Request handler

A request handler is a method used to handle each function invocation. When creating a function version, you should specify the entry point that consists of the file name and request handler name (for example, main.handler).

When invoking the handler, the runtime passes the following arguments:

1. The request body (the event parameter):

   • If the request body is a JSON document, it's converted to a dict using the json.loads method.
   • If the function was called with the integration=raw query string parameter, the HTTP request body is passed to the function as is, unhandled.

2. The invocation context (the context parameter).

   The context contains the necessary information about the function version. The structure of this object is described in Invocation context.

Handler types

A function can use both synchronous and asynchronous request handlers.

Synchronous handler

To have the execution result returned, use the return statement or raise an exception using the raise statement. A synchronous function must return a result or throw an exception.

Asynchronous handler

A handler can be an async def asynchronous function. In this case you can use the following statements:

• return: Returns the function response.
• raise: Reports an error to the runtime environment.
• await: Tracks the execution of asynchronous function invocations.

To learn more about programming using the async/await syntax, see the relevant section of the documentation.

Examples

HTTP request structure output

The following function outputs the request structure and invocation context to both the execution log and function response:

import json


def handler(event, context):
    return {
        'statusCode': 200,
        'body': json.dumps({
            'event': event,
        }),
    }