Cancelling remote function calls when TRtcResult possible freed.

[johannc]

What is the best way cancel all requests for a remote function when the TRtcResult is possibly freed before the call returns? I have tried CancelRequests and that does not seem to solve the issue.

[D.Tkalcec (RTC)]

Before destroying a TRtcResult component, close the connection used to send the remote function calls by setting AutoConnect to FALSE, calling Disconnect and looping until "isConnecting=FALSE" for the connection component in question. After that use SkipRequests, because CancelRequests will be calling "ResultAborted" events.

Best Regards,
Danijel Tkalcec

[johannc]

Ok thanks a lot for the solution.

[kavetu]

Danijel,

>Before destroying a TRtcResult component, close the connection used to send the remote function calls by >setting AutoConnect to FALSE, calling Disconnect and looping until "isConnecting=FALSE" for the >connection component in question. After that use SkipRequests, because CancelRequests will be calling >"ResultAborted" events.

>Best Regards,
>Danijel Tkalcec

Could this perhaps be packaged into a single property or procedure in the next release of RTC SDK?

Manfredt Kavetu

[D.Tkalcec (RTC)]

If you want this in a procedure, here is one way of writing it:

procedure DisconnectClient(Sender:TRtcHttpClient);
  var
    oldAutoConnect:boolean;
  begin
  if Sender.isConnecting then
    begin
    oldAutoConnect:=Sender.AutoConnect;
    Sender.AutoConnect:=False;
    Sender.Disconnect;
    if Sender.MultiThreaded then
      beigin
      while Sender.isConnecting do Sleep(10);
      end
    else if not Sender.Blocking then
      begin
      while Sender.isConnecting do
        begin
        Application.ProcessMessages;
        Sleep(10);
        end;
      end;
    Sender.SkipRequests;
    Sender.AutoConnect:=oldAutoConnect;
    end;
  end;

But ... I don't like extending the RTC SDK with procedures for doing things which can already be done with a few lines of code, so I'm not really eager to adding this as a new property or a procedure to the RTC SDK. If I start doing that, I would probably end up with hundreds of small procedures for small specific tasks, most of which used only by one or two developers and a very steep learning curve for anyone who would like to start using the RTC SDK.

Best Regards,
Danijel Tkalcec

[johannc]

Ok, this implementation works in Windows 7 Professional (64-bit) with no issues but it still continues to plague Windows XP with a call to the freed TRtcResult. So what I have done is to implement a timer that is enabled when the CloseQuery event is fired. If there are outstanding calls, we don't close the dialog, and have the timer check this Requests until all are completed.

[D.Tkalcec (RTC)]

Hi Johann,

I have to admit that I'm not a fan of forced disconnects. Even if the code I've posted above does work on newer Windows versions, I think your implementation (waiting for the response on all active requests before Quit) is a much better general solution.

Best Regards,
Danijel Tkalcec

[johannc]

Yes, I am more comfortable with that method. Allow all calls to complete based on condition and close when ready.

Thanks

[D.Tkalcec (RTC)]

Just for the record ... "DisconnectNow" method was added to the TRtcHttpClient component in one of the later RTC SDK updates (don't remember the exact version), which can be used to close a connection and wait for all events to finish execution. After calling DisconnectNow, it is safe to destroy the connection component as well as any other components used by the connection component.

Best Regards,
Danijel Tkalcec