node-feature-discovery/docs/get-started/introduction.md

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Introduction	default	1

Introduction

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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, annotations and node taints. Node Feature Discovery is compatible with any recent version of Kubernetes (v1.21+).

NFD consists of four software components:

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

NFD-GC is a daemon responsible for cleaning obsolete NodeFeature and NodeResourceTopology objects.

One instance of nfd-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/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 nfd.node.kubernetes.io/extended-resources is only placed if some extended resources were created by NFD.

Custom resources

NFD takes use of some Kubernetes Custom Resources.

NodeFeatures is 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.