web interface

[Ajar]

Hi,

I have a stand alone application which does some scientific
computations. I want to provide a web interface for this app. The app
is computationally intensive and may take long time for running. Can
someone suggest me a starting point for me? (like pointers to the
issues involved in this, or even better any of the existing tools for
doing this...)

Ajar

[Jorge Godoy]

Re: web interface

"Ajar" <ajartaknev@gma il.com> writes:
[color=blue]
> I have a stand alone application which does some scientific
> computations. I want to provide a web interface for this app. The app
> is computationally intensive and may take long time for running. Can
> someone suggest me a starting point for me? (like pointers to the
> issues involved in this, or even better any of the existing tools for
> doing this...)[/color]

For the long running task you might get some idea from cvsmonitor (Perl
code). It has a long running task that is updating some repositories and
giving feedback from time to time to the user.

One thing is: detach all what is possible from user interface and give
feedback from time to time to avoid browser timeout and the user thinking the
app hanged.


Be seeing you,
--
Jorge Godoy <godoy@ieee.org >

[Charl P. Botha]

Re: web interface

I'm using SkunkWeb [1] for building a responsive interface to a number
of long-running processes. See [2] for an example of running
long-running processes in SkunkWeb and monitoring them.

One of the advantages (to my mind) that SkunkWeb offers over many of
the other Python application servers and web frameworks is that it's
natively multi-processing vs. multi-threading.

[1] http://www.skunkweb.org/
[2] http://wiki.skunkweb.org/sw/ExampleO...RunningProcess

--
charl p. botha - http://cpbotha.net/

[John J. Lee]

Re: web interface

Jorge Godoy <godoy@ieee.org > writes:
[color=blue]
> "Ajar" <ajartaknev@gma il.com> writes:
>[color=green]
> > I have a stand alone application which does some scientific
> > computations. I want to provide a web interface for this app. The app
> > is computationally intensive and may take long time for running. Can
> > someone suggest me a starting point for me? (like pointers to the
> > issues involved in this, or even better any of the existing tools for
> > doing this...)[/color]
>
> For the long running task you might get some idea from cvsmonitor (Perl
> code). It has a long running task that is updating some repositories and
> giving feedback from time to time to the user.
>
> One thing is: detach all what is possible from user interface and give
> feedback from time to time to avoid browser timeout and the user thinking the
> app hanged.[/color]

If you're using CGI:

You usually have to start the long job by asking a separate server
process to do it -- eg. using XML RPC. Otherwise, you'll get browser
timeouts (and maybe web server timeouts too). Your little server
process can then do e.g. os.fork (unix) or subprocess.Crea teProcess
(win32) (subprocess is only available in Python 2.4) to actually start
your long job. Use a Refresh header (use a META HTML element, or set
up your web server appropriately) in your "waiting for job to finish"
web page (or reload the page from JS code) to poll the server to see
if the job has completed.


John

[Tom Anderson]

Re: web interface

On Mon, 7 Nov 2005, Ajar wrote:
[color=blue]
> I have a stand alone application which does some scientific
> computations. I want to provide a web interface for this app. The app is
> computationally intensive and may take long time for running. Can
> someone suggest me a starting point for me? (like pointers to the issues
> involved in this,[/color]

You're probably best off starting a new process or thread for the
long-running task, and having the web interface return to the user right
after starting it; you can then provide a second page on the web interface
where the user can poll for completion of the task, and get the results if
it's finished. You can simulate the feel of a desktop application to some
extent by having the output of the starter page redirect the user to the
poller page, and having the poller page refresh itself periodically.

What you really want is a 'push' mechanism, by which the web app can
notify the browser when the task is done, but, despite what everyone was
saying back in '97, we don't really have anything like that.
[color=blue]
> or even better any of the existing tools for doing this...)[/color]

Pise does what you want, and much more:

http://www.pasteur.fr/recherche/unites/sis/Pise/

But i have no idea if it's of any use to you - it was designed for
bioinformatics programs, and might not be easily adaptable to other tasks.

Old-enough-to-remember-the-push-hype-ly y'rs,
tom

--
Exceptions say, there was a problem. Someone must deal with it. If you
won't deal with it, I'll find someone who will.

[Michele Simionato]

Re: web interface

<snip nifty example of using Livepage>

I have been looking for an example like this for a while, so thanks to
J.P. Calderone.
Unfortunately, this kind of solution is pretty much browser-dependent.
For instance,
I tried it and it worked with Firefox, but not with MSIE 5.01 and it
will not work with any
browser if you disable Javascript. So, I don't think there is a real
solution
for this kind of problem as of today (I would love to be wrong,
though).

Michele Simionato