Environment files

Environment files (.env) define how a product connects to its infrastructure — database hostnames, ports, credentials, feature-specific service URLs, and runtime flags. They are the source of truth for runtime configuration.

Why they matter
File hierarchy
1. Product level
2. Feature level
Dev vs prod separation
Merge flow
1. Development (product:env --merge --dev)
2. Production (product:build)
Key variables
Who reads them
See also

Why they matter

The other sources of truth define what a product is made of (pyproject.toml), which combinations are valid (UVL), and what state features are in (manifest). Environment files define how it runs: which hostname the database listens on, which port Redis exposes, what credentials to use, and whether to seed the database on startup.

Without environment files, Docker containers cannot connect to each other, the framework cannot build a database URI, and features that depend on external services (mail, Redis, storage) cannot function.

File hierarchy

Each product and feature can declare environment files. During deployment, these are merged into a single configuration.

Product level

File	Purpose	Git-tracked
`docker/.env.dev.example`	Template for development	Yes
`docker/.env.prod.example`	Template for production (credentials as `<SET>`)	Yes
`docker/.env`	Active dev config (generated from example)	No
`docker/.env.deploy`	Active prod config (generated by `product:deploy`)	No
`docker/.env.deploy.example`	Merged template (generated by `product:build`)	No

Feature level

File	Purpose	Git-tracked
`docker/.env.example`	Default feature env template	Yes
`docker/.env.dev.example`	Dev-specific overrides	Yes
`docker/.env.prod.example`	Prod-specific overrides	Yes
`docker/.env`	Active config (generated by `product:env`)	No

Dev vs prod separation

Development and production use separate files to prevent configuration collisions:

Dev reads from docker/.env — contains dev hostnames (e.g., sample_splent_app_db), default passwords, seeding enabled.
Prod reads from docker/.env.deploy — contains deploy hostnames (e.g., sample_splent_app_db_deploy), real credentials, seeding disabled.

The production entrypoint syncs .env.deploy to .env on startup so the framework’s load_dotenv() picks up the correct values.

Never commit .env or .env.deploy files with real credentials. Only commit .example templates.

Merge flow

Development (`product:env --merge --dev`)

product/.env.dev.example  +  feature1/.env.example  +  feature2/.env.example
                                    ↓
                          product/docker/.env

Product values take priority (via setdefault). Features only add keys that the product doesn’t already define.

Production (`product:build`)

product/.env.prod.example  +  feature1/.env.example  +  feature2/.env.example
                                    ↓
                       product/docker/.env.deploy.example

Feature values override product values (via update). This allows features to inject their required variables (e.g., REDIS_URL, MAIL_SERVER).

Key variables

Variable	Set by	Used by
`SPLENT_APP`	Product	CLI, framework, startup scripts
`SPLENT_ENV`	Developer/CI	CLI (feature resolution), startup scripts
`WORKING_DIR`	Docker	CLI, framework (path resolution)
`MARIADB_HOSTNAME`	Product env	Framework (database URI), startup scripts
`MARIADB_DATABASE`	Product env	Framework, migration scripts
`MARIADB_USER` / `MARIADB_PASSWORD`	Product env	Framework, health checks, startup scripts
`REDIS_URL`	Redis feature	Framework (session store), app code
`REDIS_HOST_PORT`	Redis feature	Docker Compose (port mapping)
`MAIL_SERVER` / `MAIL_PORT`	Mail feature	Framework (Flask-Mail), app code
`RUN_DB_SEED`	Product env	Startup script `04_handle_migrations.sh`
`GUNICORN_WORKERS`	Operator	Production entrypoint (default: `2*nproc+1`)
`GUNICORN_TIMEOUT`	Operator	Production entrypoint (default: `120`)

Who reads them

Consumer	What it reads	Why
`product:env`	`.env.example` templates	Generates and merges `.env` files
`product:build`	`.env.prod.example` from product + features	Creates `.env.deploy.example`
`product:deploy`	`.env.deploy.example`	Creates `.env.deploy`, prompts for `<SET>` values
Docker Compose	`env_file:` directive	Injects vars into containers
Framework `load_dotenv`	`<product>/docker/.env`	Overrides process env vars
Startup scripts	`$MARIADB_*`, `$RUN_DB_SEED`	Database connection, seeding
Health checks	`$$MARIADB_USER`, `$$MARIADB_PASSWORD`	Docker Compose `CMD-SHELL`