Routing

Endpoint routing to your Python views

FireTail uses the operationId from each Operation Object to identify which Python function should handle each URL.

Explicit Routing:

paths:
  /hello_world:
    post:
      operationId: myapp.api.hello_world

If you provided this path in your specification POST requests to http://MYHOST/hello_world, it would be handled by the function hello_world in myapp.api module.

Optionally, you can include x-swagger-router-controller in your operation definition, making operationId relative:

paths:
  /hello_world:
    post:
      x-swagger-router-controller: myapp.api
      operationId: hello_world

Note: If you are using an OpenAPI spec, you should use x-openapi-router-controller in your operation definition, making operationId relative:

paths:
  /hello_world:
    post:
      x-openapi-router-controller: myapp.api
      operationId: hello_world

If all your operations are relative, you can use the RelativeResolver class instead of repeating the same x-swagger-router-controller or x-openapi-router-controller in every operation:

from firetail.resolver import RelativeResolver

app = firetail.FlaskApp(__name__)
app.add_api('swagger.yaml', resolver=RelativeResolver('api'))

Keep in mind that FireTail follows how HTTP methods work in Flask and therefore HEAD requests will be handled by the operationId specified under GET in the specification. If both methods are supported, firetail.request.method can be used to determine which request was made.

By default, FireTail strictly enforces the presence of a handler function for any path defined in your specification. Because of this, adding new paths without implementing a corresponding handler function will produce runtime errors and your application will not start. To allow new paths to be added to your specification, for example, in an API design first workflow, set the resolver_error to configure FireTail to provide an error response for paths that are not yet implemented:

app = firetail.FlaskApp(__name__)
app.add_api('swagger.yaml', resolver_error=501)

Automatic routing

To customize this behavior, FireTail can use alternative Resolvers—for example, RestyResolver. The RestyResolver will compose an operationId based on the path and HTTP method of the endpoints in your specification:

afrom firetail.resolver import RestyResolver

app = firetail.FlaskApp(__name__)
app.add_api('swagger.yaml', resolver=RestyResolver('api'))

paths:
  /:
    get:
       # Implied operationId: api.get
  /foo:
    get:
       # Implied operationId: api.foo.search
    post:
       # Implied operationId: api.foo.post

  '/foo/{id}':
    get:
       # Implied operationId: api.foo.get
    put:
       # Implied operationId: api.foo.put
    copy:
       # Implied operationId: api.foo.copy
    delete:
       # Implied operationId: api.foo.delete
  '/foo/{id}/bar':
    get:
       # Implied operationId: api.foo.bar.search
  '/foo/{id}/bar/{name}':
    get:
       # Implied operationId: api.foo.bar.get
       # Handler signature: `def get(id, name): ...`

RestyResolver will give precedence to any operationId encountered in the specification. It will also respect x-swagger-router-controller and x-openapi-router-controller. You may import and extend firetail.resolver.Resolver to implement your own operationId (and function) resolution algorithm.

Note: When using multiple parameters in the path, they will be collected and all passed to the endpoint handlers.

Automatic routing with MethodViewResolver

MethodViewResolver is a customized Resolver based on RestyResolver to take advantage of MethodView structure of building Flask APIs. The MethodViewResolver will compose an operationId based on the path and HTTP method of the endpoints in your specification. The path will be based on the path you provide in the app.add_api and the path provided in the URL endpoint (specified in the swagger or openapi3).

rom firetail.resolver import MethodViewResolver

app = firetail.FlaskApp(__name__)
app.add_api('swagger.yaml', resolver=MethodViewResolver('api'))

And associated YAML:

paths:
  /foo:
    get:
       # Implied operationId: api.FooView.search
    post:
       # Implied operationId: api.FooView.post

  '/foo/{id}':
    get:
       # Implied operationId: api.FooView.get
    put:
       # Implied operationId: api.FooView.put
    copy:
       # Implied operationId: api.FooView.copy
    delete:
       # Implied operationId: api.FooView.delete

The structure expects a Class to exist inside the directory api that conforms to the naming <<Classname with Capitalised name>>View. In the above yaml the necessary MethodView implementation is as follows:

import datetime

from firetail import NoContent
from flask import request
from flask.views import MethodView


class PetsView(MethodView):
    """ Create Pets service
    """
    method_decorators = []
    pets = {}

    def post(self):
      body= request.json
      name = body.get("name")
      tag = body.get("tag")
      count = len(self.pets)
      pet = {}
      pet['id'] = count + 1
      pet["tag"] = tag
      pet["name"] = name
      pet['last_updated'] = datetime.datetime.now()
      self.pets[pet['id']] = pet
      return pet, 201

    def put(self, petId):
      body = request.json
      name = body["name"]
      tag = body.get("tag")
      id_ = int(petId)
      pet = self.pets.get(petId, {"id": id_})
      pet["name"] = name
      pet["tag"] = tag
      pet['last_updated'] = datetime.datetime.now()
      self.pets[id_] = pet
      return self.pets[id_], 201

    def delete(self, petId):
      id_ = int(petId)
      if self.pets.get(id_) is None:
          return NoContent, 404
      del self.pets[id_]
      return NoContent, 204

    def get(self, petId):
      id_ = int(petId)
      if self.pets.get(id_) is None:
          return NoContent, 404
      return self.pets[id_]

    def search(self, limit=100):
      # NOTE: we need to wrap it with list for Python 3 as dict_values is not JSON serializable
      return list(self.pets.values())[0:limit]

and a __init__.py file to make the Class visible in the API directory.

from .petsview import PetsView

MethodViewResolver will give precedence to any operationId encountered in the specification. It will also respect x-swagger-router-controller and x-openapi-router-controller. You may import and extend firetail.resolver.MethodViewResolver to implement your own operationId (and function) resolution algorithm.

Parameter name sanitation

The names of query and form parameters, as well as the name of the body parameter are sanitized by removing characters that are not allowed in Python symbols that is, all characters that are not letters, digits or the underscore are removed, and finally characters are removed from the front until a letter or an under-score is encountered. As an example:

>>> re.sub('^[^a-zA-Z_]+', '', re.sub('[^0-9a-zA-Z_]', '', '$top'))
'top'

Without this sanitation it would be impossible for example, to implement an OData API.

You can also convert CamelCase parameters to snake_case automatically using a pythonic_params option:

app = firetail.FlaskApp(__name__)
app.add_api('api.yaml', ..., pythonic_params=True)

With this option enabled, FireTail firstly converts CamelCase names to snake_case. Secondly, it looks to see if the name matches a known built-in and if it does it appends an underscore to the name.

Parameter variable converters

FireTail supports Flask’s int, float, and path route parameter variable converters. Specify a route parameter’s type as integer or number or its type as string and its format as path to use these converters. For example:

paths:
  /greeting/{name}:
    # ...
    parameters:
      - name: name
        in: path
        required: true
        type: string
        format: path

This will create an equivalent Flask route /greeting/<path:name>, allowing requests to include forward slashes in the name URL variable.

API versioning and basePath

Setting a base path is useful for versioned APIs. An example of a base path would be the 1.0 in http://MYHOST/1.0/hello_world.

If you are using OpenAPI 3.x.x, you set your base URL path in the server's block of the specification. You can either specify a full URL or just a relative path.

servers:
  - url: https://MYHOST/1.0
    description: full url example
  - url: /1.0
    description: relative path example

paths:
  ...

If you are using OpenAPI 2.0, you can define a basePath on the top level of your OpenAPI 2.0 specification.

basePath: /1.0

paths:
  ...

If you don’t want to include the base path in your specification, you can provide it when adding the API to your application:

app.add_api('my_api.yaml', base_path='/1.0')

Swagger UI path

Swagger UI is available at /ui/ by default.

You can choose another path through options:

options = {'swagger_url': '/'}
app = firetail.App(__name__, options=options)

Swagger JSON

FireTail makes the OpenAPI/Swagger specification in JSON format available from swagger.json in the base path of the API.

You can disable the Swagger JSON at the application level:

app = firetail.FlaskApp(__name__, specification_dir='swagger/',
                    swagger_json=False)
app.add_api('my_api.yaml')

You can also disable it at the API level:

app = firetail.FlaskApp(__name__, specification_dir='swagger/')
app.add_api('my_api.yaml', swagger_json=False)

Related topics

• Quickstart
• ‍Command-line interface
• ‍Routing
• Request handling
• Response handling
• Security
• FireTail cookbook
• Exception handling