Quick Start¶

A Minimal Application¶

We assume you install Lamapi under lib directory and start a serverless project using Serverless Framework. Installation.

A minimal Lamapi application looks something like this:

from lib.lamapi.app import Application

def lambda_handler(event, context):
    app = Application()

    @app.route(path='/', method='GET')
    def hello(request):
        return 'Hello'

    return app.run(event)

So what did that code do?

First we import Application class, an instance of this class will help us to handle http event and return response.
Next in the lambda_handler() function (which is the entry point for the Lambda) we create an instance of this class.
Then we use the route() decorator to tell Lamapi what URL should trigger our function.
The function receives a request object and returns the message we want to display in the user’s browser.

Just save it as hello.py or something similar. Then deploy it to the AWS Lambda and API Gateway or deploy using Serverless Framework as below.

serverless deploy

Then test it as:

serverless invoke -f hello

Then you will get output as below:

blalbal

Is it as simple as Flask?

Routing¶

Routing is as simple as Flask. Use app.route descriptor to functions with path and/or methods.

Listening on path / with all methods,

def lambda_handler(event, context):
    app = Application()

    @app.route(path='/')
    def hello(request):
        return 'Hello'

    return app.run(event)

Listening on path / with GET method,

def lambda_handler(event, context):
    app = Application()

    @app.route(path='/', method='GET')
    def hello(request):
        return 'Hello'

    return app.run(event)

Use list to listen on more methods,

def lambda_handler(event, context):
    app = Application()

    @app.route(path='/', method=['GET', 'POST'])
    def hello(request):
        return 'Hello'

    return app.run(event)

Request¶

Each function will receive a request instance as parameter. You can use this object to get anything you want.

A request body from API Gateway will look like this:

{
  "body": "",
  "resource": "/hello",
  "path": "/hello",
  "httpMethod": "GET",
  "isBase64Encoded": false,
  "queryStringParameters": null,
  "pathParameters": null,
  "stageVariables": null,
  "headers": {
    "Accept": "text/html,application/xhtml+xml,application/xml;q=0.9,image/webp,*/*;q=0.8",
    "Accept-Encoding": "gzip, deflate, sdch",
    "Accept-Language": "en-US,en;q=0.8",
    "Cache-Control": "max-age=0",
    "User-Agent": "Custom User Agent String"
  }
  "requestContext": {
    //......
  }
}

Lamapi framework will store this object in request object. And you can get all you want by accessing request object’s attributes.

Request Path¶

def hello(request):
    path = request.path

Request Method¶

def hello(request):
    method = request.method

Query Parameters¶

def hello(request):
    id = request.query.get('id')
    # if request url is /hello?id=1
    # then id = 1
    name = request.query.get('name') or 'default'
    # give some default value

Form Data¶

To access form data (data transmitted in a POST or PUT request) you can use the data attributes.

def hello(request):
    name = request.data.get('name') or 'default'

Path Parameters¶

If you define some path parameters in API Gateway, you can get them by path_param. If you define your path as /hello/{name}, then requested as /hello/world, you will get path parameters as name=world.

def hello(request):
    name = request.path_param.get('name') or 'default'

Request Header¶

Headers will be stored in header attribute as a dict.

def hello(request):
    accept = request.header.get('Accept')

Response¶

Anything you return to handler function will be translated to a JSON object which will be returned to client. You can return a string, dict, list or any object can be encoded to json.

def hello(request):
    return 'hello world'

If you want to return a custom http code such as 400 or custom headers, you can build response object by yourself.

from lib.lamapi.wrappers import Response


def hello(request):
    return Response([], status=400, headers={'X-CUSTOM': 'xxx'})

Where to go next? Learn deep about Configuration.