Question

I have multiple services processing some files. Each service must have exclusive access to the file while processing. I solved this problem a while ago by creating a global mutex that uses some temp files, something like this:

function AppLocked: boolean;
begin
  result := FileExists(GetTempDir + '__MUTEX__' + LockExt);
end;

procedure AppLock;
var
  F: TextFile;
begin
  if FileExists(GetTempDir + '__MUTEX__' + LockExt) then
    exit
  else
  try
    AssignFile(F, GetTempDir + '__MUTEX__' + LockExt);
    Rewrite(F);
    Writeln(F, DateTimeToStr(Now));
    CloseFile(F);
  except
  end;
end;

procedure AppUnLock;
begin
  if FileExists(GetTempDir + '__MUTEX__' + LockExt) then
    SysUtils.DeleteFile(GetTempDir + '__MUTEX__' + LockExt);
end;

This works pretty good, and I don’t want to fix something that works, but I just wonder, is there a better solution?

Answer 1

An actual Mutex (as in win32 Mutex) is the preferred method.