Jeff Anderson wrote:
I'd like to see individual object request statistics and a method to
prefetch objects from the backend that are most frequently requested.
Perhaps also a way to prioritize objects into cache tiers based on
frequency of requests. So, for example, highly requested objects are
maintained in RAM and less frequently requested objects are cached to
disk.
Your operating system already does this today with Varnish. Squid tries
to maintain a two tier cache hierarchy without success.
If persistent storage is on its way maybe a method to assign
priority to large disk cache volumes versus memory regions.
Noted.
It might be nice to have a distributed and/or tiered cache model where a
single
master has a very large cache and potentially very long grace ability
where objects can exist even if stale. That master in turn could host
frontend caches that communicate efficiently to the master cache and
also have a tiered internal object priority.
I believe most of this can be achieved today. Stale objects will
hopefully reach the 2.0 series before the 2.1 revolutions - at least as
a patch, I hope.
Thanks,
--Jeff
On Jan 8, 2009, at 2:29 AM, Tollef Fog Heen wrote:
Hi,
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
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
- 2009-05-10: Release
--
Tollef Fog Heen
Redpill Linpro -- Changing the game!
t: +47 21 54 41 73
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--Jeff
j...@funnyordie.com
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Per Buer - Leder Infrastruktur og Drift - Redpill Linpro
Telefon: 21 54 41 21 - Mobil: 958 39 117
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