Fanout AWS Lambda

fanout.js

'use strict';
const aws = require('aws-sdk');

const lambda = new aws.Lambda({region: 'eu-west-1'});
const async = require('async');

exports.handler = (event, context, callback) => {
    /*
    Invokes a given Lambda function `event.function` in parallel for each given
    argument `event.events`

    Lambdas are invoked asynchronously and their results are gathered when the
    last Lambda returns its values. Results are returned in the master Lambda.
    */

    // Prepare tasks for parallel execution
    var tasks = [];
    event.events.forEach(function(item) {
        var taskFunc = function(callback) {
            var params = {
                FunctionName: event.function,
                InvocationType: "RequestResponse",
                LogType: "None",
                Payload: JSON.stringify(item)
            };
            lambda.invoke(params, function(err, data) {
                if (err) {
                    // an error occurred
                    console.log(err, err.stack);
                } else {
                    // successful response
                    var result = JSON.parse(data.Payload);
                    callback(null, result);
                }
            });
        };
        tasks.push(taskFunc);
    });

    // Run tasks in parallel
    async.parallel(tasks, function(err, results) {
        if (err) {
            console.log(err);
        } else {
            callback(null, results)
        }
    });
};