JS Webhooks

Webhook endpoints serve HTTP requests. The handler receives a Request object and must return a Response. Webhooks can call activities and workflows via imports or dynamic.call and make outbound HTTP requests via fetch. See Webhook Endpoints for the general model.

Prefer imports when the target function is known statically. Imports are verified when the deployment starts; use dynamic FFQN calls only when the target is constructed at runtime.

Import obelisk:webhook@1.0.0 for execution IDs and result lookup. Runtime-selected calls and schedules come from the separate obelisk:webhook-dynamic@1.0.0 module.

import * as obelisk from "obelisk:webhook@1.0.0";
import * as dynamic from "obelisk:webhook-dynamic@1.0.0";

[[webhook_endpoint_js]]
name     = "my_webhook"
location = "webhook/my_webhook.js"
routes   = [
    { methods = ["GET"],  route = "/items" },
    { methods = ["POST"], route = "/items/:id" },
]
env_vars = [{ key = "DB_URL", value = "..." }]
exposed_secrets = ["WEBHOOK_SIGNING_SECRET"]
[[webhook_endpoint_js.allowed_host]]
pattern = "https://api.example.com"
methods = ["GET"]
secrets = ["API_KEY"]
replace_in = ["headers"]

The server must register API_KEY in [secrets] and allow the same destination, method, secret, and replace_in target in [[outbound_http.allowed_host]].

WEBHOOK_SIGNING_SECRET is different: the handler must read its plaintext to validate inbound signatures. Register it under [secrets], generate a digest with obelisk generate secret-config-digest --deployment deployment.toml, and authorize the resulting component-and-secret-set digest under [secrets.WEBHOOK_SIGNING_SECRET.exposed_to]. The handler can then read process.env.WEBHOOK_SIGNING_SECRET. Regenerate the grant whenever the component or its complete exposed_secrets list changes.

Route path segments starting with : are captured and exposed as process.env entries inside the handler — process.env['segment-name'] returns the captured value as a string.

Handler signature

export default function handle(request) {
  // sync or async
  return new Response("body", {
    status: 200,
    headers: { "content-type": "text/plain" },
  });
}

Request object

Reading the request body

export default async function handle(request) {
  // As plain text
  const text = await request.text();

  // As JSON
  const data = await request.json();

  // As form data (application/x-www-form-urlencoded or multipart/form-data)
  const form = await request.formData();
  const field = form.get("field-name");

  return Response.json({ received: data });
}

Response construction

// Text response
return new Response("Hello!", {
  status: 200,
  headers: { "content-type": "text/plain" },
});

// JSON response (sets content-type: application/json automatically)
return Response.json({ key: "value" });
return Response.json([1, 2, 3], { status: 201 });

// Proxy a fetch response directly
const resp = await fetch("https://api.example.com/data");
return resp;

Calling activities and workflows

Import functions by their WIT interface path. The call blocks until the child execution completes, so the HTTP response is only sent after the child finishes.

import { serial } from "myapp:demo/workflow";

// ffqn: myapp:demo/webhook.handle
export default function handle(request) {
  const url = new URL(request.url);
  if (url.pathname === "/serial") {
    const result = serial();
    return new Response(`serial completed: ${result}`, { status: 200 });
  }
  return new Response("not found", { status: 404 });
}

For FFQNs constructed at runtime, use dynamic.call(ffqn, argArray):

import * as dynamic from "obelisk:webhook-dynamic@1.0.0";

const result = dynamic.call(ffqn, argArray);

WIT results become JavaScript values and exceptions

Webhook JavaScript APIs do not expose raw WIT result values. The adapter returns the useful value and throws on error:

Do not manually unwrap { tag, val } or another raw WIT representation. In particular, use the execution ID returned by a typed schedule, while generating and passing the ID yourself for dynamic.schedule, whose successful return value is undefined.

Path parameters

When a route contains named segments (:name), the captured values are available as process.env entries inside the handler:

[[webhook_endpoint_js]]
name    = "my_webhook"
location = "webhook/my_webhook.js"
routes  = ["/users/:user-id/items/:item-id"]

export default function handle(request) {
  const userId = process.env["user-id"];
  const itemId = process.env["item-id"];
  return Response.json({ userId, itemId });
}

Scheduling executions

Webhooks can schedule top-level executions without blocking the HTTP response. Import from the -obelisk-schedule suffix:

import { sendEmailSchedule } from "myapp:demo-obelisk-schedule/activity";

export default function handle(request) {
  const execId = sendEmailSchedule(null, "user@example.com");
  // With a delay: sendEmailSchedule({ seconds: 60 }, "user@example.com");
  return new Response(execId, { status: 202 });
}

For FFQNs constructed at runtime, use dynamic.schedule directly:

import * as obelisk from "obelisk:webhook@1.0.0";
import * as dynamic from "obelisk:webhook-dynamic@1.0.0";

const execId = obelisk.executionIdGenerate();
dynamic.schedule(execId, "myapp:demo/activity.send-email", ["user@example.com"]);

The typed schedule returns the execution ID string. dynamic.schedule returns undefined; it uses the execution ID supplied by the caller. Both throw Error if scheduling fails.

Check or retrieve a previously scheduled or running execution:

const status = obelisk.getStatus(execId);
// e.g. { status: "pendingAt"|"locked"|"paused"|"blockedByJoinSet"|"cancelling" } or { status: "finished", finishedStatus:"ok"|"err"|"executionFailure" }

const result = obelisk.tryGet(execId);
// undefined if not finished yet
// returns ok value when done, or throws obelisk.ChildError on failure

Get the execution ID of the current webhook invocation:

const myExecId = obelisk.executionIdCurrent();
// Returns the execution ID string for this webhook handler invocation

Webhook API

Import-based calls (preferred):

Dynamic calls (when FFQN isn't known statically):

Available globals

Same as JS activities: process.env, fetch, crypto.subtle, console, TextEncoder/TextDecoder, URL/URLSearchParams.

Fetch example

export default async function handle(request) {
  const someHeader = request.headers.get("x-custom");
  const api_key = process.env["API_KEY"]; // JS code only gets a short-lived token, transformed on outbound HTTP request.
  // Requires [[webhook_endpoint_js.allowed_host]] for the target
  const resp = await fetch("https://api.example.com/data", {
    headers: { accept: "application/json", authorization: `Bearer ${api_key}` },
  });
  return resp;
}