[SOLVED] HTTPMethod in Synapse is slow and freezes program operation
momentarily
lazarus / 38-Networking and Web Programming

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newman · 2011-01-31 12:40

Hi,

I have installed Apache2 server on my computer (OS: Ubuntu 10.04),
with PHP and MySqlite support.

I am using this function below to send HTTP post method to a PHP file
(that resides in a site also in my computer), I am using synapse
library. 

Code: [Select]function PostInetCommand(cPostData:string):string;
var
  HTTP: THTTPSend;
  l: tstringlist;
  cResponse:string;
  b:boolean;
begin
  HTTP := THTTPSend.Create;
  l := TStringList.Create;

  try
    if not HTTP.HTTPMethod('POST',cPostData) then
      begin
        Result:= 'Error';
      end
    else
      begin
        l.loadfromstream(Http.Document);
        Result:= l.Text;
     end;
  finally
    HTTP.Free;
    l.free;
  end;
end;


I find that the program operation freezes momentarily and the response
from PHP file is very slow (at least 3 -4 seconds), whereas the same
post operation done from a browser is instantaneous.

Please explain why this is happening ?? also how can I improve the
performance.

PS: Sorry if I could not make myself clear as I am new to network
programming.


thanks
nm

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Leledumbo · 2011-01-31 12:43

Mine here is fast, could you make sure that it's faster with php?

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Silvio Clécio · 2011-01-31 12:54

Hi newman,

Use thread, see demos with threads in:

http://code.google.com/p/lazsolutions/

Good luck.

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newman · 2011-01-31 15:28

Quote from: Leledumbo on January 31, 2011, 01:43:38 pmMine here is
fast, could you make sure that it's faster with php?

I am using PHP..and its not fast...

Just for my information how fast should the response from the server
be ?

Quote from: silvioprog on January 31, 2011, 01:54:47 pmHi newman,

Use thread, see demos with threads in:

http://code.google.com/p/lazsolutions/

Good luck.

thanks for the link, I downloaded the lazsolutions zip file, but
threads are a bit steep for me..but I am working on it...

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Silvio Clécio · 2011-01-31 15:51

Hi newman,

But isn't hardly, it's very easy, please see this:

http://code.google.com/p/lazarus-
br/source/browse/trunk/misc/BeginThread/MainFrm.pas

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theo · 2011-01-31 16:08

Quote from: silvioprog on January 31, 2011, 04:51:48 pmBut isn't
hardly, it's very easy, please see this:

How is access to MainForm.DisplayLabel.Caption synchronized in this
example?

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Leledumbo · 2011-01-31 16:22

QuoteI am using PHP..and its not fast...Then it's not HTTPMethod
problem, it's the processing of POST (in your PHP file) that's slow.
QuoteJust for my information how fast should the response from the
server be ?Too many things to consider before saying something about
this. Nevertheless, at localhost, if the request is simple (i.e. no
complicated data processing) it should be in a blink of an eye.

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Silvio Clécio · 2011-01-31 16:26

Hi theo,

Sorry but I do not understand the question.  (My English is not very
good)

(...)
var
  MainForm: TMainForm;

.
.
.

procedure HeavyProcess;
var
  I: Integer = 0;
begin
  while I < 1000 do
  begin
    MainForm.DisplayLabel.Caption := IntToStr(I);
(...)

Other situation:
http://code.google.com/p/lazsolutions/source/browse/trunk/Demos/LSSMTP
Send/Thread/MainFrm.pas#78

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theo · 2011-01-31 16:59

Quote from: silvioprog on January 31, 2011, 05:26:45 pmHi theo,
Sorry but I do not understand the question.  (My English is not very
good)

It looks like this code is updating MainForm.DisplayLabel.Caption from
within a separate thread without synchronizing with the main thread. 
Afaik this will crash sooner or later.

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Silvio Clécio · 2011-01-31 19:58

Hi theo,

How can I fix this without using global variable?

I have a solution to use in this demo, but using a global variable.

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theo · 2011-01-31 20:46

Quote from: silvioprog on January 31, 2011, 08:58:26 pmHow can I fix
this without using global variable?

I never use BeginThread(..) and friends, always TThread class.

You can see an example here (PT for you   )
http://wiki.lazarus.freepascal.org/Multithreaded_Application_Tutorial/
pt#A_classe_TThread

See: Synchronize(@Showstatus);

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Silvio Clécio · 2011-01-31 21:13

Hm..., I always forever use TThread class too, but I avoided because
this class is with memory leaks in Lazarus:

http://lists.lazarus.freepascal.org/pipermail/lazarus/2010-
October/056098.html

I will check if this error of memory leak was repaired, if the class
is normal in Lazarus now, I come back to use it.

Thanks guys.

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theo · 2011-01-31 21:21

I don't think that "bug" was really problematic.
But might be fixed in the meantime:
http://bugs.freepascal.org/view.php?id=16884

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theo · 2011-01-31 22:03

Btw. you could also use the Heartbeat feature to avoid "freezing" of
your GUI.

http://synapse.ararat.cz/doku.php/public:howto:heartbeat

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Silvio Clécio · 2011-01-31 22:05

Wow, this bug was solved:

http://bugs.freepascal.org/view.php?id=17560

Thanks.

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Silvio Clécio · 2011-01-31 22:37

Well, I solved the problem with thread not safe (using global variable
):

http://code.google.com/p/lazarus-br/source/detail?r=156

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newman · 2011-02-01 08:34

thanks everyone for the insight..I solved the problem by using INet
controls.

Thanks for the info on threads I intend to use it in my next project..