Buildout Platform Versions (BPV)

BPV lets you switch between sets of pinned dependencies more easily.

It's useful for testing a build with several dependency chains. For example, you might be using one freeze of Turbogears in production, but you might also want to test a new freeze in development.

Simple Example

Suppose that we're using flup 1.0.2 in production. We want the production build to continue to use the old flup. But, we want to flip between the production flup and a new flup on the dev box.

Developers can build and test with [production], [dev], or [newest_flup] by setting an environment variable

export PLATFORM\_ENVIRONMENT\_VARIABLE=dev

Or writing a custom develop.cfg. Here's how BPV gets the job done:

buildout.cfg

[buildout]

extensions = buildout_platform_versions

# optionally
# platform-versions-config = WHATEVER_SECTION

[platform-versions-config]
default-platform = production
sources =
    some_config_enhance_file.cfg
    another_config_enhance_file.cfg
platform-env = PLATFORM_ENVIRONMENT_VARIABLE

some_config_enhance_file.cfg

[base]
simplejson = 2.2.1
flup = 1.0.2
WebOb = 1.1.1
Jinja2 = 2.6
pymongo = 2.1

another_config_enhance_file.cfg

[production]
# the production environment uses the base config
<<= <base

[dev_flup]
# wait, there's a new flup to try
flup = 1.0.3dev

[dev]
# on dev boxes, we'll try the new flup
<<= <production
    +dev_flup

[newest_flup]
# we'll unpin and check for a new flup
<<= <production
    -dev_flup

Version File Sources

BPV can read version rosters from a number of sources. We're particularly proud of the egg source:

egg://eggname/path/to/versions.cfg
http://somewhere.com/versions/more_versions.cfg
file:///home/me/config/local_versions.cfg
relative_versions.cfg

The egg protocol support is hand crafted. Everything else relies on urllib. If no protocol is specified, BPV assumes the sources are local files relative to the buildout working directory.

A more complicated example

Using BPV to twiddle a single file is a bit overkill. Its power is more evident when you have some big freezes to manage and need a longer transition period:

[TG2.1-v1]
# frozen 2012-08-12
TurboGears2 = 2.1.1
transaction = 1.2.0
tgext.admin = 0.3.12
tgext.crud = 0.3.13
...

[TG2.1-v2]
# frozen 2013-04-01
TurboGears2 = 2.1.1
transaction = 1.4.1
tgext.admin = 0.5.4
tgext.crud = 1.0.2
...

[production]
# production versions are collected from a bunch of
# frozen projects
<<= +TG2.1-v1
    +several

[dev]
# in dev, use the production versions. But, remove
# all the pins for the first freeze of TG, insert the
# pins from the new freeze.
<<= +production
    -TG2.1-v1
    <TG2.1-v2

Develop Eggs

BPV loads the current version of develop eggs listed in {buildout:develop} and uses those versions to override the explicit pins loaded from other sources.

It will also check for develop-packages listed in the platform-versions-config section and unpin those entirely, so that they pick up whatever the highest version is.

[platform-versions-config]
default-platform = production
sources =
    some_config_enhance_file.cfg
    another_config_enhance_file.cfg
develop-packages = flup
    tgext.admin

Related Projects

[config-enhance][https://github.com/zillow/config-enhance] [buildout][https://github.com/buildout/buildout]

Source Code

[contribute][https://github.com/zillow/buildout-platform-versions]