API - Application Programming Interface¶

QTIP consists of different tools(metrics) to benchmark the NFVI. These metrics fall under different NFVI subsystems(QPI’s) such as compute, storage and network. A plan consists of one or more QPI’s, depending upon how the end-user would want to measure performance. API is designed to expose a RESTful interface to the user for executing benchmarks and viewing respective scores.

Framework¶

QTIP API has been created using the Python package Connexion. It has been chosen for a number of reasons. It follows API First approach to create micro-services. Hence, firstly the API specifications are defined from the client side perspective, followed by the implementation of the micro-service. It decouples the business logic from routing and resource mapping making design and implementation cleaner.

It has two major components:

API Specifications

The API specification is defined in a yaml or json file. Connexion follows Open API specification to determine the design and maps the endpoints to methods in python.

Micro-service Implementation: Connexion maps the operationId corresponding to every operation in API Specification to methods in python which handles request and responses.

As explained, QTIP consists of metrics, QPI’s and plans. The API is designed to provide a RESTful interface to all these components. It is responsible to provide listing and details of each individual element making up these components.

Design¶

Specification¶

API’s entry point (main) runs connexion App class object after adding API Specification using App.add_api method. It loads specification from swagger.yaml file by specifying specification_dir.

Connexion reads API’s endpoints(paths), operations, their request and response parameter details and response definitions from the API specification i.e. swagger.yaml in this case.

Following example demonstrates specification for the resource plans.

paths:
  /plans/{name}:
    get:
      summary: Get a plan by plan name
      operationId: qtip.api.controllers.plan.get_plan
      tags:
        - Plan
        - Standalone
      parameters:
        - name: name
          in: path
          description: Plan name
          required: true
          type: string
      responses:
        200:
          description: Plan information
          schema:
            $ref: '#/definitions/Plan'
        404:
          description: Plan not found
          schema:
            $ref: '#/definitions/Error'
        501:
          description: Resource not implemented
          schema:
            $ref: '#/definitions/Error'
        default:
          description: Unexpected error
          schema:
            $ref: '#/definitions/Error'
definitions:
  Plan:
    type: object
    required:
      - name
    properties:
      name:
        type: string
      description:
        type: string
      info:
        type: object
      config:
        type: object

Every operationId in above operations corresponds to a method in controllers. QTIP has three controller modules each for plan, QPI and metric. Connexion will read these mappings and automatically route endpoints to business logic.

Swagger Editor can be explored to play with more such examples and to validate the specification.

Controllers¶

The request is handled through these methods and response is sent back to the client. Connexion takes care of data validation.

@common.check_endpoint_for_error(resource='Plan')
def get_plan(name):
    plan_spec = plan.Plan(name)
    return plan_spec.content

In above code get_plan takes a plan name and return its content.

The decorator check_endpoint_for_error defined in common is used to handle error and return a suitable error response.

During Development the server can be run by passing specification file(swagger.yaml in this case) to connexion cli -

connexion run <path_to_specification_file> -v

Extending the Framework¶

Modifying Existing API:¶

API can be modified by adding entries in swagger.yaml and adding the corresponding controller mapped from operationID.

Adding endpoints:
New endpoints can be defined in paths section in swagger.yaml. To add a new resource dummy -
paths:
  /dummies:
    get:
      summary: Get all dummies
      operationId: qtip.api.controllers.dummy.get_dummies
      tags:
        - dummy
      responses:
        200:
          description: Foo information
          schema:
            $ref: '#/definitions/Dummy
        default:
          description: Unexpected error
          schema:
            $ref: '#/definitions/Error'
And then model of the resource can be defined in the definitions section.
definitions:
  Dummy:
    type: object
    required:
      - name
    properties:
      name:
        type: string
      description:
        type: string
      id:
        type: string
Adding controller methods:
Methods for handling requests and responses for every operation for the endpoint added can be implemented in controller.

In controllers.dummy
def get_dummies():
    all_dummies = [<code to get all dummies>]
    return all_dummies, httplib.OK
Adding error responses
Decorators for handling errors are defined in common.py in api.
from qtip.api import common

@common.check_endpoint_for_error(resource='dummy',operation='get')
def get_dummies()
    all_dummies = [<code to get all dummies>]
    return all_dummies

Adding new API:¶

API can easily be extended by adding more APIs to Connexion.App class object using add_api class method.

In __main__
def get_app():
app = connexion.App(__name__, specification_dir=swagger_dir)
app.add_api('swagger.yaml', base_path='/v1.0', strict_validation=True)
return app
Extending it to add new APIs. The new API should have all endpoints mapped using operationId.
from qtip.api import __main__
my_app = __main__.get_app()
my_app.add_api('new_api.yaml',base_path'api2',strict_validation=True)
my_app.run(host="0.0.0.0", port=5000)