Request headers

A request can carry its own controls. Nothing needs to be set up first, and a client that can only set default headers still reaches every control.

#Interface

#Admin page

The admin page does not attach control headers to a vendor request. Set the header on the request your application sends. Routes runs admin routes only.

x-mockingbird-restore: <name> on a vendor request restores that snapshot before the request is handled. The screen for taking and restoring snapshots is Snapshot and restore.

#Every header

#Scope

#Order

The headers on one request apply in a fixed order, whatever order they are sent in:

1. x-mockingbird-reset, x-mockingbird-restore, x-mockingbird-seed, x-mockingbird-time, x-mockingbird-advance, x-mockingbird-virtual-time.
2. The namespace's autoAdvance, its latency, then x-mockingbird-delay.
3. x-mockingbird-fault and x-mockingbird-timeout, then the namespace's stored fault rules.
4. The emulator handles the request.
5. x-mockingbird-snapshot.

#All or nothing

Every header on a request is checked before any is applied. One that cannot be honoured refuses the request and changes nothing:

The error is Mockingbird's, never the vendor's: {"error": {"type": "mockingbird_admin", "message": "…"}}.

#Example

curl -X POST localhost:8787/v1/charges \
  -H 'authorization: Bearer sk_test_mockingbird' \
  -H 'x-mockingbird-namespace: worker-3' \
  -H 'x-mockingbird-time: 2030-01-01T00:00:00Z' \
  -H 'x-mockingbird-fault: status=503; delay=2s'

The request runs in worker-3, whose clock is now frozen at midnight, waits two seconds and answers 503. The clock stays frozen afterwards; the fault does not.

#Building them

runtime.headers(...) builds the headers and checks every value, so a typo fails where it is written and not as a 400 later:

const response = await fetch("http://localhost:8787/v1/charges", {
  method: "POST",
  headers: {
    authorization: "Bearer sk_test_mockingbird",
    ...stripe.headers({ namespace: "worker-3", time: "2030-01-01T00:00:00Z", fault: "rate_limited" }),
  },
})

controlHeaders from @crvouga/mockingbird-service is the same function without a runtime.

#Response headers

#Related

• Control document for the same controls as JSON.
• Reference for every route.