[mod_python] The DOs and DONTs of mod_python: one problem found

Hi,

It took me a while to understand that although I had apache configured to run 
as me "philippe", doing an os.getenv still returned the root environment 
variables.

Maybe forcing a source of ~/.bashrc ?

Regards,

Philippe



On Tuesday 18 October 2005 11:40 pm, Philippe C. Martin wrote:
> On Tuesday 18 October 2005 11:33 pm, Graham Dumpleton wrote:
>
> Thanks,
>
> The one good thing is that I cannot afford all of these threads to attack
> the only hardware resource (the smart card) at the same time: ISO7816
> simply is not ready for it.
>
> So I will have to find a way to keep the people waiting and avoid concurent
> access.
>
> Regards,
>
> Philippe
>
> > A few additional comments on top of what Jorey has already said.
> >
> > Philippe C. Martin wrote ..
> >
> > > Please note that, although I must have bugs, the code I'm calling
> > > _seems_ to
> > > work flawlessly under Linux and Windows.
> >
> > Besides issues with multiple interpreters, if using a multithread Apache
> > MPM, such as is the case for Win32 systems and "worker" MPM on UNIX, you
> > have to contend with multithreading. Your system may work quite happily
> > if you trickle requests in serially, but get requests come in at the
> > same time and they can trample all over each other if your module isn't
> > multithread safe.
> >
> > There are also various issues because of mod_python's module reloading
> > system. Problems can also arise if you use a module which has a C code
> > component and it uses the simplified threading C APIs in Python.
> >
> > There are a lot of gotchas.
> >
> > > from mod_python import apache
> > > import os
> > > import sys
> > > if os.name == 'nt':
> > >      sys.path.append("Z:\\dev")
> > > else:
> > >      sys.path.append('/home/philippe/dev')
> >
> > You shouldn't extend sys.path in Python code when mod_python is used.
> > The main reason is that if mod_python reloads the module, everytime that
> > occurs then sys.path will be extended even if the directory is already in
> > there. Thus, sys.path could grow and grow. This is made worse by bugs
> > in mod_python.publisher in versions of mod_python < 3.2.
> >
> > > from SC.pilot.SC_Script_Processor import *
> > >
> > >
> > > def world(req):
> > >      ls = SC_Script_Processor() #INSTANTIATE A _BIG_ OBJECT ==> ***
> > > THIS IS
> > > THE KILLER THAT CRASHES APACHE ***
> > >      ll = ls.Reader_List() # get the reader list
> > >
> > >      #Grab ATR from card - assume first reader
> > >      l_appli_conn = ls.Get_Connection(r1)
> > >
> > >
> > >
> > >      req.send_http_header()
> >
> > You don't set req.content_type. How is the browser mean't to know what
> > to do with the response. You perhaps want:
> >
> >   req.content_type = 'text/plain'
> >   req.send_http_header()
> >
> > Although, in 3.X the call to 'req.send_http_header()' is actually
> > redundant. It was only required in 2.7.X.
> >
> > >      req.write("RETURN CARD ATR= " +  l_appli_conn.Get_Connection_ATR()
> > > )
> > >
> > >      return apache.OK
> >
> > I have presumed that mod_python.publisher was being used because
> > you weren't using "handler()" for the function, but "world()". If this is
> > the case, you shouldn't be returning "apache.OK" as it will result in the
> > string "0" being appended to the response sent back to the browser.
> >
> > Overall, better off perhaps saying:
> >
> >   req.content_type = 'text/plain'
> >   return "RETURN CARD ATR= " +  l_appli_conn.Get_Connection_ATR()
> >
> > Graham

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Philippe C. Martin
SnakeCard, LLC
www.snakecard.com
+1 405 694 8098
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