14 KiB
14 KiB
Runtime Architecture
The Runtime is the main entry point. It creates workers, owns the shared
infrastructure, and provides the public API for spawning actors and sending
messages.
Structure
┌─ Runtime ─────────────────────────────────────────────────────────────────┐
│ │
│ config: RuntimeConfig -- tunable knobs (see config.rs) │
│ is_running: AtomicBool -- shutdown flag, read by all workers │
│ │
│ ┌─ Shared State (lives on Arc<Runtime>) ──────────────────────────────┐ │
│ │ │ │
│ │ address_map: Arc<AddressMap> -- actor -> worker lookup │ │
│ │ inbox_registry: Arc<InboxRegistry> -- external inbox delivery │ │
│ │ placement: Placement -- round-robin worker picker │ │
│ │ worker_stats: Vec<Arc<WorkerStats>> -- atomic stat counters │ │
│ │ │ │
│ └─────────────────────────────────────────────────────────────────────┘ │
│ │
│ ┌─ Channel Endpoints ─────────────────────────────────────────────────┐ │
│ │ │ │
│ │ transfer_txs: Vec<Sender<Envelope>> -- one per worker (messages) │ │
│ │ spawn_txs: Vec<Sender<(Addr,Box)>> -- one per worker (spawns) │ │
│ │ │ │
│ └─────────────────────────────────────────────────────────────────────┘ │
│ │
│ ┌─ Mode ──────────────────────────────────────────────────────────────┐ │
│ │ │ │
│ │ SINGLE-THREADED: single_worker: Some(RefCell<Worker>) │ │
│ │ MULTI-THREADED: pending_workers: Some(Vec<Worker>) │ │
│ │ │ │
│ │ After run() is called, both are None — workers move to threads. │ │
│ │ │ │
│ └─────────────────────────────────────────────────────────────────────┘ │
│ │
└───────────────────────────────────────────────────────────────────────────┘
Two Modes of Operation
SINGLE-THREADED MULTI-THREADED
────────────── ──────────────
let rt = Runtime::new(config); let mut config = RuntimeConfig::default();
config.num_threads = 4;
let rt = Runtime::new(config);
rt.spawn(my_actor)?; rt.spawn(my_actor)?;
rt.send_to(addr, msg)?; rt.send_to(addr, msg)?;
loop { rt.tick(); } let handle = rt.run()?;
^ ^
| |
caller drives each tick workers run on their own threads
handle.join() blocks until shutdown
Single-threaded mode keeps the Worker inline and requires the caller to
call rt.tick() to advance the simulation. This is useful for deterministic
testing, WASM, or game loops where you want frame-level control.
Multi-threaded mode consumes the Runtime via run(), wraps it in an
Arc, and spawns one OS thread per worker. Returns a RuntimeHandle.
Ctx — the Actor Syscall Interface
When an actor's handle() method runs, it receives a &Ctx. This is the
only way for actors to interact with the outside world.
┌─ Ctx<'a> ─────────────────────────────────────────────────────────────────┐
│ │
│ inner: &dyn ContextInner -- polymorphic dispatch │
│ self_addr: ActorAddress -- address of the current actor │
│ │
│ ┌─ Public API ────────────────────────────────────────────────────────┐ │
│ │ │ │
│ │ ctx.self_addr() -> ActorAddress │ │
│ │ ctx.send(addr, msg) -> Result<(), Error> │ │
│ │ ctx.spawn(actor) -> Result<ActorAddress, Error> │ │
│ │ │ │
│ └─────────────────────────────────────────────────────────────────────┘ │
│ │
│ ┌─ ContextInner dispatch ─────────────────────────────────────────────┐ │
│ │ │ │
│ │ In single-threaded mode: inner = &Runtime │ │
│ │ send → transfer_txs[wid], spawn → spawn_txs[wid] │ │
│ │ │ │
│ │ In multi-threaded mode: inner = &WorkerContext │ │
│ │ send → pending_local (same worker) or transfer_txs (cross) │ │
│ │ spawn → spawn_txs[target_wid] │ │
│ │ │ │
│ └─────────────────────────────────────────────────────────────────────┘ │
│ │
└───────────────────────────────────────────────────────────────────────────┘
The ContextInner trait is the object-safe bridge. It's not public — actors
interact only through the typed Ctx wrapper.
Inbox — Receiving Messages Outside the Runtime
Inbox<M> lets external code (the "main" thread, a game loop, an HTTP
handler, etc.) receive typed messages from actors.
┌─ Creation ─────────────────────────────────────────────────────────────┐
│ │
│ let inbox = rt.new_inbox::<MyResponse>()?; │
│ │
│ Under the hood: │
│ addr = ActorAddress::new_random() │
│ receiver = Receiver::<M>::new(capacity) │
│ sender = receiver.new_sender() │
│ inbox_registry.register(addr, Arc::new(sender)) │
│ │
└────────────────────────────────────────────────────────────────────────┘
┌─ Usage ────────────────────────────────────────────────────────────────┐
│ │
│ // give inbox.addr() to actors so they know where to reply │
│ rt.send_to(greeter, GreetMsg { return_addr: *inbox.addr() })?; │
│ │
│ // poll for responses │
│ if let Some(msg) = inbox.try_recv() { ... } │
│ │
└────────────────────────────────────────────────────────────────────────┘
┌─ Delivery Path ────────────────────────────────────────────────────────┐
│ │
│ actor calls ctx.send(inbox_addr, response) │
│ │ │
│ v │
│ address_map.lookup(inbox_addr) → None (inboxes aren't actors) │
│ │ │
│ v │
│ inbox_registry.try_deliver(addr, msg) │
│ │ │
│ v │
│ downcast Box<Any> → M, push into Receiver<M> │
│ │
└────────────────────────────────────────────────────────────────────────┘
RuntimeHandle
Returned by run(). Holds Arc<Runtime> and the thread JoinHandles.
┌─ RuntimeHandle ───────────────────────────────────────────────────────────┐
│ │
│ runtime: Arc<Runtime> -- still usable for spawn/send/stats │
│ threads: Vec<JoinHandle<()>> -- one per worker │
│ │
│ handle.shutdown() → runtime.is_running.store(false) │
│ handle.join() → waits for all worker threads to exit │
│ │
└───────────────────────────────────────────────────────────────────────────┘
RuntimeStats
rt.stats() (or handle.runtime.stats()) returns a snapshot:
┌─ RuntimeStats ────────────────────────────────────────────────────────────┐
│ │
│ num_workers: usize │
│ actors: Vec<(ActorAddress, worker_id)> -- from AddressMap snapshot │
│ workers: Vec<WorkerInfo> │
│ ├─ id: usize │
│ ├─ num_actors: usize -- from atomic counter │
│ ├─ mailbox_depth: usize -- total queued messages │
│ └─ messages_processed: u64 -- cumulative count │
│ │
└───────────────────────────────────────────────────────────────────────────┘
Stats are published by workers via atomic stores at the end of each tick, so they're always slightly stale but never block.