9.2.4.3 Config Environment Separation

Config environment separation refers to maintaining distinct config content for different deployment environments — development, staging, production — ensuring each environment's services receive configuration appropriate to that specific context, rather than a single, undifferentiated configuration applied everywhere.

Defining Environment-Specific Config Files

Separate files, one per environment, hold configuration appropriate to that specific context.

config/
  app-config.dev.yaml
  app-config.staging.yaml
  app-config.prod.yaml

Selecting the Appropriate Config Through Compose Overrides

A base Compose file combined with an environment-specific override file can select the correct config source for a given deployment.

configs:
  app-config:
    file: ./config/app-config.dev.yaml

configs:
  app-config:
    file: ./config/app-config.prod.yaml

docker compose -f docker-compose.yml -f docker-compose.prod.yml up -d

Why This Separation Matters for Safety

Without clear separation, there's a real risk of accidentally deploying development-oriented configuration (verbose logging, relaxed security settings) to a production environment, or vice versa — a mistake with potentially serious consequences depending on what the misapplied configuration actually affects.

log_level: debug
allow_insecure_connections: true

Configuration values like these are reasonable for development but would be a meaningful security concern if mistakenly applied to production.

Validating Which Config Is Actually in Effect

Confirming exactly which configuration content a given deployment actually received helps catch a misconfiguration before it causes a problem in the wrong environment.

docker compose exec api cat /app/config.yaml

Why Config Environment Separation Matters

Deliberately maintaining and correctly selecting environment-specific configuration is an important safeguard against the kind of environment-mismatch mistakes that can otherwise lead to a development-oriented configuration setting being unintentionally and consequentially applied to production.