Platform Runtime Plumbing

Verified status as of March 28, 2026.

Quick View

• Complexity: Advanced
• Typical time: 25-35 minutes
• Outcome: predictable request pipeline behavior (middleware-style hooks, CORS, raw request access, events)

Request Pipeline Boundaries

FastFN request path:

1. Route resolution
2. Method/guard checks
3. Runtime dispatch
4. Response normalization

Equivalent to middleware responsibilities in other stacks: keep policy checks before business code.

CORS Matrix

Scenario	Origin	Methods	Headers	Credentials	Result
Public read API	specific domains	GET	minimal	no	safest default
Dashboard backend	trusted domain	GET,POST,PUT,DELETE	auth headers	yes	strict allowlist
Internal tools	private network	all needed	explicit list	optional	keep network-restricted

Example check:

curl -i 'http://127.0.0.1:8080/items' \
  -H 'Origin: https://app.example.com' \
  -H 'Access-Control-Request-Method: POST'

Using Raw Request Directly

Use event fields directly for edge cases:

• event.method
• event.headers
• event.query
• event.path
• event.body

This is useful for custom signature verification or low-level protocol adaptation.

Lifecycle Events and Timing

Operational events to observe:

• startup (OpenResty + runtime daemons)
• health checks (/_fn/health)
• graceful shutdown / restart
• runtime process crash + restart path

curl -sS 'http://127.0.0.1:8080/_fn/health'

Validation

• CORS preflight and simple requests behave consistently.
• Policy checks reject unauthorized traffic before runtime handler logic.
• Health endpoint reflects runtime up/down state.

Troubleshooting

• If CORS fails, confirm exact Origin and response headers.
• If preflight passes but request fails, inspect method guards and auth checks separately.
• If requests hang, verify runtime daemon socket health.

Related links

• Run and test
• Deploy to production
• Architecture

Last reviewed: March 28, 2026 · Docs on fastfn.dev