pubsub.py server memory usage and persistence using ZODB.

Lately we've been seeing that a moderately-used Python PubSub Server

    mod_pubsub/python_pubsub/pubsub.py

has been consuming more memory than we'd like.  Joyce has seen it at
30-40% memory usage at times; bouncing the server helps some, especially
if the server is run with the event pool turned on (-f in the command line).

Still, it may be worth spending some time looking at replacements of
the persistence layer with something more efficient.

Several people have suggested the Z Object Database

  http://www.amk.ca/zodb/zodb-zeo.html

so this is a heads-up to the developer list in case anyone has feedback.
Here are some comments I've gotten so far:

1. "ZODB is an easy to use choice. Its performance profile may not be ideal,
but it supports versioning and other features relevant to pubsub."

2. "So, the Z Object Database is very interesting and it would move what has 
been a useful hack (the existing python server) into a useable server, at 
least when it comes to how it archives events.  That is a good thing.  I 
think there is a choice between storage types when using this DB.  Either 
the "tired kitty" (Sleepycat) BerkeleyDB or some native thing that 
they've built.  The last time I checked, they built the custom storage 
layer to optimize for their specific case and avoid some of the pesky 
aspects of real ACIDity.  I could be wrong, I frequently am, its been a 
while since I looked into it.  My "vote" (if I get one) is for the python
server to use the Z Object Database and see where that leads the project."

3. "I'm a big Zope user, therefore a ZODB user, I'd say +1 from me :)"

Any other feedback?  Will report anything I learn back to the list.

   Adam


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