Node Feature Discovery

# Introduction

## Table of contents

This software enables node feature discovery for Kubernetes. It detects hardware features available on each node in a Kubernetes cluster, and advertises those features using node labels and optionally node extended resources and node taints.

NFD consists of four software components:

1. nfd-master
2. nfd-worker
3. nfd-topology-updater
4. nfd-topology-gc

## NFD-Master

NFD-Master is the daemon responsible for communication towards the Kubernetes API. That is, it receives labeling requests from the worker and modifies node objects accordingly.

## NFD-Worker

NFD-Worker is a daemon responsible for feature detection. It then communicates the information to nfd-master which does the actual node labeling. One instance of nfd-worker is supposed to be running on each node of the cluster,

## NFD-Topology-Updater

NFD-Topology-Updater is a daemon responsible for examining allocated resources on a worker node to account for resources available to be allocated to new pod on a per-zone basis (where a zone can be a NUMA node). It then creates or updates a NodeResourceTopology custom resource object specific to this node. One instance of nfd-topology-updater is supposed to be running on each node of the cluster.

## NFD-Topology-GC

NFD-Topology-GC is a daemon responsible for cleaning obsolete NodeResourceTopology objects, obsolete means that there is no corresponding worker node.

One instance of nfd-topology-gc is supposed to be running in the cluster.

## Feature Discovery

Feature discovery is divided into domain-specific feature sources:

- CPU
- Kernel
- Memory
- Network
- PCI
- Storage
- System
- USB
- Custom (rule-based custom features)
- Local (hooks for user-specific features)

Each feature source is responsible for detecting a set of features which. in turn, are turned into node feature labels. Feature labels are prefixed with `feature.node.kubernetes.io/` and also contain the name of the feature source. Non-standard user-specific feature labels can be created with the local and custom feature sources.

An overview of the default feature labels:

    {
      "feature.node.kubernetes.io/cpu-<feature-name>": "true",
      "feature.node.kubernetes.io/custom-<feature-name>": "true",
      "feature.node.kubernetes.io/kernel-<feature name>": "<feature value>",
      "feature.node.kubernetes.io/memory-<feature-name>": "true",
      "feature.node.kubernetes.io/network-<feature-name>": "true",
      "feature.node.kubernetes.io/pci-<device label>.present": "true",
      "feature.node.kubernetes.io/storage-<feature-name>": "true",
      "feature.node.kubernetes.io/system-<feature name>": "<feature value>",
      "feature.node.kubernetes.io/usb-<device label>.present": "<feature value>",
      "feature.node.kubernetes.io/<file name>-<feature name>": "<feature value>"
    }

## Node annotations

NFD also annotates nodes it is running on:

Annotation | Description
--- | ---
[<instance>.]nfd.node.kubernetes.io/master.version | Version of the nfd-master instance running on the node. Informative use only.
[<instance>.]nfd.node.kubernetes.io/worker.version | Version of the nfd-worker instance running on the node. Informative use only.
[<instance>.]nfd.node.kubernetes.io/feature-labels | Comma-separated list of node labels managed by NFD. NFD uses this internally so must not be edited by users.
[<instance>.]nfd.node.kubernetes.io/extended-resources | Comma-separated list of node extended resources managed by NFD. NFD uses this internally so must not be edited by users.

NOTE: the `-instance` command line flag affects the annotation names

Unapplicable annotations are not created, i.e. for example master.version is only created on nodes running nfd-master.

## Custom resources

NFD takes use of some Kubernetes Custom Resources.

NodeFeatures (EXPERIMENTAL) can be used for representing node features and requesting node labels to be generated.

NFD-Master uses NodeFeatureRules for custom labeling of nodes.

NFD-Topology-Updater creates NodeResourceTopology objects that describe the hardware topology of node resources.

Node Feature Discovery
v0.13

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This Software is under the terms of Apache License 2.0.