The core driver re-armed itself via wake_by_ref() after every poll, an
unconditional spin at scheduler speed per worker for the engine's
lifetime. The provisioning-reconciler-demo supervisor + 3 node children
burned ~750% CPU idle; now ~50% (demo churn), wakeup latency for work
delivered to an idle worker bounded by the idle interval.
- ExecutionBackend::core_idle_poll() (default Duration::ZERO = previous
immediate re-arm) lets a backend opt its drivers into idle parking.
- TokioConfig::core_idle_poll (default 500us) configures it for the
Tokio backend; from_runtime adopts the default.
- CoreDriver: busy tick (or zero interval) re-arms immediately; idle
tick arms one backend timer and parks. Every poll still runs exactly
one try_tick, so stepping-backend semantics are unchanged. The
backend is held Weak and touched only on idle transitions; if the
engine is gone the driver parks until the substrate cancels it.
- Contract tests: a parked driver observes a late external
(engine-invisible) send within the idle interval; the backend reports
its configured interval.
Introduce the swactor engine: a swactor-owned composite that retains a
selected execution substrate, drives the core runtime, and hosts the
async/blocking/timer work that backs actors. Integrations receive one
cloneable EngineHandle and never construct or borrow a raw Tokio
runtime/handle.
Engine crate (crates/engine):
- The contract: spawn / spawn_blocking / timer / interval / now, a
per-implementation capability model with construction-time binding
(require()), and engine-owned time. The engine owns all progression;
actor handlers stay synchronous and never .await.
- TokioBackend owns the Tokio runtime and schedules core ticks and
supporting futures on it; SteppingBackend is a single-threaded
deterministic scheduler with virtual time (the non-Tokio portability
proof). Core is driven through its existing tick() surface; a
self-rescheduling CoreDriver is installed at construction and is the
sole place permitted to call try_tick.
iroh-driver:
- Receives an EngineHandle instead of a raw Tokio Handle. Accepts,
reads, dials, writes, endpoint construction, and teardown schedule
through it; required capabilities (tasks/timers/io) are validated
before the endpoint binds. Engine-hosted interval pumps drive
actor-bridge, datastream, and edge ingress.
myelin:
- One node/orchestrator engine owns core, protocol tick injection, and
transport progression; the application loop only drains
integration-owned queues. Stage-shard process readers, delayed actor
messages, helper stdout/stderr, prompt RPC, and CPU sampling all
schedule through the engine (spawn_blocking / engine tasks / timers).
- Removed the split-engine APIs: install_actor_bridge_pump(period) and
spawn_protocol_ticker(period) use each component's stored engine;
deleted the no-op pump_network callback and its plumbing; deleted the
dashboard raw-Tokio/standalone-runtime conveniences.
Enforcement:
- A clippy disallowed-methods boundary forbids direct runtime/scheduling/
time/core-driving bypasses, denied in swactor-engine, iroh-driver, and
myelin. Retained excluded uses (VastAI provider, provider process
supervision/log capture, OS-signal/stdin/process-control sequencing)
carry narrow allowances with reasons.
Verification:
- Engine contract + unit tests (incl. the SteppingBackend portability
proof), iroh integration tests (capability rejection before binding,
multi-node actor behavior), and a production execution-composition
smoke test that observes engine-driven actor progress with no ambient
Tokio runtime and no manual tick/pump. Workspace all-target/all-feature
clippy and tests are green.
Specs co-located with their crates: ENGINE_SPEC.md in crates/engine,
IROH_DRIVER_SPEC.md in crates/iroh-driver. VastAI remains explicitly out
of scope pending its separate redesign.
