[Zope] Python, persistent objects and caching

2000-09-07 Thread Soren Roug 

Hi,

I'm developing a Python-based product that uses persistent objects in
ZODB to store its configuration. No surprises there, but my product is
also using volatile attributes to do a bit of caching of its own. The
thing is, when ZODB takes a sweep every 60 seconds to flush it's own
cache it will quite often flush my product as well, essentially
rendering my 15 minute caching ineffective.

If there a way I can prevent this from happening?

References:
http://www.zope.org/Members/MikeP/volatile
http://www.zope.org/Members/Zen/tips/VolatileAttributes

Soren Roug

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RE: [Zope] Python, persistent objects and caching

2000-09-07 Thread Brian Lloyd 


 I'm developing a Python-based product that uses persistent objects in
 ZODB to store its configuration. No surprises there, but my product is
 also using volatile attributes to do a bit of caching of its own. The
 thing is, when ZODB takes a sweep every 60 seconds to flush it's own
 cache it will quite often flush my product as well, essentially
 rendering my 15 minute caching ineffective.
 
 If there a way I can prevent this from happening?
 
 References:
 http://www.zope.org/Members/MikeP/volatile
 http://www.zope.org/Members/Zen/tips/VolatileAttributes
 
 Soren Roug

One approach would be to cache your data in the module's 
namespace. For ex:

mycache={}

class MyClassThatKeepsGoingAway:
  ...
  def get_data(self, id):
if mycache.has_key(id):
  return mycache[id]
else:
  ...

Note that my example is a little contrived, since using a module 
variable means that you will have to implement this in a way that 
is safe for a multi-threaded environment. You will also want to 
make sure that your module-level cache doesn't grow forever and 
take up a lot of memory.

Hope this helps!

Brian Lloyd ([EMAIL PROTECTED])

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RE: [Zope] Python, persistent objects and caching

2000-09-07 Thread Dieter Maurer 

Brian Lloyd writes:
  Soren Rough writes
   ... application level cache ...
   ... application objects flushed (including cache)

  One approach would be to cache your data in the module's 
  namespace. For ex:
  
  mycache={}
  
  class MyClassThatKeepsGoingAway:
...
def get_data(self, id):
  if mycache.has_key(id):
return mycache[id]
  else:
...
  
  Note that my example is a little contrived, since using a module 
  variable means that you will have to implement this in a way that 
  is safe for a multi-threaded environment.
You can use a "SharedResource" for this:

URL:http://www.dieter.handshake.de/pyprojects/zope/SharedResource.html


Dieter

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