@menu
* Buildbot Components::
* Requirements::
* Installing the code::
* Creating a buildmaster::
* Upgrading an Existing Buildmaster::
* Creating a buildslave::
* Upgrading an Existing Buildslave::
* Launching the daemons::
* Logfiles::
* Shutdown::
* Maintenance::
* Troubleshooting::
* Contrib Scripts::
@end menu

@node Buildbot Components
@section Buildbot Components

Buildbot is shipped in two components: the buildmaster (called @code{buildbot}
for legacy reasons) and the buildslave.  The buildslave component has far fewer
requirements, and is more broadly compatible than the buildmaster.  You will
need to carefully pick the environment in which to run your buildmaster, but
the buildslave should be able to run just about anywhere.

It is possible to install the buildmaster and buildslave on the same system,
although for anything but the smallest installation this arrangement will not
be very efficient.

@node Requirements
@section Requirements

@menu
* Common Requirements::
* Buildmaster Requirements::
@end menu

@node Common Requirements
@subsection Common Requirements

At a bare minimum, you'll need the following for both the buildmaster and a
buildslave:

@itemize @bullet
@item
Python: http://www.python.org

Buildbot requires python-2.4 or later.

@item
Twisted: http://twistedmatrix.com

Both the buildmaster and the buildslaves require Twisted-8.0.x or
later. As always, the most recent version is recommended.

Twisted is delivered as a collection of subpackages. You'll need at
least "Twisted" (the core package), and you'll also want TwistedMail,
TwistedWeb, and TwistedWords (for sending email, serving a web status
page, and delivering build status via IRC, respectively). You might
also want TwistedConch (for the encrypted Manhole debug port). Note
that Twisted requires ZopeInterface to be installed as well.

@end itemize

Of course, your project's build process will impose additional
requirements on the buildslaves. These hosts must have all the tools
necessary to compile and test your project's source code.

@heading Windows Support

Buildbot - both master and slave - runs well natively on Windows.  The slave
runs well on Cygwin, but because of problems with SQLite on Cygwin, the master
does not.

Buildbot's windows testing is limited to the most recent Twisted and Python
versions.  For best results, use the most recent available versions of these
libraries on Windows.

@node Buildmaster Requirements
@subsection Buildmaster Requirements

@itemize @bullet
@item
sqlite3: http://pypi.python.org/pypi/pysqlite

The sqlite3 package is required for python-2.5 and earlier (it is already
included in python-2.5 and later, but the version in python-2.5 has nasty bugs)

@item
simplejson: http://pypi.python.org/pypi/simplejson

The simplejson package is required for python-2.5 and earlier (it is already
included as json in python-2.6 and later)

@item
Jinja2: http://jinja.pocoo.org/

Buildbot requires Jinja version 2.1 or higher

Jinja2 is a general purpose templating language and is used by Buildbot
to generate the HTML output.

@end itemize

@node Installing the code
@section Installing the code

@cindex installation

Buildbot and Buildslave are installed using the standard python
@code{distutils} process. For either component, after unpacking the tarball,
the process is:

@example
python setup.py build
python setup.py install
@end example

where the install step may need to be done as root. This will put the bulk of
the code in somewhere like @code{/usr/lib/python2.3/site-packages/buildbot}. It
will also install the @code{buildbot} command-line tool in
@code{/usr/bin/buildbot}.

If the environment variable @code{$NO_INSTALL_REQS} is set to '1', then
@code{setup.py} will not try to install Buildbot's requirements.  This is
usually only useful when building a Buildbot package.

To test this, shift to a different directory (like @code{/tmp}), and run:

@example
buildbot --version
# or
buildslave --version
@end example

If it shows you the versions of Buildbot and Twisted, the install went
ok. If it says @code{no such command} or it gets an @code{ImportError}
when it tries to load the libaries, then something went wrong.
@code{pydoc buildbot} is another useful diagnostic tool.

Windows users will find these files in other places. You will need to
make sure that python can find the libraries, and will probably find
it convenient to have @code{buildbot} on your PATH.

If you wish, you can run the buildbot unit test suite like this:

@example
PYTHONPATH=. trial buildbot.test
# or
PYTHONPATH=. trial buildslave.test
@end example

Nothing should fail, a few might be skipped. If any of the tests fail, you
should stop and investigate the cause before continuing the installation
process, as it will probably be easier to track down the bug early.  This may
be a good time to contact the Buildbot developers for help.

If you cannot or do not wish to install the buildbot into a site-wide
location like @file{/usr} or @file{/usr/local}, you can also install
it into the account's home directory or any other location using a tool like @url{http://pypi.python.org/pypi/virtualenv,virtualenv}.

@node Creating a buildmaster
@section Creating a buildmaster

As you learned earlier (@pxref{System Architecture}), the buildmaster
runs on a central host (usually one that is publically visible, so
everybody can check on the status of the project), and controls all
aspects of the buildbot system. 

You will probably wish to create a separate user account for the buildmaster,
perhaps named @code{buildmaster}.  Do not run the buildmaster as root!

You also need to choose a directory for the buildmaster, called the
@code{basedir}. This directory will be owned by the buildmaster.  It will
contain configuration, the adtabase, and status information - including
logfiles.  On a large buildmaster this directory will see a lot of activity, so
it should be on a disk with adequate space and speed.

Once you've picked a basedir, use the @command{buildbot
create-master} command to create the directory and populate it with
startup files:

@example
buildbot create-master -r @var{basedir}
@end example

You will need to create a configuration file (@pxref{Configuration})
before starting the buildmaster. Most of the rest of this manual is
dedicated to explaining how to do this. A sample configuration file is
placed in the working directory, named @file{master.cfg.sample}, which
can be copied to @file{master.cfg} and edited to suit your purposes.

(Internal details: This command creates a file named
@file{buildbot.tac} that contains all the state necessary to create
the buildmaster. Twisted has a tool called @code{twistd} which can use
this .tac file to create and launch a buildmaster instance. twistd
takes care of logging and daemonization (running the program in the
background). @file{/usr/bin/buildbot} is a front end which runs twistd
for you.)

In addition to @file{buildbot.tac}, a small @file{Makefile.sample} is
installed. This can be used as the basis for customized daemon startup,
@xref{Launching the daemons}.

@heading Using MySQL

If you want to use MySQL as the database backend for your Buildbot, add the
@code{--db} option to the @code{create-master} invocation to specify the
connection string for the MySQL database (@pxref{Database Specification}).

@heading Buildmaster Options

This section lists options to the @command{create-master} command.
You can also type @command{buildslave create-slave --help} for an up-to-the-moment summary.

@table @code

@item --force
With this option, @command{create-master} will re-use an existing master
directory.

@item --no-logrotate
This disables internal buildslave log management mechanism. With this option
buildslave does not override the default logfile name and its behaviour giving
a possibility to control those with command-line options of twistd daemon.

@item --relocatable
This creates a "relocatable" buildbot.tac, which uses relative paths instead
of absolute paths, so that the buildmaster directory can be moved about.

@item --config
The name of the configuration file to use.  This configuration file need not
reside in the buildmaster directory.

@item --log-size
This is the size in bytes when to rotate the Twisted log files.  The default is
10MiB.

@item --log-count
This is the number of log rotations to keep around. You can either
specify a number or @code{None} to keep all @file{twistd.log} files
around.  The default is 10.

@item --db
The database that the Buildmaster should use.  This information is needed
earlier than the configuration file can be loaded.

@end table


@node Upgrading an Existing Buildmaster
@section Upgrading an Existing Buildmaster

If you have just installed a new version of the Buildbot code, and you
have buildmasters that were created using an older version, you'll
need to upgrade these buildmasters before you can use them. The
upgrade process adds and modifies files in the buildmaster's base
directory to make it compatible with the new code.

@example
buildbot upgrade-master @var{basedir}
@end example

This command will also scan your @file{master.cfg} file for
incompatibilities (by loading it and printing any errors or deprecation
warnings that occur). Each buildbot release tries to be compatible
with configurations that worked cleanly (i.e. without deprecation
warnings) on the previous release: any functions or classes that are
to be removed will first be deprecated in a release, to give you a
chance to start using the replacement.

The @code{upgrade-master} command is idempotent. It is safe to run it
multiple times. After each upgrade of the buildbot code, you should
use @code{upgrade-master} on all your buildmasters.

In general, Buildbot slaves and masters can be upgraded independently, although
some new features will not be available, depending on the master and slave
versions.

@heading Version-specific Notes

@menu
* Upgrading a Buildmaster to Buildbot-0.7.6::
* Upgrading a Buildmaster to Buildbot-0.8.0::
@end menu

@node Upgrading a Buildmaster to Buildbot-0.7.6
@subsection Upgrading a Buildmaster to Buildbot-0.7.6

The 0.7.6 release introduced the @file{public_html/} directory, which
contains @file{index.html} and other files served by the
@code{WebStatus} and @code{Waterfall} status displays. The
@code{upgrade-master} command will create these files if they do not
already exist. It will not modify existing copies, but it will write a
new copy in e.g. @file{index.html.new} if the new version differs from
the version that already exists.

@node Upgrading a Buildmaster to Buildbot-0.8.0
@subsection Upgrading a Buildmaster to Buildbot-0.8.0

Buildbot-0.8.0 introduces a database backend, which is SQLite by default.  The
@code{upgrade-master} command will automatically create and populate this
database with the changes the buildmaster has seen.  Note that, as of this
release, build history is @i{not} contained in the database, and is thus not
migrated.

The upgrade process renames the Changes pickle (@code{$basedir/changes.pck}) to
@code{changes.pck.old} once the upgrade is complete.  To reverse the upgrade,
simply downgrade Buildbot and move this file back to its original name.  You
may also wish to delete the state database (@code{state.sqlite}).

@heading Change Encoding Issues

The upgrade process assumes that strings in your Changes pickle are encoded in
UTF-8 (or plain ASCII).  If this is not the case, and if there are non-UTF-8
characters in the pickle, the upgrade will fail with a suitable error message.
If this occurs, you have two options.  If the change history is not important
to your purpose, you can simply delete @code{changes.pck}.

If you would like to keep the change history, then you will need to figure out
which encoding is in use, and use @code{contrib/fix_changes_pickle_encoding.py}
(@pxref{Contrib Scripts}) to rewrite the changes pickle into Unicode before
upgrading the master.  A typical invocation (with Mac-Roman encoding) might
look like:

@example
$ python $buildbot/contrib/fix_changes_pickle_encoding.py changes.pck macroman
decoding bytestrings in changes.pck using macroman
converted 11392 strings
backing up changes.pck to changes.pck.old
@end example

If your Changes pickle uses multiple encodings, you're on your own, but the
script in contrib may provide a good starting point for the fix.

@node Creating a buildslave
@section Creating a buildslave

Typically, you will be adding a buildslave to an existing buildmaster,
to provide additional architecture coverage. The buildbot
administrator will give you several pieces of information necessary to
connect to the buildmaster. You should also be somewhat familiar with
the project being tested, so you can troubleshoot build problems
locally.

The buildbot exists to make sure that the project's stated ``how to
build it'' process actually works. To this end, the buildslave should
run in an environment just like that of your regular developers.
Typically the project build process is documented somewhere
(@file{README}, @file{INSTALL}, etc), in a document that should
mention all library dependencies and contain a basic set of build
instructions. This document will be useful as you configure the host
and account in which the buildslave runs.

Here's a good checklist for setting up a buildslave:

@enumerate
@item
Set up the account

It is recommended (although not mandatory) to set up a separate user
account for the buildslave. This account is frequently named
@code{buildbot} or @code{buildslave}. This serves to isolate your
personal working environment from that of the slave's, and helps to
minimize the security threat posed by letting possibly-unknown
contributors run arbitrary code on your system. The account should
have a minimum of fancy init scripts.

@item
Install the buildbot code

Follow the instructions given earlier (@pxref{Installing the code}).
If you use a separate buildslave account, and you didn't install the
buildbot code to a shared location, then you will need to install it
with @code{--home=~} for each account that needs it.

@item
Set up the host

Make sure the host can actually reach the buildmaster. Usually the
buildmaster is running a status webserver on the same machine, so
simply point your web browser at it and see if you can get there.
Install whatever additional packages or libraries the project's
INSTALL document advises. (or not: if your buildslave is supposed to
make sure that building without optional libraries still works, then
don't install those libraries).

Again, these libraries don't necessarily have to be installed to a
site-wide shared location, but they must be available to your build
process. Accomplishing this is usually very specific to the build
process, so installing them to @file{/usr} or @file{/usr/local} is
usually the best approach.

@item
Test the build process

Follow the instructions in the INSTALL document, in the buildslave's
account. Perform a full CVS (or whatever) checkout, configure, make,
run tests, etc. Confirm that the build works without manual fussing.
If it doesn't work when you do it by hand, it will be unlikely to work
when the buildbot attempts to do it in an automated fashion.

@item
Choose a base directory

This should be somewhere in the buildslave's account, typically named
after the project which is being tested. The buildslave will not touch
any file outside of this directory. Something like @file{~/Buildbot}
or @file{~/Buildslaves/fooproject} is appropriate.

@item
Get the buildmaster host/port, botname, and password

When the buildbot admin configures the buildmaster to accept and use
your buildslave, they will provide you with the following pieces of
information:

@itemize @bullet
@item
your buildslave's name
@item
the password assigned to your buildslave
@item
the hostname and port number of the buildmaster, i.e. buildbot.example.org:8007
@end itemize

@item
Create the buildslave

Now run the 'buildslave' command as follows:

@example
buildslave create-slave @var{BASEDIR} @var{MASTERHOST}:@var{PORT} @var{SLAVENAME} @var{PASSWORD}
@end example

This will create the base directory and a collection of files inside,
including the @file{buildbot.tac} file that contains all the
information you passed to the @code{buildbot} command.

@item
Fill in the hostinfo files

When it first connects, the buildslave will send a few files up to the
buildmaster which describe the host that it is running on. These files
are presented on the web status display so that developers have more
information to reproduce any test failures that are witnessed by the
buildbot. There are sample files in the @file{info} subdirectory of
the buildbot's base directory. You should edit these to correctly
describe you and your host.

@file{BASEDIR/info/admin} should contain your name and email address.
This is the ``buildslave admin address'', and will be visible from the
build status page (so you may wish to munge it a bit if
address-harvesting spambots are a concern).

@file{BASEDIR/info/host} should be filled with a brief description of
the host: OS, version, memory size, CPU speed, versions of relevant
libraries installed, and finally the version of the buildbot code
which is running the buildslave.

The optional @file{BASEDIR/info/access_uri} can specify a URI which will
connect a user to the machine.  Many systems accept @code{ssh://hostname} URIs
for this purpose.

If you run many buildslaves, you may want to create a single
@file{~buildslave/info} file and share it among all the buildslaves
with symlinks.

@end enumerate

@menu
* Buildslave Options::
* Other Buildslave Configuration::
@end menu

@node Buildslave Options
@subsection Buildslave Options

There are a handful of options you might want to use when creating the
buildslave with the @command{buildslave create-slave <options> DIR <params>}
command. You can type @command{buildslave create-slave --help} for a summary.
To use these, just include them on the @command{buildslave create-slave}
command line, like this:

@example
buildslave create-slave --umask=022 ~/buildslave buildmaster.example.org:42012 myslavename mypasswd
@end example

@table @code
@item --no-logrotate
This disables internal buildslave log management mechanism. With this option
buildslave does not override the default logfile name and its behaviour giving
a possibility to control those with command-line options of twistd daemon.

@item --usepty
This is a boolean flag that tells the buildslave whether to launch child
processes in a PTY or with regular pipes (the default) when the master does not
specify.  This option is deprecated, as this particular parameter is better
specified on the master.

@item --umask
This is a string (generally an octal representation of an integer)
which will cause the buildslave process' ``umask'' value to be set
shortly after initialization. The ``twistd'' daemonization utility
forces the umask to 077 at startup (which means that all files created
by the buildslave or its child processes will be unreadable by any
user other than the buildslave account). If you want build products to
be readable by other accounts, you can add @code{--umask=022} to tell
the buildslave to fix the umask after twistd clobbers it. If you want
build products to be @emph{writable} by other accounts too, use
@code{--umask=000}, but this is likely to be a security problem.

@item --keepalive
This is a number that indicates how frequently ``keepalive'' messages
should be sent from the buildslave to the buildmaster, expressed in
seconds. The default (600) causes a message to be sent to the
buildmaster at least once every 10 minutes. To set this to a lower
value, use e.g. @code{--keepalive=120}.

If the buildslave is behind a NAT box or stateful firewall, these
messages may help to keep the connection alive: some NAT boxes tend to
forget about a connection if it has not been used in a while. When
this happens, the buildmaster will think that the buildslave has
disappeared, and builds will time out. Meanwhile the buildslave will
not realize than anything is wrong.

@item --maxdelay
This is a number that indicates the maximum amount of time the
buildslave will wait between connection attempts, expressed in
seconds. The default (300) causes the buildslave to wait at most 5
minutes before trying to connect to the buildmaster again.

@item --log-size
This is the size in bytes when to rotate the Twisted log files.  The default is
10MiB.

@item --log-count
This is the number of log rotations to keep around. You can either
specify a number or @code{None} to keep all @file{twistd.log} files
around.  The default is 10.

@end table

@node Other Buildslave Configuration
@subsection Other Buildslave Configuration

@table @code

@item unicode_encoding
This represents the encoding that buildbot should use when converting unicode
commandline arguments into byte strings in order to pass to the operating
system when spawning new processes.

The default value is what python's sys.getfilesystemencoding() returns, which
on Windows is 'mbcs', on Mac OSX is 'utf-8', and on Unix depends on your locale
settings.

If you need a different encoding, this can be changed in your build slave's
buildbot.tac file by adding a unicode_encoding argument to BuildSlave:

@item allow_shutdown
allow_shutdown can be passed to the BuildSlave constructor in buildbot.tac.

Setting allow_shutdown to 'file' will cause the buildslave to watch
'shutdown.stamp' in basedir for updates to its mtime.  The file does not need
to exist prior to starting the slave.

Setting allow_shutdown to 'signal' will set up a SIGHUP handler to start a
graceful shutdown.

The default value is None, in which case this feature will be disabled.

Both master and slave must be at least version 0.8.3 for this feature to work.

@example
s = BuildSlave(buildmaster_host, port, slavename, passwd, basedir,
               keepalive, usepty, umask=umask, maxdelay=maxdelay,
               unicode_encoding='utf-8', allow_shutdown='signal')
@end example

@end table

@node Upgrading an Existing Buildslave
@section Upgrading an Existing Buildslave

If you have just installed a new version of Buildbot-slave, you may need to
take some steps to upgrade it.  If you are upgrading to version 0.8.2 or later,
you can run

@example
buildslave upgrade-slave /path/to/buildslave/dir
@end example

@heading Version-specific Notes

@menu
* Upgrading a Buildslave to Buildbot-slave-0.8.1::
@end menu

@node Upgrading a Buildslave to Buildbot-slave-0.8.1
@subsection Upgrading a Buildslave to Buildbot-slave-0.8.1

Before Buildbot version 0.8.1, the Buildbot master and slave were part of the
same distribution.  As of version 0.8.1, the buildslave is a separate
distribution.

As of this release, you will need to install @i{buildbot-slave} to run a slave.

Any automatic startup scripts that had run @code{buildbot start} for previous versions
should be changed to run @code{buildslave start} instead.

If you are running a version later than 0.8.1, then you can skip the remainder
of this section: the @code{upgrade-slave} command will take care of this.  If
you are upgrading directly to 0.8.1, read on.

The existing @code{buildbot.tac} for any buildslaves running older versions
will need to be edited or replaced.  If the loss of cached buildslave state
(e.g., for Source steps in copy mode) is not problematic, the easiest solution
is to simply delete the slave directory and re-run @code{buildslave
create-slave}.

If deleting the slave directory is problematic, the change to
@code{buildbot.tac} is simple.  On line 3, replace

@example
from buildbot.slave.bot import BuildSlave
@end example

with

@example
from buildslave.bot import BuildSlave
@end example

After this change, the buildslave should start as usual.

@node Launching the daemons
@section Launching the daemons

Both the buildmaster and the buildslave run as daemon programs. To
launch them, pass the working directory to the @code{buildbot}
and @code{buildslave} commands, as appropriate:

@example
# start a master
buildbot start @var{BASEDIR}
# start a slave
buildslave start @var{SLAVE_BASEDIR}
@end example

The @var{BASEDIR} is option and can be omitted if the current directory
contains the buildbot configuration (the @file{buildbot.tac} file).

@example
buildbot start
@end example

This command will start the daemon and then return, so normally it
will not produce any output. To verify that the programs are indeed
running, look for a pair of files named @file{twistd.log} and
@file{twistd.pid} that should be created in the working directory.
@file{twistd.pid} contains the process ID of the newly-spawned daemon.

When the buildslave connects to the buildmaster, new directories will
start appearing in its base directory. The buildmaster tells the slave
to create a directory for each Builder which will be using that slave.
All build operations are performed within these directories: CVS
checkouts, compiles, and tests.

Once you get everything running, you will want to arrange for the
buildbot daemons to be started at boot time. One way is to use
@code{cron}, by putting them in a @@reboot crontab entry@footnote{this
@@reboot syntax is understood by Vixie cron, which is the flavor
usually provided with linux systems. Other unices may have a cron that
doesn't understand @@reboot}:

@example
@@reboot buildbot start @var{BASEDIR}
@end example

When you run @command{crontab} to set this up, remember to do it as
the buildmaster or buildslave account! If you add this to your crontab
when running as your regular account (or worse yet, root), then the
daemon will run as the wrong user, quite possibly as one with more
authority than you intended to provide.

It is important to remember that the environment provided to cron jobs
and init scripts can be quite different that your normal runtime.
There may be fewer environment variables specified, and the PATH may
be shorter than usual. It is a good idea to test out this method of
launching the buildslave by using a cron job with a time in the near
future, with the same command, and then check @file{twistd.log} to
make sure the slave actually started correctly. Common problems here
are for @file{/usr/local} or @file{~/bin} to not be on your
@code{PATH}, or for @code{PYTHONPATH} to not be set correctly.
Sometimes @code{HOME} is messed up too.

Some distributions may include conveniences to make starting buildbot
at boot time easy.  For instance, with the default buildbot package in
Debian-based distributions, you may only need to modify
@code{/etc/default/buildbot} (see also @code{/etc/init.d/buildbot}, which
reads the configuration in @code{/etc/default/buildbot}).

Buildbot also comes with its own init scripts that provide support for
controlling multi-slave and multi-master setups (mostly because they are based
on the init script from the debian package).  With a little modification these
scripts can be used both on debian and rhel based distributions and may thus
prove helpful to package maintainers who are working on buildbot (or those that
haven't yet split buildbot into master and slave packages). 

@example
# install as /etc/default|sysconfig/buildslave
master/contrib/init-scripts/buildslave.default 

# install /etc/default|sysconfig/buildslave
master/contrib/init-scripts/buildmaster.default 

# install as /etc/init.d/buildslave
slave/contrib/init-scripts/buildslave.init.sh

# install as /etc/init.d/buildmaster
slave/contrib/init-scripts/buildmaster.init.sh

# ... and tell sysvinit about them 
chkconfig buildmaster reset
# ... or
update-rc.d buildmaster defaults
@end example

@node Logfiles
@section Logfiles

@cindex logfiles

While a buildbot daemon runs, it emits text to a logfile, named
@file{twistd.log}. A command like @code{tail -f twistd.log} is useful
to watch the command output as it runs.

The buildmaster will announce any errors with its configuration file
in the logfile, so it is a good idea to look at the log at startup
time to check for any problems. Most buildmaster activities will cause
lines to be added to the log.

@node Shutdown
@section Shutdown

To stop a buildmaster or buildslave manually, use:

@example
buildbot stop @var{BASEDIR}
# or
buildslave stop @var{SLAVE_BASEDIR}
@end example

This simply looks for the @file{twistd.pid} file and kills whatever
process is identified within.

At system shutdown, all processes are sent a @code{SIGKILL}. The
buildmaster and buildslave will respond to this by shutting down
normally.

The buildmaster will respond to a @code{SIGHUP} by re-reading its
config file. Of course, this only works on unix-like systems with
signal support, and won't work on Windows. The following shortcut is
available:

@example
buildbot reconfig @var{BASEDIR}
@end example

When you update the Buildbot code to a new release, you will need to
restart the buildmaster and/or buildslave before it can take advantage
of the new code. You can do a @code{buildbot stop @var{BASEDIR}} and
@code{buildbot start @var{BASEDIR}} in quick succession, or you can
use the @code{restart} shortcut, which does both steps for you:

@example
buildbot restart @var{BASEDIR}
@end example

Buildslaves can similarly be restarted with:

@example
buildslave restart @var{BASEDIR}
@end example

There are certain configuration changes that are not handled cleanly
by @code{buildbot reconfig}. If this occurs, @code{buildbot restart}
is a more robust tool to fully switch over to the new configuration.

@code{buildbot restart} may also be used to start a stopped Buildbot
instance. This behaviour is useful when writing scripts that stop, start
and restart Buildbot.

A buildslave may also be gracefully shutdown from the
@pxref{WebStatus} status plugin. This is useful to shutdown a
buildslave without interrupting any current builds. The buildmaster
will wait until the buildslave is finished all its current builds, and
will then tell the buildslave to shutdown.

@node Maintenance
@section Maintenance

The buildmaster can be configured to send out email notifications when a
slave has been offline for a while.  Be sure to configure the buildmaster
with a contact email address for each slave so these notifications are sent
to someone who can bring it back online.

If you find you can no longer provide a buildslave to the project, please
let the project admins know, so they can put out a call for a
replacement.

The Buildbot records status and logs output continually, each time a
build is performed. The status tends to be small, but the build logs
can become quite large. Each build and log are recorded in a separate
file, arranged hierarchically under the buildmaster's base directory.
To prevent these files from growing without bound, you should
periodically delete old build logs. A simple cron job to delete
anything older than, say, two weeks should do the job. The only trick
is to leave the @file{buildbot.tac} and other support files alone, for
which find's @code{-mindepth} argument helps skip everything in the
top directory. You can use something like the following:

@example
@@weekly cd BASEDIR && find . -mindepth 2 i-path './public_html/*' -prune -o -type f -mtime +14 -exec rm @{@} \;
@@weekly cd BASEDIR && find twistd.log* -mtime +14 -exec rm @{@} \;
@end example

Alternatively, you can configure a maximum number of old logs to be kept
using the @code{--log-count} command line option when running @code{buildbot
create-slave} or @code{buildbot create-master}.

@node Troubleshooting
@section Troubleshooting

Here are a few hints on diagnosing common problems.

@menu
* Starting the buildslave::
* Connecting to the buildmaster::
@end menu

@node Starting the buildslave
@subsection Starting the buildslave

Cron jobs are typically run with a minimal shell (@file{/bin/sh}, not
@file{/bin/bash}), and tilde expansion is not always performed in such
commands. You may want to use explicit paths, because the @code{PATH}
is usually quite short and doesn't include anything set by your
shell's startup scripts (@file{.profile}, @file{.bashrc}, etc). If
you've installed buildbot (or other python libraries) to an unusual
location, you may need to add a @code{PYTHONPATH} specification (note
that python will do tilde-expansion on @code{PYTHONPATH} elements by
itself). Sometimes it is safer to fully-specify everything:

@example
@@reboot PYTHONPATH=~/lib/python /usr/local/bin/buildbot start /usr/home/buildbot/basedir
@end example

Take the time to get the @@reboot job set up. Otherwise, things will work
fine for a while, but the first power outage or system reboot you have will
stop the buildslave with nothing but the cries of sorrowful developers to
remind you that it has gone away.

@node Connecting to the buildmaster
@subsection Connecting to the buildmaster

If the buildslave cannot connect to the buildmaster, the reason should
be described in the @file{twistd.log} logfile. Some common problems
are an incorrect master hostname or port number, or a mistyped bot
name or password. If the buildslave loses the connection to the
master, it is supposed to attempt to reconnect with an
exponentially-increasing backoff. Each attempt (and the time of the
next attempt) will be logged. If you get impatient, just manually stop
and re-start the buildslave.

When the buildmaster is restarted, all slaves will be disconnected, and will
attempt to reconnect as usual. The reconnect time will depend upon how long the
buildmaster is offline (i.e. how far up the exponential backoff curve the
slaves have travelled). Again, @code{buildslave restart @var{BASEDIR}} will
speed up the process.

@node Contrib Scripts
@section Contrib Scripts

While some features of Buildbot are included in the distribution, others are
only available in @code{contrib/} in the source directory.  The latest versions
of such scripts are available at
@url{http://github.com/buildbot/buildbot/tree/master/master/contrib}.
