The communication between a debugger (like JDB or Eclipse) and a Java Virtual Machine (JVM) uses a socket connection. The debugger has therefore to know the URL of the JVM and the port number available for this socket connection. However, no port number is available by default on the JVM. Thus, in order to be able to launch the JVM with the correct arguments, the IC2D debugger connection tool is intended to give the information needed to the debugger connection.

First of all, JVMs (ProActive Runtimes) have to be started with the debug command line argument, otherwise it is not possible to establish a remote connection to these JVMs. The additional argument is of the following form:

-DdebugID=padebug_someDeploymentId -Xdebug -Xrunjdwp:transport=dt_socket,server=y,suspend=n,address=0,launch='java -cp <path/to/ProActive.jar> org.objectweb.proactive.core.debug.dconnection.DebuggeePortSetter padebug_someDeploymentId'

In the previous line, the path to the ProActive archive is the only thing to be changed. The debug id and the port number (address) will be set randomly so as to avoid conflicts between JVMs.

In order to ease the use of the debugging features, the GCMA descriptor has been extended to easily start runtimes in debug mode. One has to add the tag <debug/> as a child of the application/proactive tag. An example is shown hereafter:

<?xml version="1.0" encoding="UTF-8"?>
<GCMApplication xmlns="urn:gcm:application:1.0"
    xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
    xsi:schemaLocation="urn:gcm:application:1.0 http://proactive.inria.fr/schemas/gcm/1.0/ApplicationDescriptorSchema.xsd">

    <environment>
        <javaPropertyVariable name="proactive.home" />
        <javaPropertyVariable name="user.dir" />

        <descriptorVariable name="hostCapacity" value="2"/>
        <descriptorVariable name="vmCapacity" value="2"/>
    </environment>


    <application>
        <proactive base="root" relpath="${proactive.home}">
            <configuration>
                <applicationClasspath>
                    <pathElement base="proactive" relpath="dist/lib/ProActive_examples.jar"/>
                    <pathElement base="proactive" relpath="dist/lib/ibis-1.4.jar"/>
                    <pathElement base="proactive" relpath="dist/lib/ibis-connect-1.0.jar"/>
                    <pathElement base="proactive" relpath="dist/lib/ibis-util-1.0.jar"/>
                </applicationClasspath>
                    <debug/>
            </configuration>
            <virtualNode id="Workers" capacity="4"/>
        </proactive>

    </application>

    <resources>
        <nodeProvider id="workers">
            <file path="../GCMD_Local.xml" />
        </nodeProvider>
    </resources>
</GCMApplication>

One does not have to complete his descriptor with jvmarg tags to give arguments evoked above: it is precisely the role of the debug tag. It gives these arguments to all the created JVMs.

3.1.1. The connection

The IC2D debugger connection differs slightly from a simple debugger connection. When a user wants to connect a debugger to a remote JVM, he actually has to connect it to the local IC2D JVM. Then, it is an active object (created when the user sends the connection request) that is in charge of transmitting, through a proactive connection, the debugger information and requests to the JVM.

Figure 3.1. connection

3.1.2. How to use the IC2D debugger connection tools

When a user right clicks on a monitored JVM, he can select an option (connect a debugger) that shows him the port number of his local debugger.

Figure 3.2. Menu

The following dialog box should appear:

Figure 3.3. Debugger Choice

Then, you can select either to use the Eclipse Extended Debugger or an external one. In case of an external one, the following window should appear asking you to give the connection information:

Figure 3.4. Popup

Next, the user has just to connect his debugger. For example: The Eclipse debugger

Figure 3.5. Eclipse connection

Figure 3.6. Eclipse debugger

Figure 3.7. Communication