Changed behaviour for filestream with Windows 7 ?

Question

I have written a utility that search logfiles for exceptions and it have worked fine with Vista 64 bits. Now I have upgraded to Windows 7 64 bits and it could sometimes hang forever when reading a filestream. I think it hangs only if the log file is active and the user write to it. But this works fine before as I use fmShareDenyNone flag. I use Delphi 2007. Any idea what I could change to make this work ?

Here is the whole method that search directories for logfiles:

procedure TfrmMain.Refresh;
var
  FileData : TSearchRec;  // Used for the file searching. Contains data of the file
  vPos, i, PathIndex : Integer;
  vCurrentFile: TStringList;
  vDate: TDateTime;
  vFileStream: TFileStream;
begin
  tvMain.DataController.RecordCount := 0;
  vCurrentFile := TStringList.Create;
  memCallStack.Clear;

  try
    for PathIndex := 0 to fPathList.Count - 1 do                      // Loop 0. This loops until all directories are searched through
    begin
      if (FindFirst (fPathList[PathIndex] + '\*.log', faAnyFile, FileData) = 0) then
      repeat                                                      // Loop 1. This loops while there are .log files in Folder (CurrentPath)
        vDate := FileDateToDateTime(FileData.Time);

        if chkLogNames.Items[PathIndex].Checked and FileDateInInterval(vDate) then
        begin
          tvMain.BeginUpdate;       // To speed up the grid - delays the guichange until EndUpdate

          fPathPlusFile := fPathList[PathIndex] + '\' + FileData.Name;
          vFileStream := TFileStream.Create(fPathPlusFile, fmShareDenyNone);
          vCurrentFile.LoadFromStream(vFileStream);

          fUser := FindDataInRow(vCurrentFile[0], 'User');          // FindData Returns the string after 'User' until ' '
          fComputer := FindDataInRow(vCurrentFile[0], 'Computer');  // FindData Returns the string after 'Computer' until ' '

          Application.ProcessMessages;                  // Give some priority to the User Interface

          if not CancelForm.IsCanceled then
          begin
            CancelForm.lblLogFile.Caption := fPathPlusFile;
            if rdException.Checked then
              for i := 0 to vCurrentFile.Count - 1 do
              begin
                vPos := AnsiPos(MainExceptionToFind, vCurrentFile[i]);
                if vPos > 0 then
                  UpdateView(vCurrentFile[i], i, MainException);

                vPos := AnsiPos(ExceptionHintToFind, vCurrentFile[i]);
                if vPos > 0 then
                  UpdateView(vCurrentFile[i], i, HintException);
              end
            else if rdOtherText.Checked then
              for i := 0 to vCurrentFile.Count - 1 do
              begin
                vPos := AnsiPos(txtTextToSearch.Text, vCurrentFile[i]);
                if vPos > 0 then
                  UpdateView(vCurrentFile[i], i, TextSearch)
              end
          end;

          vFileStream.Destroy;
          tvMain.EndUpdate;     // Now the Gui can be updated
        end;
      until(FindNext(FileData) <> 0) or (CancelForm.IsCanceled);     // End Loop 1
    end;                                                          // End Loop 0
  finally
    FreeAndNil(vCurrentFile);
  end;
end;

Answer 1

Quick shot: When you have a file that is written quite often like a log file, you should disable the indexing of the contents for that file. Otherwise the Windows indexer service will constantly reindex that file and meanwhile blocking any other request.

You can find the context indexing attribute under "file properties" - "extended attributes".

IMHO it was not the best decision from Microsoft to enable the content indexing in Windows 7 by default.