The msgqueue Module for Drupal

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Message-oriented middleware is a common means to enable communication between heterogeneous systems. For example, if a Java system wants to know about events happening in Drupal, this messaging module is one way to provide such information. Other ways are possible too.

The "msgqueue" module integrates Drupal with messaging system like Apache ActiveMQ (a JMS implementation). This module accesses Drupal events by implementing hooks for users, nodes, and comments, and is licensed under GPLv2. The hooks supply events when any insert, update, or delete action takes place for any user, node or comment. An XML message about any such Drupal event is sent to the messaging system. The module formats XML messages using minixml, and puts them into a queue via the Stomp protocol of ActiveMQ.

Installing Module

• Download the msgqueue.zip file and expand it into /sites/all/modules/ as described by standard module install instructions for Drupal 5. (This module can probably run under Drupal 4, but has only been tested on 5.)
• After installation, remember to enable the module using menus administer > site building > modules.

Testing Messages

• Download and install Java JDK if you don't have it already.
• On a command line, "java -version" should tell you v.5 or better; the JDK also provides javac, which will be used later.

java -version

javac -version

• Download and install Ant if you don't have it already (on a command line, "ant -version" should say v.6 or better)

ant -version

• Download Apache ActiveMQ v. 4 or greater and unzip it somewhere (installation is just unzipping).
• Start ActiveMQ via a script in the /bin/ directory of the ActiveMQ installation: use the script "activemq.bat" for Windows, "activemq" for other platforms. At startup, the following console output should show that the message server is listening for the Stomp protocol on port 61613 (see colorized line below; HAM6 is just the name of a test server):

...
INFO  TransportConnector             - Connector openwire Started
INFO  TransportServerThreadSupport   - Listening for connections at: ssl://HAM6:61617
INFO  TransportConnector             - Connector ssl Started
INFO  TransportServerThreadSupport   - Listening for connections at: stomp://HAM6:61613
INFO  TransportConnector             - Connector stomp Started
INFO  NetworkConnector               - Network Connector default-nc Started
INFO  BrokerService                  - ActiveMQ JMS Message Broker (localhost, ID:HAM6-14x1-11xxxxxx62-1:0) started

In order to see the messages coming into the queue from Drupal, we will test with a sample client that is provided by the ActiveMQ installation.

• While the message server above continues running, and also Drupal is running, start a shell (a Command Prompt in Windows) and navigate to the ActiveMQ installation, and the "example" directory

        $ cd apache-activemq-4.1.1/example

• Run the 'consumer' example by using ant:

        $ ant consumer

The output should look something like this:

larry@HAM6 ~/tools/apache-activemq-4.1.1/example
$ ant consumer
Buildfile: build.xml

init:
    [mkdir] Created dir: C:\tools\apache-activemq-4.1.1\example\target\classes
    [mkdir] Created dir: C:\tools\apache-activemq-4.1.1\example\src\ddl

compile:
    [javac] Compiling 8 source files to C:\tools\apache-activemq-4.1.1\example\target\classes
    [javac] Note: Some input files use unchecked or unsafe operations.
    [javac] Note: Recompile with -Xlint:unchecked for details.

consumer:
     [echo] Running consumer against server at $url = tcp://localhost:61616 for subject $subject = TEST.FOO
     [Java] Connecting to URL: tcp://localhost:61616
     [Java] Consuming queue: TEST.FOO
     [Java] Using a non-durable subscription
     [Java] We are about to wait until we consume: 10 message(s) then we will shutdown

The last line reports that the consumer is waiting for events to print.

• Return to the Drupal screen and click Create content->Article and submit a new article, edit an article, delete an article, and do similar actions for comments and users. For each action, an event should print on the consumer console, like the following for inserting a comment, user, and node, respectively:

     [Java] Received: <?xml version="1.0"?>
     [Java] <msg>
     [Java]   <comment op="insert"...
     [Java] Received: <?xml version="1.0"?>
     [Java] <MSG>
     [Java]   <user op="insert" ui...
     [Java] Received: <?xml version="1.0"?>
     [Java] <MSG>
     [Java]   <node op="insert" ni...
	 

The Consumer example code truncates messages to only 50 characters, so what you see above are just a small parts of the messages. If you want to see the full message, edit the Java class in examples/src/ named ConsumerTool.java and comment out the lines:

                    if (msg.length() > 50) {
                        MSG = msg.substring(0, 50) + "...";
                    }

and just run 'ant consumer' again--it will automatically recompile and run.

Message Formats

All messages are delimited with a <msg> tag, followed by a 'payload' tag of <node>, <comment> or <user>. The first attribute of the payload tag is the operation attribute "op", which describes whether this message is [insert, delete, update]. The rest of the attributes depend on the payload. User-entered text is found in child tags, within CDATA delimiters. Dates are in ISO 8601 format, using the server's local timezone.

Node message sample:

      <MSG>
        <node op="insert" nid="13" vid="13" type="article" uid="1" 
              created="2007-12-10T12:47:18-0800" status="1" 
              changed="2007-12-10T12:47:18-0800"
              comment="2" promote="1" sticky="0" >
          <title><![CDATA[test article subject]]></title>
          <body><![CDATA[test article body]]></body>
        </node>
      </MSG>

Comment message sample:

       
      <MSG>
        <comment op="insert" cid="3" nid="13" uid="1">
          <subject><![CDATA[test comment subject]]></subject>
          <body><![CDATA[test comment body]]></body>
        </comment>
      </MSG>

User message sample:

      
      <MSG>
        <user op="insert" uid="4" name="testuser" mail="x@y.com" 
              mode="0" created="2007-12-10T12:47:18-0800" 
              access="0" login="0" status="1" language="" />
      </MSG>

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