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1   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 start the application with desired settings based on environment variables.

2   Getting started

2.1   Easy to use

./settings/default_settings.py
-------------------
SERVER_PORT = 8000
DOMAIN = 'example.com'
ADMIN_EMAIL = '[email protected]'

./settings/dev_settings.py
---------------
SERVER_PORT = 9000
import settings
print(settings.SERVER_PORT)  # 9000
print(settings.DOMAIN)  # example.com
print(settings.get('VAR_THAT_DOESNT_EXIST'))  # None

2.2   Install

pip install converge

2.3   Supported environment variables

_All directives are optional._

APP_MODE

Valid values are

  • dev (default)
  • test
  • staging
  • beta
  • prod

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

SETTINGS_DIR

Defaults to "settings".

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

export SETTINGS_DIR='appsettings'
export GIT_SETTINGS_REPO='[email protected]:shon/converge-test-settings.git'
export GIT_SETTINGS_SUBDIR='myapp1'

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

Example

export APP_MODE='test'
export SETTINGS_DIR='settings'
export GIT_SETTINGS_REPO='[email protected]:shon/converge-test-settings.git'
export GIT_SETTINGS_SUBDIR='myapp1'

3   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

4   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
    class DB:
    HOST = 'db.example.com'
    PORT = 1234
  • Use simple string operations to avoid repetition
    BASE_DOMAIN = 'example.com'
API_URL = 'api.' + BASE_DOMAIN``

5   Overriding settings

Defining module veriables in site_settings.py

5.1   Example

default_settings.py

SERVER_PORT = 9999

site_settings.py

SERVER_PORT = 8888

6   Overriding partial settings

Example:

default_settings.py

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

site_settings.py

DB.PORT = 1111

7   (Slightly) Advanced usage

In case if you want to keep all settings.py files in a directory. Use SETTINGS_DIR environment variable.

7.1   Using SETTINGS_DIR

export APP_MODE='prod'
export 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
     |
     |