README - raindrops-0.17.0 Documentation

# 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 unicorn, but should support any Rack HTTP server 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 __sync builtins (_sync{add,sub}_and_fetch()):

gcc.gnu.org/onlinedocs/gcc/_005f_005fsync-Builtins.html

For non-GCC 4+ users, we also support compilation with the libatomic_ops package starting with Raindrops 0.4.0:

github.com/ivmai/libatomic_ops

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

## 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 (raindrops-public@bogomips.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:

- bogomips.org/raindrops.git

- 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 licensed under the LGPL-2.1+

## Contact¶ ↑

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

Mailing list archives are available over HTTPS and NNTP:

- bogomips.org/raindrops-public/

- nntp://news.public-inbox.org/inbox.comp.lang.ruby.raindrops