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Web framework for the serverless domain

Project description

circle pypi version apache license

A web framework that facilitates the development of serverless applications using AWS resources. Minik natively supports request from the API Gateway and the Application Load Balancer.

Installing

Install the latest release:

>>> pip install minik
✨🍰✨

Only Python 3.6+ is supported.

Simple Example

In it’s most basic form; quite honestly, it’s only form. This is how your lambda function should look like:

from minik.core import Minik, BadRequestError

app = Minik()

@app.route('/hello/{name}')
def hello_view(name: str):

    if name == 'FINDME':
        # Returns a 400 status code with the message as the body.
        raise BadRequestError(msg='This is not a supported name.')

    # A simple way of getting the current request as json.
    request_payload = app.request.json_body
    return {'hello': name}

HTTP Methods

With minik you can also specify the HTTP methods for a given view. If you don’t define the methods, every single HTTP method will be allowed by default.

from minik.core import Minik

app = Minik()

@app.route('/events/{location}')
def events_view(location: str):
    # This route will be invoked for GET, POST, PUT, DELETE...
    return {'data': ['granfondo MD', 'Silver Spring Century']}

@app.route('/events', methods=['POST', 'PUT'])
def create_event_view():
    create_event(app.request.json_body)
    return {'result': 'complete'}

If your view is associated with a single HTTP method, you can use the decorator version.

from minik.core import Minik

app = Minik()

@app.get('/events/{location}')
def get_view(location: str):
    return {'data': ['granfondo MD', 'Silver Spring Century']}

@app.post('/events')
def post_view():
    create_event(app.request.json_body)
    return {'result': 'complete'}

Route Parameter Validation

Minik uses function annotations to validate the value of a route. If the type of an expected parameter is not valid, minik will respond with a 404 not found status code.

@app.route('/articles/{author}/{year}/')
def get_articles_view(author: str, year: int):
    # Type conversion: isinstance(author, str) and isinstance(year, int)
    return {'author_name': author, 'year': year}

To learn more checkout out the route validation page.

Custom Headers

To update the values of the HTTP response, minik exposes a response object at the app level. By default minik will create a Response instance with a status code of 200 and a set of default headers. The headers include a default content-type value of application/json.

For instance, to set the CORS headers in a view and change the content type, a view would look like:

app = Minik()

@app.get('/articles/{author}/{year}/')
def get_articles_view(author: str, year: int):
    app.response.headers = {
        "Content-Type": "Content-Type": "text/html; charset=utf-8",
        "Access-Control-Allow-Origin": "*",
        "Access-Control-Allow-Methods": "GET",
        "Access-Control-Allow-Headers": "Content-Type,X-Amz-Date",
        "Authorization": "X-Api-Key,X-Amz-Security-Token"
    }

    return f"A very short article by {author}"

Debug Mode

For unhandled exceptions, minik will respond with a 500 status code and a generic error message. To get more details from the response including the stack trace and information about the exception, run the app in debug mode.

By default the debug mode is set to False.

app = Minik(debug=True)

Initializing the app in debug mode will relay the stack trace back to the consumer.

ALB Support

Along with having a native integration with the API Gateway, minik can now be used to handle requests coming from an Application Load Balancer (ALB). The definition of the web application is identical in both cases. There is no additional code required to use minik with an ALB.

If a lambda function is the target of an ALB, minik will parse the raw event, find the view associated with the route and execute the view with the correct context.

from minik.core import Minik

app = Minik()

@app.get('/greetings')
def get_greetings():
    app.response.headers = {"Content-Type": "text/html; charset=utf-8"}

    return """
    <html>
    <head>
        <title>Hello World!</title>
        <style>
        html, body {
        margin: 0; padding: 0;
        font-family: arial; font-weight: 700; font-size: 3em;
        text-align: center;
        }
        </style>
    </head>
    <body>
        <p>Hello World!</p>
    </body>
    </html>"""

Notice that there is nothing specific about the source that will eventually invoke this lambda function. This codeblock can be used to handle a request either from the API Gateway or from an ALB.

Request Object

Any view has access to the app.request instance as a way to retrieve the general information of a request. The fields of this object include the query parameters, the path parameters, headers, payload… Given that different sources might have a set of additional fields, minik will store a copy of the original event in the app.request instance.

For instance, the API Gateway has the concept of stage variables that is missing from an event received from the ALB. In this case, the generic app.request instance will not have a field called stage_variables. Instead, minik keeps a copy of the original event and context objects in the request. In this case a developer can access these values using the app.request.aws_event[‘StageVariables’]. Where the aws_event is the event minik received as the handler of the lambda function.

from minik.core import Minik

app = Minik()

@app.post('/events')
def post_view():
    # app.request.json_body: The payload of a post request as a JSON object.
    # app.request.aws_event: The raw event sent by a source to the lambda function.
    # app.request.aws_context: The context of the lambda function.
    return {'result': 'complete'}

Motivation

The team behind this framework is adopting a very minimal set of features to enhance and streamline web development in the serverless space. These were the business needs that encouraged us to build minik:

  • Ability to write an API using a familiar (Flask like) syntax using serverless services.
  • Flexibility on how to build and deploy lambda functions. I do not want my framework to dictate these processes for me. I want to own them!
  • When installing a web framework, I want to get only the framework. I don’t want any additional tooling or any additional process-based workflows.
  • When using the microframework I am responsible for the configuration required to associate my lambda function to its endpoints.

The features of this library should be absolutely driven by a very specific business need. So far, the minimal approach has been sufficient for our team to write and expose an API using AWS services.

Just the framework

Things to be aware of when working using minik:

  • When used in your lambda function, you’re responsible for including the source code of minik in your .zip artifact. For packaging purposes we recommend using Juniper.
  • Minik is service agnostic, as a web framework it natively supports requests from the API Gateway and an Application Load Balancer (ALB).
  • Unlike other frameworks like Flask or Django, where using the decorator is sufficient to define the routes of the web app, in minik, you’re responsible for linking a lambda function to the API Gateway. We recommend using a SAM template.
  • Minik does not include a local development server! For testing purposes, you can either deploy your lambda to AWS using sam package and sam deploy. For local deployment purposes you can use sam local.

Quickstart

Minik is just one of the pieces that you need to build serverless APIs. If you are curious to learn more about best practices and how to get started with this microframework, checkout out getting started guide.

The quickstart uses a very simple example, which is included in this codebase, as a way to highlight the benefits of the framework.

Contributing

For guidance on setting up a development environment and how to make a contribution to Minik, see the contributing guidelines.

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