iii-http

The iii-http worker exposes registered functions as HTTP endpoints. It runs an HTTP server on the configured host/port, matches each inbound request against the http triggers you bind, and invokes the bound function with the request. The handler returns a response envelope that the worker serializes to the wire — JSON, plain text, or bytes, depending on the Content-Type the handler sets.

The worker has no callable functions of its own — you never invoke an http::* id. Its surface is the http trigger TYPE plus a middleware chain that runs before each handler. You expose an endpoint by registering a normal function and binding an http trigger to it.

Do NOT stand up your own web server

This is the way to serve HTTP on iii, and the only one: register a function, then bind an http trigger to it. Do NOT write or run your own web server — no express, no http.createServer, no fastify, no framework listening on a port. iii does not route to a server you start yourself; such a process is unreachable as an iii endpoint, and running it as a foreground process (e.g. inside a sandbox) just hangs. If you are reaching for a web framework or a listen() call, stop — that instinct is from another ecosystem. The iii equivalent is one iii.registerTrigger({ type: 'http', ... }) per route; this worker is the server.

Get the contract from the engine

This page explains WHEN and HOW to serve HTTP; the engine is the source of truth for the exact shapes. Before you bind a trigger or write a handler, fetch the contract and build to it — do not guess field names, types, or defaults from memory:

engine::triggers::info { id: "http" }

returns three schemas: configuration_schema (the route fields — path, method, optional route gating, per-route middleware), request_schema (the request envelope your handler receives), and response_schema (the response envelope your handler must return). Build to all three. Use engine::triggers::list to discover trigger types in the first place.

Set the right HTTP status

YOUR handler chooses the HTTP status code — it is a field on the response envelope whose exact name is in the response_schema from engine::triggers::info { id: "http" } (read it; do not guess the field name from memory). The status is NOT inferred from the body, so a handler that just returns a value or an error object yields 200 by default. For error cases, set the matching status explicitly: a not-found path returns 404, a bad request 400, and so on. Returning 200 with an { error: ... } body is a bug — it "isn't a 500," but it also isn't the status the requirement asked for, and callers (and tests) will read it as success. Avoiding a crash is not the same as returning the right status.

When to Use

• Expose a function as a REST endpoint without standing up a separate HTTP server.
• You need URL path parameters or query strings parsed and handed to the handler.
• You want condition-gated routes or per-route preHandler middleware.
• You need a single not-found handler for unmatched routes.

Boundaries

• No callable functions — the worker is never reached through an http::* id; routes are bound with iii.registerTrigger, not called.
• Two routes on the same path + method conflict; the router resolves to the most recently registered one.
• Query-string parsing is single-valued — a repeated key keeps only the last value; pre-encode multi-valued params yourself.
• Middleware runs BEFORE body parsing, so it sees headers, path, and query but not the body — use it for preconditions, not response logic (that belongs in the handler).

Binding a route

Register your handler as a normal function, then bind an http trigger to it with iii.registerTrigger using the http trigger type. Shape the trigger config to what engine::triggers::info { id: "http" } describes — the route path and method, an optional gating function evaluated before the handler, and per-route middleware. Path segments you declare in the route arrive as string path parameters on the request; the gating function, if set, can veto a request before the handler runs.

Where your route is served

Your bound route is served by the iii-http worker on its configured host and port — NOT on a port you pick. The default port is 3111 (host 0.0.0.0), so a route with path /example is reachable at http://localhost:3111/example on a default deployment. Do NOT guess other ports (3000, 8080, the engine's WS port): if the deployment overrides the default, read the live host/port from the iii-http worker's configuration (config.yaml) or its status rather than probing. Verify a live endpoint with web::fetch against that base URL, never curl.

Middleware

Register a middleware function when the same logic must run before multiple routes — authentication, rate limiting, request logging, header normalization. A middleware is a regular registered function that receives a subset of the request (without the body) and either lets the request proceed (optionally enriching its context) or short-circuits with an immediate response. Target middleware two ways:

• Globally — via the worker's middleware config in config.yaml; runs on every matched route, in priority order.
• Per-route — via the trigger's middleware list; runs after the global chain, in the order given.

The full preHandler order per request: route match → global middleware → route gating function → per-route middleware → body parsing → handler.

Configuration

The worker is configured in config.yaml: the listen host and port, request timeout, concurrency and body-size limits, proxy trust and request-id header, trailing-slash handling, a not-found handler function, CORS, and the global middleware chain. For the full set of keys and their defaults, read the worker's configuration rather than hardcoding values from memory.