Networked Media Open Specifications
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APIs

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This document covers common aspects of the Connection API.

API Specifications

The Connection API is specified using:

Examples of JSON format output are provided in the examples folder.

API Validation

JSON schemas are included with the RAML API definitions. These include validation for values used within the APIs. It is RECOMMENDED that implementers of a Connection API use these JSON schemas as part of a validation stage when receiving requests from clients. Invalid requests SHOULD cause a 400 (Bad Request) HTTP error to be returned to the client.

Content Types

All APIs MUST provide a JSON representation signalled via Content-Type: application/json headers. This SHOULD be the default content type in the absence of any requested alternative by clients. Other content types (such as HTML) are permitted if they are explicitly requested via Accept headers.

API Paths

All NMOS APIs MUST use a path in the following format. Other HTTP resources MAY be presented on the same port by the Node, provided all NMOS resources are available from the /x-nmos/ path as follows:

http(s)://<ip address or hostname>:<port>/x-nmos/<api type>/<api version>/

At each level of the API from the base resource upwards, the response SHOULD include a JSON format array of the child resources available from that point.

Versioning

All public APIs are versioned as follows:

Example

A v1.1 API response can include:

Common API Base Resource

[
  "v1.0/",
  "v2.0/",
  "v3.0/"
]

URLs: Approach to Trailing Slashes

For consistency and in order to adhere to how these APIs are specified in RAML, the ‘primary’ path for every resource has the trailing slash omitted.

In order to overcome shortcomings in some common libraries, the following requirements are imposed for the support of URL paths with or without trailing slashes.

GET and HEAD Requests

All Other Requests (PUT, POST, DELETE, OPTIONS, etc.)

Client Behaviour

When a server implementation needs to indicate an API URL via an href or similar attribute, it is valid to either include a trailing slash or not provided that the listed path is accessible and follows the above rules. Clients appending paths to href type attributes MUST support both cases, avoiding doubled or missing slashes.

Error Codes & Responses

The NMOS APIs use HTTP status codes to indicate success, failure and other cases to clients as per RFC 7231 and related standards. Where the RAML specification of an API specifies explicit response codes it is expected that a client will handle these cases in a particular way. Explicit handling of every possible HTTP response code is not expected, but clients are expected to implement generic handling for ranges of response codes (1xx, 2xx, 3xx, 4xx and 5xx).

For HTTP codes 400 and upwards, a JSON format response MUST be returned as follows:

Example Error Response

{
  "code": 400,
  "error": "Human readable message which is suitable for user interface display, and helpful to the user",
  "debug": "Programmer / debugging detail or traceback"
}

code SHOULD match the HTTP status code. error MUST always be present and in string format. debug MAY be null if no further debug information is available.

Further details on when APIs will respond with particular codes is covered in the Behaviour section.

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