How can i consume sqs messages at my existing nodejs server

Question

I want to receive and trigger email when new message receive at SQS, Now I already have nodejs server running, How can I make it work? I dont really want to trigger that function. But I want that when there's new message in SQS this consumer will consume and do the business logic of sending email.

But I am not getting any trigger at my function. Note: I am not calling this function, I want that it automatically trigger when new message is available at SQS.

const AWS = require('aws-sdk');
const mongoose = require('mongoose');

//
// Configure the aws details
//
AWS.config.update({
    region: process.env['AWS_REGION'],
    accessKeyId: process.env['AWS_ACCESS_KEY_ID'],
    secretAccessKey: process.env['AWS_SECRET_ACCESS_KEY']
  });


const sqs = new AWS.SQS({apiVersion: '2012-11-05'});

var queueURL = "https://sqs.us-east-1.amazonaws.com/xxxxx/demo-lambda-to-email-sqs"



var params = {
    AttributeNames: [
        "SentTimestamp"
     ],
    MaxNumberOfMessages: 1,
    MessageAttributeNames: [
       "All"
    ],
    QueueUrl: queueURL,
    VisibilityTimeout: 20,
    WaitTimeSeconds: 0
   };

   sqs.receiveMessage(params, function(err, data) {
    if (err) {
      console.log("Receive Error", err);
    } else if (data.Messages) {
      console.log('--------------------------- MESSAGE RECEIVED -------------')
      var deleteParams = {
        QueueUrl: queueURL,
        ReceiptHandle: data.Messages[0].ReceiptHandle
      };
      sqs.deleteMessage(deleteParams, function(err, data) {
        if (err) {
          console.log("Delete Error", err);
        } else {
          console.log("Message Deleted", data);
        }
      });
    }
  });

Answer 1

SQS is a queuing service, for this reason it needs to be consumed via a pull based mechanism not a push based.

This function can only be invoked if you have functionality that will poll the SQS queue, then trigger the function when a message comes in.

If you do not want to maintain a consumer script, you should look at migrating this script into a Lambda function. When this option is used the Lambda Service will act as the consumer of the queue and trigger the Lambda function only when a message is added.

More information about Using AWS Lambda with SQS Queues is available in the documentation.

Answer 2

You are only call it once without using long polling. So it starts and its gets an empty response. So you need a pull based mechanism, a basic implementation could run receiveMessage inside a SetInterval. Something like:

setInterval(function() {
    sqs.receiveMessage(params, function(err, data){
      // your logic here!
    });
}, 10000);
// Run every 10s

WaitTimeSeconds greater than 1s enables long polling and helps reduce the cost of using Amazon SQS by eliminating the number of empty responses.

Answer 3

The following code calls SQS every 30 seconds asking for messages. Every call waits up to 20 seconds to receive messages.

const AWS = require('aws-sdk')
AWS.config.update({
    region: 'us-east-1',
    accessKeyId: '...',
    secretAccessKey: '...'
})
const sqs = new AWS.SQS()

receiveMessage = () => sqs.receiveMessage({
    QueueUrl: 'https://sqs.us-east-1.amazonaws.com/.../...',
    WaitTimeSeconds: 20
}, (error, data) => {
    if (error) console.error("ERROR:", error)
    if (data.Messages) data.Messages.forEach(m => console.info(m.Body))
})

setInterval(receiveMessage, 30000)