Webhooks

Instead of polling, register an HTTPS endpoint and SocialTap sends it an event when something happens: a job ends, your credits run low. Deliveries follow Standard Webhooks exactly, so its verification libraries work too.

Register an endpoint

POST /v1/webhook_endpoints takes the url and the events it receives: event types, a family such as job.*, or * for all. The answer is the only time you see its signing secret (whsec_…): store it with your other secrets. An account has at most 16 endpoints.

The URL must use https, on port 443 or a port above 1023, without credentials, and its host must resolve only to public addresses: private, loopback, link-local and cloud metadata addresses are refused when you register it and checked again before every delivery. Redirects are not followed: a 3xx answer is a failed delivery, so register the final URL.

A job can also notify one of these endpoints that its subscriptions don't cover: set the job's webhook_url to the endpoint's URL.

What a delivery looks like

Each delivery is a POST of the event as JSON, with these headers:

The body is small, a summary and links, never a job's results: fetch those from the links when you need them.

Verify every delivery

Compute the HMAC-SHA256 of webhook-id.webhook-timestamp.<raw body> with the secret's bytes (the base64 after whsec_), and accept the delivery only when one of the v1,<signature> entries of webhook-signature matches, compared in constant time, and the timestamp is within 5 minutes of your clock. Use the raw body as it arrived: parsing and re-serializing JSON changes the bytes.

import { createHmac, timingSafeEqual } from "node:crypto";

/** The verified event, or null: pass the RAW body, before any JSON parsing. */
export function verify(rawBody: string, headers: Record<string, string>, secret = process.env.SOCIALTAP_WEBHOOK_SECRET!): unknown {
  const id = headers["webhook-id"], ts = headers["webhook-timestamp"], sigs = headers["webhook-signature"];
  if (!id || !ts || !sigs || Math.abs(Date.now() / 1000 - Number(ts)) > 300) return null;
  const key = Buffer.from(secret.replace(/^whsec_/, ""), "base64");
  const want = createHmac("sha256", key).update(`${id}.${ts}.${rawBody}`).digest();
  const ok = sigs.split(" ").some((s) => {
    const [version, b64] = s.split(",", 2);
    const got = Buffer.from(b64 ?? "", "base64");
    return version === "v1" && got.length === want.length && timingSafeEqual(got, want);
  });
  return ok ? JSON.parse(rawBody) : null; // deduplicate on its id
}

import base64, hashlib, hmac, json, os, time

def verify(raw_body: bytes, headers: dict, secret: str = os.environ["SOCIALTAP_WEBHOOK_SECRET"]):
    """The verified event, or None: pass the RAW body, before any JSON parsing."""
    msg_id, ts, sigs = headers.get("webhook-id"), headers.get("webhook-timestamp"), headers.get("webhook-signature")
    if not msg_id or not ts or not sigs or abs(time.time() - int(ts)) > 300:
        return None
    key = base64.b64decode(secret.removeprefix("whsec_"))
    want = base64.b64encode(hmac.new(key, f"{msg_id}.{ts}.".encode() + raw_body, hashlib.sha256).digest()).decode()
    for part in sigs.split(" "):
        version, _, got = part.partition(",")
        if version == "v1" and hmac.compare_digest(got, want):
            return json.loads(raw_body)  # deduplicate on its id
    return None

// Verify returns the raw event when one signature matches: pass the RAW body.
func Verify(body []byte, h http.Header, secret string) ([]byte, bool) {
	id, ts, sigs := h.Get("webhook-id"), h.Get("webhook-timestamp"), h.Get("webhook-signature")
	t, err := strconv.ParseInt(ts, 10, 64)
	if id == "" || sigs == "" || err != nil || math.Abs(float64(time.Now().Unix()-t)) > 300 {
		return nil, false
	}
	key, err := base64.StdEncoding.DecodeString(strings.TrimPrefix(secret, "whsec_"))
	if err != nil {
		return nil, false
	}
	mac := hmac.New(sha256.New, key)
	mac.Write([]byte(id + "." + ts + "."))
	mac.Write(body)
	want := base64.StdEncoding.EncodeToString(mac.Sum(nil))
	for _, part := range strings.Split(sigs, " ") {
		if version, got, ok := strings.Cut(part, ","); ok && version == "v1" && hmac.Equal([]byte(got), []byte(want)) {
			return body, true // deduplicate on the event's id
		}
	}
	return nil, false
}

The same check ships in the TypeScript SDK, and any Standard Webhooks library verifies these deliveries.

Retries

A delivery that doesn't get a 2xx within 15 seconds is retried on this schedule, each delay varied by a little so retries don't arrive in lockstep:

On 429, 502 and 504, a longer retry-after from your server is respected. A 410 Gone answer disables the endpoint at once; an endpoint whose deliveries keep failing for 5 days is disabled too. A disabled endpoint's disabled_reason says why; set its status back to enabled with PATCH /v1/webhook_endpoints/{id} once it works.

A target that has stopped answering at all gets a shorter timeout, 5 seconds, on most of its attempts until it answers again. One that answers slowly keeps 15 seconds.

Pacing

Deliveries are paced per account and per host so that no one's traffic holds up anyone else's: a delivery over the pace waits, pending with a later next_attempt_at, and is never dropped.

Delivery logs and redelivery

GET /v1/webhook_endpoints/{id}/deliveries lists every delivery to an endpoint with its last status code, duration, the start of your server's answer and when the next attempt is due:

POST /v1/events/{id}/redeliver sends an event again (with the same webhook-id), to one endpoint or to every endpoint subscribed to it. POST /v1/webhook_endpoints/{id}/test sends a webhook.test event to one endpoint, to check your handler end to end.

Rotate a secret

POST /v1/webhook_endpoints/{id}/rotate_secret issues a new secret, shown once. For previous_secret_expires_in seconds (default and maximum 1 day) every delivery carries two signatures, one per secret, so you can deploy the new secret without dropping a delivery. Verify against both during the switch.

Keys

Reading webhook endpoints and their deliveries needs the account:read scope; creating, changing, deleting, rotating, testing and redelivering need admin.