Drift · Atomic: Triggers

Triggers

An HTTP route is one way to reach a function. A queue and a schedule are the other two, and neither needs a caller: the slice invokes the function on your behalf.

Queue-triggered functions

A function doesn't have to be called over HTTP. Give it method: queue and name the queue as its route and the slice polls a Backbone queue on your behalf:

Driftfile

atomic:
  functions:
    - route: orders
      method: queue
      handler: handle_order

Python

def handle_order(body, req):
    # body is the message that was pushed onto the "orders" queue
    drift.backbone.nosql.collection("orders").insert(body)
    return 200, "OK", {"stored": True}

A queue handler takes the body shape, (body, req), and the popped message is the body. It returns the same three (or four, in Go) values an HTTP handler does.

Behaviour	Value
Poll interval	500 ms
Retries	3. A failed message is requeued with its retry count; once exhausted it moves to `<queue>-dlq`.
What counts as a failure	The invocation errored, or the handler returned a `5xx` status.
Reachability	Registered under a synthetic `queue` method that no HTTP request can match, so a queue handler has no URL.
Booking	The slice books it under the name you declared — `queue:orders` — exactly like an HTTP function.

None of those defaults are configurable. Since any HTTP function has a public URL, a post:… function is your webhook receiver. Point Stripe, GitHub or your provider straight at it.

Scheduled functions

A schedule is not an identity — it is something a function also does. Give any function a cron: and it runs on that schedule in addition to its own trigger. Same code, two ways in:

Driftfile

atomic:
  functions:
    - route: nightly-rollup
      method: post
      handler: PostNightlyRollup
      cron: "0 2 * * *"        # 02:00 daily, and still callable over HTTP
    - route: hourly-cleanup
      method: post
      handler: PostHourlyCleanup
      cron: "0 * * * *"

Standard 5-field POSIX cron: minute hour day-of-month month day-of-week. Seconds and the 6-field quartz format are not supported. The schedule registers as part of the deploy, with no post-deploy step, and the deploy is refused if it would push the slice past its scheduled-job allowance.

Each fire delivers a small JSON body, so a scheduled handler takes the body shape:

JSON

{ "fired_at": "<RFC 3339 timestamp>", "schedule": "0 2 * * *" }

Anything else the handler needs comes from secrets or Backbone.