nfs_share/v0

Overview

This integration interface describes the expected behavior of any charm claiming to be able to interface with an NFS share provider or consumer.

Usage

Charmed operators claiming to provide this interface must implement and support the Network File System (NFS) protcol. Providing charmed operators should support exporting NFS share endpoints while Requiring charms should support mounting NFS shares. In most cases, communication between Providers and Requirers will be accomplished using the nfs_interfaces library, however, charm developers are free to provide alternative libraries such that they fulfill the behavioral and schematic requirements described in this document.

Direction

The nfs_share interface implements a provider/requirer pattern. The consumer is a charm that wishes to act as an NFS client with the ability to mount exported NFS shares. The provider is a charm exposing an NFS share endpoint, and does not need to be an NFS server itself. The provider can be a proxy that exports an NFS share endpoint from a non-charmed NFS storage appliance.

        flowchart TD
    Requirer -- name, allowlist, size --> Provider
    Provider -- endpoint --> Requirer
    

Behavior

The Provider and the Requirer must adhere to a certain set of criteria to be considered compatible with the interface.

Provider

• Is expected to publish an NFS Uniform Resource Locator in its application databag as share endpoint. The endpoint is expected to have the following structure:

  nfs://[ingress hostname/address]:[port number]/[path to NFS share]

  Port number is not required in the URL as almost all NFS implementations automatically negotiate the port number, packet size, transport protocol, and NFS version to use.

Requirer

• Is expected to publish a name/alias that can be used as a unique identifier for a requested NFS share in its application databag.

• Is expected to optionally publish a size, in gigabytes (GB), for how large to make a requested NFS share in its application databag.

• Is expected to optionally publish an allowlist of hostnames that should be granted read/write access to the requested NFS share.

Relation Data

Provider

Provider provides its NFS share endpoints. The NFS share endpoints should be placed in the application databag.

Example

application_data: {
  endpoint: "nfs://10.152.28.100/volumes/polaris-research-data"
}

Requirer

Example

application-data: {
  name: "/polaris-research-data",
  size: "100",
  allowlist: "192.168.0.15/24,10.152.28.100/24,"
}