Add temporary storage support for collective.recipe.filestorage and plone.recipe.zope2zeoserver

[Jean Jordaan]

When load balancing without session affinity in a ZEO cluster, the Zope session should be served from the ZEO master to ensure that all clients have a consistent view of the session.

This old post still seems to be valid today: http://longsleep.org/1/howto/sharesessionwithzeo

See also http://plone.org/documentation/how-to/sticky-sessions-and-mod_proxy_balancer and http://www.linux.co.uk/docs/center/how-to/load-balancing-apache-and-plone for reports of failure in the absence of session affinity.

To enable this using buildout, I added a 'temporary-storage = zeo' directive to the [filestorage] part. If this is present, then the zope.conf files contain a stanza like this:

<zodb_db temporary>
  <zeoclient>
    server 8025
    storage temp
    name tempstorage
    var /home/zope/instances/iwlearn/parts/instance1/var
  </zeoclient>
  mount-point /temp_folder
  container-class Products.TemporaryFolder.TemporaryContainer
</zodb_db>

where %(zeo_address)s and %(zeo_client_var)s have been interpolated. The zeo.conf file contains a stanza like this:

%import tempstorage
<temporarystorage temp>
  name temporary storage for sessioning
</temporarystorage>

The zope2zeoserver recipe gains a directive like this: 'zeo-temporary-storage', which works the same as the 'temporary-storage' directive.

The patch does the job, but could probably be refined.