Core Concepts

How go-faas stores scripts, injects input, wraps languages, and returns results.

Script Paths and Versions

Each script is identified by a logical path string (for example math/add).
Paths must not contain ...
Storage keys use MD5 of the path, not the raw path string.
Each upload creates a Unix-timestamp version and updates latest on the meta hash.
POST /run/*path without version runs the latest revision; ?version= selects a specific timestamp.

Mode	Endpoint	Persistence	Typical use
Stored run	`POST /run/*path`	Code loaded from Redis	Deployed functions
Immediate	`POST /run-now`	No Redis write	Trials, one-shots

Both modes share the same sandbox execution path after code is resolved.

Request body field input is a JSON string. Handlers pass it to the wrapper as part of stdin payload:

{"code": "...", "input": "{"a": 1}"}

Wrappers parse input into an object and expose:

Global	Meaning
`event`	Parsed JSON object from `input`
`input`	Same object (alias)

Scripts typically return a value; wrappers serialize the return as JSON on stdout.

Language	Runtime	Wrapper	Notes
Python	`python3`	`internal/resource/wrapper.py`	User code wrapped in `__user_main__` so top-level `return` works; `-u` for unbuffered stdout
JavaScript	`node`	`internal/resource/wrapper.js`	`event` / `input` globals
TypeScript	`tsx`	`internal/resource/wrapper.ts`	Linux bwrap also binds project `node_modules` via `NODE_PATH`

Unsupported languages are rejected at upload / run-now with HTTP 400.

CODE_MAX_SIZE (default 256KB) is applied via http.MaxBytesReader when binding run bodies.

Non-stream responses detect the last valid JSON line of stdout:

Noisy Node warnings are filtered in cleanOutput before type detection.

When stream: true:

Response headers become text/event-stream.
Intermediate stdout lines are emitted as event: log (previous line pattern — final line held as result).
Completion sends result or error, then the connection is hijacked closed.

Timeouts use TIMEOUT_SCRIPT plus a fixed Redis timeout buffer for request context.