Dynamodb Stream to Elasticsearch

aws_es_post.js

/*
  https://aws.amazon.com/blogs/aws/amazon-elasticsearch-service-support-for-es-5-1/
*/
var AWS = require('aws-sdk');
var path = require('path');

//Object for all the ElasticSearch Domain Info
var esDomain = {
    region: process.env.RegionForES,
    endpoint: process.env.EndpointForES,
    index: process.env.IndexForES,
    doctype: 'onboardingrecords'
};
//AWS Endpoint from created ES Domain Endpoint
var endpoint = new AWS.Endpoint(esDomain.endpoint);
//The AWS credentials are picked up from the environment.
var creds = new AWS.EnvironmentCredentials('AWS');

console.log('Loading function');
exports.handler = (event, context, callback) => {
    //console.log('Received event:', JSON.stringify(event, null, 2));
    console.log(JSON.stringify(esDomain));
    
    event.Records.forEach((record) => {
        console.log(record.eventID);
        console.log(record.eventName);
        console.log('DynamoDB Record: %j', record.dynamodb);
       
        var dbRecord = JSON.stringify(record.dynamodb);
        postToES(dbRecord, context, callback);
    });
};

function postToES(doc, context, lambdaCallback) {
    var req = new AWS.HttpRequest(endpoint);

    req.method = 'POST';
    req.path = path.join('/', esDomain.index, esDomain.doctype);
    req.region = esDomain.region;
    req.headers['presigned-expires'] = false;
    req.headers['Host'] = endpoint.host;
    req.body = doc;

    var signer = new AWS.Signers.V4(req , 'es');  // es: service code
    signer.addAuthorization(creds, new Date());

    var send = new AWS.NodeHttpClient();
    send.handleRequest(req, null, function(httpResp) {
        var respBody = '';
        httpResp.on('data', function (chunk) {
            respBody += chunk;
        });
        httpResp.on('end', function (chunk) {
            console.log('Response: ' + respBody);
            lambdaCallback(null,'Lambda added document ' + doc);
        });
    }, function(err) {
        console.log('Error: ' + err);
        lambdaCallback('Lambda failed with error ' + err);
    });
}