Plugin development

OpenMOLE is a plugable platform. It means that you can easily include you own java/scala code, and plug it into OpenMOLE. This tutorial explains how to write an OpenMOLE plugin using Scala and SBT. OpenMOLE is based on the JVM so you can create OpenMOLE plugins using Scala or any other JVM based languages such as Java, Groovy, Clojure, Jython...

OpenMOLE plugins are generally used to import you own code and libraries in OpenMOLE. They are actually simple OSGi bundles. The prerequisites are to have git and SBT installed on your system.

The first step is to clone the code available here:
git clone git://github.com/openmole/myopenmoleplugin.git

This repository contains a template to help you to create OpenMOLE plugins easily. The hello directory contains the source code of the plugin and the materials to build it:

package myopenmoleplugin

trait Hello {
def world(i: Int) = i * 2
}

object Hello extends Hello

The file build.sbt contains the building instructions for SBT. The most important part are the OSGi instructions:

OsgiKeys.exportPackage := Seq("myopenmoleplugin.*")

OsgiKeys.importPackage := Seq("*;resolution:=optional")

OsgiKeys.privatePackage := Seq("!scala.*,*")

The exportPackage instruction makes the myopenmole package visible to OpenMOLE. The importPackage instruction means that every package that is not included into the plugin should be imported. The privatePackage means that every package in the project, or in the dependencies, should be embedded except for the package starting by the scala word. The scala packages provided by OpenMOLE will be used by the plugin instead.

To build the plugin execute: sbt osgi-bundle

SBT constructs the plugin in target/scala-2.11/myopenmoleplugin_2.11-1.0.jar. This JAR file contains the classes you have developed (*.class) along with the metadata realtive to imports and exports in the MANIFEST.INF file:

META-INF/MANIFEST.MF
myopenmoleplugin/
myopenmoleplugin/Hello$.class
myopenmoleplugin/Hello.class

To load this plugin in the platform, you can:

• either use the -p option when starting OpenMOLE console: ./openmole -c -p target/scala-2.11/myopenmoleplugin_2.11-1.0.jar -c
• or upload it from the GUI plugin panel. This way, the plugins will be loaded every time OpenMOLE starts.

You can now use the Hello object in your workflows:

// Declare the variable
val i = Val[Int]

// Hello task
val hello = ScalaTask("i = myopenmoleplugin.Hello.world(i)") set (
inputs += i,
outputs += i,
plugins += pluginsOf(myopenmoleplugin.Hello)
)

val exploration = ExplorationTask(i in (0 to 2))

exploration -< (hello hook ToStringHook())