s4u.upgrade 1.3

This package implements a very minimal upgrade framework for use in Python applications. Its design consists of three parts:

1. context providers, which are responsible for setting up the context required for an upgrade step. For example establishing a connection to a SQL server or configuring SQLALchemy.

2. upgrade steps, which are functions that perform the actual upgrade steps.

3. a commandline tool to run the upgrade steps and required context providers.

In order to keep the framework minimal there are a few things which are deliberately not supported:

• No versioning of the environment is done; the tool will always run all all upgrade steps. Each step must support being run multiple times without unexpected results.

• Downgrades are not supported.

• Depdendencies between upgrade steps are not supported.

Here is a basic context provider which configures SQLAlchemy:

@upgrade_context('sql')
def setup_sqlalchemy(options):
    engine = create_engine('postgresql:///projectA')
    return {'sql-engine': engine}

Here is an example upgrade step to add missing tables and indices in a project using SQLALchemy:

@upgrade_step(require=['sql'])
def add_missing_tables(environment):
    meta.metadata.create_all(environment['sql-engline'])

And this is how you run the upgrade:

$ bin/upgrade --scan my.package