Hello World (Simple)

Let's build a simple RabbitMQ-based Hello World application.

Getting ready

Navigate to your source code examples folder and locate the folder Hello-World. Here you will find two files: producer.js and consumer.js required for this task. Our Hello World application is simple; we have a producer which creates messages and sends them to an exchange, and the exchange delivers the messages to a queue. A consumer will read and process the messages from the queue.

How to do it...

Let's take a look at the producer.js script.

  1. First, we import the amqp module and call createConnection on that module, returning a connection to the RabbitMQ server. This connection will have the following default properties:
    {host: 'localhost', port: 5672, login: 'guest', password: 'guest', vhost: '/'}

    For more information, navigate to www.rabbitmq.com/uri-spec.html.

  2. Then, we create an array of messages.
  3. We wait on a connection ready event.
  4. When the connection ready event fires, we create an exchange. Here we use the default exchange, which is a direct exchange type.
  5. We then create a queue named 'hello', and wait for a queueDeclareOk event to fire.
  6. When the queueDeclareOk event fires, we bind the queue to the exchange using a binding key hash (#), which means to accept all messages delivered on the queue, ignoring the routing key. We then wait on the queueBindOk event.
  7. When the event queueBindOk has fired, we publish our messages.
  8. We loop through the messages; the ex.publish call publishes the message to the default exchange with a routing key hello.
    var connect = require('amqp').createConnection();
var messages = [];
messages.push(' (\-/)'),
messages.push(" ('.')  –> hello world");
messages.push('(") (")'),

connect.on('ready', function() {
    var ex = connect.exchange();
    var q = connect.queue('hello'),
    q.on('queueDeclareOk', function(args) {
        q.bind('#'),
        q.on('queueBindOk', function() {
            messages.forEach(function(message) {
                ex.publish('hello', message, {});
            });
        });
    });
});

Let us now take a look at the consumer.js script.

  1. First, we import the amqp module and call createConnection on that module, returning a connection to the RabbitMQ server.
  2. We wait on a connection ready event.
  3. When the ready event fires, we create a queue called 'hello' and wait for a queueDeclareOk event to be fired.
  4. When the queueDeclareOk event is fired, we bind the queue to the exchange using a binding key hash (#), and we wait on the queueBindOk event.
  5. When the event queueBindOk has fired, we subscribe to the queue, parse, and then print the incoming messages to the console.
      var connect = require('amqp').createConnection();
  connect.on('ready', function() {
    var q = connect.queue('hello'),
    q.on('queueDeclareOk', function(args) {
        q.bind('#'),
        q.on('queueBindOk', function() {
            q.subscribe(function(message) {
             console.log(message.data.toString());
            });
        });
    });
});
  6. Open a command-line console and start RabbitMQ:
    rabbitmq-server
  7. Open a command-line console, navigate to our source code examples folder, and locate the folder Hello-World. Execute the following command:
    Hello-World> node consumer
  8. Open another command-line console, and again execute the following command:
    Hello-World> node producer

The following screenshot shows the output of running the Hello World consumer/producer application—in the RabbitMQ style.

How to do it...

How it works...

AMQP 0-9-1 is structured as a logical grouping of AMQP methods. The AMQP 0-9-1 reference www.rabbitmq.com/amqp-0-9-1-quickref.html has a complete list of all the AMQP methods. If you would like to get under the covers and see the AMQP methods firing in real-time, consider using Wireshark, a network protocol analyzer that lets you capture and interactively browse the traffic running on a computer network. Wireshark allows you to monitor AMQP traffic by simply adding amqp to the filter. You can download Wireshark from www.wireshark.org/download.html.

Following is an example analysis of the consumer application from this task.

How it works...

You can see in the Info column the various AMQP methods required in order to consume a message. Wireshark is a great tool for debugging AMQP-based messaging applications.

Note

The web-based UI port for RabbitMQ versions prior to 3.0 is 55672.

There's more...

The RabbitMQ management plugin (www.rabbitmq.com/management.html) enables management and monitoring of your RabbitMQ server. In order to install the RabbitMQ management plugin, run the following command from your RabbitMQ installation sbin subfolder:

  rabbitmq-plugins enable rabbitmq_management

The management plugin includes three different methods for managing RabbitMQ:

  • The web-based UI is located at localhost:15672
  • The HTTP API and its documentation are both located localhost:55672/api/
  • A command-line tool, rabbitmqadmin, located at localhost:55672/cli/

For more information navigate to www.rabbitmq.com/management-cli.html.

Let's login to the web-based UI:

Navigate to http://server-name:15672 and enter the default username and password:

username guest
password: guest

When logged in you should see the following real-time overview of the RabbitMQ server. The overview includes the number of queued messages. There are tabbed options for viewing Connections, Channels, Exchanges, and Queues.

The CLI command-line tool can perform all of the functionalities available to you in the web-based management tool as follows:

There's more...

Let's again run the example from this chapter. Execute the following command to produce messages:

Hello-World> node producer

You should now see the number of queued messages on your management UI increase. If you run the following command, it will consume those messages and the number of queued messages will display 0, emptying the queue.

Hello-World> node consumer

Please play around with the example and get comfortable with it. Add more messages to our producer.js script's message array.

Also try the command-line tool, rabbitmqadmin, which allows you to perform all of the same functions available to you via the management UI:

List all connections

rabbitmqctl list_connections

List all exchanges

rabbitmqctl list_exchanges

List all bindings

rabbitmqctl list_bindings

List all queues

rabbitmqctl list_queues

List all channels

rabbitmqctl list_channels

For a full list of commands, visit www.rabbitmq.com/man/rabbitmqctl.1.man.html.

AMQP is a multi-channeled protocol. The Node.js client node-amqp (unlike some other clients) abstracts away the concept of channels. Channels provide a way to multiplex a heavyweight TCP/IP connection into several lightweight connections. Whenever you create a queue or exchange with the node-amqp, you are creating a channel; exchanges and queues are a subclass of channel.

..................Content has been hidden....................

You can't read the all page of ebook, please click here login for view all page.
Reset
3.12.108.175