zulip/docs/subsystems/settings.md

Settings system

The page documents the Zulip settings system, and hopefully should help you decide how to correctly implement new settings you're adding to Zulip.

We have two types of administrative settings in Zulip:

• Server settings are set via configuration files, and apply to the whole Zulip installation.
• Realm settings (or organization settings) are usually set via the /#organization page in the Zulip web application, and apply to a single Zulip realm/organization. (Which, for most Zulip servers, is the only realm on the server).

Philosophically, the goals of the settings system are to make it convenient for:

• Zulip server administrators to configure Zulip's featureset for their server without needing to patch Zulip
• Realm administrators to configure settings for their organization independently without needing to talk with the server administrator.
• Secrets (passwords, API keys, etc.) to be stored in a separate place from shareable configuration.

Server settings

Zulip uses the Django settings system, which means that the settings files are Python programs that set a lot of variables with all-capital names like EMAIL_GATEWAY_PATTERN. You can access these anywhere in the Zulip Django code using e.g.:

from django.conf import settings
print(settings.EMAIL_GATEWAY_PATTERN)

Additionally, if you need to access a Django setting in a shell script (or just on the command line for debugging), you can use e.g.:

$ ./scripts/get-django-setting EMAIL_GATEWAY_PATTERN
%s@localhost:9991

Zulip has separated those settings that we expect a system administrator to change (with nice documentation) from the ~1000 lines of settings needed by the Zulip Django app. As a result, there are a few files involved in the Zulip settings for server administrators. In a production environment, we have:

• /etc/zulip/settings.py (the template is in the Zulip repo at zproject/prod_settings_template.py) is the main system administrator-facing settings file for Zulip. It contains all the server-specific settings, such as how to send outgoing email, the hostname of the PostgreSQL database, etc., but does not contain any secrets (e.g. passwords, secret API keys, cryptographic keys, etc.). The way we generally do settings that can be controlled with shell access to a Zulip server is to put a default in zproject/default_settings.py, and then override it here.

• /etc/zulip/zulip-secrets.conf (generated by scripts/setup/generate_secrets.py as part of installation) contains secrets used by the Zulip installation. These are read using the standard Python ConfigParser, and accessed in zproject/computed_settings.py by the get_secret function. All secrets/API keys/etc. used by the Zulip Django application should be stored here, and read using the get_secret function in zproject/config.py.

• zproject/settings.py is the main Django settings file for Zulip. It imports everything from zproject/configured_settings.py and zproject/computed_settings.py.

• zproject/configured_settings.py imports everything from zproject/default_settings.py, then in a prod environment imports /etc/zulip/settings.py via a symlink.

• zproject/default_settings.py has the default values for the settings the user would set in /etc/zulip/settings.py.

• zproject/computed_settings.py contains all the settings that are constant for all Zulip installations or computed as a function of zproject/configured_settings.py (e.g. configuration for logging, static assets, middleware, etc.).

In a development environment, we have zproject/settings.py, and additionally:

• zproject/dev_settings.py has the settings for the Zulip development environment; it mostly just imports prod_settings_template.py.

• zproject/dev-secrets.conf replaces /etc/zulip/zulip-secrets.conf.

• zproject/test_settings.py imports everything from zproject/settings.py and zproject/test_extra_settings.py.

• zproject/test_extra_settings.py has the (default) settings used for the Zulip tests (both backend and Puppeteer), which are applied on top of the development environment settings.

When adding a new server setting to Zulip, you will typically add it in two or three places:

• zproject/default_settings.py, with a default value for production environments.

• If the settings has a secret key, you'll add a get_secret call in zproject/computed_settings.py (and the user will add the value when they configure the feature).

• In an appropriate section of zproject/prod_settings_template.py, with documentation in the comments explaining the setting's purpose and effect.

• Possibly also zproject/dev_settings.py and/or zproject/test_settings.py, if the desired value of the setting for Zulip development and/or test environments is different from the default for production.

Most settings should be enabled in the development environment, to maximize convenience of testing all of Zulip's features; they should be enabled by default in production if we expect most Zulip sites to want those settings.

Testing non-default settings

You can write tests for settings using e.g. with self.settings(GOOGLE_CLIENT_ID=None). However, this only works for settings which are checked at runtime, not settings which are only accessed in initialization of Django (or Zulip) internals (e.g. DATABASES). See the Django docs on overriding settings in tests for more details.

Realm settings

Realm settings are preferred for any configuration that is a matter of organizational policy (as opposed to technical capabilities of the server). As a result, configuration options for user-facing functionality is almost always added as a new realm setting, not a server setting. The new feature tutorial documents the process for adding a new realm setting to Zulip.

So for example, the following server settings will eventually be replaced with realm settings:

• NAME_CHANGES_DISABLED
• INLINE_IMAGE_PREVIEW
• ENABLE_GRAVATAR
• Which authentication methods are allowed should probably appear in both places; in server settings indicating the capabilities of the server, and in the realm settings indicating which methods the realm administrator wants to allow users to log in with.