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`Buildout <https://pypi.python.org/pypi/zc.buildout>`_ composes your application for you, according to your rules.
To compose your application you must define the eggs you need, which version, what configuration files Buildout has to generate for you, what to download and compile, and so on.
Buildout downloads the eggs you requested and resolves all dependencies. You might need five different eggs, but in the end, Buildout has to install 300 eggs, all with the correct version in order to resolve all the dependencies.
Buildout does this without touching your system Python or affecting any other package. The commands created by buildout bring all the required packages into into the Python environment. Each command it creates my use different libraries or even different versions of the same library.
Plone needs folders for logfiles, databases and configuration files. Buildout assembles all of this for you.
You will need a lot of functionality that Buildout does not provide out of the box, so you'll need several extensions.
Some extensions provide new functionality, like mr.developer, the best way to manage your checked out sources.
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The syntax of Buildout configuration files is similar to classic ini files. You write a parameter name, an equals sign and the value. If you enter another value in the next line and indent it, Buildout understands that both values belong to the parameter name, and the parameter stores all values as a list.
A Buildout consists of multiple sections. Sections start with the section name in square brackets. Each section declares a different part of your application. As a rough analogy, your Buildout file is a cookbook with multiple recipes.
There is a special section, called `[buildout]`. This section can change the behavior of Buildout itself. The variable :samp:`parts` defines, which of the existing sections should actually be used.
Buildout itself has no idea how to install Zope. Buildout is a plugin based system, it comes with a small set of plugins to create configuration files and download eggs with their dependencies and the proper version. To install a Zope site, you need a third-party plugin. The plugin provide new recipes that you have to declare and configure in a section.
One example is the section
[instance]
recipe = plone.recipe.zope2instance
user = admin:adminThis uses the python-package plone.recipe.zope2instance to create and configure the Zope 2 instance which we use to run Plone. All the lines after recipe = xyz are the configuration of the used recipe.
.. seealso::
http://www.buildout.org/en/latest/docs/recipelist.html
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Buildout allows you to use references in the configuration. A variable declaration may not only hold the variable value, but also a reference to where to look for the variable value.
If you have a big setup with many Plone sites with minor changes between each configuration, you can generate a template configuration, and each site references everything from the template and overrides just what needs to be changed.
Even in smaller buildouts this is a useful feature. We are using `collective.recipe.omelette <https://pypi.python.org/pypi/collective.recipe.omelette>`_. A very practical recipe that creates a virtual directory that eases the navigation to the source code of each egg.
The omelette-recipe needs to know which eggs to reference. We want the same eggs as our instance uses, so we reference the eggs of the instance instead of repeating the whole list.
Another example: Say you create configuration files for a webserver like nginx, you can define the target port for the reverse proxy by looking it up from the zope2instance recipe.
Configuring complex systems always involves a lot of duplication of information. Using references in the buildout configuration allows you to minimize these duplications.
Let us walk through the buildout.cfg for the training and look at some important variables:
[buildout]
parts =
instance
packages
codeintel
zopeskel
extends =
http://dist.plone.org/release/4.3.3/versions.cfg
versions.cfg
find-links = http://dist.plone.org
extensions = mr.developer
sources = sources
auto-checkout = *
versions = versions
# If you do _not_ use vagrant please add a '#' at the beginning of the
# following line and uncomment the line after.
# This will set the location of three directories:
# file-storage: set in [instance] defines where the ZODB is stored
# blob-storage: set in [instance] defines where Binary Files are stored
# packages-dir: set in [packages] defines a location for symlinks to all eggs
buildout_dir = /home/vagrant
#buildout_dir = ${buildout:directory}
eggs =
Plone
Pillow
# development tools
z3c.jbot
plone.api
plone.reload
Products.PDBDebugMode
plone.app.debugtoolbar
Paste
# 3rd party addons
Products.PloneFormGen
collective.plonetruegallery
collective.js.datatables
eea.facetednavigation
collective.behavior.banner
# dexterity default types
plone.app.contenttypes
# our addons
# ploneconf.site
# starzel.votable_behavior
[instance]
recipe = plone.recipe.zope2instance
user = admin:admin
eggs = ${buildout:eggs}
http-address = 8080
file-storage = ${buildout:buildout_dir}/var/filestorage/Data.fs
blob-storage = ${buildout:buildout_dir}/var/blobstorage
[packages]
recipe = collective.recipe.omelette
eggs = ${buildout:eggs}
location = ${buildout:buildout_dir}/packages
[codeintel]
recipe = corneti.recipes.codeintel
eggs = ${buildout:eggs}
[zopeskel]
recipe = zc.recipe.egg
eggs =
ZopeSkel
Paste
PasteDeploy
PasteScript
zopeskel.diazotheme
zopeskel.dexterity
zest.releaser
${buildout:eggs}
[sources]
# ploneconf.site = fs ploneconf.site full-path=${buildout:directory}/src/ploneconf.site
collective.behavior.banner = git https://github.com/collective/collective.behavior.banner.git pushurl[email protected]:collective/collective.behavior.banner.git rev=af2dc1f21b23270e4b8583cf04eb8e962ade4c4d
starzel.votable_behavior = git git://github.com/collective/starzel.votable_behavior.gitWhen you run ./bin/buildout without any arguments, Buildout will look for this file.
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Let us look closer at some variables.
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.. code-block:: cfg
extends =
http://dist.plone.org/release/4.3.3/versions.cfg
versions.cfg
This line tells Buildout to read more configuration files. You can refer to configuration files on your computer or to configuration files on the Internet, reachable via http. You can use multiple configuration files to share configurations between multiple Buildouts, or to separate different aspects of your configuration into different files. Typical examples are version specifications, or configuration that differ between different environments.
.. code-block:: cfg
eggs =
Plone
Pillow
z3c.jbot
plone.api
plone.reload
Products.PDBDebugMode
plone.app.debugtoolbar
Paste
Products.PloneFormGen
collective.plonetruegallery
collective.js.datatables
eea.facetednavigation
collective.behavior.banner
plone.app.contenttypes
# ploneconf.site
# starzel.votable_behavior
This is the list of eggs that we configure to be available for Zope. These eggs are put in the python-path of the script ``bin/instance`` with which we start and stop Plone.
The egg ``Plone`` is a wrapper without code. Among its dependencies is ``Products.CMFPlone`` which is the egg that is at the center of Plone.
The rest are addons we already used or will use later. The last eggs are commented out so they will not be installed by Buildout.
The file ``versions.cfg`` that is included by the ``extends = ...`` statement hold the version-pinnings:
.. code-block:: cfg
[versions]
# dev tools
z3c.jbot = 0.7.2
plone.api = 1.1.0
plone.app.debugtoolbar = 1.0a3
...
This is another special section. It has become a special section by declaration. In our :samp:`[buildout]` section we set a variable :samp:`versions = versions`. This told buildout, that there is a section named versions, containing version information. When Buildout installs eggs it will use the version defined in this section.
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There are many more important things to know, and we can't go through them in all the detail but I want to focus on one specific feature: **mr.developer**
With mr.developer you can declare which packages you want to check out from which version control system and which repository URL. You can check out sources from git, svn, bzr, hg and maybe more. Also, you can say that some source are in your local file system.
``mr.developer`` comes with a command, ``./bin/develop``. You can use it to update your code, to check for changes and so on. You can activate and deactivate your source checkouts. If you develop your extensions in eggs with separate checkouts, which is a good practice, you can plan releases by having all source checkouts deactivated, and only activate them, when you write changes that require a new release. You can activate and deactivate eggs via the ``develop`` command or the Buildout configuration. You should always use the Buildout way. Your commit serves as documentation.
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You might have noticed that most if not all functionality is only available via plugins. One of the things that Buildout excels at without any plugin, is the dependency resolution. You can help Plone in dependency resolution by declaring exactly which version of an egg you want. This is only one use case. Another one is much more important: If you want to have a repeatable Buildout, one that works two months from now also, you *must* declare all your egg versions. Else Buildout might install newer versions.
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As you can see, you can build very complex systems with Buildout. It is time for some warnings. Be selective in your recipes. Supervisor is a program to manage running servers, its pretty good. There is a recipe for it.
The configuration for this recipe is more complicated than the supervisor configuration itself! By using this recipe, you force others to understand the recipes specific configuration syntax *and* the supervisor syntax. For such cases, `collective.recipe.template <https://pypi.python.org/pypi/collective.recipe.template>`_ is a better match.
Another problem is error handling. Buildout tries to install a weird dependency you do not actually want? Buildout will not tell you, where it is coming from.
If there is a problem, you can always run Buildout with ``-v``, to get more verbose output, sometimes it helps.
.. code-block:: bash
$ ./bin/buildout -v
If strange egg versions are requested, check the dependencies declaration of your eggs and your version pinnings.
Some parts of Buildout interpret egg names case-sensitive, others won't. This can result in funny problems.
Always check out the ordering of your extends, always use the :samp:`annotate` command of Buildout to see if it interprets your configuration differently than you. Restrict yourself to simple Buildout files. You can reference variables from other sections, you can even use a whole section as a template. We learned that this does not work well with complex hierarchies and had to abandon that feature.
In the chapter :doc:`deployment_sites` we will have a look at a production-ready for Plone that has many useful features.
.. seealso::
Buildout-Documentation
* http://docs.plone.org/old-reference-manuals/buildout/index.html
* http://www.buildout.org/en/latest/docs/index.html
Troubleshooting
http://docs.plone.org/manage/troubleshooting/buildout.html
A minimal buildout for Plone 4
https://github.com/collective/minimalplone4
The buildout of the unified installer has some valuable documentation as inline-comment
* https://github.com/plone/Installers-UnifiedInstaller/blob/master/buildout_templates/buildout.cfg
* https://github.com/plone/Installers-UnifiedInstaller/blob/master/base_skeleton/base.cfg
* https://github.com/plone/Installers-UnifiedInstaller/blob/master/base_skeleton/develop.cfg
mr.developer
https://pypi.python.org/pypi/mr.developer/