Workflow processes with AI scheduling

Create a new folder to hold this project. Run the following command to create a new Quarkus project:

We will be creating a simple BPMN that models the following process:

Go to the Kogito BPMN Editor, a free online editor for editing and creating BPMN files, no account required. You should be greeted with the following screen:

Click on the edit button next to new-file.bpmn and name it something more appropriate, like flight-process. Now click the "Properties" button on the right sidebar

Replace the auto-generated name in the "Name" field with "Flight Process" and the auto-generated id in the "Id" field with "flightProcess". Enter "com.company" into the "Package" field.

Before proceeding, we need to know our business process' variables (that is, what data is processed by the business process). Expand the "Process Data" tab in the Properties Sidebar and click the "+" icon in the "Process Variable" table. In this case, we only have one process variable: the flight we are planning. Enter "flight" into the "Name" field, and in the "Type" field, select "Custom…​" and enter "com.company.Flight".

Now we get to design the actual business process. Create a start node by clicking on the Green Circle in the toolbar on the left, and drag the "Start" row somewhere on the canvas.

Now we are going to create a User Task to finalize the passenger list. Click on the Rectangle in the toolbar on the left, then drag the "User Task" row next to the start node.

Click on the start node, then click on the solid arrow icon, then click on the newly created User Task to create a sequence flow from "Start" to "Task" (this tell the process that after it is started, to go to the "Task" node).

Click on the "Task" node to open up its properties (if you closed the properties panel from earlier, you can open it up again by clicking on the properties icon). Rename the task to "Finalize Passenger List". Open its "Implementation/Execution" tab. Change the "Task Name" field to "finalizePassengerList"; this field will be used to determine the REST endpoint for this task.

Now we are going to model passengers ordering tickets for the flight. Create an Event-based subprocess by clicking on the Rectangle with an inner filled rectangle on the left toolbar, and drag the "Event" row above the start node and task.

If the Event-based subprocess is covering other nodes, you can move it by dragging the Event-based subprocess. Open the Event-based subprocess properties by clicking on it (opening the properties sidebar if necessary), and rename it to "Passenger Requests Ticket Subprocess". This subprocess can have its own variables, and also inherits the main process' variables. In this case, we need two additional variables:

Expand the "Process Data" tab and create two new variables in the same manner you created the "flightProcess" variable:

Now we need to model the event of a passenger requesting a ticket. This can be modelled by a "Start Signal" event. Click the green circle on the left toolbar and drag the "Start Signal" row into "Passenger Requests Ticket Subprocess".

Click on the "Start Signal" event you just created and open its properties. Rename the event to "Passenger Request Ticket". In the Implementation/Execution section, select "New…​" in the "Signal" field and enter "passengerRequestTicket". Finally, in the "Data Assignment" section, click on the Edit icon beneath "Assignments" to open a Task Data I/O modal. Click the "Add" button in the modal to add a new assignment. Put "passenger" for Name, select "Custom…​" and enter "com.company.Passenger" for Type, and select "passenger" for Target. Click save to add the assignment.

Now create a new User Task and drag it into the "Passenger Requests Ticket Subprocess". Rename it to "Approve Passenger for Flight". In its "Implementation/Execution" tab, change "Task Name" to "approvePassengerForFlight". Click on the edit icon beneath "Assignments" and add a row for both "Data Inputs and Assignments" and "Data Outputs and Assignments". For the "Data Inputs and Assignments" row, put "passenger" for Name, "com.company.Passenger" for Type and select "passenger" for source. For the "Data Outputs", put "isPassengerApprovedBySecurity" for Name, select "Boolean" for Type, and select "isPassengerApprovedBySecurity" for Target.

Now we need to model a decision being made in the process: should we add the passenger to the flight or not? We model decisions in the process with "Exclusive" Gateways. Click on the diamond in the left toolbar and drag the "Exclusive" row into "Passenger Requests Ticket Subprocess".

The "Passenger Requests Ticket Subprocess" might be running out of space now, so drag the subprocess to a place that has more room and increase it size by dragging the dot on the bottom-right corner of the subprocess.

Now we need to create the two potential outcomes of the decision: either we end the process immediately or we add the passenger to the flight. We are going to model adding a passenger to the flight first. Create a "Service Task" by clicking the rectangle icon in the left toolbar and dragging the "Service Task" row into "Passenger Requests Ticket Subprocess".

Rename the "Service Task" to "Add Passenger To Flight". In the "Implementation/Execution" section, put "com.company.FlightService" for "Interface", "addPassengerToFlight" for "Operation". And add the following two input assignments (in the same manner you did input assignments for "Approve Passenger for Flights"):

Now create two "End" nodes; one for the "Passenger is not approved" path and the other for the passenger is approved path. Click the red circle and drag the "End" row underneath the "Exclusive Gateway" and again under "Add Passenger To Flight".

Now create the following sequence flows (click on the "From" node, then click the arrow, then click the "To" node):

Click on the arrow from "Exclusive Gateway" to "Add Passenger To Flight". In its "Implementation/Execution" section, put in the following code in the "Expression" text box:

Now click on the arrow from "Exclusive Gateway" to "First End". In its "Implementation/Execution" section, put in the following code in the "Expression" text box:

We are now done with the "Passenger Requests Ticket Subprocess". Since we can add passengers to our flight, it is now time to integrate OptaPlanner into our BPMN. Create a new "Service Task" in the main process (not in "Passenger Requests Ticket Subprocess") and create a sequence flow from "Finalize Passenger List" to it. Rename it to "Create Seat Assignments", and in the "Implementation/Execution" section, put "com.company.FlightService" for "Interface", "createSeatAssignments" for "Operation". Add the following input and output assignments:

(Yes, both input and output have the same values for their respective columns; this is not an error)

We are almost finished with the BPMN. Create an "End" node in the main process and create a sequence flow from "Create Seat Assignments" to it. Here is the final BPMN diagram:

Click on the "Download" button at the top right of the page to download the BPMN diagram. Create the directories "src/main/resources/com/company" and move the downloaded file there.

In our BPMN, we referenced Java classes and services we still need to create. In particular:

We’ll be using the following domain model for our classes:

Now that we have our domain model, we can create our services. For the addPassengerToFlight service, we can simply add the passenger to the flight’s passenger list. For the createSeatAssignments service, we can use SolverManager to create a Solver for us and wait for the final best solution.

Finally, we need to modify application.properties so the Solver know when to terminate. Modify your application.properties to look like the following:

We can use the Constraint Stream API to create the constraints of our application in Java. We’ll have two constraints:

To do this, we create a ConstraintProvider that implements these constraints:

Now we are ready to test out the Flight Application we just created! Run the following command in the terminal to start the server:

You can see the generated API methods by copying http://localhost:8080/openapi to The Swagger Editor. Let’s try creating a flight. Run the following command :

You should get a response that looks like the following:

Let add a few passengers to our flight (replace ${id} with the id you got from the previous command).

Now let look at our tasks:

You should get a response that look like this:

Let looks at one of our passengers (replace ${taskId} with the id of the "approvePassengerForFlight" you want to inspect):

Let approve "Amy Cole" and "John Smith":

(run the command twice; one for the "approvePassengerForFlight" task for Amy Cole, and one for the "approvePassengerForFlight" task for John Smith).

And let deny "Bad Guy":

(replace ${taskId} with Bad Guy’s "approvePassengerForFlight" task id)

Finally, let create the seat assignments:

(Use "finalizePassengerList" task’s id here)

This request will take several seconds to return as it waits for OptaPlanner to optimize the flight seating. It will return a JSON containing the process variables, including the optimized seat assignments in the "flight" field:

In the above example, "Amy Cole" is assigned to seat "1A" and "John Smith" is assigned to seat "1B".

Now we have a fully functional REST service, we can easily extend it by:

You can find an extended version of the flight example created in this blog at the Kogito Examples repository, which has a full UI and poll for the latest solution from the solver instead of waiting for solving to finish.