= raindrops - real-time stats for preforking Rack servers

Raindrops is a real-time stats toolkit to show statistics for Rack HTTP
servers.  It is designed for preforking servers such as Rainbows! and
Unicorn, but should support any Rack HTTP server under Ruby 2.0, 1.9,
1.8 and Rubinius on platforms supporting POSIX shared memory.  It may
also be used as a generic scoreboard for sharing atomic counters across
multiple processes.

== Features

* counters are shared across all forked children and lock-free

* counters are kept on separate cache lines to reduce contention under SMP

* may expose server statistics as a Rack Middleware endpoint
  (default: "/_raindrops")

* middleware displays the number of actively processing and writing
  clients from a single request regardless of which worker process
  it hits.

== Linux-only Extra Features!

* Middleware response includes extra stats for bound TCP and
  Unix domain sockets (configurable, it can include stats from
  other TCP or UNIX domain socket servers).

* TCP socket stats use efficient inet_diag facilities via netlink
  instead of parsing /proc/net/tcp to minimize overhead.
  This was fun to discover and write.

* TCP_Info reporting may be used to check stat for every accepted client
  on TCP servers

Users of older Linux kernels need to ensure that the the "inet_diag"
and "tcp_diag" kernel modules are loaded as they do not autoload correctly

== Install

We recommend GCC 4+ (or compatible) to support the
{atomic builtins}[http://gcc.gnu.org/onlinedocs/gcc/Atomic-Builtins.html]
(__sync_{add,sub}_and_fetch()).  For non-GCC 4+ users, we also support
compilation with the
{libatomic_ops}[http://www.hpl.hp.com/research/linux/atomic_ops/]
package starting with Raindrops 0.4.0.

If you're using a packaged Ruby distribution, make sure you have a C
compiler and the matching Ruby development libraries and headers.

If you use RubyGems:

    gem install raindrops

Otherwise grab the latest tarball from:

http://raindrops.bogomips.org/files/

Unpack it, and run "ruby setup.rb"

== Usage

See Raindrops::Middleware and Raindrops::LastDataRecv documentation for
use Rack servers.  The entire library is fully-documented and we are
responsive on the mailing list (mailto:raindrops@librelist.org) if you
have any questions or comments.

== Development

You can get the latest source via git from the following locations:

  git://bogomips.org/raindrops.git
  git://repo.or.cz/raindrops.git (mirror)

You may browse the code from the web and download the latest snapshot
tarballs here:

* http://bogomips.org/raindrops.git (cgit)
* http://repo.or.cz/w/raindrops.git (gitweb)

Inline patches (from "git format-patch") to the mailing list are
preferred because they allow code review and comments in the reply to
the patch.

We will adhere to mostly the same conventions for patch submissions as
git itself.  See the Documentation/SubmittingPatches document
distributed with git on on patch submission guidelines to follow.  Just
don't email the git mailing list or maintainer with raindrops patches.

raindrops is currently dual-licensed under the LGPLv2.1 and LGPLv3.  To
allow for a transition to future versions of the LGPL, contributors are
required to sign-off changes allowing allowing the project leader to
relicense raindrops under newer versions of the LGPL (which should be
similar in spirit to the existing LGPL).

== Contact

All feedback (bug reports, user/development discussion, patches, pull
requests) go to the mailing list: mailto:raindrops@librelist.org

The mailing list is mirrored to Gmane, all information about the
group is here:

http://gmane.org/info.php?group=gmane.comp.lang.ruby.raindrops.general

Mailing list archives in mbox format may be downloaded here:

http://raindrops.bogomips.org/archives/
