AWS: Events

Overview

AWS provides 2 different means of providing inter-application messaging

• SNS - Simple Notification Service
• SQS - Simple Queue Service

Class Outline

Learning Objectives

Students will be able to

Describe and Define

• The differences between SNS and SQS
• Use cases for each
• FIFO Queues
• The publisher/subscriber relationship

Execute

• Create a notification topic that triggers an action
• Create a Queue that retains messages

Notes

SNS - Working with Notifications in Code

Publishing (Pushing) a message with SNS

This sample application contacts SNS and publishes a single message

const AWS = require('aws-sdk');
AWS.config.update({region:'us-west-2'});

const sns = new AWS.SNS();

const topic = 'arn:aws:sns:us-west-2:335083857671:alert';

const payload = {
  Message: 'Hello from John',
  TopicArn: topic,
};

sns.publish(payload).promise()
  .then(data => {
    console.log(data);
  })
  .catch(console.error);
;

Subscribe to a topic

A node application such as below will continually run, waiting on notifications to be pushed to it, and will respond as they occur

const AWS = require('aws-sdk');
AWS.config.update({region: 'us-west-2'});
const sns = new AWS.SNS();

const topic = 'arn:aws:sns:us-west-2:335083857671:TaskComplete';

var params = {
  Protocol: 'sms',
  TopicArn: topic,
  Endpoint: '+12065551212',
  ReturnSubscriptionArn: true || false,
};

sns.subscribe(params).promise()
  .then( data => console.log('OK', data) )
  .catch( console.error );

SQS - Queues

Publishing with Node.js

const uuid = require('uuid').v4;
const { Producer } = require('sqs-producer');

const producer = Producer.create({
  queueUrl: `https://sqs.us-west-2.amazonaws.com/335083857671/john-testing-queue`,
  region: `us-west-2`,
});

let counter = 0;

setInterval(async () => {

  try {
    const message = {
      id: uuid(),
      body: `This is message #${counter++}`,
    };

    const response = await producer.send(message);
    console.log(response);
  } catch (e) {
    console.error(e);
  }
}, Math.floor(Math.random() * 1000));

Subscribing with Node.js

'use strict';

const { Consumer } = require('sqs-consumer');

const app = Consumer.create({
  queueUrl: 'https://sqs.us-west-2.amazonaws.com/335083857671/sqs-testing',
  handleMessage: handler,
});

function handler(message) {
  console.log(message.Body);
}

app.on('error', (err) => {
  console.error(err.message);
});

app.on('processing_error', (err) => {
  console.error(err.message);
});

app.start();