lab_assignment.md

Lab class Week 11

Exercise 1

Write a RabbitMQ produces that adds messages to RabbitMQ on regular interval.

Write a Node.js consumer that consumes the messages from that queue and prints tham out to stdout.

There is a nice library for Node.js named amqp

npm install amqp --save

That can be used as follows.

var amqp = require('amqp');

var connection =
  amqp.createConnection({url: "amqp://guest:guest@localhost:5672"},
                                  {defaultExchangeName: "amq.topic"});

connection.on('ready', function () {
  connection.queue("foobar",{autoDelete:false}, function(queue){
    queue.bind('#'); 
    queue.subscribe(function (message) {
      var encoded_payload = unescape(message.data)
      var payload = JSON.parse(encoded_payload)
      console.log('Recieved a message:')
      console.log(payload)
    })
  })
})

The aim of this execise is for you to install RabbitMQ on your machine and produce and consume messages in two different languages.

Exercise 2

Write an API with the following routes

• POST /order
• GET /order/<order_id>

When you post to order, order id is generated and a message with the order details is added to queue named "incoming_orders". When the message has been added to the queue, the order_id is written to the response.

You can do a get on /order/<orderid> to see the status of the order. Implement two statuses, "not-done" or "done".

You can store the order state in a sqlite database using SQLAlchemy or in Memcached.

Then write a consumer in Python that listens to the queue, picks up the message, sleeps for 4 seconds and updates the order to a done-state.

This is similar to our pizza example written in class.