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Runtime

Production hardening, logging, HTTP errors.

Default-secure or refuse to boot. The app declines to start in production unless authentication is required and the DB role is the read-write app role, not the migration owner. Everything else (limits, tracing, log shape) is wired so a missing piece is visible, not silent.

Production hardening

Wired in cora/api/main.py:create_app().

  • Body size limit. BodySizeLimitMiddleware returns 413 over Settings.max_request_body_size_bytes (default 1 MiB). Production also enforces at the reverse proxy.
  • Prometheus /metrics. Per-app CollectorRegistry (global crashes on a second TestClient(create_app())). Hidden from its own counters and from OpenAPI.
  • OpenTelemetry tracing. Settings.otel_exporter: none/console/otlp. OTLP honours OTEL_EXPORTER_OTLP_* env vars. Trace context is the source of truth for correlation: current_correlation_id() returns UUID(int=trace_id). Handler spans via with_tracing in wire.py; name <bc>.<command|query>.<command_name>.
  • Auth (X-Principal-Id). get_principal_id trusts the header. Absent: Settings.require_authenticated_principal controls fallback (False = SYSTEM_PRINCIPAL_ID; True = 401). Production MUST front with an auth proxy that verifies credentials, strips client-supplied headers, and sets the verified UUID.
  • Production startup gate. Refuses to boot if app_env in {"prod","production"} AND require_authenticated_principal=False. Opt in: APP_ENV=prod, REQUIRE_AUTHENTICATED_PRINCIPAL=true, DATABASE_URL=postgresql://cora_app:.../cora.
  • DB role separation. cora_app has SELECT + INSERT on events + entries_*; UPDATE/DELETE/TRUNCATE revoked. Migrations run as the database owner. proj_* tables get full DML.

Logging

Two patterns:

  • Handlers: <verb>.<event> (register_actor.start, register_actor.denied, register_actor.success). Every handler emits start plus denied or success. Decider failures propagate as exceptions.
  • Cross-cutting: <concern>.<event> (idempotency.cache_hit, body_size_limit.rejected).

Field names:

  • correlation_id: request correlation (str-cast UUID)
  • causation_id: command handlers only; upstream event id (null for HTTP/MCP root). Always emitted.
  • principal_id: calling principal (str-cast UUID)
  • command_name / query_name: dataclass name
  • actor_id (or <aggregate>_id): aggregate id when in scope. One key per concept.

HTTP errors

  • In routes: raise HTTPException(...). FastAPI idiom.
  • In exception handlers: return JSONResponse(...). Raising HTTPException inside a handler creates nested-exception pitfalls (FastAPI guidance).

Routes raise; handlers return. Same JSON shape over the wire.