Configuring Buildbot¶
The buildbot's behavior is defined by the config file, which
normally lives in the master.cfg
file in the buildmaster's base
directory (but this can be changed with an option to the
buildbot create-master command). This file completely specifies
which Builder
s are to be run, which slaves they should use, how
Change
s should be tracked, and where the status information is to be
sent. The buildmaster's buildbot.tac
file names the base
directory; everything else comes from the config file.
A sample config file was installed for you when you created the buildmaster, but you will need to edit it before your buildbot will do anything useful.
This chapter gives an overview of the format of this file and the various sections in it. You will need to read the later chapters to understand how to fill in each section properly.
Config File Format¶
The config file is, fundamentally, just a piece of Python code which
defines a dictionary named BuildmasterConfig
, with a number of
keys that are treated specially. You don't need to know Python to do
basic configuration, though, you can just copy the syntax of the
sample file. If you are comfortable writing Python code,
however, you can use all the power of a full programming language to
achieve more complicated configurations.
The BuildmasterConfig
name is the only one which matters: all
other names defined during the execution of the file are discarded.
When parsing the config file, the Buildmaster generally compares the
old configuration with the new one and performs the minimum set of
actions necessary to bring the buildbot up to date: Builder
s which are
not changed are left untouched, and Builder
s which are modified get to
keep their old event history.
The beginning of the master.cfg
file
typically starts with something like:
BuildmasterConfig = c = {}
Therefore a config key like change_source
will usually appear in
master.cfg
as c['change_source']
.
See Buildmaster Configuration Index for a full list of BuildMasterConfig
keys.
Basic Python Syntax¶
The master configuration file is interpreted as Python, allowing the full flexibility of the language. For the configurations described in this section, a detailed knowledge of Python is not required, but the basic syntax is easily described.
Python comments start with a hash character #
, tuples are defined with
(parenthesis, pairs)
, and lists (arrays) are defined with [square,
brackets]
. Tuples and lists are mostly interchangeable. Dictionaries (data
structures which map keys to values) are defined with curly braces:
{'key1': value1, 'key2': value2}
. Function calls (and object
instantiation) can use named parameters, like w =
html.Waterfall(http_port=8010)
.
The config file starts with a series of import
statements, which make
various kinds of Step
s and Status
targets available for
later use. The main BuildmasterConfig
dictionary is created, then it is
populated with a variety of keys, described section-by-section in subsequent
chapters.
Predefined Config File Symbols¶
The following symbols are automatically available for use in the configuration file.
basedir
the base directory for the buildmaster. This string has not been expanded, so it may start with a tilde. It needs to be expanded before use. The config file is located in
os.path.expanduser(os.path.join(basedir, 'master.cfg'))
__file__
- the absolute path of the config file. The config file's directory is located in
os.path.dirname(__file__)
.
Testing the Config File¶
To verify that the config file is well-formed and contains no deprecated or
invalid elements, use the checkconfig
command, passing it either a master
directory or a config file.
% buildbot checkconfig master.cfg
Config file is good!
# or
% buildbot checkconfig /tmp/masterdir
Config file is good!
If the config file has deprecated features (perhaps because you've upgraded the buildmaster and need to update the config file to match), they will be announced by checkconfig. In this case, the config file will work, but you should really remove the deprecated items and use the recommended replacements instead:
% buildbot checkconfig master.cfg
/usr/lib/python2.4/site-packages/buildbot/master.py:559: DeprecationWarning: c['sources'] is
deprecated as of 0.7.6 and will be removed by 0.8.0 . Please use c['change_source'] instead.
Config file is good!
If you have errors in your configuration file, checkconfig will let you know:
% buildbot checkconfig master.cfg
Configuration Errors:
c['slaves'] must be a list of BuildSlave instances
no slaves are configured
builder 'smoketest' uses unknown slaves 'linux-002'
If the config file is simply broken, that will be caught too:
% buildbot checkconfig master.cfg
error while parsing config file:
Traceback (most recent call last):
File "/home/buildbot/master/bin/buildbot", line 4, in <module>
runner.run()
File "/home/buildbot/master/buildbot/scripts/runner.py", line 1358, in run
if not doCheckConfig(so):
File "/home/buildbot/master/buildbot/scripts/runner.py", line 1079, in doCheckConfig
return cl.load(quiet=quiet)
File "/home/buildbot/master/buildbot/scripts/checkconfig.py", line 29, in load
self.basedir, self.configFileName)
--- <exception caught here> ---
File "/home/buildbot/master/buildbot/config.py", line 147, in loadConfig
exec f in localDict
exceptions.SyntaxError: invalid syntax (master.cfg, line 52)
Configuration Errors:
error while parsing config file: invalid syntax (master.cfg, line 52) (traceback in logfile)
Loading the Config File¶
The config file is only read at specific points in time. It is first read when the buildmaster is launched.
Reloading the Config File (reconfig)¶
If you are on the system hosting the buildmaster, you can send a SIGHUP
signal to it: the buildbot tool has a shortcut for this:
buildbot reconfig BASEDIR
This command will show you all of the lines from twistd.log
that relate to the reconfiguration. If there are any problems during
the config-file reload, they will be displayed in these lines.
When reloading the config file, the buildmaster will endeavor to
change as little as possible about the running system. For example,
although old status targets may be shut down and new ones started up,
any status targets that were not changed since the last time the
config file was read will be left running and untouched. Likewise any
Builder
s which have not been changed will be left running. If a
Builder
is modified (say, the build process is changed) while a Build
is currently running, that Build
will keep running with the old
process until it completes. Any previously queued Build
s (or Build
s
which get queued after the reconfig) will use the new process.
Warning
Buildbot's reconfiguration system is fragile for a few difficult-to-fix reasons:
- Any modules imported by the configuration file are not automatically reloaded. Python modules such as http://pypi.python.org/pypi/lazy-reload may help here, but reloading modules is fraught with subtleties and difficult-to-decipher failure cases.
- During the reconfiguration, active internal objects are divorced from the service hierarchy, leading to tracebacks in the web interface and other components. These are ordinarily transient, but with HTTP connection caching (either by the browser or an intervening proxy) they can last for a long time.
- If the new configuration file is invalid, it is possible for Buildbot's internal state to be corrupted, leading to undefined results. When this occurs, it is best to restart the master.
- For more advanced configurations, it is impossible for Buildbot to tell if the configuration for a
Builder
orScheduler
has changed, and thus theBuilder
orScheduler
will always be reloaded. This occurs most commonly when a callable is passed as a configuration parameter.
The bbproto project (at https://github.com/dabrahams/bbproto) may help to construct large (multi-file) configurations which can be effectively reloaded and reconfigured.
Reconfig by Debug Client¶
The debug tool
(buildbot debugclient
--master HOST:PORT
) has a Reload .cfg button which will also
trigger a reload.