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Manages automatic updates and evolutions which are better suited outside schema migrations

Project description

About tgext.evolve

tgext.evolve is a TurboGears2 extension for generic migrations and evolutions.

tgext.evolve *is safe to be used in multiprocessing and multithreading environments*
as it relies on a distributed lock on your database to perform evolutions.

During the evolution period the application will respond with a **503** status code,
feel free to configure TurboGears to trap it and use your ErrorController to provide
a custom page.


tgext.evolve can be installed from pypi::

pip install tgext.evolve

should just work for most of the users.


To enable tgext.evolve put inside your application
``config/`` the following::

import tgext.evolve
tgext.evolve.plugme(base_config, options={
'evolutions': [
# ... Your evolutions ...

or you can use ``tgext.pluggable`` when available::

from tgext.pluggable import plug
plug(base_config, 'tgext.evolve', evolutions=[
# ... Your evolutions ...

tgext.evolve can then be disabled using the ``tgext.evolve.enabled = false``
option in your configuration files. This is often the case during test suites.

Using Evolutions

Evolutions are a subclass of ``tgext.evolve.Evolution`` that
must provide an ``evolution_id`` property and an ``evolve()``

Here is a sample evolution that does not much apart waiting for 10 seconds::

import time
from tgext.evolve import Evolution

class TestEvolution1(Evolution):
evolution_id = 'test_evolution_1'

def evolve(self):

Please note that in case you modify data or touch the database
through ``model.DBSession`` or other manners you must ``flush``
and ``commit`` your UnitOfWork and Transaction yourself as evolutions
are performed outside the transaction manager in a separated thread.

Then you can register your evolution with something like::

from tgext.pluggable import plug
plug(base_config, 'tgext.evolve', evolutions=[

In case your evolution requires parameters you can register an
instance of it instead of registering the class.

.. note::

There is no opposite to the ``evolve()`` method as there is no
guarantee that evolutions are reversible. In case you need
reversible migrations for database schemas please use a
schema migration framework.



* Allow disabling tgext.evolve using ``tgext.evolve.enabled = False`` in *.ini files.


* First release with only MongoDB/Ming support.

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