                                lbcd 3.4.2
                      (responder for load balancing)
               Maintained by Russ Allbery <eagle@eyrie.org>

  Copyright 1993-1994, 1996-1998, 2000, 2003-2009, 2012-2013 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.

WARNING

  This package is not maintained.  Although I believe it is still useful,
  I no longer use this method of DNS load balancing and am no longer
  maintaining this package.  If you would like to pick up maintenance of
  it, please feel free.  Contact me if you would like this page to
  redirect to its new home.

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

  lbcd provides a lightweight way to query a system via unauthenticated
  UDP for system load information plus some related information that may
  be relevant to determining which system to hand out.  It was designed
  for use with the lbnamed DNS load balancer [1].  System load, number of
  logged-in users, free /tmp space, and system uptime are always returned.
  lbcd can also be configured to probe various local services and modify
  the returned weights based on whether those services are reachable, or
  to return a static weight for round-robin load balancing.

  [1] https://www.stanford.edu/~riepel/lbnamed/

  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.
  However, lbcd with lbnamed works quite well for smaller scale problems,
  scales well to multiple load balance pools for different services,
  provides a simple UDP health check service, 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.

  It was originally written by Roland Schemers.  Larry Schwimmer rewrote
  it to add protocol version 3 with some additional features and service
  probing, and then I rewrote it again to update the coding style and use
  my standard portability layer.

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 and requires the
  IO::Socket::INET6 module for IPv6 support.

  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.

BUILDING AND INSTALLATION

  You can build and install lbcd with the standard commands:

      ./configure
      make
      make install

  If you are building from a Git clone, first run ./bootstrap in the
  source directory to generate the build files.  make install will
  probably have to be done as root.  Building outside of the source
  directory is also supported, if you wish, by creating an empty directory
  and then running configure with the correct relative path.

  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.

  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
  compiler warnings (requires either GCC or Clang and may require a
  relatively current version of the compiler).

  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 test suite, which you can run after building with:

      make check

  If a test fails, you can run a single test with verbose output via:

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

  Do this instead of running the test program directly since it will
  ensure that necessary environment variables are set up.

  Currently, the test suite only checks the portability and utility
  libraries, not the functionality of lbcd or lbcdclient.

  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.

SUPPORT

  This package is not currently maintained and will not get further
  releases or bug fixes.  I do not recommend using it unless you're
  willing to take over maintenance.

  The lbcd web page at:

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

  has the last released version, its documentation, and pointers to any
  additional resources.

SOURCE REPOSITORY

  lbcd was maintained using Git.  You can access the current source on
  GitHub at:

      https://github.com/rra/lbcd

  or by cloning the repository at:

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

  or view the repository via the web at:

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

LICENSE

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

    Copyright 1993-1994, 1996-1998, 2000, 2003-2009, 2012-2013
        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.

  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, and detailed information about the
  licensing of each file, are recorded in the LICENSE file.

  Files covered by a license with an assigned SPDX License Identifier
  include SPDX-License-Identifier tags to enable automated processing of
  license information.  See https://spdx.org/licenses/ for more
  information.

  For any copyright range specified by files in this package as YYYY-ZZZZ,
  the range specifies every single year in that closed interval.
