JWT Monitoring

Introduction

We want to give to JWT the ability to monitor workflow engines (ie AgilPro, Bonita...) at thein runtime; to give the user the ability to check the state of a workflow from Eclipse.

Ideas

• We think that "monitoring a workflow" is a synonymous for "getting full workflow state"
• To define a workflow state, we need a generic API to define a workflow. This API must fit with most of workflow engines. This introspection and query API can be usefully complemented by a consistent workflow management API.
• The monitoring tool must be able to support several workflow engines, and several ways to access them (WebService, RMI, ...)

Workflow State Model

• Workflow Engine
  • Process(*)
    • name(1) String
    • Project(1)
      • name(1) String
      • version(0..1) String
      • properties(*)
        • name(1) String
        • value(1) String
    • Activity(1)
      • name(1) String
      • state(1) String
      • properties(*)
        • name(1) String
        • value(1) String
• Query facilities ADDED 201009
  • Processes
    • start int
    • end int
    • sizeint
  • ProcessQuery
    • returnProperties boolean
    • start int
    • end int
    • filterProcesses(*) Process

Concretely

• As this work has been done in the context of SCorWare SCA project, first implementation is done with the aim of monitoring a Workflow Engine (Bonita) through WebServices. SCorWare uses CXF webservice engine, with Aegis databinding. That is the only technologies that are currently supported.
• However, we made some efforts to make the architecture extensible enough to handle other bindings; so that it might be easy to add a support for RMI, or an Eclipse internal Workflow Engine (eg MWE) or anything else. This is made by using extension points.

How do I monitor another workflow engine over another binding with this plugin?

1. Implement an interface (WorkflowService) with your favorite workflow engine. (We use the "Adapter" design-pattern)
2. Make this service accessible to the user who wants to monitor it in Eclipse (you can use webservices, rmi, or anything you are able to write a client programmaticaly)
3. Implement an extension plug-in which defines the way to access the service (so called a service provider) from inside Eclipse.

Screenshot

These are a screenshot of what we currently have. Obviously, it can be improved...

Implementation

General Schema

Comments

• The UI is implemented as an Eclipse View
• The view uses the interface WorkflowService, and creates the tree wih the beans that WorkflowService methods provide. Those beans are then embedded in a composite pattern, to fit with TreeViewer requirements.
• The interface WorkflowService is an adapter. Each workflow engine that is to be supported in JWT must implement this interface according to its own specifications.
• When accessing a Workflow Service, the plug-in calls a method from a plug-in linked to the base plug-in through extension point. This extension provides an implementation for the interface WorkflowServiceProvider, and more specifically for its "processServiceAdd" method.
• This way, we can consider that we have one plug-in per binding. (That's why SCA could be useful => One plug-in for several bindings)

Code

WorkflowService API combines both workflow Query and Management APIs :

package org.eclipse.jwt.runtime.workflow;
import org.eclipse.jwt.runtime.workflow.bean.Activity;
import org.eclipse.jwt.runtime.workflow.bean.Process;
import org.eclipse.jwt.runtime.workflow.bean.Processes;
import org.eclipse.jwt.runtime.workflow.bean.Project;
import org.eclipse.jwt.runtime.workflow.bean.Projects;
 
 
/**
 * @author gdecarnin
 * 
 * NB. These methods do not "officially" throw BonitaServerException because
 * it will rather result in an UndeclaredThrowableException in a ws client.
 */
public interface WorkflowService {
 
    public Projects listProjects(boolean returnProperties, boolean startableOnly, String login);
 
    public Project getProjectProperties(Project project, String login);
 
    public Process instanciateProject(Process process, String login);
 
    public Processes listUserActivities(boolean returnProperties, boolean returnTerminated, String login);
 
    public Process startActivity(Process process, String login);
 
    public Activity getActivityProperties(Process process, String login);
 
    public Activity setActivityProperties(Process process, String login);
 
    public Process terminateActivity(Process process, String login);
 
    /**
     * Allows pagination and server-side filtering. ADDED 201009
     * @param processQuery
     * @param login
     * @return
     */
    public Processes listUserActivities(ProcessQuery processQuery, String login);
}

With SCA

• SCA is aimed to make binding between several components (eg a Workflow Engine that promotes a service to monitor it, and a client to this service that monitor it in another application...) become more abstract. When possible, we could use SCA to manage theses bindings in JWT.
• We could provide a composite generator binary (for SCA) in the base plugin. This is possible by adding a binary without problem of license (see java2wsdl binary in STP), so that it could be part of an official release.