# NFD-Master · Node Feature Discovery
NFD-Master NFD-Master is responsible for connecting to the Kubernetes API server and updating node objects. More specifically, it modifies node lab...
Author: Kubernetes SIGs

Node Feature Discovery
This documentation is for Node Feature Discovery version that is no longer supported. Please upgrade and visit the documentation of the latest stable release.

# NFD-Master

NFD-Master is responsible for connecting to the Kubernetes API server and updating node objects. More specifically, it modifies node labels, taints and extended resources based on requests from nfd-workers and 3rd party extensions.

## NodeFeature controller

EXPERIMENTAL Controller for NodeFeature objects can be enabled with the `-enable-nodefeature-api` command line flag. When enabled, features from NodeFeature objects are used as the input for the NodeFeatureRule processing pipeline. In addition, any labels listed in the NodeFeature object are created on the node (note the allowed label namespaces are controlled).

> NOTE: NodeFeature API must also be enabled in nfd-worker with its `-enable-nodefeature-api` flag.

## NodeFeatureRule controller

NFD-Master acts as the controller for NodeFeatureRule objects. It applies the rules specified in NodeFeatureRule objects on raw feature data and creates node labels accordingly. The feature data used as the input can be received from nfd-worker instances through the gRPC interface or from NodeFeature objects. The latter requires that the NodeFeaure controller has been enabled.

> NOTE: when gRPC is used for communicating the features (the default mechanism), (re-)labelling only happens when a request is received from nfd-worker. That is, in practice rules are evaluated and labels for each node are created on intervals specified by the `core.sleepInterval` configuration option of nfd-worker instances. This means that modification or creation of NodeFeatureRule objects does not instantly cause the node labels to be updated. Instead, the changes only come visible in node labels as nfd-worker instances send their labelling requests. This limitation is not present when gRPC interface is disabled and NodeFeature API is used.

## Deployment notes

NFD-Master runs as a deployment, by default it prefers running on the cluster's master nodes but will run on worker nodes if no master nodes are found.

For High Availability, you should simply increase the replica count of the deployment object. You should also look into adding inter-pod affinity to prevent masters from running on the same node. However note that inter-pod affinity is costly and is not recommended in bigger clusters.

> NOTE: If the NodeFeature controller is enabled the replica count should be 1.

If you have RBAC authorization enabled (as is the default e.g. with clusters initialized with kubeadm) you need to configure the appropriate ClusterRoles, ClusterRoleBindings and a ServiceAccount in order for NFD to create node labels. The provided template will configure these for you.

Node Feature Discovery
v0.12

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This Software is under the terms of Apache License 2.0.