Reloading of django views.py in modjy

[David Johansson]

Hi all,

I'm new here so if this is the wrong place for this question don't
hesitate to yell at me :-)

I'm trying to run django inside a WAR file with modjy on a JBoss 4.2.2
Application server. (Next step is to integrate it into  a jboss seam
project)
The deployment time isn't great so I'm trying to get jython/modjy to
reload my django application on change of a source file, as in the
development server of django.

I tried a lot of things. modjy will reload application.py on
modification, so I tried to manually reload my views.py. Something
like:

def handler(environ, start_response):
    os.putenv("DJANGO_SETTINGS_MODULE", "clean.settings")
    h = wsgi.WSGIHandler()
    import hello.views
    reload(hello.views)
    return h(environ, start_response)

Didn't work. So I tried further to remove the views$py.class file, and
indeed it get's compiled if I remove it manually and touch
application.py causing modjy to reload it and in turn triggers my
import.
An judging by changing filesize of views$py.class it would seem it's
the updated views.py it compiles, but it still runs the old code! If I
remove both views.py and it's class, then touch application.py i get a
"No module named views" error...

So basically:
  1) Has anyone done anything like this?
  2) Why does it not execute the compile code? (is it a java thing?)
  3) Am I barking up the wrong tree?

If anyone has any clue what I could try next It would be greatly appriated!

Thanks!
/davidj

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[Leo Soto M.]

On Tue, Jun 16, 2009 at 12:23 PM, David Jensen<david.lgj@...> wrote:

> Hi all,
>
> I'm new here so if this is the wrong place for this question don't
> hesitate to yell at me :-)
>
> I'm trying to run django inside a WAR file with modjy on a JBoss 4.2.2
> Application server. (Next step is to integrate it into  a jboss seam
> project)
> The deployment time isn't great so I'm trying to get jython/modjy to
> reload my django application on change of a source file, as in the
> development server of django.
>
> I tried a lot of things. modjy will reload application.py on
> modification, so I tried to manually reload my views.py. Something
> like:
>
> def handler(environ, start_response):
>    os.putenv("DJANGO_SETTINGS_MODULE", "clean.settings")
>    h = wsgi.WSGIHandler()
>    import hello.views
>    reload(hello.views)
>    return h(environ, start_response)
>
> Didn't work.

First, I'm not familiar with modjy's reloading logic. But I can shed
some light on some of your questions.

First, unfortunately reload(foo) isn't enough as a reload strategy. It
will make Jython to recompile the module, will update it's entry on
sys.modules and will *return* the updated module. But if other modules
have a binding with the old module (which is what import do!), such
bindings won't be refreshed.

So, what's happening here is that Django holds a reference to the
non-updated hello.views module.


> So I tried further to remove the views$py.class file, and
> indeed it get's compiled if I remove it manually and touch
> application.py causing modjy to reload it and in turn triggers my
> import.
> An judging by changing filesize of views$py.class it would seem it's
> the updated views.py it compiles, but it still runs the old code!

That supports my explanation given above.

[...]
> So basically:
>  1) Has anyone done anything like this?
>  2) Why does it not execute the compile code? (is it a java thing?)
>  3) Am I barking up the wrong tree?

I don't have good answers here. If you already have discarded the
usage of the development server (jython manage.py runserver), I'd like
to hear why. Perhaps we can improve it and solve your problem.

But my take on the issue is that modjy's reloading strategy is falling
short on your use case and should be improved. If you fill an issue on
<http://bugs.jython.org> (so this doesn't get forgotten) you will
probably be helping to make Jython better!
--
Leo Soto M.
http://blog.leosoto.com

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[Alan Kennedy-2]

[Leo]
> But my take on the issue is that modjy's reloading strategy is falling
> short on your use case and should be improved. If you fill an issue on
> <http://bugs.jython.org> (so this doesn't get forgotten) you will
> probably be helping to make Jython better!

Modjy permits two ways to specify an application.

1. By directory/filename/callable_name triple.

http://opensource.xhaus.com/projects/modjy/wiki/ModjyAppExecFile

The contents of the file specified by directory/filename are
execfile()d, and the callable name extracted from the resulting
namespace.

If the "reload_on_mod" flag is true, then the file containing the
application code is checked for modification, and re-execfile()ed if
the file has been modified.

If there are dependent modules that are imported as a result of the
execfile, then those dependent modules should also be re-compiled and
imported.

2. By specifying an importable name.

http://opensource.xhaus.com/projects/modjy/wiki/ModjyAppImportable

When an applicaiton is specified this way, e.g.
"some_framework.web.handlers.WSGIHandlerClass()", the name is
imported, and perhaps instantiated, using the standard jython import
machinery.

As stated on the above page, source reloading *is not supported* when
using the importable name mechanism.

In this scenario, the only way to get an application reload is to
restart the entire web application, AFAIK.

So, some questions to the OP

1. What application mechanism are you using?
2. Are you using the "reload_on_mod" flag?

Probably best if you could tell us the values of all of the modjy
configuration variables you are using.

Alan.

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