Buildouts

The word "buildout" refers to a description of a set of parts and the software to create and assemble them. It is often used informally to refer to an installed system based on a buildout definition. For example, if we are creating an application named "Foo", then "the Foo buildout" is the collection of configuration and application-specific software that allows an instance of the application to be created. We may refer to such an instance of the application informally as "a Foo buildout".

This document describes how to define buildouts using buildout configuration files and recipes. There are three ways to set up the buildout software and create a buildout instance:

  1. Install the zc.buildout egg with easy_install and use the buildout script installed in a Python scripts area.
  2. Use the buildout bootstrap script to create a buildout that includes both the setuptools and zc.buildout eggs. This allows you to use the buildout software without modifying a Python install. The buildout script is installed into your buildout local scripts area.
  3. Use a buildoput command from an already installed buildout to bootstrap a new buildout. (See the section on bootstraping later in this document.)

Often, a software project will be managed in a software repository, such as a subversion repository, that includes some software source directories, buildout configuration files, and a copy of the buildout bootstrap script. To work on the project, one would check out the project from the repository and run the bootstrap script which installs setuptools and zc.buildout into the checkout as well as any parts defined.

We have a sample buildout that we created using the bootstrap command of an existing buildout (method 3 above). It has the absolute minimum information. We have bin, develop-eggs, eggs and parts directories, and a configuration file:

>>> ls(sample_buildout)
d  bin
-  buildout.cfg
d  develop-eggs
d  eggs
d  parts

The bin directory contains scripts.

>>> ls(sample_buildout, 'bin')
-  buildout
>>> ls(sample_buildout, 'eggs')
-  setuptools-0.6-py2.4.egg
-  zc.buildout-1.0-py2.4.egg

The develop-eggs and parts directories are initially empty:

>>> ls(sample_buildout, 'develop-eggs')
>>> ls(sample_buildout, 'parts')

The develop-eggs directory holds egg links for software being developed in the buildout. We separate develop-eggs and other eggs to allow eggs directories to be shared across multiple buildouts. For example, a common developer technique is to define a common eggs directory in their home that all non-develop eggs are stored in. This allows larger buildouts to be set up much more quickly and saves disk space.

The parts directory provides an area where recipes can install part data. For example, if we built a custom Python, we would install it in the part directory. Part data is stored in a sub-directory of the parts directory with the same name as the part.

Buildouts are defined using configuration files. These are in the format defined by the Python ConfigParser module, with extensions that we'll describe later. By default, when a buildout is run, it looks for the file buildout.cfg in the directory where the buildout is run.

The minimal configuration file has a buildout section that defines no parts:

>>> cat(sample_buildout, 'buildout.cfg')
[buildout]
parts =

A part is simply something to be created by a buildout. It can be almost anything, such as a Python package, a program, a directory, or even a configuration file.

Recipes

A part is created by a recipe. Recipes are always installed as Python eggs. They can be downloaded from a package server, such as the Python Package Index, or they can be developed as part of a project using a "develop" egg.

A develop egg is a special kind of egg that gets installed as an "egg link" that contains the name of a source directory. Develop eggs don't have to be packaged for distribution to be used and can be modified in place, which is especially useful while they are being developed.

Let's create a recipe as part of the sample project. We'll create a recipe for creating directories. First, we'll create a recipes source directory for our local recipes:

>>> mkdir(sample_buildout, 'recipes')

and then we'll create a source file for our mkdir recipe:

>>> write(sample_buildout, 'recipes', 'mkdir.py',
... """
... import logging, os, zc.buildout
...
... class Mkdir:
...
...     def __init__(self, buildout, name, options):
...         self.name, self.options = name, options
...         options['path'] = os.path.join(
...                               buildout['buildout']['directory'],
...                               options['path'],
...                               )
...         if not os.path.isdir(os.path.dirname(options['path'])):
...             logging.getLogger(self.name).error(
...                 'Cannot create %s. %s is not a directory.',
...                 options['path'], os.path.dirname(options['path']))
...             raise zc.buildout.UserError('Invalid Path')
...
...
...     def install(self):
...         path = self.options['path']
...         logging.getLogger(self.name).info(
...             'Creating directory %s', os.path.basename(path))
...         os.mkdir(path)
...         return path
...
...     def update(self):
...         pass
... """)

Currently, recipes must define 3 methods [1]:

  • a constructor,
  • an install method, and
  • an update method.

The constructor is responsible for updating a parts options to reflect data read from other sections. The buildout system keeps track of whether a part specification has changed. A part specification has changed if it's options, after adjusting for data read from other sections, has changed, or if the recipe has changed. Only the options for the part are considered. If data are read from other sections, then that information has to be reflected in the parts options. In the Mkdir example, the given path is interpreted relative to the buildout directory, and data from the buildout directory is read. The path option is updated to reflect this. If the directory option was changed in the buildout sections, we would know to update parts created using the mkdir recipe using relative path names.

When buildout is run, it saves configuration data for installed parts in a file named ".installed.cfg". In subsequent runs, it compares part-configuration data stored in the .installed.cfg file and the part-configuration data loaded from the configuration files as modified by recipe constructors to decide if the configuration of a part has changed. If the configuration has changed, or if the recipe has changed, then the part is uninstalled and reinstalled. The buildout only looks at the part's options, so any data used to configure the part needs to be reflected in the part's options. It is the job of a recipe constructor to make sure that the options include all relevant data.

Of course, parts are also uninstalled if they are no-longer used.

The recipe defines a constructor that takes a buildout object, a part name, and an options dictionary. It saves them in instance attributes. If the path is relative, we'll interpret it as relative to the buildout directory. The buildout object passed in is a mapping from section name to a mapping of options for that section. The buildout directory is available as the directory option of the buildout section. We normalize the path and save it back into the options directory.

The install method is responsible for creating the part. In this case, we need the path of the directory to create. We'll use a path option from our options dictionary. The install method logs what it's doing using the Python logging call. We return the path that we installed. If the part is uninstalled or reinstalled, then the path returned will be removed by the buildout machinery. A recipe install method is expected to return a string, or an iterable of strings containing paths to be removed if a part is uninstalled. For most recipes, this is all of the uninstall support needed. For more complex uninstallation scenarios use Uninstall recipes.

The update method is responsible for updating an already installed part. An empty method is often provided, as in this example, if parts can't be updated. An update method can return None, a string, or an iterable of strings. If a string or iterable of strings is returned, then the saved list of paths to be uninstalled is updated with the new information by adding any new files returned by the update method.

We need to provide packaging information so that our recipe can be installed as a develop egg. The minimum information we need to specify [2] is a name. For recipes, we also need to define the names of the recipe classes as entry points. Packaging information is provided via a setup.py script:

>>> write(sample_buildout, 'recipes', 'setup.py',
... """
... from setuptools import setup
...
... setup(
...     name = "recipes",
...     entry_points = {'zc.buildout': ['mkdir = mkdir:Mkdir']},
...     )
... """)

Our setup script defines an entry point. Entry points provide a way for an egg to define the services it provides. Here we've said that we define a zc.buildout entry point named mkdir. Recipe classes must be exposed as entry points in the zc.buildout group. we give entry points names within the group.

We also need a README.txt for our recipes to avoid an annoying warning from distutils, on which setuptools and zc.buildout are based:

>>> write(sample_buildout, 'recipes', 'README.txt', " ")

Now let's update our buildout.cfg:

>>> write(sample_buildout, 'buildout.cfg',
... """
... [buildout]
... develop = recipes
... parts = data-dir
...
... [data-dir]
... recipe = recipes:mkdir
... path = mystuff
... """)

Let's go through the changes one by one:

develop = recipes

This tells the buildout to install a development egg for our recipes. Any number of paths can be listed. The paths can be relative or absolute. If relative, they are treated as relative to the buildout directory. They can be directory or file paths. If a file path is given, it should point to a Python setup script. If a directory path is given, it should point to a directory containing a setup.py file. Development eggs are installed before building any parts, as they may provide locally-defined recipes needed by the parts.

parts = data-dir

Here we've named a part to be "built". We can use any name we want except that different part names must be unique and recipes will often use the part name to decide what to do.

[data-dir]
recipe = recipes:mkdir
path = mystuff

When we name a part, we also create a section of the same name that contains part data. In this section, we'll define the recipe to be used to install the part. In this case, we also specify the path to be created.

Let's run the buildout. We do so by running the build script in the buildout:

>>> import os
>>> os.chdir(sample_buildout)
>>> buildout = os.path.join(sample_buildout, 'bin', 'buildout')
>>> print system(buildout),
Develop: '/sample-buildout/recipes'
Installing data-dir.
data-dir: Creating directory mystuff

We see that the recipe created the directory, as expected:

>>> ls(sample_buildout)
-  .installed.cfg
d  bin
-  buildout.cfg
d  develop-eggs
d  eggs
d  mystuff
d  parts
d  recipes

In addition, .installed.cfg has been created containing information about the part we installed:

>>> cat(sample_buildout, '.installed.cfg')
[buildout]
installed_develop_eggs = /sample-buildout/develop-eggs/recipes.egg-link
parts = data-dir
<BLANKLINE>
[data-dir]
__buildout_installed__ = /sample-buildout/mystuff
__buildout_signature__ = recipes-c7vHV6ekIDUPy/7fjAaYjg==
path = /sample-buildout/mystuff
recipe = recipes:mkdir

Note that the directory we installed is included in .installed.cfg. In addition, the path option includes the actual destination directory.

If we change the name of the directory in the configuration file, we'll see that the directory gets removed and recreated:

>>> write(sample_buildout, 'buildout.cfg',
... """
... [buildout]
... develop = recipes
... parts = data-dir
...
... [data-dir]
... recipe = recipes:mkdir
... path = mydata
... """)
>>> print system(buildout),
Develop: '/sample-buildout/recipes'
Uninstalling data-dir.
Installing data-dir.
data-dir: Creating directory mydata
>>> ls(sample_buildout)
-  .installed.cfg
d  bin
-  buildout.cfg
d  develop-eggs
d  eggs
d  mydata
d  parts
d  recipes

If any of the files or directories created by a recipe are removed, the part will be reinstalled:

>>> rmdir(sample_buildout, 'mydata')
>>> print system(buildout),
Develop: '/sample-buildout/recipes'
Uninstalling data-dir.
Installing data-dir.
data-dir: Creating directory mydata

Error reporting

If a user makes an error, an error needs to be printed and work needs to stop. This is accomplished by logging a detailed error message and then raising a (or an instance of a subclass of a) zc.buildout.UserError exception. Raising an error other than a UserError still displays the error, but labels it as a bug in the buildout software or recipe. In the sample above, of someone gives a non-existent directory to create the directory in:

>>> write(sample_buildout, 'buildout.cfg',
... """
... [buildout]
... develop = recipes
... parts = data-dir
...
... [data-dir]
... recipe = recipes:mkdir
... path = /xxx/mydata
... """)

We'll get a user error, not a traceback.

>>> print system(buildout),
Develop: '/sample-buildout/recipes'
data-dir: Cannot create /xxx/mydata. /xxx is not a directory.
While:
  Installing.
  Getting section data-dir.
  Initializing part data-dir.
Error: Invalid Path

Recipe Error Handling

If an error occurs during installation, it is up to the recipe to clean up any system side effects, such as files created. Let's update the mkdir recipe to support multiple paths:

>>> write(sample_buildout, 'recipes', 'mkdir.py',
... """
... import logging, os, zc.buildout
...
... class Mkdir:
...
...     def __init__(self, buildout, name, options):
...         self.name, self.options = name, options
...
...         # Normalize paths and check that their parent
...         # directories exist:
...         paths = []
...         for path in options['path'].split():
...             path = os.path.join(buildout['buildout']['directory'], path)
...             if not os.path.isdir(os.path.dirname(path)):
...                 logging.getLogger(self.name).error(
...                     'Cannot create %s. %s is not a directory.',
...                     options['path'], os.path.dirname(options['path']))
...                 raise zc.buildout.UserError('Invalid Path')
...             paths.append(path)
...         options['path'] = ' '.join(paths)
...
...     def install(self):
...         paths = self.options['path'].split()
...         for path in paths:
...             logging.getLogger(self.name).info(
...                 'Creating directory %s', os.path.basename(path))
...             os.mkdir(path)
...         return paths
...
...     def update(self):
...         pass
... """)

If there is an error creating a path, the install method will exit and leave previously created paths in place:

>>> write(sample_buildout, 'buildout.cfg',
... """
... [buildout]
... develop = recipes
... parts = data-dir
...
... [data-dir]
... recipe = recipes:mkdir
... path = foo bin
... """)
>>> print system(buildout),
Develop: '/sample-buildout/recipes'
Uninstalling data-dir.
Installing data-dir.
data-dir: Creating directory foo
data-dir: Creating directory bin
While:
  Installing data-dir.
<BLANKLINE>
An internal error occured due to a bug in either zc.buildout or in a
recipe being used:
<BLANKLINE>
OSError:
[Errno 17] File exists: '/sample-buildout/bin'

We meant to create a directory bins, but typed bin. Now foo was left behind.

>>> os.path.exists('foo')
True

If we fix the typo:

>>> write(sample_buildout, 'buildout.cfg',
... """
... [buildout]
... develop = recipes
... parts = data-dir
...
... [data-dir]
... recipe = recipes:mkdir
... path = foo bins
... """)
>>> print system(buildout),
Develop: '/sample-buildout/recipes'
Installing data-dir.
data-dir: Creating directory foo
While:
  Installing data-dir.
<BLANKLINE>
An internal error occured due to a bug in either zc.buildout or in a
recipe being used:
<BLANKLINE>
OSError:
[Errno 17] File exists: '/sample-buildout/foo'

Now they fail because foo exists, because it was left behind.

>>> remove('foo')

Let's fix the recipe:

>>> write(sample_buildout, 'recipes', 'mkdir.py',
... """
... import logging, os, zc.buildout
...
... class Mkdir:
...
...     def __init__(self, buildout, name, options):
...         self.name, self.options = name, options
...
...         # Normalize paths and check that their parent
...         # directories exist:
...         paths = []
...         for path in options['path'].split():
...             path = os.path.join(buildout['buildout']['directory'], path)
...             if not os.path.isdir(os.path.dirname(path)):
...                 logging.getLogger(self.name).error(
...                     'Cannot create %s. %s is not a directory.',
...                     options['path'], os.path.dirname(options['path']))
...                 raise zc.buildout.UserError('Invalid Path')
...             paths.append(path)
...         options['path'] = ' '.join(paths)
...
...     def install(self):
...         paths = self.options['path'].split()
...         created = []
...         try:
...             for path in paths:
...                 logging.getLogger(self.name).info(
...                     'Creating directory %s', os.path.basename(path))
...                 os.mkdir(path)
...                 created.append(path)
...         except:
...             for d in created:
...                 os.rmdir(d)
...             raise
...
...         return paths
...
...     def update(self):
...         pass
... """)

And put back the typo:

>>> write(sample_buildout, 'buildout.cfg',
... """
... [buildout]
... develop = recipes
... parts = data-dir
...
... [data-dir]
... recipe = recipes:mkdir
... path = foo bin
... """)

When we rerun the buildout:

>>> print system(buildout),
Develop: '/sample-buildout/recipes'
Installing data-dir.
data-dir: Creating directory foo
data-dir: Creating directory bin
While:
  Installing data-dir.
<BLANKLINE>
An internal error occured due to a bug in either zc.buildout or in a
recipe being used:
<BLANKLINE>
OSError:
[Errno 17] File exists: '/sample-buildout/bin'

we get the same error, but we don't get the directory left behind:

>>> os.path.exists('foo')
False

It's critical that recipes clean up partial effects when errors occur. Because recipes most commonly create files and directories, buildout provides a helper API for removing created files when an error occurs. Option objects have a created method that can be called to record files as they are created. If the install or update method returns with an error, then any registered paths are removed automatically. The method returns the files registered and can be used to return the files created. Let's use this API to simplify the recipe:

>>> write(sample_buildout, 'recipes', 'mkdir.py',
... """
... import logging, os, zc.buildout
...
... class Mkdir:
...
...     def __init__(self, buildout, name, options):
...         self.name, self.options = name, options
...
...         # Normalize paths and check that their parent
...         # directories exist:
...         paths = []
...         for path in options['path'].split():
...             path = os.path.join(buildout['buildout']['directory'], path)
...             if not os.path.isdir(os.path.dirname(path)):
...                 logging.getLogger(self.name).error(
...                     'Cannot create %s. %s is not a directory.',
...                     options['path'], os.path.dirname(options['path']))
...                 raise zc.buildout.UserError('Invalid Path')
...             paths.append(path)
...         options['path'] = ' '.join(paths)
...
...     def install(self):
...         paths = self.options['path'].split()
...         for path in paths:
...             logging.getLogger(self.name).info(
...                 'Creating directory %s', os.path.basename(path))
...             os.mkdir(path)
...             self.options.created(path)
...
...         return self.options.created()
...
...     def update(self):
...         pass
... """)
>>> remove(sample_buildout, 'recipes', 'mkdir.pyc')

We returned by calling created, taking advantage of the fact that it returns the registered paths. We did this for illustrative purposes. It would be simpler just to return the paths as before.

If we rerun the buildout, again, we'll get the error and no directories will be created:

>>> print system(buildout),
Develop: '/sample-buildout/recipes'
Installing data-dir.
data-dir: Creating directory foo
data-dir: Creating directory bin
While:
  Installing data-dir.
<BLANKLINE>
An internal error occured due to a bug in either zc.buildout or in a
recipe being used:
<BLANKLINE>
OSError:
[Errno 17] File exists: '/sample-buildout/bin'
>>> os.path.exists('foo')
False

Now, we'll fix the typo again and we'll get the directories we expect:

>>> write(sample_buildout, 'buildout.cfg',
... """
... [buildout]
... develop = recipes
... parts = data-dir
...
... [data-dir]
... recipe = recipes:mkdir
... path = foo bins
... """)
>>> print system(buildout),
Develop: '/sample-buildout/recipes'
Installing data-dir.
data-dir: Creating directory foo
data-dir: Creating directory bins
>>> os.path.exists('foo')
True
>>> os.path.exists('bins')
True

Configuration file syntax

As mentioned earlier, buildout configuration files use the format defined by the Python ConfigParser module with extensions. The extensions are:

  • option names are case sensitive
  • option values can use a substitution syntax, described below, to refer to option values in specific sections.

The ConfigParser syntax is very flexible. Section names can contain any characters other than newlines and right square braces ("]"). Option names can contain any characters other than newlines, colons, and equal signs, can not start with a space, and don't include trailing spaces.

It is likely that, in the future, some characters will be given special buildout-defined meanings. This is already true of the characters ":", "$", "%", "(", and ")". For now, it is a good idea to keep section and option names simple, sticking to alphanumeric characters, hyphens, and periods.

Variable substitutions

Buildout configuration files support variable substitution. To illustrate this, we'll create an debug recipe to allow us to see interactions with the buildout:

>>> write(sample_buildout, 'recipes', 'debug.py',
... """
... class Debug:
...
...     def __init__(self, buildout, name, options):
...         self.buildout = buildout
...         self.name = name
...         self.options = options
...
...     def install(self):
...         items = self.options.items()
...         items.sort()
...         for option, value in items:
...             print option, value
...         return ()
...
...     update = install
... """)

This recipe doesn't actually create anything. The install method doesn't return anything, because it didn't create any files or directories.

We also have to update our setup script:

>>> write(sample_buildout, 'recipes', 'setup.py',
... """
... from setuptools import setup
... entry_points = (
... '''
... [zc.buildout]
... mkdir = mkdir:Mkdir
... debug = debug:Debug
... ''')
... setup(name="recipes", entry_points=entry_points)
... """)

We've rearranged the script a bit to make the entry points easier to edit. In particular, entry points are now defined as a configuration string, rather than a dictionary.

Let's update our configuration to provide variable substitution examples:

>>> write(sample_buildout, 'buildout.cfg',
... """
... [buildout]
... develop = recipes
... parts = data-dir debug
... log-level = INFO
...
... [debug]
... recipe = recipes:debug
... File 1 = ${data-dir:path}/file
... File 2 = ${debug:File 1}/log
...
... [data-dir]
... recipe = recipes:mkdir
... path = mydata
... """)

In this example, we've used ConfigParser substitutions for file2 and file3. This type of substitution uses Python string format syntax. Valid names are options in the same section and options defined in the DEFAULT section.

We used a string-template substitution for file1. This type of substitution uses the string.Template syntax. Names substituted are qualified option names, consisting of a section name and option name joined by a colon.

Now, if we run the buildout, we'll see the options with the values substituted.

>>> print system(buildout),
Develop: '/sample-buildout/recipes'
Uninstalling data-dir.
Installing data-dir.
data-dir: Creating directory mydata
Installing debug.
File 1 /sample-buildout/mydata/file
File 2 /sample-buildout/mydata/file/log
recipe recipes:debug

Note that the substitution of the data-dir path option reflects the update to the option performed by the mkdir recipe.

It might seem surprising that mydata was created again. This is because we changed our recipes package by adding the debug module. The buildout system didn't know if this module could effect the mkdir recipe, so it assumed it could and reinstalled mydata. If we rerun the buildout:

>>> print system(buildout),
Develop: '/sample-buildout/recipes'
Updating data-dir.
Updating debug.
File 1 /sample-buildout/mydata/file
File 2 /sample-buildout/mydata/file/log
recipe recipes:debug

We can see that mydata was not recreated.

Note that, in this case, we didn't specify a log level, so we didn't get output about what the buildout was doing.

Section and option names in variable substitutions are only allowed to contain alphanumeric characters, hyphens, periods and spaces. This restriction might be relaxed in future releases.

Automatic part selection and ordering

When a section with a recipe is referred to, either through variable substitution or by an initializing recipe, the section is treated as a part and added to the part list before the referencing part. For example, we can leave data-dir out of the parts list:

>>> write(sample_buildout, 'buildout.cfg',
... """
... [buildout]
... develop = recipes
... parts = debug
... log-level = INFO
...
... [debug]
... recipe = recipes:debug
... File 1 = ${data-dir:path}/file
... File 2 = ${debug:File 1}/log
...
... [data-dir]
... recipe = recipes:mkdir
... path = mydata
... """)

It will still be treated as a part:

>>> print system(buildout),
Develop: '/sample-buildout/recipes'
Updating data-dir.
Updating debug.
File 1 /sample-buildout/mydata/file
File 2 /sample-buildout/mydata/file/log
recipe recipes:debug
>>> cat('.installed.cfg') # doctest: +ELLIPSIS
[buildout]
installed_develop_eggs = /sample-buildout/develop-eggs/recipes.egg-link
parts = data-dir debug
...

Note that the data-dir part is included before the debug part, because the debug part refers to the data-dir part. Even if we list the data-dir part after the debug part, it will be included before:

>>> write(sample_buildout, 'buildout.cfg',
... """
... [buildout]
... develop = recipes
... parts = debug data-dir
... log-level = INFO
...
... [debug]
... recipe = recipes:debug
... File 1 = ${data-dir:path}/file
... File 2 = ${debug:File 1}/log
...
... [data-dir]
... recipe = recipes:mkdir
... path = mydata
... """)

It will still be treated as a part:

>>> print system(buildout),
Develop: '/sample-buildout/recipes'
Updating data-dir.
Updating debug.
File 1 /sample-buildout/mydata/file
File 2 /sample-buildout/mydata/file/log
recipe recipes:debug
>>> cat('.installed.cfg') # doctest: +ELLIPSIS
[buildout]
installed_develop_eggs = /sample-buildout/develop-eggs/recipes.egg-link
parts = data-dir debug
...

Multiple configuration files

A configuration file can "extend" another configuration file. Options are read from the other configuration file if they aren't already defined by your configuration file.

The configuration files your file extends can extend other configuration files. The same file may be used more than once although, of course, cycles aren't allowed.

To see how this works, we use an example:

>>> write(sample_buildout, 'buildout.cfg',
... """
... [buildout]
... extends = base.cfg
...
... [debug]
... op = buildout
... """)
>>> write(sample_buildout, 'base.cfg',
... """
... [buildout]
... develop = recipes
... parts = debug
...
... [debug]
... recipe = recipes:debug
... op = base
... """)
>>> print system(buildout),
Develop: '/sample-buildout/recipes'
Uninstalling debug.
Uninstalling data-dir.
Installing debug.
op buildout
recipe recipes:debug

The example is pretty trivial, but the pattern it illustrates is pretty common. In a more practical example, the base buildout might represent a product and the extending buildout might be a customization.

Here is a more elaborate example.

>>> other = tmpdir('other')
>>> write(sample_buildout, 'buildout.cfg',
... """
... [buildout]
... extends = b1.cfg b2.cfg %(b3)s
...
... [debug]
... op = buildout
... """ % dict(b3=os.path.join(other, 'b3.cfg')))
>>> write(sample_buildout, 'b1.cfg',
... """
... [buildout]
... extends = base.cfg
...
... [debug]
... op1 = b1 1
... op2 = b1 2
... """)
>>> write(sample_buildout, 'b2.cfg',
... """
... [buildout]
... extends = base.cfg
...
... [debug]
... op2 = b2 2
... op3 = b2 3
... """)
>>> write(other, 'b3.cfg',
... """
... [buildout]
... extends = b3base.cfg
...
... [debug]
... op4 = b3 4
... """)
>>> write(other, 'b3base.cfg',
... """
... [debug]
... op5 = b3base 5
... """)
>>> write(sample_buildout, 'base.cfg',
... """
... [buildout]
... develop = recipes
... parts = debug
...
... [debug]
... recipe = recipes:debug
... name = base
... """)
>>> print system(buildout),
Develop: '/sample-buildout/recipes'
Uninstalling debug.
Installing debug.
name base
op buildout
op1 b1 1
op2 b2 2
op3 b2 3
op4 b3 4
op5 b3base 5
recipe recipes:debug

There are several things to note about this example:

  • We can name multiple files in an extends option.
  • We can reference files recursively.
  • Relative file names in extended options are interpreted relative to the directory containing the referencing configuration file.

Loading Configuration from URLs

Configuration files can be loaded from URLs. To see how this works, we'll set up a web server with some configuration files.

>>> server_data = tmpdir('server_data')
>>> write(server_data, "r1.cfg",
... """
... [debug]
... op1 = r1 1
... op2 = r1 2
... """)
>>> write(server_data, "r2.cfg",
... """
... [buildout]
... extends = r1.cfg
...
... [debug]
... op2 = r2 2
... op3 = r2 3
... """)
>>> server_url = start_server(server_data)
>>> write('client.cfg',
... """
... [buildout]
... develop = recipes
... parts = debug
... extends = %(url)s/r2.cfg
...
... [debug]
... recipe = recipes:debug
... name = base
... """ % dict(url=server_url))
>>> print system(buildout+ ' -c client.cfg'),
Develop: '/sample-buildout/recipes'
Uninstalling debug.
Installing debug.
name base
op1 r1 1
op2 r2 2
op3 r2 3
recipe recipes:debug

Here we specified a URL for the file we extended. The file we downloaded, itself referred to a file on the server using a relative URL reference. Relative references are interpreted relative to the base URL when they appear in configuration files loaded via URL.

We can also specify a URL as the configuration file to be used by a buildout.

>>> os.remove('client.cfg')
>>> write(server_data, 'remote.cfg',
... """
... [buildout]
... develop = recipes
... parts = debug
... extends = r2.cfg
...
... [debug]
... recipe = recipes:debug
... name = remote
... """)
>>> print system(buildout + ' -c ' + server_url + '/remote.cfg'),
While:
  Initializing.
Error: Missing option: buildout:directory

Normally, the buildout directory defaults to directory containing a configuration file. This won't work for configuration files loaded from URLs. In this case, the buildout directory would normally be defined on the command line:

>>> print system(buildout
...              + ' -c ' + server_url + '/remote.cfg'
...              + ' buildout:directory=' + sample_buildout
...              ),
Develop: '/sample-buildout/recipes'
Uninstalling debug.
Installing debug.
name remote
op1 r1 1
op2 r2 2
op3 r2 3
recipe recipes:debug

User defaults

If the file $HOME/.buildout/default.cfg, exists, it is read before reading the configuration file. ($HOME is the value of the HOME environment variable. The '/' is replaced by the operating system file delimiter.)

>>> old_home = os.environ['HOME']
>>> home = tmpdir('home')
>>> mkdir(home, '.buildout')
>>> write(home, '.buildout', 'default.cfg',
... """
... [debug]
... op1 = 1
... op7 = 7
... """)
>>> os.environ['HOME'] = home
>>> print system(buildout),
Develop: '/sample-buildout/recipes'
Uninstalling debug.
Installing debug.
name base
op buildout
op1 b1 1
op2 b2 2
op3 b2 3
op4 b3 4
op5 b3base 5
op7 7
recipe recipes:debug

A buildout command-line argument, -U, can be used to suppress reading user defaults:

>>> print system(buildout + ' -U'),
Develop: '/sample-buildout/recipes'
Uninstalling debug.
Installing debug.
name base
op buildout
op1 b1 1
op2 b2 2
op3 b2 3
op4 b3 4
op5 b3base 5
recipe recipes:debug
>>> os.environ['HOME'] = old_home

Log level

We can control the level of logging by specifying a log level in out configuration file. For example, so suppress info messages, we can set the logging level to WARNING

>>> write(sample_buildout, 'buildout.cfg',
... """
... [buildout]
... log-level = WARNING
... extends = b1.cfg b2.cfg
... """)
>>> print system(buildout),
name base
op1 b1 1
op2 b2 2
op3 b2 3
recipe recipes:debug

Uninstall recipes

As we've seen, when parts are installed, buildout keeps track of files and directories that they create. When the parts are uninstalled these files and directories are deleted.

Sometimes more clean up is needed. For example, a recipe might add a system service by calling chkconfig --add during installation. Later during uninstallation, chkconfig --del will need to be called to remove the system service.

In order to deal with these uninstallation issues, you can register uninstall recipes. Uninstall recipes are registered using the 'zc.buildout.uninstall' entry point. Parts specify uninstall recipes using the 'uninstall' option.

In comparison to regular recipes, uninstall recipes are much simpler. They are simply callable objects that accept the name of the part to be uninstalled and the part's options dictionary. Uninstall recipes don't have access to the part itself since it maybe not be able to be instantiated at uninstallation time.

Here's a recipe that simulates installation of a system service, along with an uninstall recipe that simulates removing the service.

>>> write(sample_buildout, 'recipes', 'service.py',
... """
... class Service:
...
...     def __init__(self, buildout, name, options):
...         self.buildout = buildout
...         self.name = name
...         self.options = options
...
...     def install(self):
...         print "chkconfig --add %s" % self.options['script']
...         return ()
...
...     def update(self):
...         pass
...
...
... def uninstall_service(name, options):
...     print "chkconfig --del %s" % options['script']
... """)

To use these recipes we must register them using entry points. Make sure to use the same name for the recipe and uninstall recipe. This is required to let buildout know which uninstall recipe goes with which recipe.

>>> write(sample_buildout, 'recipes', 'setup.py',
... """
... from setuptools import setup
... entry_points = (
... '''
... [zc.buildout]
... mkdir = mkdir:Mkdir
... debug = debug:Debug
... service = service:Service
...
... [zc.buildout.uninstall]
... service = service:uninstall_service
... ''')
... setup(name="recipes", entry_points=entry_points)
... """)

Here's how these recipes could be used in a buildout:

>>> write(sample_buildout, 'buildout.cfg',
... """
... [buildout]
... develop = recipes
... parts = service
...
... [service]
... recipe = recipes:service
... script = /path/to/script
... """)

When the buildout is run the service will be installed

>>> print system(buildout)
Develop: '/sample-buildout/recipes'
Uninstalling debug.
Installing service.
chkconfig --add /path/to/script
<BLANKLINE>

The service has been installed. If the buildout is run again with no changes, the service shouldn't be changed.

>>> print system(buildout)
Develop: '/sample-buildout/recipes'
Updating service.
<BLANKLINE>

Now we change the service part to trigger uninstallation and re-installation.

>>> write(sample_buildout, 'buildout.cfg',
... """
... [buildout]
... develop = recipes
... parts = service
...
... [service]
... recipe = recipes:service
... script = /path/to/a/different/script
... """)
>>> print system(buildout)
Develop: '/sample-buildout/recipes'
Uninstalling service.
Running uninstall recipe.
chkconfig --del /path/to/script
Installing service.
chkconfig --add /path/to/a/different/script
<BLANKLINE>

Now we remove the service part, and add another part.

>>> write(sample_buildout, 'buildout.cfg',
... """
... [buildout]
... develop = recipes
... parts = debug
...
... [debug]
... recipe = recipes:debug
... """)
>>> print system(buildout)
Develop: '/sample-buildout/recipes'
Uninstalling service.
Running uninstall recipe.
chkconfig --del /path/to/a/different/script
Installing debug.
recipe recipes:debug
<BLANKLINE>

Uninstall recipes don't have to take care of removing all the files and directories created by the part. This is still done automatically, following the execution of the uninstall recipe. An upshot is that an uninstallation recipe can access files and directories created by a recipe before they are deleted.

For example, here's an uninstallation recipe that simulates backing up a directory before it is deleted. It is designed to work with the mkdir recipe introduced earlier.

>>> write(sample_buildout, 'recipes', 'backup.py',
... """
... import os
... def backup_directory(name, options):
...     path = options['path']
...     size = len(os.listdir(path))
...     print "backing up directory %s of size %s" % (path, size)
... """)

It must be registered with the zc.buildout.uninstall entry point. Notice how it is given the name 'mkdir' to associate it with the mkdir recipe.

>>> write(sample_buildout, 'recipes', 'setup.py',
... """
... from setuptools import setup
... entry_points = (
... '''
... [zc.buildout]
... mkdir = mkdir:Mkdir
... debug = debug:Debug
... service = service:Service
...
... [zc.buildout.uninstall]
... uninstall_service = service:uninstall_service
... mkdir = backup:backup_directory
... ''')
... setup(name="recipes", entry_points=entry_points)
... """)

Now we can use it with a mkdir part.

>>> write(sample_buildout, 'buildout.cfg',
... """
... [buildout]
... develop = recipes
... parts = dir debug
...
... [dir]
... recipe = recipes:mkdir
... path = my_directory
...
... [debug]
... recipe = recipes:debug
... """)

Run the buildout to install the part.

>>> print system(buildout)
Develop: '/sample-buildout/recipes'
Uninstalling debug.
Installing dir.
dir: Creating directory my_directory
Installing debug.
recipe recipes:debug
<BLANKLINE>

Now we remove the part from the configuration file.

>>> write(sample_buildout, 'buildout.cfg',
... """
... [buildout]
... develop = recipes
... parts = debug
...
... [debug]
... recipe = recipes:debug
... """)

When the buildout is run the part is removed, and the uninstall recipe is run before the directory is deleted.

>>> print system(buildout)
Develop: '/sample-buildout/recipes'
Uninstalling dir.
Running uninstall recipe.
backing up directory /sample-buildout/my_directory of size 0
Updating debug.
recipe recipes:debug
<BLANKLINE>

Now we will return the registration to normal for the benefit of the rest of the examples.

>>> write(sample_buildout, 'recipes', 'setup.py',
... """
... from setuptools import setup
... entry_points = (
... '''
... [zc.buildout]
... mkdir = mkdir:Mkdir
... debug = debug:Debug
... ''')
... setup(name="recipes", entry_points=entry_points)
... """)

Command-line usage

A number of arguments can be given on the buildout command line. The command usage is:

buildout [options and assignments] [command [command arguments]]

The following options are supported:

-h (or --help)
Print basic usage information. If this option is used, then all other options are ignored.
-c filename The -c option can be used to specify a configuration file, rather than buildout.cfg in the current directory.
-v Increment the verbosity by 10. The verbosity is used to adjust the logging level. The verbosity is subtracted from the numeric value of the log-level option specified in the configuration file.
-q Decrement the verbosity by 10.
-U Don't read user-default configuration.
-o Run in off-line mode. This is equivalent to the assignment buildout:offline=true.
-O Run in non-off-line mode. This is equivalent to the assignment buildout:offline=false. This is the default buildout mode. The -O option would normally be used to override a true offline setting in a configuration file.
-n Run in newest mode. This is equivalent to the assignment buildout:newest=true. With this setting, which is the default, buildout will try to find the newest versions of distributions available that satisfy its requirements.
-N Run in non-newest mode. This is equivalent to the assignment buildout:newest=false. With this setting, buildout will not seek new distributions if installed distributions satisfy it's requirements.

Assignments are of the form:

section_name:option_name=value

Options and assignments can be given in any order.

Here's an example:

>>> write(sample_buildout, 'other.cfg',
... """
... [buildout]
... develop = recipes
... parts = debug
... installed = .other.cfg
... log-level = WARNING
...
... [debug]
... name = other
... recipe = recipes:debug
... """)

Note that we used the installed buildout option to specify an alternate file to store information about installed parts.

>>> print system(buildout+' -c other.cfg debug:op1=foo -v'),
Develop: '/sample-buildout/recipes'
Installing debug.
name other
op1 foo
recipe recipes:debug

Here we used the -c option to specify an alternate configuration file, and the -v option to increase the level of logging from the default, WARNING.

Options can also be combined in the usual Unix way, as in:

>>> print system(buildout+' -vcother.cfg debug:op1=foo'),
Develop: '/sample-buildout/recipes'
Updating debug.
name other
op1 foo
recipe recipes:debug

Here we combined the -v and -c options with the configuration file name. Note that the -c option has to be last, because it takes an argument.

>>> os.remove(os.path.join(sample_buildout, 'other.cfg'))
>>> os.remove(os.path.join(sample_buildout, '.other.cfg'))

The most commonly used command is 'install' and it takes a list of parts to install. if any parts are specified, only those parts are installed. To illustrate this, we'll update our configuration and run the buildout in the usual way:

>>> write(sample_buildout, 'buildout.cfg',
... """
... [buildout]
... develop = recipes
... parts = debug d1 d2 d3
...
... [d1]
... recipe = recipes:mkdir
... path = d1
...
... [d2]
... recipe = recipes:mkdir
... path = d2
...
... [d3]
... recipe = recipes:mkdir
... path = d3
...
... [debug]
... recipe = recipes:debug
... """)
>>> print system(buildout),
Develop: '/sample-buildout/recipes'
Uninstalling debug.
Installing debug.
recipe recipes:debug
Installing d1.
d1: Creating directory d1
Installing d2.
d2: Creating directory d2
Installing d3.
d3: Creating directory d3
>>> ls(sample_buildout)
-  .installed.cfg
-  b1.cfg
-  b2.cfg
-  base.cfg
d  bin
-  buildout.cfg
d  d1
d  d2
d  d3
d  develop-eggs
d  eggs
d  parts
d  recipes
>>> cat(sample_buildout, '.installed.cfg')
[buildout]
installed_develop_eggs = /sample-buildout/develop-eggs/recipes.egg-link
parts = debug d1 d2 d3
<BLANKLINE>
[debug]
__buildout_installed__ =
__buildout_signature__ = recipes-PiIFiO8ny5yNZ1S3JfT0xg==
recipe = recipes:debug
<BLANKLINE>
[d1]
__buildout_installed__ = /sample-buildout/d1
__buildout_signature__ = recipes-PiIFiO8ny5yNZ1S3JfT0xg==
path = /sample-buildout/d1
recipe = recipes:mkdir
<BLANKLINE>
[d2]
__buildout_installed__ = /sample-buildout/d2
__buildout_signature__ = recipes-PiIFiO8ny5yNZ1S3JfT0xg==
path = /sample-buildout/d2
recipe = recipes:mkdir
<BLANKLINE>
[d3]
__buildout_installed__ = /sample-buildout/d3
__buildout_signature__ = recipes-PiIFiO8ny5yNZ1S3JfT0xg==
path = /sample-buildout/d3
recipe = recipes:mkdir

Now we'll update our configuration file:

>>> write(sample_buildout, 'buildout.cfg',
... """
... [buildout]
... develop = recipes
... parts = debug d2 d3 d4
...
... [d2]
... recipe = recipes:mkdir
... path = data2
...
... [d3]
... recipe = recipes:mkdir
... path = data3
...
... [d4]
... recipe = recipes:mkdir
... path = ${d2:path}-extra
...
... [debug]
... recipe = recipes:debug
... x = 1
... """)

and run the buildout specifying just d3 and d4:

>>> print system(buildout+' install d3 d4'),
Develop: '/sample-buildout/recipes'
Uninstalling d3.
Installing d3.
d3: Creating directory data3
Installing d4.
d4: Creating directory data2-extra
>>> ls(sample_buildout)
-  .installed.cfg
-  b1.cfg
-  b2.cfg
-  base.cfg
d  bin
-  buildout.cfg
d  d1
d  d2
d  data2-extra
d  data3
d  develop-eggs
d  eggs
d  parts
d  recipes

Only the d3 and d4 recipes ran. d3 was removed and data3 and data2-extra were created.

The .installed.cfg is only updated for the recipes that ran:

>>> cat(sample_buildout, '.installed.cfg')
[buildout]
installed_develop_eggs = /sample-buildout/develop-eggs/recipes.egg-link
parts = debug d1 d2 d3 d4
<BLANKLINE>
[debug]
__buildout_installed__ =
__buildout_signature__ = recipes-PiIFiO8ny5yNZ1S3JfT0xg==
recipe = recipes:debug
<BLANKLINE>
[d1]
__buildout_installed__ = /sample-buildout/d1
__buildout_signature__ = recipes-PiIFiO8ny5yNZ1S3JfT0xg==
path = /sample-buildout/d1
recipe = recipes:mkdir
<BLANKLINE>
[d2]
__buildout_installed__ = /sample-buildout/d2
__buildout_signature__ = recipes-PiIFiO8ny5yNZ1S3JfT0xg==
path = /sample-buildout/d2
recipe = recipes:mkdir
<BLANKLINE>
[d3]
__buildout_installed__ = /sample-buildout/data3
__buildout_signature__ = recipes-PiIFiO8ny5yNZ1S3JfT0xg==
path = /sample-buildout/data3
recipe = recipes:mkdir
<BLANKLINE>
[d4]
__buildout_installed__ = /sample-buildout/data2-extra
__buildout_signature__ = recipes-PiIFiO8ny5yNZ1S3JfT0xg==
path = /sample-buildout/data2-extra
recipe = recipes:mkdir

Note that the installed data for debug, d1, and d2 haven't changed, because we didn't install those parts and that the d1 and d2 directories are still there.

Now, if we run the buildout without the install command:

>>> print system(buildout),
Develop: '/sample-buildout/recipes'
Uninstalling d2.
Uninstalling d1.
Uninstalling debug.
Installing debug.
recipe recipes:debug
x 1
Installing d2.
d2: Creating directory data2
Updating d3.
Updating d4.

We see the output of the debug recipe and that data2 was created. We also see that d1 and d2 have gone away:

>>> ls(sample_buildout)
-  .installed.cfg
-  b1.cfg
-  b2.cfg
-  base.cfg
d  bin
-  buildout.cfg
d  data2
d  data2-extra
d  data3
d  develop-eggs
d  eggs
d  parts
d  recipes

Alternate directory and file locations

The buildout normally puts the bin, eggs, and parts directories in the directory in the directory containing the configuration file. You can provide alternate locations, and even names for these directories.

>>> alt = tmpdir('sample-alt')
>>> write(sample_buildout, 'buildout.cfg',
... """
... [buildout]
... develop = recipes
... parts =
... develop-eggs-directory = %(developbasket)s
... eggs-directory = %(basket)s
... bin-directory = %(scripts)s
... parts-directory = %(work)s
... """ % dict(
...    developbasket = os.path.join(alt, 'developbasket'),
...    basket = os.path.join(alt, 'basket'),
...    scripts = os.path.join(alt, 'scripts'),
...    work = os.path.join(alt, 'work'),
... ))
>>> print system(buildout),
Creating directory '/sample-alt/scripts'.
Creating directory '/sample-alt/work'.
Creating directory '/sample-alt/basket'.
Creating directory '/sample-alt/developbasket'.
Develop: '/sample-buildout/recipes'
Uninstalling d4.
Uninstalling d3.
Uninstalling d2.
Uninstalling debug.
>>> ls(alt)
d  basket
d  developbasket
d  scripts
d  work
>>> ls(alt, 'developbasket')
-  recipes.egg-link

You can also specify an alternate buildout directory:

>>> rmdir(alt)
>>> alt = tmpdir('sample-alt')
>>> write(sample_buildout, 'buildout.cfg',
... """
... [buildout]
... directory = %(alt)s
... develop = %(recipes)s
... parts =
... """ % dict(
...    alt=alt,
...    recipes=os.path.join(sample_buildout, 'recipes'),
...    ))
>>> print system(buildout),
Creating directory '/sample-alt/bin'.
Creating directory '/sample-alt/parts'.
Creating directory '/sample-alt/eggs'.
Creating directory '/sample-alt/develop-eggs'.
Develop: '/sample-buildout/recipes'
>>> ls(alt)
-  .installed.cfg
d  bin
d  develop-eggs
d  eggs
d  parts
>>> ls(alt, 'develop-eggs')
-  recipes.egg-link

Logging control

Three buildout options are used to control logging:

log-level
specifies the log level
verbosity
adjusts the log level
log-format
allows an alternate logging for mat to be specified

We've already seen the log level and verbosity. Let's look at an example of changing the format:

>>> write(sample_buildout, 'buildout.cfg',
... """
... [buildout]
... develop = recipes
... parts =
... log-level = 25
... verbosity = 5
... log-format = %(levelname)s %(message)s
... """)

Here, we've changed the format to include the log-level name, rather than the logger name.

We've also illustrated, with a contrived example, that the log level can be a numeric value and that the verbosity can be specified in the configuration file. Because the verbosity is subtracted from the log level, we get a final log level of 20, which is the INFO level.

>>> print system(buildout),
INFO Develop: '/sample-buildout/recipes'

Predefined buildout options

Buildouts have a number of predefined options that recipes can use and that users can override in their configuration files. To see these, we'll run a minimal buildout configuration with a debug logging level. One of the features of debug logging is that the configuration database is shown.

>>> write(sample_buildout, 'buildout.cfg',
... """
... [buildout]
... parts =
... """)
>>> print system(buildout+' -vv'),
Installing 'zc.buildout', 'setuptools'.
We have a develop egg: zc.buildout 1.0.0.
We have the best distribution that satisfies 'setuptools'.
Picked: setuptools = 0.6
<BLANKLINE>
Configuration data:
[buildout]
bin-directory = /sample-buildout/bin
develop-eggs-directory = /sample-buildout/develop-eggs
directory = /sample-buildout
eggs-directory = /sample-buildout/eggs
executable = /usr/local/bin/python2.3
installed = /sample-buildout/.installed.cfg
log-format =
log-level = INFO
newest = true
offline = false
parts =
parts-directory = /sample-buildout/parts
python = buildout
verbosity = 20
<BLANKLINE>

All of these options can be overridden by configuration files or by command-line assignments. We've discussed most of these options already, but let's review them and touch on some we haven't discussed:

bin-directory
The directory path where scripts are written. This can be a relative path, which is interpreted relative to the directory option.
develop-eggs-directory
The directory path where development egg links are created for software being created in the local project. This can be a relative path, which is interpreted relative to the directory option.
directory
The buildout directory. This is the base for other buildout file and directory locations, when relative locations are used.
eggs-directory
The directory path where downloaded eggs are put. It is common to share this directory across buildouts. Eggs in this directory should never be modified. This can be a relative path, which is interpreted relative to the directory option.
executable
The Python executable used to run the buildout. See the python option below.
installed
The file path where information about the results of the previous buildout run is written. This can be a relative path, which is interpreted relative to the directory option. This file provides an inventory of installed parts with information needed to decide which if any parts need to be uninstalled.
log-format
The format used for logging messages.
log-level
The log level before verbosity adjustment
parts
A white space separated list of parts to be installed.
parts-directory
A working directory that parts can used to store data.
python
The name of a section containing information about the default Python interpreter. Recipes that need a installation typically have options to tell them which Python installation to use. By convention, if a section-specific option isn't used, the option is looked for in the buildout section. The option must point to a section with an executable option giving the path to a Python executable. By default, the buildout section defines the default Python as the Python used to run the buildout.
verbosity
A log-level adjustment. Typically, this is set via the -q and -v command-line options.

Creating new buildouts and bootstrapping

If zc.buildout is installed, you can use it to create a new buildout with it's own local copies of zc.buildout and setuptools and with local buildout scripts.

>>> sample_bootstrapped = tmpdir('sample-bootstrapped')
>>> print system(buildout
...              +' -c'+os.path.join(sample_bootstrapped, 'setup.cfg')
...              +' init'),
Creating '/sample-bootstrapped/setup.cfg'.
Creating directory '/sample-bootstrapped/bin'.
Creating directory '/sample-bootstrapped/parts'.
Creating directory '/sample-bootstrapped/eggs'.
Creating directory '/sample-bootstrapped/develop-eggs'.
Generated script '/sample-bootstrapped/bin/buildout'.

Note that a basic setup.cfg was created for us.

>>> ls(sample_bootstrapped)
d  bin
d  develop-eggs
d  eggs
d  parts
-  setup.cfg
>>> ls(sample_bootstrapped, 'bin')
-  buildout
>>> _ = (ls(sample_bootstrapped, 'eggs'),
...      ls(sample_bootstrapped, 'develop-eggs'))
-  setuptools-0.6-py2.3.egg
-  zc.buildout-1.0-py2.3.egg

(We list both the eggs and develop-eggs directories because the buildout or setuptools egg could be installed in the develop-eggs directory if the original buildout had develop eggs for either buildout or setuptools.)

Note that the buildout script was installed but not run. To run the buildout, we'd have to run the installed buildout script.

If we have an existing buildout that already has a buildout.cfg, we'll normally use the bootstrap command instead of init. It will complain if there isn't a configuration file:

>>> sample_bootstrapped2 = tmpdir('sample-bootstrapped2')
>>> print system(buildout
...              +' -c'+os.path.join(sample_bootstrapped2, 'setup.cfg')
...              +' bootstrap'),
While:
  Initializing.
Error: Couldn't open /sample-bootstrapped2/setup.cfg
>>> write(sample_bootstrapped2, 'setup.cfg',
... """
... [buildout]
... parts =
... """)
>>> print system(buildout
...              +' -c'+os.path.join(sample_bootstrapped2, 'setup.cfg')
...              +' bootstrap'),
Creating directory '/sample-bootstrapped2/bin'.
Creating directory '/sample-bootstrapped2/parts'.
Creating directory '/sample-bootstrapped2/eggs'.
Creating directory '/sample-bootstrapped2/develop-eggs'.
Generated script '/sample-bootstrapped2/bin/buildout'.

Newest and Offline Modes

By default buildout and recipes will try to find the newest versions of distributions needed to satisfy requirements. This can be very time consuming, especially when incrementally working on setting up a buildout or working on a recipe. The buildout newest option can be used to to suppress this. If the newest option is set to false, then new distributions won't be sought if an installed distribution meets requirements. The newest option can be set to false using the -N command-line option.

The offline option goes a bit further. If the buildout offline option is given a value of "true", the buildout and recipes that are aware of the option will avoid doing network access. This is handy when running the buildout when not connected to the internet. It also makes buildouts run much faster. This option is typically set using the buildout -o option.

Preferring Final Releases

Currently, when searching for new releases, the newest available release is used. This isn't usually ideal, as you may get a development release or alpha releases not ready to be widely used. You can request that final releases be preferred using the prefer final option in the buildout section:

[buildout]
...
prefer-final = true

When the prefer-final option is set to true, then when searching for new releases, final releases are preferred. If there are final releases that satisfy distribution requirements, then those releases are used even if newer non-final releases are available. The buildout prefer-final option can be used to override this behavior.

In buildout version 2, final releases will be preferred by default. You will then need to use a false value for prefer-final to get the newest releases.

Dependency links

By default buildout will obey the setuptools dependency_links metadata when it looks for dependencies. This behavior can be controlled with the use-dependency-links buildout option:

[buildout]
...
use-dependency-links = false

The option defaults to true. If you set it to false, then dependency links are only looked for in the locations specified by find-links.

Controlling the installation database

The buildout installed option is used to specify the file used to save information on installed parts. This option is initialized to ".installed.cfg", but it can be overridden in the configuration file or on the command line:

>>> write('buildout.cfg',
... """
... [buildout]
... develop = recipes
... parts = debug
...
... [debug]
... recipe = recipes:debug
... """)
>>> print system(buildout+' buildout:installed=inst.cfg'),
Develop: '/sample-buildout/recipes'
Installing debug.
recipe recipes:debug
>>> ls(sample_buildout)
-  b1.cfg
-  b2.cfg
-  base.cfg
d  bin
-  buildout.cfg
d  develop-eggs
d  eggs
-  inst.cfg
d  parts
d  recipes

The installation database can be disabled by supplying an empty buildout installed option:

>>> os.remove('inst.cfg')
>>> print system(buildout+' buildout:installed='),
Develop: '/sample-buildout/recipes'
Installing debug.
recipe recipes:debug
>>> ls(sample_buildout)
-  b1.cfg
-  b2.cfg
-  base.cfg
d  bin
-  buildout.cfg
d  develop-eggs
d  eggs
d  parts
d  recipes

Note that there will be no installation database if there are no parts:

>>> write('buildout.cfg',
... """
... [buildout]
... parts =
... """)
>>> print system(buildout+' buildout:installed=inst.cfg'),
>>> ls(sample_buildout)
-  b1.cfg
-  b2.cfg
-  base.cfg
d  bin
-  buildout.cfg
d  develop-eggs
d  eggs
d  parts
d  recipes

Extensions

An experimental feature allows code to be loaded and run after configuration files have been read but before the buildout has begun any processing. The intent is to allow special plugins such as urllib2 request handlers to be loaded.

To load an extension, we use the extensions option and list one or more distribution requirements, on separate lines. The distributions named will be loaded and any zc.buildout.extensions entry points found will be called with the buildout as an argument.

Let's create a sample extension in our sample buildout created in the previous section:

>>> mkdir(sample_bootstrapped, 'demo')
>>> write(sample_bootstrapped, 'demo', 'demo.py',
... """
... def ext(buildout):
...     print 'ext', list(buildout)
... """)
>>> write(sample_bootstrapped, 'demo', 'setup.py',
... """
... from setuptools import setup
...
... setup(
...     name = "demo",
...     entry_points = {'zc.buildout.extension': ['ext = demo:ext']},
...     )
... """)

Our extension just prints out the word 'demo', and lists the sections found in the buildout passed to it.

We'll update our buildout.cfg to list the demo directory as a develop egg to be built:

>>> write(sample_bootstrapped, 'buildout.cfg',
... """
... [buildout]
... develop = demo
... parts =
... """)
>>> os.chdir(sample_bootstrapped)
>>> print system(os.path.join(sample_bootstrapped, 'bin', 'buildout')),
Develop: '/sample-bootstrapped/demo'

Now we can add the extensions option. We were a bit tricky and ran the buildout once with the demo develop egg defined but without the extension option. This is because extensions are loaded before the buildout creates develop eggs. We needed to use a separate buildout run to create the develop egg. Normally, when eggs are loaded from the network, we wouldn't need to do anything special.

>>> write(sample_bootstrapped, 'buildout.cfg',
... """
... [buildout]
... develop = demo
... extensions = demo
... parts =
... """)

We see that our extension is loaded and executed:

>>> print system(os.path.join(sample_bootstrapped, 'bin', 'buildout')),
ext ['buildout']
Develop: '/sample-bootstrapped/demo'
[1]In the future, additional methods may be added. Older recipes with fewer methods will still be supported.
[2]If we wanted to create a distribution from this package, we would need specify much more information. See the setuptools documentation.