[Erp5-dev] Memcached tool

[Pelletier Vincent]

Hi.

I just added a memcached tool.
This tool provides an interface to a memcached server.

It is disabled by default because it would ad a dependence on python-memcached
and we want it to fail loudly if python-memcached is not present and the tool
is needed.

Features :

 - Presents memcached as a dictionary
 - Allows multiple uses of the same memcached using one connection
 - Reads are cached during the transaction : prevents multiple reads of the
   same value from memcached
 - Writes to memcached are queued until transaction ends : prevents duplicate
   writes
Remember : Each time memcached is restarted, the content is lost.

Quick tutorial :

In all cases (part 1) :
 - Install python-memcached (see links below)
 - Install & start a mamcached server somewhere on your network (see links
   below)
 - touch Products/ERP5Type/USE_MEMCACHED_TOOL (otherwise the tool will be in
   disabled mode)

If you're updating from an older site :
 - Update your products to get the latest version
 - Go to Zope Managment Interface on your portal object (most likely /erp5)
 - Select 'ERP5Type Tool' in the 'add' menu
 - Select 'ERP5 Memcached Tool' in the offered choices
 - Click 'Add'

In all cases (part 2) :
 - Go to portal_memcached management screens
 - Setup tht ip:port of your memcached server

It's ready to use !

Quick sample script :

# Begin
memcached_dict = context.getPortalObject().portal_memcached.getMemcachedDict(key_prefix='my_first_test')
value = memcached_dict['some_key']
print value
if value is None:
  value = 0
memcached_dict['some_key'] = value + 1
return printed
# End

The printed values should be None, then 1, then 2, ...
If you restart memcached, the count wil stall at None until python-memcached
reconnects to memcached.

Memcached : http://www.danga.com/memcached/
python-memcached : ftp://ftp.tummy.com/pub/python-memcached/
                   (linked from the "client API" page on memcached site)

-- 
Vincent Pelletier