A business process is typically a collection of related and structured activities or tasks, that depicts a business use case and produces a specific service or output. For example, a banking customer requesting a bank load and getting loan approval is a simple process. An instance of this process is a specific example of this process workflow. So, Mr. Smith requesting for 50,000 USD and getting approval for it is an instance of the "bank loan approval" process. Every time a banking customer makes a request for a loan, that request triggers a new process instance in the BPM system, which flows through the elements of the process workflow according to its design.
At a particular time, there can be numerous instances of a single process. Follow the instructions below to access process instances.
1. Log in to the management console and select "Business Processes -> Instances" in the "Main" menu.
2. The "Instances Created" window opens.
- Instance ID:
- Process ID:
- Date Started:
- Last Active:
- Total Instances:
3. Click on an Instance ID to view "Instance Information". For example,
The following details can be accessed:
Details of the process instance as described above.
Root Scope Information
- Scope ID:
- Scope Name:
<To be added>
4. In the "Instances Created" window, click on selected process ID.
5. The "Process Information" window opens. For more information on each section, refer to Deploy, Undeploy and Manage a BPEL Process.
Process Instance Events
WSO2 BPS generates events to facilitate tracking the activities of the engine and produces detailed information about process executions. These events are persisted in BPS's database and can be queried using the BPS Management API. The default behavior of the BPS engine is to generate events for every executed action. However, for better performance, it is recommended to deactivate selected or all events depending on your requirements as these events usually cause a non-negligible overhead in the system.
The following table depicts the event types generated by ODE:
|ActivityEnabledEvent||Scope||An activity is enabled (just before it's started)||activityLifecycle|
|ActivityDisabledEvent||Scope||An activity is disabled (due to dead path elimination)||activityLifecycle|
|ActivityExecStartEvent||Scope||An activity starts its execution||activityLifecycle|
|ActivityExecEndEvent||Scope||An activity execution terminates||activityLifecycle|
|ActivityFailureEvent||Scope||An activity failed||activityLifecycle|
|CompensationHandlerRegistered||Scope||A compensation handler gets registered on a scope||scopeHandling|
|CorrelationMatchEvent||Process||A matching correlation has been found upon reception of a message||correlation|
|CorrelationNoMatchEvent||Process||No matching correlation has been found upon reception of a message||correlation|
|CorrelationSetWriteEvent||Scope||A correlation set value has been initialized||dataHandling|
|NewProcessInstanceEvent||Process||A new process instance is created||instanceLifecycle|
|PartnerLinkModificationEvent||Scope||A partner link has been modified (a new value has been assigned to it)||dataHandling|
|ProcessCompletionEvent||Process||A process instance completes||instanceLifecycle|
|ProcessInstanceStartedEvent||Process||A process instance starts||instanceLifecycle|
|ProcessInstanceStateChangeEvent||Process||The state of a process instance has changed||instanceLifecycle|
|ProcessMessageExchangeEvent||Process||A process instance has received a message||instanceLifecycle|
|ProcessTerminationEvent||Process||A process instance terminates||instanceLifecycle|
|ScopeCompletionEvent||Scope||A scope completes||scopeHandling|
|ScopeFaultEvent||Scope||A fault has been produced in a scope||scopeHandling|
|ScopeStartEvent||Scope||A scope started||scopeHandling|
|VariableModificationEvent||Scope||The value of a variable has been modified||dataHandling|
|VariableReadEvent||Scope||The value of a variable has been read||dataHandling|
The second column specifies whether an event is associated with the process itself or with one of its scopes. The event type is used for filtering events.
It is possible to tweak event generation by having filters in the process deployment descriptor inside the <dd:deploy> element.
Process level event filtering can be done using one of the following stanza:
This configuration allows the generation of all the events of an execution. This can be achieved by not adding any event filterings also since this is the default behavior.
With this configuration, no events are generated. This configuration provides a performance gain also.
This form allows you to define types of events that are generated. One or more following event types are allowed here: instanceLifecycle, activityLifecycle, dataHandling, scopeHandling, correlation
It is also possible to define filtering for each scope of the process. This overrides the settings defined in the process. In order to define event filtering on a scope, the scope activity MUST have a name in your process definition. Scopes are referenced by name in the deployment descriptor:
It is futile to enable an event associated with the process itself, when filtering events on scope. The filter defined on a scope is automatically inherited by its inner scopes. So, if no filter is defined on a scope, it will use the settings of its closest parent scope which has event filters (up to the process). The full list of selected events gets inherited; not each event definition individually.
WSO2 BPS allows to register your own event listeners to analyze all produced events and perform desired actions with them.
To create a listener, simply implement the org.apache.ode.bpel.iapi.BpelEventListener interface. Then add the implementation in the server's classpath ($PRODUCT_HOME/repository/components/lib) and add a property in bps.xml bye specifying your fully-qualified implementation class name:
You can try the sample event listener that is shipped with WSO2 BPS by adding the above configuration to the bps.xml and restarting the server. The source of the sample implementation of event listener can be found here.