Api Gateways are important infrastructure elements, as a simple Lambda function is only available from inside AWS ecosystem. REST Api is a common, easy to implement standard to share resource.

To make our Lambda function publicly available we are going to update our previous code base with two things: tell the serverless to create the Api Gateway for our stack and upgrade the response of our utc-time-teller.

Let’s start with the python code changes. As we are going to communicate on HTTP channel JSON is a good model structure to respond with. Edit our handler’s code as following:

import datetime
import json

def handler(event, context) -> str:
    dt = datetime.datetime.now(datetime.timezone.utc)
    utc_time = dt.replace(tzinfo=datetime.timezone.utc)

    return {
        "statusCode": 200,
        "headers": {
            "Content-Type": "application/json"
        },
        "body": json.dumps({
            "utc ": str(utc_time)
        })
    }

We are returning a default HTTP response with statusCode of 200 (everything is OK), telling the receiver that the message is in JSON format (“Content-Type”: “application/json”) and of course adding the body itself.

The Lambda is still testable using the previously shown method:

We can continue with the serverless.yml:

Add these few lines to the end of our function:

    events:
      - http:
          path: /{proxy+}
          method: any
      - http:
          path: /
          method: any

This will generate the API Gateway on AWS. The whole serverless.yml looks like this:

service: BlogDavidPythonLambdaDeploy

provider:
  name: aws
  region: eu-west-1

functions:
  utc-time-teller:
    name: utc-time-teller
    handler: src/lambda_handler.handler
    memorySize: 128
    timeout: 30
    runtime: python3.8
    events:
      - http:
          path: /{proxy+}
          method: any
      - http:
          path: /
          method: any

Now call our deployment script from a command line tool:

serverless deploy

Serverless CLI should add new lines to the logs under the category “endpoints”. Copy the one without {proxy+} ending to the browser and enjoy our newly created API gateway response: