                            lbcd version 3.5.2
                      (responder for load balancing)
               Maintained by Russ Allbery <eagle@eyrie.org>

  Copyright 1993, 1994, 1996, 1997, 1998, 2000, 2003, 2004, 2005, 2006,
  2007, 2008, 2009, 2012, 2013, 2014 The Board of Trustees of the Leland
  Stanford Junior University.  This software is distributed under a
  BSD-style license.  Please see the section LICENSE below for more
  information.

BLURB

  lbcd is a daemon that runs on a UNIX system and answers UDP queries with
  information about system load, number of logged-on users, uptime, and
  free /tmp space.  This information can be used to accumulate system
  status across a cluster with light-weight queries or can be used as
  input to a load-balancing system to choose the best system to which to
  direct new incoming connections.

DESCRIPTION

  The lbcd daemon runs on a UNIX system and answers UDP queries (by
  default on port 4330) with information about system load, number of
  logged on users, uptime, and free /tmp space.  This information can be
  used to accumulate system status across a cluster with light-weight
  queries or can be used as input to a load-balancing system to choose
  the best system to which to direct new incoming connections.  It was
  designed for use with the lbnamed DNS load balancer, available at:

      <http://www.stanford.edu/~riepel/lbnamed/>

  It was originally written by Roland Schemers, was rewritten by Larry
  Schwimmer to add protocol version 3 with some additional features and
  service probing, and is currently maintained by Russ Allbery.

  The information provided isn't particularly sophisticated, and a good
  hardware load balancer will be able to consider such things as
  connection latency and responsiveness to make better decisions, but lbcd
  with lbnamed works quite well for smaller scale problems, scales well to
  multiple load balance pools for different services, and is much simpler
  and cheaper to understand and deploy.

  Included in this package is a small client program, lbcdclient, which
  can query an lbcd server and display a formatted version of the returned
  information.

REQUIREMENTS

  lbcd is written in C, so you'll need a C compiler.  It also uses kernel
  calls to obtain load and uptime information, and at present has only
  been ported to Linux, Solaris, AIX, various BSD systems, Mac OS X,
  HP-UX, IRIX, and Tru64.  It is currently primarily tested on Linux.
  Platforms not listed may require some porting effort, as may old or
  unusual platforms that aren't regularly tested.

  The lbcdclient program requires Perl 5.6 or later.  For IPv6 support, it
  requires the IO::Socket::INET6 module.  It will fall back on only using
  IPv4 if that module is not available.

  To run the full test suite, Perl 5.6.2 or later is required.  The
  following additional Perl modules will be used if present:

      Test::MinimumVersion
      Test::Perl::Critic
      Test::Pod
      Test::Spelling
      Test::Strict

  All are available on CPAN.  Those tests will be skipped if the modules
  are not available.

  To enable tests that don't detect functionality problems but are used to
  sanity-check the release, set the environment variable RELEASE_TESTING
  to a true value.  To enable tests that may be sensitive to the local
  environment or that produce a lot of false positives without uncovering
  many problems, set the environment variable AUTHOR_TESTING to a true
  value.

  To bootstrap from a Git checkout, or if you change the Automake files
  and need to regenerate Makefile.in, you will need Automake 1.11 or
  later.  For bootstrap or if you change configure.ac or any of the m4
  files it includes and need to regenerate configure or config.h.in, you
  will need Autoconf 2.64 or later.

INSTALLATION

  You can build and install remctl with the standard commands:

      ./configure
      make
      make install

  Pass --enable-silent-rules to configure for a quieter build (similar to
  the Linux kernel).  Use make warnings instead of make to build with full
  GCC compiler warnings (requires a relatively current version of GCC).

  The last step will probably have to be done as root.  By default, remctl
  installs itself under /usr/local; you can change that path by passing
  the --prefix=PATH argument to configure.

  lbcd looks for $sysconfdir/nolbcd and returns the maximum load if that
  file is present, allowing one to effectively drop a system out of a
  load-balanced pool by touching that file.  By default, the path is
  /usr/local/etc/nolbcd, but you may want to pass --sysconfdir=/etc to
  configure to use /etc/nolbcd.

  lbcdclient is written in Perl, so you may have to edit the first line of
  the script to point to the correct Perl location on your system.  It
  does not use any sophisticated Perl features or add-on modules.

  You will generally want to start lbcd at system boot.  All that is
  needed is a simple init script to start lbcd with the appropriate
  options or kill it again.  It writes its PID into /var/run/lbcd.pid by
  default (and this can be changed with the -P option).  On many systems,
  lbcd will need to run as root or as a member of particular groups to
  obtain system load average and uptime information.

TESTING

  lbcd comes with a rudimentary test suite, which you can run after
  building lbcd with:

      make check

  If a test case fails, please run the that individual test case with
  verbose output using:

      tests/runtests -o <name-of-test>

  and send me the output when reporting the problem.  Currently, the test
  suite only checks the portability and utility libraries; tests for lbcd
  and lbcdclient are coming in later releases.

SUPPORT

  The lbcd web page at:

      http://www.eyrie.org/~eagle/software/lbcd/

  will always have the current version of this package, the current
  documentation, and pointers to any additional resources.

  New lbcd releases are announced on the low-volume lbnamed-users mailing
  list.  To subscribe or see the list archives, go to:

      https://mailman.stanford.edu/mailman/listinfo/lbnamed-users

  I welcome bug reports and patches for this package at eagle@eyrie.org.
  However, please be aware that I tend to be extremely busy and work
  projects often take priority.  I'll save your mail and get to it as soon
  as I can, but it may take me a couple of months.

SOURCE REPOSITORY

  lbcd is maintained using Git.  You can access the current source by
  cloning the repository at:

      git://git.eyrie.org/system/lbcd.git

  or view the repository via the web at:

      http://git.eyrie.org/?p=system/lbcd.git

  When contributing modifications, patches (possibly generated by
  git-format-patch) are preferred to Git pull requests.

LICENSE

  The lbcd package as a whole is covered by the following copyright
  statement and license:

    Copyright 1993, 1994, 1996, 1997, 1998, 2000, 2003, 2004, 2005, 2006,
        2007, 2008, 2009, 2012, 2013, 2014 The Board of Trustees of the
        Leland Stanford Junior University

    Permission is hereby granted, free of charge, to any person obtaining
    a copy of this software and associated documentation files (the
    "Software"), to deal in the Software without restriction, including
    without limitation the rights to use, copy, modify, merge, publish,
    distribute, sublicense, and/or sell copies of the Software, and to
    permit persons to whom the Software is furnished to do so, subject to
    the following conditions:

    The above copyright notice and this permission notice shall be
    included in all copies or substantial portions of the Software.

    THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND,
    EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF
    MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT.
    IN NO EVENT SHALL THE AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY
    CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER IN AN ACTION OF CONTRACT,
    TORT OR OTHERWISE, ARISING FROM, OUT OF OR IN CONNECTION WITH THE
    SOFTWARE OR THE USE OR OTHER DEALINGS IN THE SOFTWARE.

  All individual files without an explicit exception below are released
  under this license.  Some files may have additional copyright holders as
  noted in those files.  There is detailed information about the licensing
  of each file in the LICENSE file in this distribution.

  Some files in this distribution are individually released under
  different licenses, all of which are compatible with the above general
  package license but which may require preservation of additional
  notices.  All required notices are preserved in the LICENSE file.
