AWS Lambda For The Impatient Part 1
Written by Nikos Vaggalis   
Monday, 02 January 2017
Article Index
AWS Lambda For The Impatient Part 1
The API Gateway
Actions and Testing
CloudWatch log files

Step 3 - Hooking up the Actions

Back to our API Gateway and our LambdaMicroServiceHelloWorldNodeJS API.This time we are going to define the HTTP methods that our API will listen to as well as how to react to their invocation.As Lambdas work only with POST requests, we add just the POST method:

Actions->Create Method->POST->POST Setup
Integration Type:HTTP
Endpoint URL:

If all goes well we should be presented with a screen similar to:

Step 4 - The real test with Postman

Download the Postman Chrome extension.The nice thing with it is that Postman can be also installed as a standalone desktop app, so go ahead and make that choice when prompted for it.

Now from within Postman pick POST as the method and enter our URL endpoint to the input box next to it:

As for Authorization pick No Auth

On the Headers tab enter
Content-Type    application/json

On the Body tab, choose raw and type {"key1":"value1"} as the payload which is going to be forwarded through our endpoint to our backend Lambda function.

Finally, push Send and watch Postman receive a successful (hopefully) reply that echoes back the value sent the function:


Let's look in detail what our function did:

'use strict';

exports.handler = (event, context, callback) => {
    console.log('Received event:',
                 JSON.stringify(event, null, 2));
    var inputObj = JSON.parse(event["body"]);

    callback(null, {
    "statusCode": 200,
    "headers": { },
    // Echo back the first key value
     "body": JSON.stringify( {"received":inputObj.key1})

Seems that the call to our trigger fired an event that encapsulated the POST request's body, that is our JSON string {"key1":"value1"}, which among others, got forwarded to our function.

After parsing the string into a JSON object, we call it's key1 property through inputObj.key1 which replies with value1. We pack that reply into a JSON string with {"received":inputObj.key1} and push it back to our client, Postman in this case.

As a matter of fact let's change client and see if the same call works through Powershell

$json = "{
          ""key1"" : ""value1""

Invoke-WebRequest -Uri -usebasicparsing -Method POST -ContentType "application/json" -Body $json

Last Updated ( Tuesday, 03 January 2017 )