On Tue, 14 Aug 2012, Leonardo M. Ramé wrote:
On 2012-08-14 09:47:41 +0200, Michael Schnell wrote:
AFAIK, a web application uses the plain old standard mechanism, a
web server uses to work with a CGI application. it start the
application and when same ends, the web server retrieves its output
and sends it to the browser. So the web application just does not
live long to be able to wait for anything.
To create a longer living web enabled process it takes a lot more effort.
You can try several approaches:
- purely propriety: Use a second process (a long living daemon) and
have the web application communicate with same (e.g. via TCP/IP or
Pipe)
- fast CGI: here the (Apache) Web Server does exactly this
communication on it's own account
- ISAPI: here a (Microsoft) Web server communicates with a DLL
My colleagues do a combination of (1) and (3) with one of their
(Delphi) project very successfully:
They created a very simple ISAPI DLL (using RemObjects to do the
ISAPI communication)
They created a Windows service and used RemObjects (using the
"Windows Message" transport) to have the ISAPI DLL communicate with
the service.
(RemObjects is a commercial product that is specified to work as
well with Delphi as with FreePascal.)
-Michael
Thanks Michael, I'm testing a different approach, based on a temporary
file. It works this way:
1) The client asks for a TaskId, for example 1234.
2) With the TaskId generated by the server, the client calls a CGI
method called runLongTask(myTaskId). This method writes a temporary file
which name is the taskId.
3) The client can ask for status by using a method called
getTaskStatus(myTaskId).
This way I can run a long task without having to create a daemon.
That is exactly what I do.
Michael.
--
_______________________________________________
Lazarus mailing list
Lazarus@lists.lazarus.freepascal.org
http://lists.lazarus.freepascal.org/mailman/listinfo/lazarus
