Noe: Kubernetes Mutating Webhook for Node Architecture Selection

Blog post announcing and explaining the effort behind Noe

Noe is a Kubernetes mutating webhook that dynamically assigns node architectures to match the requirements of container images within a Pod. It simplifies mixed-architecture deployments (e.g. ARM and x86) by ensuring that Pods are scheduled on nodes capable of executing all their images.

Features

• Automatically adjusts node affinities based on container images' supported architectures
• Improves deployment efficiency by removing the need for manual node selector configuration
• Facilitates seamless mixed-architecture deployments by ensuring compatibility between ARM and x86 nodes

Running Tests

Run all tests using the following command:

go test ./...

Installing Noe

Noe provides a Helm chart, available exclusively from the code repository. The simplest way to install it is to use ArgoCD and define an application such as:

apiVersion: argoproj.io/v1alpha1
kind: Application
spec:
  source:
    repoURL: https://github.com/adevinta/noe.git
    path: charts/noe
    targetRevision: HEAD

Helm chart values

Noe's Helm chart is designed to work in standard configurations. Below is a comprehensive guide on how to customize the Helm chart values to match your Kubernetes configuration.

Customise Noe deployed image

This section defines the Docker image details used by the deployment.

image:
  registry: ghcr.io
  repository: adevinta/noe
  tag: latest

Manage docker registries rate limits

Forces the use of registry proxies for specific images. This helps better manage the requests to public docker registries and prevent requests to be rate limited, or suffer from registries downtime.

Default:

proxies: []

Example:

proxies:
- docker.io=docker-proxy.company.corp
- quay.io=quay-proxy.company.corp

Example:

proxies:
  - docker.io=docker-proxy.company.corp
  - quay.io=quay-proxy.company.corp

Further pod scheduling constraints

Ensure pod and nodes have similar labels

Specify a list of label names that pods must have in common with the node they run on. Those labels constraints are added to the node selectors computed by the architectures images supports.

Default:

matchNodeLabels: []

Example:

matchNodeLabels:
  - kubernetes.io/arch
  - failure-domain.beta.kubernetes.io/region

With this configuration, a pod with label failure-domain.beta.kubernetes.io/region=eu-west-3 would only be scheduled on nodes with label failure-domain.beta.kubernetes.io/region=eu-west-3. Pods without any failure-domain.beta.kubernetes.io/region label will be scheduled on any node.

Restrict image architectures

List of architectures that can be scheduled. Any other architecture supported by images will be ignored.

Default:

schedulableArchitectures: []

Example:

schedulableArchitectures:
  - amd64
  - arm64

Configuring accesses to private images

While Noe handles the imagePullSecret fields, it can also be configured to transparently authenticate requests to private registries. Because of its design, it considers that node-level private registry authentication is consistent across the whole cluster.

kubeletConfig

Configuration for the kubelet credentials configuration. All those paths will automatically be mounted from the host to noe's container so Noe can retrieve image configurations.

Default:

kubeletConfig:

Example:

kubeletConfig:
  binDir: /etc/eks/image-credential-provider
  configDir: /etc/eks/image-credential-provider
  config: config.json

containerdConfigPathCandidates

Paths to the containerd configuration files. All those paths will automatically be mounted from the host to noe's container so Noe can retrieve image configurations.

Default:

containerdConfigPathCandidates:
  - /etc/containerd

dockerConfigPathCandidates

This setting specifies the possible paths where the configuration files using the Docker format can be found on the host. Specifying those values will automatically mount the host paths inside Noe's containers.

Default:

dockerConfigPathCandidates:
  - /var/lib/kubelet/config.json

Additional metadata

You can customize the labels and annotations of Kubernetes objects as followed. Customizable objects are: pod, issuer, certificate, mutatingwebhookconfiguration, rolebinding, clusterrole, clusterrolebinding, serviceaccount, deployment

Default:

pod:
  # labels:
  #   some: label
  # annotations:
  #   some: annotations

Example:

pod:
  labels:
    app: my-application
  annotations:
    prometheus.io/scrape: "true"
    prometheus.io/port: "8080"

Hinting preferred and supported target architectures

By default, Noe will automatically select the appropriate architecture when only one is supported by all the containers in the Pod. If more than one is available, Noe will select the system-defined preferred one if available. This preference can be chosen in the command line for Noe (defaults to amd64 if unspecified):

./noe -preferred-arch amd64

This preference can also be overridden at the Pod level by adding the label:

labels:
  arch.noe.adevinta.com/preferred: amd64

Noe will always prioritize a running Pod, so if the preference is not supported by all the containers in the Pod, the common architecture will be selected.

You can restrict the acceptable common architectures in the command line for Noe:

./noe -cluster-schedulable-archs amd64,arm64

If you specify both a preferred architecture and a list of supported architectures in the command line, the default architecture must be part of the list. Otherwise Noe will fail to start.

If a preferred architecture is specified at the Pod level and is not compatible with the supported architectures listed in the command line, it will be ignored.