Serving files (mime-type determination failures), TG 2.0.1, a hack...

[Mike C. Fletcher-2]

I have code failing (again) with the "feature" where mime-type
declarations are ignored and the system attempts to find a template
engine for something that doesn't need a template based on file-name
extensions.  My code is explicitly setting the response's mime-type
(correctly), but for some reason, in some bloody-hard-to-reproduce
situations (i.e. one time in a thousand, with some unknown end-user's
mobile device) I wind up with an error where the code that attempts to
find the template engine shows up and tries to look up "" as a key.

To try to get around it for now I'm doing this:

# TODO: remove this *ridiculous* hack!!!
dec = Decoration.get_decoration( DownloadController.raw )
lte = dec.lookup_template_engine
def lookup_template_engine( request ):
    """Mask the broken TG mime-type stuff"""
    try:
        return lte( request )
    except KeyError, err:
        log.error( """Caught low-level error for lookup-template-engine,
ignoring""" )
        return None,None,[]
dec.lookup_template_engine = lookup_template_engine

The code that uses it looks like this (simplified):

    @expose(content_type=CUSTOM_CONTENT_TYPE)
    def raw(
        self, *args, **named
    ):
        """Provide raw download of bytes..."""
        ...
        pylons.response.headers['Content-Type'] = 'application/octet-stream'
        pylons.response.headers['Content-Disposition'] =
'attachment;filename=%s'%(basename,)
        ...
        return file_data

where the URL would look like /downloads/raw/somefile.cod  (basically a
binary application-specific data-file).  Anyway, just in case anyone
else is running into these tracebacks, there's the hack:

 File
'.../lib/python2.5/site-packages/Pylons-0.9.7-py2.5.egg/pylons/controllers/core.py',
line 221 in __call__
   response = self._dispatch_call()
 File
'.../lib/python2.5/site-packages/Pylons-0.9.7-py2.5.egg/pylons/controllers/core.py',
line 172 in _dispatch_call
   response = self._inspect_call(func)
 File
'.../lib/python2.5/site-packages/Pylons-0.9.7-py2.5.egg/pylons/controllers/core.py',
line 107 in _inspect_call
   result = self._perform_call(func, args)
 File
'.../lib/python2.5/site-packages/TurboGears2-2.0.1-py2.5.egg/tg/controllers.py',
line 835 in _perform_call
   self, controller, params, remainder=remainder)
 File
'.../lib/python2.5/site-packages/TurboGears2-2.0.1-py2.5.egg/tg/controllers.py',
line 182 in _perform_call
   response = self._render_response(controller, output)
 File
'.../lib/python2.5/site-packages/TurboGears2-2.0.1-py2.5.egg/tg/controllers.py',
line 294 in _render_response
   controller.decoration.lookup_template_engine(pylons.request)
 File
'.../lib/python2.5/site-packages/TurboGears2-2.0.1-py2.5.egg/tg/decorators.py',
line 138 in lookup_template_engine
   engine, template, exclude_names = self.engines[content_type]
 KeyError: ''

If someone has a real solution, I'd love to hear about it.  Note, having
apache serve the files is *not* an option, as the content needs to be
altered in some instances and I need (complex) authorization to
determine if the file is going to be provided.

Take care,
Mike

--
________________________________________________
  Mike C. Fletcher
  Designer, VR Plumber, Coder
  http://www.vrplumber.com
  http://blog.vrplumber.com


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[Mike C. Fletcher-2]

Mike C. Fletcher wrote:

Sigh, wrong copy of the hack-code:
...
> dec = Decoration.get_decoration( DownloadController.raw )
> lte = dec.lookup_template_engine
> def lookup_template_engine( request ):
>     """Mask the broken TG mime-type stuff"""
>     return pylons.response.headers['Content-Type'],None,None,[]
> dec.lookup_template_engine = lookup_template_engine
>  
Still would rather not have it at all,
Mike

--
________________________________________________
  Mike C. Fletcher
  Designer, VR Plumber, Coder
  http://www.vrplumber.com
  http://blog.vrplumber.com


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[Jean-Denis Girard]

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Hash: SHA1

Mike C. Fletcher a écrit :
| If someone has a real solution, I'd love to hear about it.  Note, having
| apache serve the files is *not* an option, as the content needs to be
| altered in some instances and I need (complex) authorization to
| determine if the file is going to be provided.

This is working fine for me on tg2.0:

~   @expose()
~   @allow_only(predicates.not_anonymous())
~   def serve_file(self, date=None, file=None):
~      import paste.fileapp
~      f =
paste.fileapp.FileApp('/usr/share/games/xmoto/Textures/Musics/speeditup.ogg',
~            **{'Content-Disposition': 'attachment; filename=' +
'test.ogg'})
~      from tg import use_wsgi_app
~      return use_wsgi_app(f)


Thanks,
- --
Jean-Denis Girard

SysNux                  Systèmes  Linux  en Polynésie française
http://www.sysnux.pf/   Tél: [phone] / GSM: [phone]
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[Mike C. Fletcher-2]

Jean-Denis Girard wrote:
...

> This is working fine for me on tg2.0:
>
> ~   @expose()
> ~   @allow_only(predicates.not_anonymous())
> ~   def serve_file(self, date=None, file=None):
> ~      import paste.fileapp
> ~      f =
> paste.fileapp.FileApp('/usr/share/games/xmoto/Textures/Musics/speeditup.ogg',
> ~            **{'Content-Disposition': 'attachment; filename=' +
> 'test.ogg'})
> ~      from tg import use_wsgi_app
> ~      return use_wsgi_app(f)

That seems to work fine for me.  There's a note here:

    http://trac.turbogears.org/ticket/2385

that seems to suggest that use_wsgi_app has been removed for TurboGears
2.1 (i.e. it is deprecated).  The replacement (WSGIAppController)
doesn't seem to be appropriate, though I suppose I could try hooking
into object dispatch to return a different controller for each file in
the directory.

Thanks for the pointer,
Mike
--
________________________________________________
  Mike C. Fletcher
  Designer, VR Plumber, Coder
  http://www.vrplumber.com
  http://blog.vrplumber.com


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[Jorge Vargas]

On Wed, Oct 28, 2009 at 9:03 AM, Mike C. Fletcher
<mcfletch@...> wrote:

>
> Jean-Denis Girard wrote:
> ...
>> This is working fine for me on tg2.0:
>>
>> ~   @expose()
>> ~   @allow_only(predicates.not_anonymous())
>> ~   def serve_file(self, date=None, file=None):
>> ~      import paste.fileapp
>> ~      f =
>> paste.fileapp.FileApp('/usr/share/games/xmoto/Textures/Musics/speeditup.ogg',
>> ~            **{'Content-Disposition': 'attachment; filename=' +
>> 'test.ogg'})
>> ~      from tg import use_wsgi_app
>> ~      return use_wsgi_app(f)
> That seems to work fine for me.  There's a note here:
>
>    http://trac.turbogears.org/ticket/2385
>
> that seems to suggest that use_wsgi_app has been removed for TurboGears
> 2.1 (i.e. it is deprecated).  The replacement (WSGIAppController)
> doesn't seem to be appropriate, though I suppose I could try hooking
> into object dispatch to return a different controller for each file in
> the directory.
>

I encourage you to upgrade WSGIAppController to support this usecase.

In theory it should support passing the app as a parameter. So you
could simply do.

return WSGIAppController(paste.fileapp.FileApp(....)).default() It's a
little ugly which is why I suggest looking for a better solution.

Also note that use_wsgi_app is a very thin rapper that only delegates
to the parameter. It has a bug when mounted at a non-root URL, which
is why WSGIAppController was born.

Regarding the removal of use_wsgi_app it is still there, so we can
keep it around until there is a better solution. I have updated the
ticket to reflect this.

As for the original content type issue I strongly suggest you use the
2.1 version of the code as we had a very hard to fix bug, please
follow this documentation
http://www.turbogears.org/2.1/docs/main/ResponseTypes.html#setting-the-content-type
(the ticket is linked from there)

> Thanks for the pointer,
> Mike
> --
> ________________________________________________
>  Mike C. Fletcher
>  Designer, VR Plumber, Coder
>  http://www.vrplumber.com
>  http://blog.vrplumber.com
>
>
> >
>

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[Mike C. Fletcher-2]

Jorge Vargas wrote:
> On Wed, Oct 28, 2009 at 9:03 AM, Mike C. Fletcher
> <mcfletch@...> wrote:
>  
...
> encourage you to upgrade WSGIAppController to support this usecase.
>  
...
> As for the original content type issue I strongly suggest you use the
> 2.1 version of the code as we had a very hard to fix bug, please
> follow this documentation
> http://www.turbogears.org/2.1/docs/main/ResponseTypes.html#setting-the-content-type
> (the ticket is linked from there)
>  
That fix is, in essence, what I did, but with a hack decorator that
eliminates the template engine lookup in the decorators module.  I can't
update the production system to use 2.1 just yet (alpha isn't something
they'll like :) ).  I'm really not looking for the full FileApp support,
so simply fixing the attempt to look up the templating engine is all *I*
need.  The fact that the fix is in 2.1 for this usage is sufficient for
my clients needs, as we will eventually move to 2.1.  Only thing I can
imagine needing the full fileapp stuff for is serving up big media files
(GBs) without needing to load into ram.

Thanks,
Mike

--
________________________________________________
  Mike C. Fletcher
  Designer, VR Plumber, Coder
  http://www.vrplumber.com
  http://blog.vrplumber.com


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