Few Simple steps for integrating Rabbit MQ with Grails

Rabbit MQ as defined by rabbitmq.com is a robust messaging for applications. We used RabbitMQ to achieve asynchronous communication between two parts of the application.

I would like to share the same in a step by step fashion.

Here are few simple steps that I followed to make my grails application use rabbitmq:

1.Install rabbitmq :

Download the installable from http://www.rabbitmq.com/download.html. Install the same on your machine.

2.Install the rabbitmq grails plugin:

[java] grails install-plugin rabbitmq[/java]

3.Configure the rabbit server and a queue in the Config.groovy:

[java]
// grails-app/conf/Config.groovy
rabbitmq {
connectionfactory {
username = ‘guest’
password = ‘guest’
hostname = ‘localhost’
consumers = 5
}

retryPolicy.maxAttempts = 3

queues = {
myTestQueue autoDelete: false, durable: true, exclusive: false
}
}
[/java]

4.Write a method to populate messages in the queue:
rabbitmq plugin injects a rabbitSend() method in all the services and controllers

[java]
//This method could be defined in any service.
populateQueue(){
rabbitSend(‘myTestQueue’, "some id:1,some action: do this")
// Message has to be a String
}
[/java]

5.Write a handler Service which shall handle the messages that are put in the queue:

[java]
class QueueBasedMyTestService {

static rabbitQueue = ‘myTestQueue’
def solrSearchService

// This method gets called by the plugin whenever there is any new message in the queue.
// We can configure n number of parallel handlers
void handleMessage(message){
log.info("Message Received ${message}")
// We have recieved the message from the rabbitmq server’s queue
}
}
[/java]

Hope this helps!!!