Delphi WebBroker / ISAPI versus Threading

Question

I'm trying to make some work after a response producer.

In order to not hold time responses, I trying do this work in a Thread.

This thread create a DataModule, and do certain stuff (send emails, process file operations, etc) but the execution is blocking the main thread.

I don't use variables or any other interactions with the main thread. I don't see anything that can issuing blocks.

Can anyone help?

Thread code:

---

unit wdm_Thread;  

interface

uses
    System.SysUtils, System.Classes, Web.HTTPApp, Web.HTTPProd, Web.DSProd,Data.DB, Data.Win.ADODB;

type
    TwdmThread = class(TDataModule)  
        dbConnection: TADOConnection;  
        spVisualizador: TADOStoredProc;  
        spVisualizadorProc: TADOStoredProc;  
        spVisualizadorProcFim: TADOStoredProc;  
        spVisualizadorProcInicio: TADOStoredProc;  
        ppVisualizadorOn: TDataSetPageProducer;  
        spVisualizadorMiniProc: TADOStoredProc;  
    end;  

    colaboreThread = class(TThread)  
    private  
        FDataModule: TwdmThread;  
        FPreviewPath: String;  
        FSessionID: String;  
        FUniqueID: String;  
        FUniqueIDVersao: String;  
    public  
        procedure Execute(); override;  
        class procedure Thumbnail(APreviewPath, ASessionID, AUniqueID, AUniqueIDVersao: String);  
    end;   

implementation  

uses  
    WinAPI.Windows, WinAPI.ActiveX;  

{%CLASSGROUP 'System.Classes.TPersistent'}  

{$R *.dfm}  

{ threadThumbnail }  

procedure colaboreThread.Execute;  
begin  
    try  
        FDataModule := TwdmThread.Create(nil);  
        with FDataModule do  
        begin  
            spVisualizador.Parameters[1].Value := FSessionID;  
            spVisualizador.Parameters[2].Value := FUniqueID;  
            spVisualizador.Parameters[3].Value := FUniqueIDVersao;  
            spVisualizador.Parameters[4].Value := False;  
            spVisualizador.Open();  

            if spVisualizador.RecordCount > 0 then  
            try  
                DeleteFile(PWideChar(FPreviewPath + FUniqueIDVersao + spVisualizador.FieldByName('Extensao').AsString));  

                CopyFile(PWideChar(spVisualizador.FieldByName('ArmazenamentoCaminho').AsString + FUniqueIDVersao), PWideChar(FPreviewPath + FUniqueIDVersao + spVisualizador.FieldByName('Extensao').AsString), true);  

                spVisualizadorMiniProc.Parameters[1].Value := FSessionID;  
                spVisualizadorMiniProc.Parameters[2].Value := FUniqueID;  
                spVisualizadorMiniProc.Parameters[3].Value := FUniqueIDVersao;  
                spVisualizadorMiniProc.Parameters[4].Value := FPreviewPath;  
                spVisualizadorMiniProc.ExecProc();  
            finally  
                DeleteFile(PWideChar(FPreviewPath + FUniqueIDVersao + spVisualizador.FieldByName('Extensao').AsString));  
        end  
    end;  
  finally  
    FreeAndNil(FDataModule);  
  end;  

end;  

class procedure colaboreThread.Thumbnail(APreviewPath, ASessionID, AUniqueID, AUniqueIDVersao: String);  
begin  
  with colaboreThread.Create(True) do  
  begin  
    FreeOnTerminate := True;  
    FPreviewPath := APreviewPath;  
    FSessionID := ASessionID;  
    FUniqueID := AUniqueID;  
    FUniqueIDVersao := FUniqueIDVersao;  
    if FUniqueIDVersao = '' then FUniqueIDVersao := FUniqueID;  

    Execute();  
  end;  
end;  

initialization  
  CoInitializeEx(NIL, COINIT_MULTITHREADED or COINIT_SPEED_OVER_MEMORY);  

end.  

WebModule implementation:

---

...

procedure TwdmColaboreUP.wdmTopWebUploadwaiUploadAction(Sender: TObject;
  Request: TWebRequest; Response: TWebResponse; var Handled: Boolean);  
begin  
  colaboreThread.Thumbnail(FPreviewPath, FSessionID, FArquivoUniqueID, FArquivoUniqueIDVersao);  
end;  

...

Answer 1

You are calling Execute on the thread, but you should not call it directly. You start the thread using Resume (or by omitting the Suspended parameter in its constructor). Then, the Execute method will be started in the background.

If you start Execute yourself, like you do now, it is run in the main thread as any other method.

  with colaboreThread.Create(True) do  
  begin  
    FreeOnTerminate := True;  
    FPreviewPath := APreviewPath;  
    FSessionID := ASessionID;  
    FUniqueID := AUniqueID;  
    FUniqueIDVersao := FUniqueIDVersao;  
    if FUniqueIDVersao = '' then FUniqueIDVersao := FUniqueID;  

    // Execute();  <--- Not this

    Resume; // <--- but this
  end;