customresourcedefinition.apiextensions.k8s.io/fpgaregions.fpga.intel.com created
...
clusterrole.rbac.authorization.k8s.io/fpga-reader created
clusterrolebinding.rbac.authorization.k8s.io/default-fpga-reader created
...
Create webhook deployment
deployment.extensions/intel-fpga-webhook-deployment created
Create webhook service
service/intel-fpga-webhook-svc created
Register webhook
mutatingwebhookconfiguration.admissionregistration.k8s.io/fpga-mutator-webhook-cfg created

The script needs the CA bundle used for signing certificate requests in your cluster. By default, the script fetches the bundle stored in the configmap extension-apiserver-authentication. However, your cluster may use a different signing certificate that is passed in the option --cluster-signing-cert-file to kube-controller-manager. In this case, you must point the script to the actual signing certificate as follows:

$ ./scripts/webhook-deploy.sh --ca-bundle-path /var/run/kubernetes/server-ca.crt

Mappings

Mappings is a an essential part of the setup that gives a flexible instrument to a cluster administrator to manage FPGA bitstreams and to control access to them. Being a set of custom resource definitions they are used to configure the way FPGA resource requests get translated into actual resources provided by the cluster.

For the following mapping

apiVersion: fpga.intel.com/v1
kind: AcceleratorFunction
metadata:
  name: arria10.dcp1.1-nlb0
spec:
  afuId: d8424dc4a4a3c413f89e433683f9040b
  interfaceId: 9926ab6d6c925a68aabca7d84c545738
  mode: af

requested FPGA resources are translated to AF resources. For example, fpga.intel.com/arria10.dcp1.1-nlb0 is translated to fpga.intel.com/9926ab6d6c925a68aabca7d84c54573d8424dc4a4a3c413f89e433683f9040b. The first 31 characters of the resource name part (9926ab6d6c925a68aabca7d84c54573) is the first 31 characters of the region interface ID for Arria10 with DCP1.1 firmware. The next 32 characters (d8424dc4a4a3c413f89e433683f9040b) is an accelerator function ID. The format of resource names (e.g. arria10.dcp1.1-nlb0) can be any and is up to a cluster administrator.

The same mapping, but with its mode field set to region, translates fpga.intel.com/arria10.dcp1.1-nlb0 to fpga.intel.com/region-9926ab6d6c925a68aabca7d84c545738, and the corresponding AF IDs are set in environment variables for the container. The FPGA CRI-O hook then loads the requested bitstream to a region before the container is started.

Mappings of resource names are configured with objects of AcceleratorFunction and FpgaRegion custom resource definitions found respectively in ./deployment/fpga_admissionwebhook/af-crd.yaml and ./deployment/fpga_admissionwebhook/region-crd.yaml

Mappings between 'names' and 'ID's are controlled by the admission controller mappings collection file found in ./deployments/fpga_admissionwebhook/mappings-collection.yaml. This mappings file is deployed alongside the admission controller as part of the webhook deploy script.

Note that the mappings are scoped to the namespaces they were created in and they are applicable to pods created in the corresponding namespaces.

Next steps

Continue with FPGA prestart CRI-O hook.