TitanRt

Model-first, typed reactive runtime for real-time systems. The runtime focuses on models that own their connectors/streams and publish/translate cheap, lock-free state snapshots (StateCell<T>). The control thread handles lifecycle (start/restart/hot-reload/shutdown/kill), back-pressure and cooperative cancellation; your model pulls typed events from its streams and pushes typed actions back.

• Predictable back-pressure via unified TX/RX traits.
• Typed boundaries between model, I/O adapters and state.
• Graceful, hierarchical cancellation and optional core pinning.
• Hot-reload of configuration, but logic is still in the model and user depended on.
• Health flags and lock-free state snapshots.
• When using the built-in connector, a model-side hook selects which events are emitted.
• This is related also to the state payload. It is user-defined: you choose T for StateCell<T>.

Install

Add with Cargo (no version pinning; you always pull the latest):

cargo add titanrt

# or, if you plan to use stream/connector APIs:

cargo add titanrt --features connector

Quick start: a minimal model

BaseModel declares your config, output transport, event, and context types. The runtime drives initialize → execute → stop, and you may handle external events via on_event and apply config updates via hot_reload.

use anyhow::Result;
use titanrt::prelude::*;            // config, model, runtime, io::base re-exports
use titanrt::io::base::NullTx;      // no-op output
// Events: use the provided unit marker
// use titanrt::model::NullEvent;   // already in prelude via model::*

#[derive(Clone)]
struct AppCtx;
impl ModelContext for AppCtx {}

struct MyModel {
   _cancel: CancelToken,
}

impl BaseModel for MyModel {
   type Config = String;       // any serde-deserializable type
   type OutputTx = NullTx;       // output channel (no-op here)
   type Event = NullEvent;    // typed external events
   type Ctx = AppCtx;

   fn initialize(
      _ctx: AppCtx,
      _cfg: String,
      _reserved_core: Option<usize>,
      _out: NullTx,
      cancel: CancelToken,
   ) -> Result<Self> {
      Ok(Self { _cancel: cancel })
   }

   fn execute(&mut self) -> ExecutionResult {
      // single hot-loop tick; do useful work or drain streams here
      ExecutionResult::Relax    // yield (spin/yield/sleep backoff)
   }

   fn on_event(&mut self, _e: Self::Event) { /* handle external events from outside of the runtime */ }

   fn stop(&mut self, _kind: StopKind) -> StopState {
      // cancel streams, join workers, flush state, etc.
      StopState::Done
   }

   fn hot_reload(&mut self, config: &Self::Config) -> Result<()> {
      // reload configuration, apply changes, etc.
      Ok(())
   }
}

fn main() -> Result<()> {
   let cfg = RuntimeConfig {
      init_model_on_start: true,
      core_id: None,                    // optionally pin runtime thread
      max_inputs_pending: Some(1024),   // control-plane ring capacity
      max_inputs_drain: Some(64),      // max inputs per drain pass
      stop_model_timeout: Some(5),      // seconds
   };

   let ctx = AppCtx;
   let model_cfg = "hello".to_string();
   let output_tx = NullOutputTx;

   Runtime::<MyModel>::spawn(cfg, ctx, model_cfg, output_tx)?
      .run_blocking()
}

Driving the runtime (control-plane)

Use the control sender to post typed events or lifecycle/config commands:

use titanrt::control::inputs::{Input, CommandInput};
use serde_json::json;

let mut rt = Runtime::<MyModel>::spawn(cfg, ctx, model_cfg, outputs)?;

// Start (if not auto-started)
rt.control_tx().try_send(Input::Command(CommandInput::Start)).ok();

// Send a typed event to your model
rt.control_tx().try_send(Input::Event(NullEvent)).ok();

// Hot-reload configuration (your `hot_reload` receives the deserialized value)
rt.control_tx().try_send(Input::Command(
CommandInput::HotReload(json!({"foo": 42})),
)).ok();

// Graceful stop or full shutdown
rt.control_tx().try_send(Input::Command(CommandInput::Stop)).ok();
rt.control_tx().try_send(Input::Command(CommandInput::Shutdown)).ok();

// Block until the runtime thread finishes (or drop a guard for auto-shutdown)
rt.run_blocking() ?;

The control thread also listens to OS termination signals (via signal-hook) and will request a cooperative shutdown.

Streams & connectors (optional feature)

Enable the connector feature to build typed streams (worker threads) managed by your model. The crate exposes:

• connector::StreamDescriptor — describes a stream (venue/kind, channel bounds, core policy, initial health).
• connector::StreamRunner/StreamSpawner — spawn a worker with typed action/event channels, StateCell<S>, HealthFlag and a child CancelToken.
• connector::Stream — handle owned by the model: id, health, state, action_tx, event_rx, etc.

You write your own connector facade (implementing BaseConnector) that holds shared resources and spawns streams via StreamSpawner. Your model keeps the Stream handle(s), drains events each execute() tick, and publishes actions as needed.

Tip: use CoreStats and CorePickPolicy to pick CPU cores (round-robin, minimum threads, specific cores) for each stream worker.

Channels & back-pressure

A small, unified transport layer:

• Traits: BaseTx / BaseRx (+ TxPairExt / RxPairExt helpers) give try_send/try_recv, blocking send/recv with CancelToken + optional timeouts, and draining (drain, drain_max).

• Implementations:

  • io::ringbuffer::RingBuffer — lock-free ring buffer (bounded).
  • io::mpmc::MpmcChannel — Crossbeam MPMC (bounded).
  • io::base::NullTx/NullRx — no-op ends for unit/empty flows.

Choose the channel per stream; the model only sees the BaseTx/BaseRx abstractions.

State & health

• utils::StateCell<S> — lock-free snapshot cell with versioning (publish, load, seq), where S: StateMarker ( usually a small “view”).
• utils::HealthFlag — cheap AtomicBool wrapped to avoid false sharing (up, down, get).
• utils::CancelToken — hierarchical cooperative cancellation (child(), cancel(), is_cancelled()).

Configuration & hot-reload

• BaseModel::Config must be Clone + Send + serde::Deserialize.
• The control plane accepts CommandInput::HotReload(serde_json::Value); your model implements hot_reload(&Config) ( default is a no-op).

Pinning & per-core stats

utils::CoreStats tracks per-core thread counts; CorePickPolicy lets you request minimum-threads, **round-robin **, or specific core(s). The runtime can also pin its own control thread (RuntimeConfig::core_id).

Examples

A complete runnable example is included under example/ in the repository: a toy model + connector/stream demonstrating actions, events, state snapshots, core policies and cancellation.

Feature flags

• connector — enables connector/stream APIs (descriptors, spawners, runners, stream handle).

Documentation

API reference on docs.rs:

• https://docs.rs/titanrt

License

Dual-licensed under MIT or Apache-2.0.