Three write bounds were configured independently: the inbound-write
gateway's 10 s Ask, DriverHostActor's fixed 8 s Ask of the child, and the
child's own write timeout (5 s + up to 2 s grace) with a fixed 8 s queue
budget. An outer Ask that fires first reports the write failed and the node
reverts while the child is still driving the device, so any write timeout
above ~6 s (or a write dequeued late in its 8 s budget) let the device take
a value the client was told failed.
DriverWriteBounds (Runtime) derives them all from DriverWrites:Timeout:
token cancel = Timeout
abandon = Timeout + min(Timeout/2, 2 s) (RunBound)
queue budget = RunBound
child replies <= queue budget + RunBound (ReplyBound)
host Ask = ReplyBound + 1 s
gateway Ask = host Ask + 1 s
Default Timeout is 10 s (the Tier C Write timeout, so no tier default is
capped below its own policy); host Ask 25 s, gateway Ask 26 s. Tier A/B
writes are still cancelled first by their 2 s / 4 s tier timeouts.
- DriverHostActor takes writeBounds + writeClock, spawns children with them,
and runs its Ask deadline as a token on the write clock (Infinite Akka
timeout), so host and child bounds share one clock.
- WriteAttribute gains IssuedAt (write-clock timestamp, stamped by the
host): the queue budget counts mailbox time too, and a write past it is
failed BadTimeout and never started - including on arrival. Stale queued
writes are expired across the whole queue, not only up to a free slot.
- ActorNodeWriteGateway's default Ask = Default.GatewayAsk; the hosted
service passes the configured one.
- Startup validation (Host DriverWriteBoundsBinding, same warn-and-clamp
style as ScriptingOptionsBinding): unparsable / non-positive -> default,
above 5 min -> clamped, and each tier whose default Write timeout exceeds
the write timeout is named in a Warning (its policy would never take
effect). The derived bounds are logged at Information. Per-instance
ResilienceConfig Write overrides arrive with a deployment, so
DriverCapabilityInvokerFactory warns at spawn (writeTimeoutCeiling).
- appsettings.json documents DriverWrites:Timeout.
Tests (manual clock):
- DriverHostActorWriteAskTests: a held write under a 9 s timeout survives
an 8.5 s step and succeeds; a token-ignoring write is answered by the
child's BadTimeout at 9 s + grace, not by the Ask; the Infinite-timeout
Ask ends exactly at its clock deadline.
- DriverInstanceActorConcurrentWriteTests: a write issued longer ago than
the queue budget is failed and never reaches the driver; positive control
at exactly the budget is written.
- DriverWriteBoundsTests: every outer bound covers the inner ones for 0.5 s
to 300 s timeouts.
- DriverWriteBoundsBindingTests: default fits every tier; 3 s timeout is
caught at startup with Tier B and C named (not A); bad values fall back
with a warning; over-max clamps.
- DriverCapabilityInvokerFactoryTests: spawn warns when a Write override
exceeds the ceiling; no warning within it or without a ceiling.
Mutation checks: a fixed 8 s host Ask on the same clock fails both 9 s host
tests; stamping arrival time instead of IssuedAt fails the issued-at test;
dropping the tier check / factory check fails their tests.
Runtime.Tests 961 passed / 3 skipped at AKKA_TEST_TIMEFACTOR 3 and 1;
Host.Tests 232/232 at 3 and 1; Core.Tests 361 passed / 1 skipped.
Solution Release build: 0 warnings.
ContinuousHistorizationRecorderTypedValueTests (historian) deliberately
left for the historian lane.
Claude-Session: https://claude.ai/code/session_01GT67AEHd2Acv1YPwGfXEoV
Joseph Doherty