RO DataSnap: Client doesn't close all threads on excpetion at server

Remoting SDK
1

Hello,

when the TRODataSnapModule raises an exception on the server, the client catches that exception, but keeps an thread running. So when I close the client, it doesn’t close at all. It’s still running in the background.

See attached sample:
RO DataSnap DllChannel.zip (2.2 MB)

When you run the sample the Delphi IDE you will get a “database not connected” error, and the debugger doesn’t close when you close the client. You will also notice that there an additional thread running.

2

I can’t reproduce this issue.

my steps:

  • project in debug mode was launched
  • Open button was pressed
  • I received exceptions in debugger and
---------------------------
Dllchannelserverclient
---------------------------
Cannot locate C:\Dokumente und Einstellungen\Administrator\Eigene Dateien\RAD Studio\Projekte\RO DataSnap DllChannel\DLLChannelServer.dll.
---------------------------
OK   
---------------------------
  • application was closed
3

Please change the dll path in the TRODLLChannel compoenent in the client project, regarding your directory. I had to hardcode that path in order the IDE could find the dll server.

4

In this case I’ve

---------------------------
Debugger Exception Notification
---------------------------
Project DLLChannelServerClient.exe raised exception class EIBInterBaseError with message 'unavailable database'.
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Break   Continue   Help   
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and later this exception in loop:

---------------------------
Debugger Exception Notification
---------------------------
Project DLLChannelServerClient.exe raised exception class $C0000025 with message 'non-continuable exception at 0x7739017c'.
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Break   Continue   Help   
---------------------------

later

---------------------------
Debugger Exception Notification
---------------------------
Project DLLChannelServerClient.exe raised exception class $C00000FD with message 'stack overflow at 0x77363792'.
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Break   Continue   Help   
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all these exceptions were raised in IBX.IB.pas at

procedure IBDataBaseError(FGDSLibrary : IGDSLibrary);
..
    raise EIBInterBaseError.Create(sqlcode, IBErrorCode, usr_msg)  //<<<<<<<<<<< here
  else
    raise EIBInterBaseRoleError.Create(sqlcode, IBErrorCode, usr_msg)
end;
5

When you close the appliction, is there also an invisible process running in the background or in debug mode, the debugger doesn’t close, since there is a hidden thread running?

The point is, when I use the IBX component in a single exe application, I don’t have that “hanging” thread and program closes. It seems it is related to the DLL and threading.

Do you have any hints, how I can get rid of that “hanging” thread?

6

I can’t close/contitue application because when I ignore those errors in debugger, I have this exception in loop :

---------------------------
Debugger Exception Notification
---------------------------
Project DLLChannelServerClient.exe raised exception class $C0000005 with message 'access violation at 0x77310125: read of address 0x00090e84'.
---------------------------
Break   Continue   Help   
---------------------------

I can recommend to recompile your project and .dll with “use debug .dcus” option.
this allow to see problems inside native delphi code.

Re this issue, I can recommend to change IBX to something else, like DBX/FireDAC or other DB library.

7

Found the issue.
The IBX components are using internally a IBSQLMonitorHook which creates a seperate thread, but doesn’t close it when used in DLLs.

Workaround: I disabled the IBSQLMonitorHook globally.

uses IBSQLMonitor

MonitorHook.Enabled := false;