https://github.com/pcrespov/sample-app-settings
App sample that captures configuration from env vars
https://github.com/pcrespov/sample-app-settings
pydantic python twelve-factor
Last synced: about 2 months ago
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App sample that captures configuration from env vars
- Host: GitHub
- URL: https://github.com/pcrespov/sample-app-settings
- Owner: pcrespov
- Created: 2021-06-05T13:30:03.000Z (over 4 years ago)
- Default Branch: main
- Last Pushed: 2021-10-09T13:19:53.000Z (almost 4 years ago)
- Last Synced: 2025-01-30T06:12:29.837Z (8 months ago)
- Topics: pydantic, python, twelve-factor
- Language: Python
- Homepage:
- Size: 22.5 KB
- Stars: 0
- Watchers: 2
- Forks: 0
- Open Issues: 1
-
Metadata Files:
- Readme: README.md
Awesome Lists containing this project
README
# App settings
- A [twelve-factor] app [stores config in environment variables](https://12factor.net/config) (often shortened to *env vars* or *env*)
- Every deployment uses a different configuration which is defined in a envfile or with secrets (see e.g. https://github.com/ITISFoundation/osparc-ops/tree/master/services/simcore)
- The variables in the configuration might change with different app versions (adds/removes/modifies)
- Need an easy way to reproduce envfiles
## Requirements:
- app's configuration is stored in a [pydantic] ``Settings`` instance
- ``Settings`` instance automatically captures *envs* and *secrets* upon construction
- Note that any other construction mechanisms is intentionally avoided
- a sigle ``Settings`` per app initialized upon startup
- each app submodule might define its own ``BaseSettings`` class but instances are added as sections in the app ``Settings`` and initialized at the same time
- fields are *const* after construction (i.e. frozen or faux-immutable in python jargon)
- field names are **capitalized** to simplify identifying the corresponding env name (multiple env captures must be really justified)
- CLI can print *envfiles* or json configurations
## Demo
This app assumes three modules:
- **postgres** is a common module so the app uses the settings provided in ``settingslib``
- **mod1** and **mod2** are two custom modules with arbitrary settings
Assuming that all required envs are in place (e.g. rename any of the ``.env-*`` samples as ``.env``) we can display the
configuration resolved by the app:
```commandline
$ python app settings --as-json
{
"APP_HOST": "localhost",
"APP_PORT": 80,
"APP_POSTGRES": {
"POSTGRES_HOST": "localhost",
"POSTGRES_PORT": 5432,
"POSTGRES_USER": "foo",
"POSTGRES_PASSWORD": "secret",
"POSTGRES_DB": "foodb",
"POSTGRES_MINSIZE": 1,
"POSTGRES_MAXSIZE": 50
},
"APP_MODULE_1": {
"MYMODULE_VALUE": 10
},
"APP_MODULE_2": {
"MYMODULE2_SOME_OTHER_VALUE": 33
}
}
```
Can actually get the json-schema as
```commandline
python app settings --as-json-schema
{
"title": "Settings",
"description": "The app settings",
"type": "object",
"properties": {
"APP_HOST": {
"title": "App Host",
...
```
The app captures the ``Settings`` from the *env vars* and it can be printed as an *envfile*
```commandline
$ python app settings --verbose
APP_HOST=localhost
APP_PORT=80
# --- APP_POSTGRES ---
POSTGRES_HOST=localhost
POSTGRES_PORT=5432
POSTGRES_USER=foo
POSTGRES_PASSWORD=secret
# Database name
POSTGRES_DB=foodb
# Maximum number of connections in the pool
POSTGRES_MINSIZE=1
# Minimum number of connections in the pool
POSTGRES_MAXSIZE=50
# --- APP_MODULE_1 ---
# Some value for module 1
MYMODULE_VALUE=10
# --- APP_MODULE_2 ---
MYMODULE2_SOME_OTHER_VALUE=33
```
or even more compact using json as values
```commandline
$ python app settings --verbose --compact
APP_HOST=localhost
APP_PORT=80
APP_POSTGRES={"POSTGRES_HOST": "localhost", "POSTGRES_PORT": 5432, "POSTGRES_USER": "foo", "POSTGRES_PASSWORD": "secret", "POSTGRES_DB": "foodb", "POSTGRES_MINSIZE": 1, "POSTGRES_MAXSIZE": 50}
# Some Module Example
APP_MODULE_1={"MYMODULE_VALUE": 10}
APP_MODULE_2={"MYMODULE2_SOME_OTHER_VALUE": 33}
```
## Usage
```commandline
$ python app settings --help
Usage: app settings [OPTIONS]
Resolves settings and prints envfile
Options:
--as-json / --no-as-json [default: False]
--as-json-schema / --no-as-json-schema
[default: False]
--compact / --no-compact Print compact form [default: False]
--verbose / --no-verbose [default: False]
--help Show this message and exit.
```
## References
- The [twelve-factor] app
- [pydantic] settings
- [typer] CLI
- Original trials: https://github.com/pcrespov/sandbox-python/tree/master/compose-settings
[twelve-factor]:https://12factor.net
[pydantic]:https://pydantic-docs.helpmanual.io/
[typer]:https://typer.tiangolo.com/