deploy

# Elixir/Phoenix Deployment Reference Quick reference for deploying Elixir/Phoenix applications. ## Iron Laws — Never Violate These 1. **Config at runtime, not compile time** — Secrets in `config.exs` get baked into the release binary. Use `runtime.exs` with env vars so secrets are resolved at boot 2. **Graceful shutdown ≥ 60 seconds** — Shorter timeouts kill in-flight requests and WebSocket connections mid-operation, causing data loss for users 3. **Health checks required** — Without startup/liveness/readiness endpoints, orchestrators can't distinguish a booting node from a dead one, leading to cascading restarts 4. **SSL verification for database** — Skipping `verify: :verify_peer` allows MITM attacks between your app and database; production data traverses the connection 5. **No CPU limits** — The BEAM scheduler assumes it owns all cores; cgroups CPU limits cause scheduler collapse where the VM thinks it has more cores than it can use, leading to latency spikes 6. **Guard optional service credentials** — `runtime.exs` runs whenever a release boots, including `eval`-based migration commands. Only require S3, Redis, and similar credentials when that integration is enabled ## Quick Configuration ### runtime.exs (Essential) ```elixir if config_env() == :prod do database_url = System.get_env("DATABASE_URL") || raise "DATABASE_URL is required" secret_key_base = System.get_env("SECRET_KEY_BASE") || raise "SECRET_KEY_BASE is required" host = System.get_env("PHX_H...