2.1 plans

Tollef Fog Heen tfheen at linpro.no
Thu Jan 8 11:29:31 CET 2009


a short while before Christmas, I wrote up a small document pointing to
what I would like to get into 2.1 and when I'd like milestones to
happen.  This is a suggestion, I'm open to ideas and comments on both
feature set as well as if my guesstimates for dates is completely off:

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
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

 - 2009-01-15: New hash algorithm working
 - 2009-02-15: Web UI
 - 2009-03-15: Persistent storage
 - 2009-04-01: Feature complete
 - 2009-05-20: Release candidate
 - 2009-05-01: No release critical bugs left
 - 2009-05-10: Release

Tollef Fog Heen 
Redpill Linpro -- Changing the game!
t: +47 21 54 41 73

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