delphi XE6 TIdHTTP.Get (Indy 10) memory consuption

Question

I have this function

function doHTTPRequest(const AUrl: String): String;
// ------------------------------------------------------------------------
// return the response for a http request
var
   aIdHTTP : TIdHTTP;
begin
   Result  := '';

   aIdHTTP := TIdHTTP.Create(nil);
   try
     aIdHTTP.HandleRedirects := true;
     aIdHTTP.RedirectMaximum := 5;
     aIdHTTP.ConnectTimeout  := 5000;
     aIdHTTP.ReadTimeout     := 10000;

     Result := aIdHTTP.Get(aUrl);

     aIdHTTP.Disconnect(false); 

     if Assigned(aIdHTTP.IOHandler) then
        aIdHTTP.IOHandler.InputBuffer.Clear;

   finally
      if Assigned(aIdHTTP) then FreeAndNil(aIdHTTP);
   end;
end;

Every time I call this function, the process in "task manager" increase private working set memory of 200 Byte (more or less).

where am I wrong?

I already use FastMM and AQTime but no memory leak have been found

this is an example of what i can see in task manager, from the begin to end the memory is increased by 200 Byte and it is never released...

doHTTPRequest 
    begin = 3.480 KB
    end   = 3.652 KB
    ----------------
    diff.     184 Byte

doHTTPRequest return value is html string (about 20 KB)

doHTTPRequest is called by TIdHttpServer like this:

procedure TServer.CommandGet(AContext: TIdContext; ARequestInfo: TIdHTTPRequestInfo; AResponseInfo: TIdHTTPResponseInfo);
begin
   AResponseInfo.ContentText := doHTTPRequest('http://example.com/foo.html');
end

Answer 1

First, there is no need to call Disconnect() or InputBuffer.Clear() if you are just going to free the TIdHTTP object immediately afterwards. The destructor will close and free the socket for you if it is still connected.

Second, TIdHTTP.Get() does allocate memory internally when downloading content, but it also frees any memory it allocates. In your example, Get() is returning a final String representation of whatever content was downloaded. You have to keep in mind that Delphi's memory manager ( FastMM by default) DOES NOT return freed memory back to the OS, the memory is cached for later re-use. That is what Task Manager is showing you. Task Manager only knows about the memory that your process has allocated from the OS, but it does not know how your process is actually using that memory. You cannot use Task Manager to diagnose memory leaks. You have to use FastMM's own leak tracking features instead, since only it knows which memory is actually leaked or not. You can enable the global ReportMemoryLeaksOnShutdown variable in the System unit, but the default installation of FastMM has minimal leak reporting enabled. For more detailed reporting, install the full version of FastMM into your project and configure it as needed.