Webware for Python

At 02:22 PM 5/23/01 +0200, J=F6rn Schrader wrote:
>Hello,
>
>I would like to use MiddleKit in a WebKit Application. Can anyone =
describe
>the best way to embed a middlekit store in the WebKit Application, so =
that I
>dont have to open it for each request.
>
>Thanks a lot, Joern.

Create a module that opens up the MiddleKit store when it is=20
imported.  Then any servlet that needs the store can just import the =
module=20
and use the store.  For example (untested code):


# MyObjectStore.py
from MiddleKit.Run.MySQLObjectStore import MySQLObjectStore
store =3D MySQLObjectStore()
store.readModelFileNamed('MyMiddleKitModel')


# MyPage.py
from MyObjectStore import store
from WebKit.Page import Page
class MyPage(Page):
     def writeContent(self):
         # Here you can just use the store.


Python's import statement ensures that code inside of it only gets =
executed=20
once (unless you use reload).  And it also locks the threads so that so =

other thread can import the same module at the same time.  So this =
solution=20
is safe even in a threaded environment like WebKit.


--

- Geoff Talvola
   gtalvola@...

J=F6rn Schrader <Joern.Schrader@...> wrote:
> I would like to use MiddleKit in a WebKit Application. Can anyone desc=
ribe
> the best way to embed a middlekit store in the WebKit Application, so =
that I
> dont have to open it for each request.

I have a SitePage class that all pages inherit from.  I include a
method:

	def store(self):
		if not hasattr(self, "_store"):
			self._store =3D MySQLObjectStore(user=3D'username', passwd=3D'passwor=
d')
			self._store.readModelFileNamed(os.path.join('Gallery'))
		return self._store

Then I just call self.store() to get the store.

It might be better to do:

    def store(self):
        try:
            return self._store
        except AttributeError:
            self._store =3D [...]
            return self._store

  Ian

At 11:53 AM 5/23/01 -0500, Ian Bicking wrote:
>J=F6rn Schrader <Joern.Schrader@...> wrote:
> > I would like to use MiddleKit in a WebKit Application. Can anyone =
describe
> > the best way to embed a middlekit store in the WebKit Application, =
so=20
> that I
> > dont have to open it for each request.
>
>I have a SitePage class that all pages inherit from.  I include a
>method:
>
>         def store(self):
>                 if not hasattr(self, "_store"):
>                         self._store =3D =
MySQLObjectStore(user=3D'username',=20
> passwd=3D'password')
>=20
>self._store.readModelFileNamed(os.path.join('Gallery'))
>                 return self._store
>
>Then I just call self.store() to get the store.
>
>It might be better to do:
>
>     def store(self):
>         try:
>             return self._store
>         except AttributeError:
>             self._store =3D [...]
>             return self._store
>
>   Ian

This isn't thread-safe -- 2 servlets could create the store at the same =
time.

You're better off putting the store initialization into a module that =
gets=20
imported -- then Python automatically ensures that only one thread =
imports=20
it at once.  (Either that or you should explicitly use a threading.Lock =

object to make it thread-safe.)

If you want to "pre-load" the store when the app server starts up to =
reduce=20
response time, then you can put the import into the __init__.py in your =

context directory.  __init__.py automatically gets imported when the =
app=20
server starts.


--

- Geoff Talvola
   gtalvola@...

Hey guys,

My webware is running great, except that I'm caching
objects in user sessions that webware can't cache to
disk.  Then, when they come back, or when I try to
restart Webware, I get errors and my whole application
is hosed until i do a rm -rf * in the Sessions
directory.  Can I just turn off disk-caching
altogether?  I tried doing:

 'SessionStore':         'Memory',  

In Application.config, but that didn't work.

Thanks
Brad


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OK,

I just did a "chmod a-w" on the Sessions directory. 
That fixes my problem, but I suppose isn't the ideal
fix.  Is there a better way?

Brad


--- Bradley Marshall <bradmars@...> wrote:
> 
> Hey guys,
> 
> My webware is running great, except that I'm caching
> objects in user sessions that webware can't cache to
> disk.  Then, when they come back, or when I try to
> restart Webware, I get errors and my whole
> application
> is hosed until i do a rm -rf * in the Sessions
> directory.  Can I just turn off disk-caching
> altogether?  I tried doing:
> 
>  'SessionStore':         'Memory',  
> 
> In Application.config, but that didn't work.
> 
> Thanks
> Brad
> 
> 
> __________________________________________________
> Do You Yahoo!?
> Yahoo! Auctions - buy the things you want at great
> prices
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> 
> _______________________________________________
> Webware-discuss mailing list
> Webware-discuss@...
>
http://lists.sourceforge.net/lists/listinfo/webware-discuss


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I think that the "Memory" session store still tries to store all sessions 
to disk when the app server exits, and it still tries to read in all 
sessions when the app server starts.  It just doesn't do any disk access 
while the app server is running.

What exactly is the problem you're having?  Are you trying to store Python 
class instances in sessions?  This is known not to work, and nobody has 
tried to fix it yet.  If this is your problem, someone else recently worked 
around the problem by calling pickle.dumps() when storing an object in the 
session, and calling pickle.loads() when loading the object from the 
session.  That way you're only really storing strings.

The session code internally uses pickle, so I'm not sure why it doesn't 
work.  I'd love to look into the problem but I don't have time right now.

Alternatively, if you really want a purely in-memory session store that 
never saves sessions to disk, you could modify your copy of 
SessionMemoryStore.py and just comment out the parts that do the saving and 
loading.


At 11:25 AM 5/23/01 -0700, Bradley Marshall wrote:

>OK,
>
>I just did a "chmod a-w" on the Sessions directory.
>That fixes my problem, but I suppose isn't the ideal
>fix.  Is there a better way?
>
>Brad
>
>
>--- Bradley Marshall <bradmars@...> wrote:
> >
> > Hey guys,
> >
> > My webware is running great, except that I'm caching
> > objects in user sessions that webware can't cache to
> > disk.  Then, when they come back, or when I try to
> > restart Webware, I get errors and my whole
> > application
> > is hosed until i do a rm -rf * in the Sessions
> > directory.  Can I just turn off disk-caching
> > altogether?  I tried doing:
> >
> >  'SessionStore':         'Memory',
> >
> > In Application.config, but that didn't work.
> >
> > Thanks
> > Brad
> >
> >
> > __________________________________________________
> > Do You Yahoo!?
> > Yahoo! Auctions - buy the things you want at great
> > prices
> > http://auctions.yahoo.com/
> >
> > _______________________________________________
> > Webware-discuss mailing list
> > Webware-discuss@...
> >
>http://lists.sourceforge.net/lists/listinfo/webware-discuss
>
>
>__________________________________________________
>Do You Yahoo!?
>Yahoo! Auctions - buy the things you want at great prices
>http://auctions.yahoo.com/
>
>_______________________________________________
>Webware-discuss mailing list
>Webware-discuss@...
>http://lists.sourceforge.net/lists/listinfo/webware-discuss

--

- Geoff Talvola
   gtalvola@...

> What exactly is the problem you're having?  Are you
> trying to store Python 
> class instances in sessions?  

Yes.  I realize that won't work, so I just wanted a
simple way to turn the disk caching off altogether. 
The current solution is to simply not give the app
permission to write to the seeions dir.

Brad




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Geoff Talvola <gtalvola@...> wrote:
> The session code internally uses pickle, so I'm not sure why it doesn't 
> work.  I'd love to look into the problem but I don't have time right now.

Probably when you pickle and unpickle on your own, you are doing so
somewhere where you have access to the class definitions in a way that
Session doesn't.

Hmm... after looking at pickle, it seems like it saves the module and
class name for instances.  That should work, assuming
.__class.__module__ and .__class__.__name__ are an accurate way of
retrieving the object.  Which, with all the sys.path manipulation
might not be true, perhaps.

I dunno, just a few ideas.  There are some methods you can add to a
class to control how it is pickled as well.  Maybe those could help.

  Ian

OK, I couldn't resist looking into this -- my curiosity was killing 
me.  The last time I investigated why pickling class instances wasn't 
working, it looked like the fact that we were exec'ing our servlets instead 
of importing them was confusing pickle.  But we recently switched (in 
Webware CVS) from exec'ing servlets to importing servlets as modules in a 
package.  So I thought, maybe we are now able to pickle class objects in 
sessions...

So I wrote a simple test servlet, and it works!  I can shut down and 
restart my app server and everything works fine and the sessions are 
preserved.  I've included my test servlet -- a variation of the CountVisits 
example that stores the count in a simple class.

So Brad, you could consider switching to a CVS version of Webware.  The 
current tip of CVS seems quite stable to me.

It's possible that there are problems with more complex cases, but this at 
least shows that it's possible to store class instances in sessions.


# PickleTest.py
from WebKit.Page import Page

class Counter:
         def __init__(self):
                 self._count = 0
         def incrementCount(self):
                 self._count = self._count + 1
         def count(self):
                 return self._count


class PickleTest(Page):
         def writeContent(self):
                 counter = self.session().value('counter', None)
                 if counter is None:
                         counter = Counter()
                         self.session().setValue('counter', counter)
                 counter.incrementCount()
                 count = counter.count()

                 if count>1:
                         plural = 's'
                 else:
                         plural = ''
                 self.writeln("<p> You've been here %d time%s." % (count, 
plural))
                 self.writeln('<p> Try hitting RELOAD now.')





--

- Geoff Talvola
   gtalvola@...

Wow, great!

I think I'll hold off until this change comes out in a
tested release, but nice work!

Brad

--- Geoff Talvola <gtalvola@...> wrote:
> OK, I couldn't resist looking into this -- my
> curiosity was killing 
> me.  The last time I investigated why pickling class
> instances wasn't 
> working, it looked like the fact that we were
> exec'ing our servlets instead 
> of importing them was confusing pickle.  But we
> recently switched (in 
> Webware CVS) from exec'ing servlets to importing
> servlets as modules in a 
> package.  So I thought, maybe we are now able to
> pickle class objects in 
> sessions...
> 
> So I wrote a simple test servlet, and it works!  I
> can shut down and 
> restart my app server and everything works fine and
> the sessions are 
> preserved.  I've included my test servlet -- a
> variation of the CountVisits 
> example that stores the count in a simple class.
> 
> So Brad, you could consider switching to a CVS
> version of Webware.  The 
> current tip of CVS seems quite stable to me.
> 
> It's possible that there are problems with more
> complex cases, but this at 
> least shows that it's possible to store class
> instances in sessions.
> 
> 
> # PickleTest.py
> from WebKit.Page import Page
> 
> class Counter:
>          def __init__(self):
>                  self._count = 0
>          def incrementCount(self):
>                  self._count = self._count + 1
>          def count(self):
>                  return self._count
> 
> 
> class PickleTest(Page):
>          def writeContent(self):
>                  counter =
> self.session().value('counter', None)
>                  if counter is None:
>                          counter = Counter()
>                         
> self.session().setValue('counter', counter)
>                  counter.incrementCount()
>                  count = counter.count()
> 
>                  if count>1:
>                          plural = 's'
>                  else:
>                          plural = ''
>                  self.writeln("<p> You've been here
> %d time%s." % (count, 
> plural))
>                  self.writeln('<p> Try hitting
> RELOAD now.')
> 
> 
> 
> 
> 
> --
> 
> - Geoff Talvola
>    gtalvola@...
> 
> _______________________________________________
> Webware-discuss mailing list
> Webware-discuss@...
>
http://lists.sourceforge.net/lists/listinfo/webware-discuss


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