This is a draft proposal for RESTful API Design Specification within ONAP. This draft has not be approved by TSC yet.

URI Construction

RESTful APIs use Uniform Resource Identifiers (URIs) to address resources, ONAP projects should comply with a unified URI standard to implement the microservices.

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• A plural noun should be used for collection names (Mandatory)
  For example, the URI for a collection of dog documents uses the plural noun form of its contained resources: /api/petstore/v1/pets/dogs
• A singular noun should be used for document names (Mandatory)
  For example, the URI for a single dog document would have the singular form: /api/petstore/v1/pets/dogs/bailey
  
  

Versioning

API is a public contract between a Server and a Consumer, so it's crucial to make sure the changes are backwards compatible. We need to introduce new versions of the API while still allowing old versions to be accessible when it's necessary. So a versioning mechanism should be considered.

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Need to be discussed: Should ONAP adopt a version discovery mechanism like OpenStack?  :https://wiki.openstack.org/wiki/VersionDiscovery

HTTP response status codes

The server should always return the right HTTP status code to the client. (Recommended)

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Need to be discussed: Should ONAP define a unified error response format across projects?

Security

• Token Based Authentication (Recommended)
  Ideally, microservices should be stateless so the service instances can be scaled out easily and the client requests can be routed to multiple independent service providers. A token based authentication mechanism should be used instead of session based authentication 
• API-Token Authentication (Recommended)
  ONAP is supposed to be accessed by third-party apps such as OSS/BSS, in the authentication process a user is not involved. API-Token can be used in such cases.
• Centralized Authentication/Authorization (Recommended)
  The MSB API Gateway can serve as the entry point to authenticate client requests and forwards them to the backend services, which might in turn invoke other services.
  MSB doesn't do the authentication itself, instead, MSB can work with a security provider to provide centralized Authentication or ONAP with its pluggable architecture.
• Use https for external communication for security reason
  The MSB External API Gateway can translate the https request from the external systems to light weight http communication inside ONAP system. The individual projects don't have to handle the trivial details such as certification configuration and avoid the overhead of https inside ONAP system. 

Multiple tenants support

TBD

API Documentation(Swagger)

• All the RESTful API must follow Swagger Specification for API documentation: http://swagger.io/specification (Recommended)
  The ONAP-Components must provide swagger files for its RESTful API definitions, there are two possible approaches. 
  • The developers write the Swagger file, then use CI system to generate the stub codes for implementation.
  • The developers write the Swagger annotation in the source codeI, then use CI system to generate the Swagger file.
• The Swagger file should be placed under the base url of the service so the API definition could be discovered by clients or management tools at runtime.  (Recommended)
  For example, if the base url of peststore service is /api/petstore/v1/, the URL of swagger file should be /api/petstore/v1/Swagger.json

Appendix

Swagger Specification http://swagger.io/specification

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