Varnish 4.0.0 released

[Lasse Karstensen]

Dear Varnish community.

It is my pleasure to announce the release of Varnish 4.0.0.

This is a major feature release with a lot of big changes from the
last version released 2.5 years ago. Some prominent examples include:

* Full support for streaming objects through from the backend on a cache miss.
Bytes will be sent to 1..n requesting clients as they come in from the backend
server.

* Background (re)fetch of expired objects. On a cache miss where a stale copy
is available, serve the client the stale copy while fetching an updated copy
from the backend in the background.

* New varnishlog query language, allowing automatic grouping of requests when
debugging ESI or a failed backend request. (among much more)

* Comprehensive request timestamp and byte counters.

* Security improvements, including disabling of run-time changes to security
sensitive parameters.

For the full detailed list of changes, see the changes.rst[1] file.
Source version of the software can be downloaded from:

    https://repo.varnish-cache.org/source/varnish-4.0.0.tar.gz

Debian and Redhat packages will be available shortly.

Existing users will need to adapt their VCL files before running Varnish 4. The
changes needed are outlined in the upgrade documentation[2].

The development team would like to thank Amedia AS and Redpill Linpro AS for
their help in testing Varnish 4.0 on production traffic. We couldn't have made
this release without it.

We're celebrating this release by having Varnish 4 release parties around the
world. See our web site[3] to find the one nearest you!

Varnish Cache is developed under the Varnish Moral License and is currently
looking for funding to continue the development. If you or your business can
help out, see Poul-Henning's VML pages[4].


1: https://www.varnish-cache.org/trac/browser/doc/changes.rst
2: https://www.varnish-cache.org/docs/trunk/whats-new/upgrading.html
3: http://v4party.varnish-cache.org/
4: http://phk.freebsd.dk/VML/

-- 
Lasse Karstensen
Varnish Cache release manager