converge 1.0.1

Ultra simple settings management for (only) Python apps

Contents

• 1 What is it?

• 2 Getting started

  • 2.1 Easy to use

  • 2.2 Install

• 3 .convergerc

  • 3.1 Supported directives

• 4 Supported settings files

• 5 Guidelines

• 6 Overriding settings

  • 6.1 Example

• 7 Overriding partial settings

• 8 (Slightly) Advanced usage

  • 8.1 Using SETTINGS_DIR

  • 8.2 Using environment variables

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 load desired application settings.

2 Getting started

2.1 Easy to use

default_settings.py
-------------------
SERVER_PORT = 8000
DOMAIN = 'example.com'
ADMIN_EMAIL = '[e-mail]'

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

3 .convergerc

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

3.1 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 = '[e-mail]: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 = '[e-mail]:shon/converge-test-settings.git'
GIT_SETTINGS_SUBDIR = 'myapp1'

4 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

5 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``

6 Overriding settings

Defining module veriables in site_settings.py

6.1 Example

default_settings.py

SERVER_PORT = 9999

site_settings.py

SERVER_PORT = 8888

7 Overriding partial settings

Example:

default_settings.py

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

site_settings.py

DB.PORT = 1111

8 (Slightly) Advanced usage

In case if you want to keep all settings.py files in a directory. Use SETTINGS_DIR directive in .convergerc file.

8.1 Using SETTINGS_DIR

>> 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
     |
     |

8.2 Using environment variables

It is possible use environment variables, which is useful in cases wheere you want to start multiple instances of same app directory. Any of the supported directive can exported as environment variable.

export SETTINGS_DIR='settings/site1'
gunicorn --workers=2 service:app

export SETTINGS_DIR='settings/site2'
gunicorn --workers=2 service:app