stackato-buildpack-python

This is a simple but functional buildpack for (Active)Python meant to be used with Stackato v3 or higher.

This is a variant of the basic buildpack provided by ActiveState.

To use this buildpack, you can:

• structure your application like a python package, and provide a setup.py. This will be straightforwardly invoked and the application's package will be available globally within the docker container. pip will be used to install the requirements associated to the application's package

• specify your Python dependencies in one, or both, of the following files. Note that those dependencies will be also processed if you have structured your application as a python package. - requirements.txt: pip will be used to install these. Optional pip

  parameters can be specified by providing a $PIP_OPTS environment variable in the stackato manifest file.

  • requirements.pypm: pypm will be used to install these. Optional pypm parameters can be specified by providing a $PYPM_OPTS environment variable in the stackato manifest file.

Selecting an alternate runtime

By default, Python 2.7 will be used unless the $PYTHON_VERSION environment variable is set in the stackato manifest file.

Alternatively, a runtime.txt file can be bundled with the application, with the following content:

Python-<python_version>

Currently supported versions are 2.7 and 3.3.

Python wheels support and caching

By default, the buildpack will use the default stackato cache directory to cache downloaded packages and generated wheels. An alternative location can be provided by defining the $PYTHON_CACHE_DIR environment variable.

Warning

As of version 3.0.x, stackato appears to discard the cache entirely on each staging attempt. This greatly diminishes the value of this mechanism.

One way to remedy this problem is to define a custom stackato filesystem to be used for this caching.

The following stackato manifest outlines how this could be done:

name: myapp
instances: 1
buildpack: https://github.com/kapouille/stackato-buildpack-python.git
services:
   python-install-cache:
     type: filesystem
stackato:
   env:
     PYTHON_CACHE_DIR:
       default: $STACKATO_FILESYSTEM_PYTHON_INSTALL_CACHE

When pip is used for install (in all cases apart from when providing a requirements.pypm file), the buildpack will generate and cache python wheels for all required packages. This means that packages that need long compilation times should be instantly installed on subsequent deployments, provided the cache wasn't cleared.

Debugging support

Additional debug logs can be enabled by setting the $BUILDPACK_DEBUG environment variable.