State machine with different state and cancel option

Question

State machine with different state and cancel option

Markus Freitag 3,791

Hello,

enter image description here Optimization statemachine. I am looking for a sample solution.

If I enable Cancel, how can I run it again? With new var source = new CancellationTokenSource();

Does anyone have any good approaches? Thank you.

source.Cancel();

See my code in the attachment.

ProtoType_WinForms_cs.TXT

Hui Liu-MSFT 48,681 Microsoft External Staff

Hi,@Markus Freitag.

You could try to use the following code test to see if it meets your needs.

In this updated code, the cancellation is handled by throwing an OperationCanceledException when a cancellation is requested. The CancelProcess() method cancels the process by calling MyCancellationTokenSource.Cancel() and sets the CurrentState to NotDefine. This allows you to restart the process by creating a new instance of PrinterProcess when needed.

public partial class Form1 : Form
{
    ...
    private void btnCancel_Click(object sender, EventArgs e)
    {
        CurrentPrinter.CancelProcess();
    }
}




public class PrinterProcess
{
    public STATE CurrentState;
    public ServerDataList ServerData;
    public List<bool> ListPossibleToMark;
    public CancellationTokenSource MyCancellationTokenSource;

    public PrinterProcess()
    {
        CurrentState = STATE.NotDefine;
        MyCancellationTokenSource = new CancellationTokenSource();
    }

    public void CancelProcess()
    {
        MyCancellationTokenSource.Cancel();
        CurrentState = STATE.NotDefine;
    }

    public async Task<string> DoProcess()
    {
        ServerData = new ServerDataList();
        ListPossibleToMark = new List<bool>();
        MyCancellationTokenSource = new CancellationTokenSource();

        var token = MyCancellationTokenSource.Token;

        try
        {
            while (true)
            {
                // Check if cancellation was requested
                if (token.IsCancellationRequested)
                {
                    token.ThrowIfCancellationRequested();
                }

                switch (CurrentState)
                {
                    case STATE.In:
                        await DoIn(token, "DoIn taskIn");
                        await DoInCamera(token, "DoIn taskInCamera");
                        CurrentState = STATE.NotDefine;
                        break;

                    case STATE.START:
                        await DoStart(token, "DoStart taskStart");
                        CurrentState = STATE.NotDefine;
                        break;

                    case STATE.OUT:
                        await DoOut(token, "DoOut taskOut");
                        CurrentState = STATE.NotDefine;
                        break;

                    case STATE.CANCEL:
                        // The cancellation request will be handled at the beginning of the loop
                        CurrentState = STATE.NotDefine;
                        break;

                    default:
                        // Handle other states or raise an exception
                        break;
                }

                // Add a small delay between iterations to prevent CPU usage
                await Task.Delay(10);
            }
        }
        catch (OperationCanceledException)
        {
            Trace.WriteLine("The wait operation was canceled.");
            throw;
        }

        return "Ready Order";
    }

    private async Task DoIn(CancellationToken token, string text)
    {
        for (var i = 0; i < 10; i++)
        {
            Trace.WriteLine($"{text} loop DataFromServer Code= '{i,22:D22}'");

            ServerData.Add(new ServerData()
            {
                BestBefore = "12/2023",
                Code = $"{i,22:D22}",
                Index = i
            });

            // Check if cancellation was requested
            if (token.IsCancellationRequested)
            {
                token.ThrowIfCancellationRequested();
            }

            // Simulate work
            await Task.Delay(600);
        }
    }

    private async Task DoInCamera(CancellationToken token, string text)
    {
        for (var i = 0; i < 10; i++)
        {
            Trace.WriteLine($"{text} loop check with camera, free for marking pos= '{i,4:D4}'");

            ListPossibleToMark.Add(i % 2 == 0);

            // Check if cancellation was requested
            if (token.IsCancellationRequested)
            {
                token.ThrowIfCancellationRequested();
            }

            // Simulate work
            await Task.Delay(1600);
        }
    }

    private async Task DoStart(CancellationToken token, string text)
    {
        foreach (var item in ServerData)
        {
            if (ListPossibleToMark[item.Index])
                Trace.WriteLine($"{text} loop PrintTheData {item.ToString()} mark possible");
            else
                Trace.WriteLine($"{text} loop PrintTheData {item.ToString()} not possible");

            // Check if cancellation was requested
            if (token.IsCancellationRequested)
            {
                token.ThrowIfCancellationRequested();
            }

            // Simulate work
            await Task.Delay(500);
        }
    }

    private async Task DoOut(CancellationToken token, string text)
    {
        // Perform the desired actions for the OUT state
        // ...
        // Check if cancellation was requested
        if (token.IsCancellationRequested)
        {
            token.ThrowIfCancellationRequested();
        }

        // Simulate work
        await Task.Delay(500);
    }
}

Markus Freitag 3,791

Hello,

//########################################## is not calling after I press Cancel. Please look here (the items /markings with the ## character). Is not working.

It is not called after I press Cancel. I have changed the code.

Do you know why and do you have a solution? Thanks in advance! I think I need two states. One sensor that can always signal and one logical state.

// *** Summary
// *** State for sensor
// *** State logical

//The sensor can see something every now and then.
//Therefore, I probably need a logical state.
//What could the pattern look like?

//Can you check the code.


public class PrinterProcess
{
	public STATE CurrentState;
	public ServerDataList ServerData;
	public List<bool> ListPossibleToMark;
	public CancellationTokenSource MyCancellationTokenSource;


	public void CancelProcess()
	{
		MyCancellationTokenSource.Cancel();
		CurrentState = STATE.NotDefine;
	}


public async Task<string> DoProcess()
{
	var token = MyCancellationTokenSource.Token;

..
...
          case STATE.CANCEL:   // not working!!! Because I'm waitung in the START state, when not possible!
					//MyCancellationTokenSource.Cancel();
					//Trace.WriteLine($"Cancel State machine");
					//########################################## is not calling after I press Cancel.
					CurrentState = STATE.NotDefine;
					break;
    
Thread.Sleep(10);
					

Task DoInCamera(CancellationToken token, string text)
{

	return Task.Run(() =>
	{
		for (var i = 0; i < 10; ++i)
		{
			Trace.WriteLine($"{text} loop check with camera, free for marking pos= '{i,4:D4}'");
			//var qry = ServerData.Where(y => y.Index == i).FirstOrDefault();

			ListPossibleToMark.Add(i % 2 == 0);

			//qry.IsFreeForMarking = true;

			if (token.IsCancellationRequested)
			{
				token.ThrowIfCancellationRequested();
				//return $"{text} cancelled";
			}
			try
			{
				// Make work
				Thread.Sleep(1600);
			}
			catch (OperationCanceledException)
			{
			//########################################## is not calling after I press Cancel.
				Trace.WriteLine("DoInCamera      The wait operation was canceled.");
				throw;
			}
		}
		//    return $"{text} Done";
	});
}

State_WinForms_CS_With_Logical_States.TXT

2 answers

Your answer

Answer 1

Bruce (SqlWork.com) 78,086 Volunteer Moderator

your code is not clear. what triggers a cancel? also a state is usually:

current state -> process input -> new state

you are combining a state machine with background threads. what is the interaction? is the input process async? is the state machine a separate thread?

you keep showing a transport belt with sensors. what do the sensor report? what is the actual use of each sensor. you show a product passing sensors, can a product be a sensor start and another at sensor end at the same time?

Markus Freitag 3,791 Reputation points

2023-06-22T16:40:49.2466667+00:00
Hello,

I have a conveyor belt. The belt transports a product from the IN sensor to the OUT sensor. The sensors only say product present, yes or no. (digital)

your code is not clear. what triggers a cancel? also a state is usually:

Cancel can be. Product blocking Printer error Camera error Stop /Cancel / Emergency button of the production process. The process runs in a separate TASK.

private void btnIN_Click(object sender, EventArgs e) { CurrentPrinter.CurrentState = Core.STATE.In; } private void btnCancel_Click(object sender, EventArgs e) { CurrentPrinter.CurrentState = Core.STATE.CANCEL; }

I have simulated this with WinForms buttons.

In the IN state, I can immediately query the data while the product is still being transported. In the START state, I can mark when all data are available. Between IN and START I may need to check something else, so I use a task at IN. Sample:
A camera checks the product is inserted correctly. Starts another request (TASK) in the IN state. In the START state both TASK must give a GOOD signal, a release.

I am looking for a sample solution for this process. I get the details solved independently. Error handling and so on. The basic framework must be right, which is the reason for my requests.

It is a loop, I can produce up to 1000 products per order

Hope now clear for you and you can help me.

Task for process

Task for data from server

Task for product valid, checking some items

Task for marking

See my code. For a correction, help I would be very grateful.

Picture: --> I press Task printer (1) --> (2) (3) nearly the same time --> Then (4) Cancel

State_WinForms_CS.TXT
Markus Freitag 3,791 Reputation points

2023-06-26T17:29:19.2266667+00:00

Hello @Bruce (SqlWork.com) ,

Do you have a good tip, a good example.

Thank you for a quick answer in advance. Got it.

Do you have any questions, is the process not clear? Let me know.
Bruce (SqlWork.com) 78,086 Reputation points Volunteer Moderator

2023-06-26T18:45:24.3033333+00:00

still not clear. can sensor in/start/out be on at the same time? how is your code delivering the status? is it polling? how often? what sensors fire during the product loop? is it all three during the process of a single product? if do a 100 products, when is the server data fetch done? is it a fetch per product? what if the fetch takes too long? what about the send to the printer? can it be late?

what are the errors?

what if you see in then out, but no start? what if start fires before in?

if cancel is received, do you ignore sensor data? what is the sensor data on restart? do you receive a restart event?

what is the point of the printer task button?
Markus Freitag 3,791 Reputation points

2023-06-27T18:09:51.6133333+00:00

still not clear. can sensor in/start/out be on at the same time?

No, the product ist moving from IN to OUT.

how is your code delivering the status? is it polling? how often?

Yes all 10 ms. See State_WinForms_CS.TXT

what sensors fire during the product loop?

Then the condition should be ignored. State machine.

is it all three during the process of a single product? if do a 100 products, when is the server data fetch done?

is it a fetch per product?

Only one product with up to 50 entries is queried at a time. Mostly there are between 2 and 5.

what if the fetch takes too long? what about the send to the printer? can it be late?

Then a timeout message must be sent to the user

what are the errors?

Transport error, marking error, clamp, no more timte, empty ink cartridge.

what if you see in then out, but no start? what if start fires before in?

Well, this must be solved by the Statemachine.

START may only be executed if I am currently in the IN state.

if cancel is received, do you ignore sensor data?

Yes.

what is the sensor data on restart? do you receive a restart event?

Yes, After Cancel I press the Printer task button and start with the process task again.

what is the point of the printer task button?

Have you seen the file? It starts the Task process.

State_WinForms_CS.TXT

Hope the info are sufficient for a model, for a small software architecture.

To see how I could fix it.

Thanks in advance.

State_WinForms_CS.TXT

I try it with logical state. Can you check it? Is it good or bad?

State_WinForms_CS_With_Logical_States.TXT

Answer 2

Bruce (SqlWork.com) 78,086 Volunteer Moderator

you state machine makes no sense.

you have 4 inputs per state:

public class StateInputValues
{
   int _InSensorOn;  
   int _StartSensorOn;
   int _OutSensorOn;
   int _CancelOn;

   public bool InSensorOn 
   {
      get {return _InSensorOn == 1;}
      set 
      { 
         if (value) Interlocked.Or(ref _InSensorOn,1);  
         else Interlocked.And(ref _InSensorOn,0);
      }
   }
   ....

}

each state should map the 4 inputs to the next state. each state can have optional processing.

other than a background process thread to free the ui you haven't explained the need for threads.

I would assume threads are used to get the status of the sensors, but this is outside the state loop. you just need to use locks or the InterLock class to update the sensor values. but your ui is performing this in you prototype.

the actual send data to printer is async with a timeout, but this could be exposed as sync. it probably add a new state input variable for communication error (maybe for all sensors).

Markus Freitag 3,791 Reputation points

2023-06-29T18:35:09.1566667+00:00

each state should map the 4 inputs to the next state. each state can have optional processing.

Good, can you show this in detail? That would be very good.

I would assume threads are used to get the status of the sensors, but this is outside the state loop.

Yes right, I want to be able to confirm the button while the process is running. Without task, thread this is not possible. You mean with interlock. I don't know that well. Can you still explain in detail?

Can you show me the state change from IN to START or preferably all three states? Four with cancel.

Maybe it's not so hard. I need to have done it and know what is possible. That is why the request here
Bruce (SqlWork.com) 78,086 Reputation points Volunteer Moderator

2023-06-29T21:42:14.4766667+00:00

as I don't know the required state transitions. you would need to supply a state transition diagram/chart or a lot better explanation of the behavior and interaction of the sensors, printer and cancel. also how is recovery done? also is it continue with mutilple jobs, or one run a job? I assume you will need know the travel time between sensors, but the speed will vary. how do you handle startup and shutdown of the transport?

normally you would reduce the states based on their actions/next state, but you have not defined any.

the Interlock library works with the machine hardware to perform thread safe updates to integer values.

I suggest you produce a physical model (say with pieces of paper). model a couple print jobs. keep a timing log of all the possible steps, and what must be done. try actual real events, like the boxes are different distances apart. the printer is out of ink. the sensors do not respond. the transport belt starts.
Markus Freitag 3,791 Reputation points

2023-07-02T18:28:03.0533333+00:00

A siemens PLC is responsible for the transport, not my job . The PLC reports the state change via socket(TCP/IP) C# DesktopApp is server ------- PLC is Client I simulate this with a button first, as it is easier. In the next test phase, this interface to PLC must be done. Do you know a good TCP/IP library, full duplex operation?

IN: When the PLC signals the IN state, I need to query the labeling data for a product at the Manufacturing execution systems (MES). Always for a product. Data sets can be between 1 and 10. While the product moves to the marking position, the camera must perform a position detection of the product, correctly inserted and is free space for the marking. The camera sends an event via TCP/Socket if there was a view error, detection error. This must trigger a stop, cancel for me.

Picture 1 and 2

START: (WorkingPosition) Conveyor belt is stopped, printhead is moving. Not my job. After marking, OCR recognition is performed. If ACTUAL = TARGET, the part is good, otherwise it is bad.

Picture 3

OUT: Product ready - server

The data can be sent immediately after printing, until the product reaches the OUT sensor, I know release or stop. The server (MES) decides further transport or stop. Picture 4

The project is in development. Not everything has to be perfect. I would like to know the possibilities, approaches and I am very grateful for help.

Picture 5
Bruce (SqlWork.com) 78,086 Reputation points Volunteer Moderator

2023-07-02T20:56:31.4433333+00:00

If there are 20 packages on the line, can one be at in, one at start and one at out at the same time, or is the distance between in and out less than the size of a package?

you say you get data at in, what do you mean by data sets between 1 and 10? If you get 10, is this the data for the next 9 in states?

at start you say the print and compare happen. Is there a success/fail event or only fail?

what do you mean by data can be sent until out?

what does release or stop mean?
Markus Freitag 3,791 Reputation points

2023-07-03T08:30:30.45+00:00

If there are 20 packages on the line, can one be at in, one at start and one at out at the same time, or is the distance between in and out less than the size of a package?

There is always only one package on the conveyor belt

you say you get data at in, what do you mean by data sets between 1 and 10? If you get 10, is this the data for the next 9 in states?

There is a product, there come only once data on it. There are products that still have children. Then I get more data.

at start you say the print and compare happen. Is there a success/fail event or only fail?

I get data, these are to be marked. Then an actual-target comparison takes place.

what do you mean by data can be sent until out? what does release or stop mean?

--> If equal, release given otherwise rejection.

Three good, on bad. The server can decide to continue transport or stop and manual removal. If the parts are cheap all must be good. If the parts are expensive, one or two parts may be bad.

In the sample three good on bad. Server can say, all ok, continue or stop. Hope now all is clear for a basic model. Thanks for your help.
Markus Freitag 3,791 Reputation points

2023-07-22T18:58:43.3366667+00:00

Do you have another tip for me?

Would be nice, otherwise I close the thread.

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State machine with different state and cancel option

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