Get started with RabbitMQ

RabbitMQ is an open-source implementation of AMQP. If you don't know what AMQP is, I encourage you to check it out on the official web site, or alternatively read articles listed on the reference page. Here I want to mention only the reasons why it drew my attention as an Erlang enthusiast and Java developer working in financial industry:

• AMQP is a replacement for TIBCO Randezvous;
  
• in terms of functionality it's a superset of JMS;
  
• it's written in Erlang, which means fault-tolerance, reliability and high performance.

In this blog post I just want to show how to install RabbitMQ on Ubuntu box, and verify that it works with simple Groovy client.

Installing RabbitMQ server

As everything with Ubuntu, this step is pretty trivial:

$ sudo apt-get install rabbitmq-server

The only requirement for this package is Erlang distribution. If you already have Erlang installed on your system, the installation of rabbitmq-server is a quick procedure. The following directories will be created during the installation:

/usr/lib/rabbitmq/bin	executables added to the path
/usr/lib/erlang/lib/rabbitmq_server-1.x.x	compiled modules
/var/lib/rabbitmq/mnesia	persistent storage for messages
/var/log/rabbitmq	log files (e.g. startup_log, rabbit.log)

After installation is finished the RabbitMQ server is started and listens to incoming requests on port 5672. You can check /var/log/rabbitmq/startup_log file to see if everything was ok.

Groovy clients

I followed official Java client API to build two scripts: consumer.groovy

import com.rabbitmq.client.*

@Grab(group='com.rabbitmq', module='amqp-client', version='1.7.2')
params = new ConnectionParameters(
    username: 'guest',
    password: 'guest',
    virtualHost: '/',
    requestedHeartbeat: 0
)
factory = new ConnectionFactory(params)
conn = factory.newConnection('lab.ndpar.com', 5672)
channel = conn.createChannel()

exchangeName = 'myExchange'; queueName = 'myQueue'

channel.exchangeDeclare exchangeName, 'direct'
channel.queueDeclare queueName
channel.queueBind queueName, exchangeName, 'myRoutingKey'

def consumer = new QueueingConsumer(channel)
channel.basicConsume queueName, false, consumer

while (true) {
    delivery = consumer.nextDelivery()
    println "Received message: ${new String(delivery.body)}"
    channel.basicAck delivery.envelope.deliveryTag, false
}
channel.close()
conn.close()

and publisher.groovy

import com.rabbitmq.client.*

@Grab(group='com.rabbitmq', module='amqp-client', version='1.7.2')
params = new ConnectionParameters(
    username: 'guest',
    password: 'guest',
    virtualHost: '/',
    requestedHeartbeat: 0
)
factory = new ConnectionFactory(params)
conn = factory.newConnection('lab.ndpar.com', 5672)
channel = conn.createChannel()

channel.basicPublish 'myExchange', 'myRoutingKey', null, "Hello, world!".bytes

channel.close()
conn.close()

Now start consumer in one terminal window

$ groovy consumer.groovy

and run publisher in another:

$ groovy publisher.groovy

On the consumer window you should see Received message: Hello, world! text, which means RabbitMQ works correctly.

Monitoring logs

You can check RabbitMQ logs by doing tail -f /var/log/rabbitmq/rabbit.log For example, starting the consumer results the following log entries:

=INFO REPORT==== 14-Mar-2010::11:20:53 ===
accepted TCP connection on 0.0.0.0:5672 from 192.168.2.10:62424

=INFO REPORT==== 14-Mar-2010::11:20:53 ===
starting TCP connection <0.24154.1> from 192.168.2.10:62424

Running the publisher:

=INFO REPORT==== 14-Mar-2010::11:22:08 ===
accepted TCP connection on 0.0.0.0:5672 from 192.168.2.10:62432

=INFO REPORT==== 14-Mar-2010::11:22:08 ===
starting TCP connection <0.24232.1> from 192.168.2.10:62432

=INFO REPORT==== 14-Mar-2010::11:22:08 ===
closing TCP connection <0.24232.1> from 192.168.2.10:62432

Now if we terminate the consumer by ^C there will be a warning

=WARNING REPORT==== 14-Mar-2010::11:25:03 ===
exception on TCP connection <0.24154.1> from 192.168.2.10:62424
connection_closed_abruptly

=INFO REPORT==== 14-Mar-2010::11:25:03 ===
closing TCP connection <0.24154.1> from 192.168.2.10:62424

but the connection is closed properly by the server.

That's it for now. Stay tuned for the future updates on my RabbitMQ experience.

Links

• Rapid application prototyping with Groovy DSL

Installing ejabberd on Ubuntu

Recently I've installed ejabberd server on Ubuntu box. Thanks to this nice document, the process was pretty straightforward. My experience was little bit different from the author's one, so I want to show here exact steps I did to make it work, maybe it will be helpful for you too.

The first step is to install the required package. You can use Synaptic Package Manager or just command line:

sudo apt-get install ejabberd

During the installation a new user, ejabberd, will be created in the system. This is the user the server will be running on. When installation is finished ejabberd server is started. To configure the server you need to stop it

sudo /etc/init.d/ejabberd stop

Next step is to configure administrator and hosts. Open /etc/ejabberd/ejabberd.cfg file for edit and make the following change

%% Admin user
{acl, admin, {user, "andrey", "jabber.ndpar.com"}}.
%% Hostname
{hosts, ["localhost", "ubuntu", "jabber.ndpar.com"]}.

For admin you need to specify the user name and domain name that you want to use as a Jabber ID. By default it's localhost and it's functional but it's better to change it to something meaningful. The list of hostnames is tricky. In theory you can provide there just localhost but in practice it didn't work for me. After digging into some Erlang exceptions I got while registering admin account (see next step) I came to conclusion that in the list of hostnames there must be a short hostname of the box. You can get it by running hostname -s command (in my case it was "ubuntu"). In addition you can provide other hostnames you like, but the short one is mandatory.

When you are done with editing, start the server

sudo /etc/init.d/ejabberd start

Now it's time to register the admin user we configured on the previous step. Run the following command replacing password placeholders with the actual password and providing user name and domain name from ejabberd.cfg file

sudo ejabberdctl register andrey jabber.ndpar.com xxxxxx

That's it! You have now working XMPP server with one registered user. To verify that everything is ok, in your browser go to the admin page of the server (http://jabber.ndpar.com:5280/admin) and check the statistics. You'll be asked to type your JID and password, so use the information you entered on the previous step



As a note, I didn't create my own SSL certificate because for isolated intranet the default one is quite enough. If you are not comfortable with that feel free to create a new certificate following the steps from the original article.

Now you are ready to add newly created account to your Jabber client. In Adium, for example, go to File -> Add Acount -> Jabber and provide server hostname/IP, JID and password.





Click OK button, accept security certificate permanently and go online.

Now, to really enjoy IM you need more users on your server. The best part here is that you can create new users just from your Jabber client. You can actually do many things from the client, and you don't need to ssh to the remote server and run command for that. Just go to File -> your ejabberd account, and chose whatever you need from the menu



Pretty cool, eh — client and admin tool in one place.