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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](https://www.stanford.edu/~riepel/lbnamed/).  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.

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 GCC 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](https://www.eyrie.org/~eagle/software/lbcd/) has the
last released version, its documentation, and pointers to any additional
resources.

## Source Repository