converge 0.9.8

.. contents::
.. sectnum::


What is it?
-----------

If you are a Python developer who likes to keep application configuration in simple Python modules and that your app have some default settings and production/dev/test setting files, **converge** can help you merge settings and load desired application settings.

.. raw:: html

<a href="https://asciinema.org/a/155855?autoplay=1&speed=3"><img src="https://asciinema.org/a/155855.png"/></a>


Getting started
----------------

Easy to use
~~~~~~~~~~~~

.. code:: bash

default_settings.py
-------------------
SERVER_PORT = 8000
DOMAIN = 'example.com'
ADMIN_EMAIL = 'admin@example.com'

dev_settings.py
---------------
SERVER_PORT = 9000


.. code:: python

import settings
print(settings.SERVER_PORT) # 9000
print(settings.DOMAIN) # example.com
print(settings.get('VAR_THAT_DOESNT_EXIST')) # None


Install
~~~~~~~

.. code:: bash

pip install converge

.convergerc
------------

.convergerc file helps converge choose application mode and in turn load correct settings file.

Supported directives
~~~~~~~~~~~~~~~~~~~~

_All directives are optional._

**APP_MODE**

Valid values are

- prod
- dev
- test
- staging
- beta

Based on ``mode`` appropriate settings module would be used (if available)

**SETTINGS_DIR**

If your settings files are in different directory, use SETTINGS_DIR to point converge to correct path.

.. note:: Remember to drop __init__.py in settings directory.


**GIT_SETTINGS_REPO**

Fetching application settings from a git repository is supported too. If such configuration is specified, git repository is cloned into `SETTINGS_DIR`.

**GIT_SETTINGS_SUBDIR**

In case you
- use same git repository to host configurations of more than one applications and
- say settings files are in different subdirectories

Example

::

my-git-repo/
|
|- myapp1
| |
| |- default_settings.py
| |- prod_settings.py
|
|
|- myapp2

::

cat .convergerc

SETTINGS_DIR = 'appsettings'
GIT_SETTINGS_REPO = 'git@github.com:shon/converge-test-settings.git'
GIT_SETTINGS_SUBDIR = 'myapp1'

In this case all \*_settings.py files in myapp1/ would be copied to appsettings.


**Example**

::

.convergerc
-----------

APP_MODE = 'test'
SETTINGS_DIR = 'settings'
GIT_SETTINGS_REPO = 'git@github.com:shon/converge-test-settings.git'
GIT_SETTINGS_SUBDIR = 'myapp1'


Supported settings files
-------------------------

- Defaults: default_settings.py

- Mode
- production: prod_settings.py
- development: dev_settings.py
- test: test_settings.py
- staging: staging_settings.py
- beta: beta_settings.py

- Deployment specific: site_settings.py


Guidelines
-----------

Settings files are usual Python files that can contain valid python code however here are some guidelines for user

- Use module variables for global application wide configuration
- Use UPPERCASE while naming settings variables
- For values prefer basic python datatypes such as string, integer,
tuples
- eg. ``SERVER_PORT = 1234``
- Avoid complex python operations
- Use simple classes for config sections
.. code:: python

class DB:
HOST = 'db.example.com'
PORT = 1234

- Use simple string operations to avoid repetition
.. code:: python

BASE_DOMAIN = 'example.com'
API_URL = 'api.' + BASE_DOMAIN``

Overriding settings
-------------------

Defining module veriables in site_settings.py

Example
~~~~~~~

**default_settings.py**

``SERVER_PORT = 9999``

**site_settings.py**

``SERVER_PORT = 8888``

Overriding partial settings
---------------------------

Example:

**default_settings.py**

.. code:: python

class DB:
HOST = 'db.example.com'
PORT = 1234

**site_settings.py**

.. code:: python

DB.PORT = 1111

(Slightly) Advanced usage
---------------------------
In case if you want to keep all settings.py files in a directory. Use `SETTINGS_DIR` directive in .convergerc file.

Example
~~~~~~~


.. code:: bash

>> cat .convergerc

APP_MODE = 'prod'
SETTINGS_DIR = 'settings/fat_server'

This is useful when you have to deploy multiple instances of an app with different configs

::

`-- settings/
|
|-- server1/
| |
| |--default_settings.py
| |--prod_settings.py
|
|-- server2/
| |--default_settings.py
| |--prod_settings.py
|
|