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-- Which framework has been used and why
-- How to extend to more api
+**********************************************
+QTIP RESTful Application Programming Interface
+**********************************************
+
+Abstract
+########
+
+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.
+
+.. code-block:: python
+
+ @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``
+
+ .. code-block:: python
+
+ 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``.
+
+ .. code-block:: python
+
+ 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__``
+
+ .. code-block:: python
+
+ 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``.
+
+ .. code-block:: python
+
+ 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)
+
+
+.. _Connexion: https://connexion.readthedocs.io/en/latest/
+.. _Open API specification: https://github.com/OAI/OpenAPI-Specification/blob/master/versions/2.0.md
+.. _Swagger Editor: http://editor.swagger.io/