Varnish 2.1 release plan

The theme for Varnish 2.1 is "scalability", particularly trying to
address the needs of sites like finn.no which has a lot of objects and
where priming the cache takes a long time, leading to long periods of
higher load on the backend servers.

The main feature is persistent storage, see
http://varnish.projects.linpro.no/wiki/ArchitecturePersistentStorage
for design notes. Another important scalability feature is a new
lockless hash algorithm which scales much better than the current
one.  Poul-Henning already has an implementation of this in the tree,
but it's still fresh.

Minor features which would be nice to get in are:

* Web UI, showing pretty graphs as well as allowing easy configuration
  of a cluster of Varnish machines.

* Expiry randomisation.  This reduces the "lemmings" effect where you
  end up with a many objects with almost the same TTL (typically on
  startup) which then expire at the same time.  The feature will allow
  you to set the TTL to plus/minus X %.

* Dynamic, user-defined counters that can be read and written from VCL

* Forced purges, where a thread walks the list of purged objects and
  removes them.

The schedule
------------

Alphas:
 - 2009-01-15: New hash algorithm working
 - 2009-02-15: Web UI
 - 2009-03-15: Persistent storage
Beta:
 - 2009-04-01: Feature complete
Release
 - 2009-05-20: Release candidate
 - 2009-05-01: No release critical bugs left