bam queue

Using BAM to implement a queuing service.

Demo

Messaging lets a servlet delegate processing to a batch process either on the same machine or on a separate machine. The servlet creates a message and sends it to a queue. The servlet immediately completes and when the batch process is ready, it processes the message.

Messaging is therefore comprised of three main components:

• A Producer creates messages and sends them to a Consumer, continuing processing. The Producer could be a Servlet or PHP page that sends a request to a backend consumer and continues the web response without waiting for the task to complete.
• A Consumer processes messages as they become available. In BAM, the Consumer extends SimpleBamService to receive the messages.
• The Queue buffers messages from the Produces and provides them to a Consumer when the Consumer is ready. The Queue is part of the BAM messaging system.

In this example, the Producer is a Servlet which sends a simple message. The Producer creates a BamClient to send the message.

import com.caucho.bam.BamClient;

public void send()
{
  BamClient client = new BamClient();

  ExampleMessage message = new ExampleMessage("sample message");

  client.message("consumer@", message);

  client.close();
}

<?php

$msg = java("example.ExampleMessage", "sample message");

bam_send_message("consumer@", $msg);

?>

The Queue delivers message to the Consumer one by one. When the Consumer finishes processing a message the Queue will deliver the next available message. The Consumer implements com.caucho.bam.BamService.

In this example, the Consumer just logs the message.

package example;

import com.caucho.bam.SimpleBamService;
import com.caucho.bam.annotation.Message;

public class ExampleService extends SimpleBamService
{
  @Message
  public void onMessage(String to, String from, ExampleMessage message)
  {
    System.out.println("Message: " + message + " from=" + from);
  }
}

The PHP version of the service implements a bam_message method to handle the message and calls bam_dispatch() to dispatch the message. The PHP service will call the bam_queue.php when it receives a message.

<?php

function bam_message($to, $from, $value)
{
  resin_debug($value);
}

bam_dispatch();

?>

<web-app xmlns="http://caucho.com/ns/resin">

  <bam-service name="java-consumer"
               class="example.ExampleService"/>

  <bam-service name="php-consumer"
               uri="caucho.php:">
    <init script="WEB-INF/php/bam_queue.php"/>
  </bam-service>

</web-app>

Demo