Stopping a TimedTask

[dexter 0]

Hi,

 

In a console application I have defined a timed task, which sends an empty string once per minute to keep alive a connection:

 

  FKeepAlive := Parallel.TimedTask.Every(60 * 1000).Execute(
    procedure()
    begin
      FConn.SendStr(''); // will send just ENTER each minute
    end
    );

When the application is closing - I'm trying to stop the task with following code:

 

      FKeepAlive.Stop;
      FKeepAlive.Terminate(5000); // <-- here error is raised

And I'm getting System Error: Invalid window handle

 

How is the proper way to stop a timed task?

 

Edited June 30, 2020 by dexter

[Sonjli 6]

Hi,

I think your problem is FConn. It seems a class field, and maybe it is destroyed before the timer ends?

 

Regards,

Eddy

[dexter 0]

Hi,

 

The full destructor code is:

destructor TjBASEComm.Destroy;
begin
  if Assigned(FKeepAlive) then
    try
      FKeepAlive.Stop;
      FKeepAlive.Terminate(5000); // <-- here error is raised
    except
    end;

  try
    FConn.Free;
  except
  end;

  inherited;
end;

As you can see - connection is freed after.

Can it be because application is a console app?

 

[Sonjli 6]

The only problem I know about console apps is about "omni messaging system". Look at documentation http://www.omnithreadlibrary.com/book/chap05.html#introotl-messagelooprequired-console

 

Maybe after 5 seconds the parallel timer is not terminated.

Try this:

destructor TjBASEComm.Destroy;
begin
  if Assigned(FKeepAlive) then
    try
      FKeepAlive.Stop;
      FKeepAlive.Terminate;
      FKeepAlive.WaitFor; // This wait until the task is REALLY terminated. If it is stuck then the problem is elsewhere
    except
    end;

  try
    FConn.Free;
  except
  end;

  inherited;
end;

There is also a doubt about "FConn.SendStr('')": what does it do?

 

Regards,

Eddy

[dexter 0]

Hi Eddy,

 

the problem is not in FConn. I have removed the call to FConn.SendStr('') from TimedTask execution, and the problem persists.

And exception is raised during FKeepAlive.Terminate, FKeepAlive.WaitFor does not help.

See attached the call stack to exception.

[Sonjli 6]

Hi,

I am pretty sure the problem is related to this: http://www.omnithreadlibrary.com/book/chap05.html#introotl-messagelooprequired-console

 

Regards,

Eddy

[dexter 0]

Hi,

 

I have updated the destructor but it did not help:

 

      FKeepAlive.Stop;
      while integer(PeekMessage(Msg, 0, 0, 0, PM_REMOVE)) <> 0 do
      begin
        TranslateMessage(Msg);
        DispatchMessage(Msg);
      end;
      FKeepAlive.Terminate(5000);

 

And it fails during call to Terminate(5000) after about 1 second.

 

[Sonjli 6]

Ok, this is my last chance... after this you must wait for @Primož Gabrijelčič

 

Try something like this:

procedure ProcessMessages;
   var
     Msg: TMsg;
   begin
     while integer(PeekMessage(Msg, 0, 0, 0, PM_REMOVE)) <> 0 do begin
       TranslateMessage(Msg);
       DispatchMessage(Msg);
     end;
   end;

...
	FKeepAlive.Stop;
    repeat
    	ProcessMessages;
    until FKeepAlive.Terminate(1000);
...

 

[dexter 0]

Same problem, fails with Invalid Window Handle during first .Terminate(1000) call.

[Primož Gabrijelčič 223]

Can I get a minimal reproducible example project, please?