How do you structure sequential AWS service calls within lambda given all the calls are asynchronous?

Question

I\'m coming from a java background so a bit of a newbie on Javascript conventions needed for Lambda.

I\'ve got a lambda function which is meant to do several AWS tasks i

Answer 1

I like the answer from @jonathanbaraldi but I think it would be better if you manage control flow with Promises. The Q library has some convenience functions like nbind which help convert node style callback API's like the aws-sdk into promises.

So in this example I'll send an email, and then as soon as the email response comes back I'll send a second email. This is essentially what was asked, calling multiple services in sequence. I'm using the then method of promises to manage that in a vertically readable way. Also using catch to handle errors. I think it reads much better just simply nesting callback functions.

var Q = require('q');
var AWS = require('aws-sdk');    
AWS.config.credentials = { "accessKeyId": "AAAA","secretAccessKey": "BBBB"};
AWS.config.region = 'us-east-1';

// Use a promised version of sendEmail
var ses = new AWS.SES({apiVersion: '2010-12-01'});
var sendEmail = Q.nbind(ses.sendEmail, ses);

exports.handler = function(event, context) {

    console.log(event.nome);
    console.log(event.email);
    console.log(event.mensagem);

    var nome = event.nome;
    var email = event.email;
    var mensagem = event.mensagem;

    var to = ['email@company.com.br'];
    var from = 'site@company.com.br';

    // Send email
    mensagem = ""+nome+"||"+email+"||"+mensagem+"";

    console.log(mensagem);

    var params = { 
        Source: from, 
        Destination: { ToAddresses: to },
        Message: {
        Subject: {
            Data: 'Form contact our Site'
        },
        Body: {
            Text: {
                Data: mensagem,
            }
        }
    };

    // Here is the white-meat of the program right here.
    sendEmail(params)
        .then(sendAnotherEmail)
        .then(success)
        .catch(logErrors);

    function sendAnotherEmail(data) {
        console.log("FIRST EMAIL SENT="+data);

        // send a second one.
        return sendEmail(params);
    }

    function logErrors(err) {
        console.log("ERROR="+err, err.stack);
        context.done();
    }

    function success(data) {
        console.log("SECOND EMAIL SENT="+data);
        context.done();
    }
}