347 lines
15 KiB
Rust
347 lines
15 KiB
Rust
// SPDX-License-Identifier: AGPL-3.0-only
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//! Threaded `tokio` runtime bridge between the async network and the synchronous simulation.
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use std::net::SocketAddr;
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use std::sync::{Arc, OnceLock};
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use std::thread;
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use shared::protocol::chunk::{ChunkMessage, ChunkSubscribe};
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use shared::protocol::{ClientHello, HandshakeAck};
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use tracing::{info, warn};
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use crate::chunk::{ChunkSink, ChunkSubscriber, chunk_stream_task, client_chunk_task};
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use crate::endpoint::{client_endpoint, server_endpoint};
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use crate::error::NetError;
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use crate::handshake::{ServerConnection, accept_connection, connect};
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use crate::stats::{self, NetCounters, NetStats};
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/// Channel receiver delivering the outcome of a background client connect: the negotiated [`HandshakeAck`] on success, or a human-readable error string on failure.
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pub type ConnectOutcome = crossbeam_channel::Receiver<Result<HandshakeAck, String>>;
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/// Bounded receiver of chunks delivered by the server, drained by the UI thread with `try_recv`.
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pub type ChunkStream = tokio::sync::mpsc::Receiver<ChunkMessage>;
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/// Capacity of the client's chunk-delivery channel, in [`ChunkMessage`]s.
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// TODO: revisit once meshing moves to a worker pool; the right depth follows the UI's consume rate, so this is a candidate to derive from the meshing budget / view distance in a config layer rather than a hand-set constant.
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const CHUNK_DELIVERY_CAPACITY: usize = 32;
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/// Handles a background client connection exposes to the synchronous UI thread.
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///
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/// The network task keeps the QUIC connection alive on its own thread; this bundle is how the winit loop observes the handshake outcome, pushes subscription updates, and drains chunk deliveries, all without touching the async runtime.
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pub struct ClientLink {
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/// Handshake outcome, drained once for the negotiated ack or the failure reason.
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pub handshake: ConnectOutcome,
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/// Sends subscription updates (center and radius) to the server as the camera moves.
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pub subscribe: ChunkSubscriber,
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/// Receives chunk deliveries from the server, drained non-blocking each frame.
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pub chunks: ChunkStream,
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/// The live QUIC connection, published by the network thread once the handshake completes. Held privately so the `quinn` types stay inside this crate; the UI thread reads through [`ClientLink::stats`].
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connection: Arc<OnceLock<quinn::Connection>>,
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/// Application-level message counters shared with the chunk task.
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counters: Arc<NetCounters>,
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}
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impl ClientLink {
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/// Snapshots the connection's transport statistics.
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///
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/// Safe to call before the handshake completes; the result then reports the disconnected state rather than failing.
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#[must_use]
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pub fn stats(&self) -> NetStats {
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stats::snapshot(self.connection.get(), &self.counters)
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}
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}
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/// An event surfaced by the network thread to the synchronous server loop.
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#[derive(Debug)]
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pub enum ServerEvent {
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/// A client completed the Synvael handshake. Carries the stable per-session id, the `ClientHello` it presented, and the sink the simulation loop uses to deliver chunks to this connection's chunk stream.
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ClientConnected {
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/// Stable identifier assigned to this session for the lifetime of the connection.
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id: u64,
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/// The identity and build parameters the client advertised.
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hello: ClientHello,
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/// Outbound handle for delivering [`shared::protocol::chunk::ChunkMessage`]s to this client. The simulation loop retains it, keyed by `id`, until the matching [`ServerEvent::ClientDisconnected`].
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chunks: ChunkSink,
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},
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/// A previously connected client's session ended.
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ClientDisconnected {
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/// Identifier of the session that ended, matching the earlier [`ServerEvent::ClientConnected`].
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id: u64,
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/// Human-readable description of why the connection closed.
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reason: String,
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},
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/// A connected client updated its chunk subscription: the initial subscribe on connect, or a later update as its center chunk moves.
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ChunkSubscribe {
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/// Identifier of the session that sent the subscription, matching its [`ServerEvent::ClientConnected`].
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id: u64,
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/// The center and radius the client wants resident.
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request: ChunkSubscribe,
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},
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}
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/// Handle to the background networking thread and its owned `tokio` runtime.
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#[derive(Debug)]
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pub struct NetworkServer {
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/// Events produced by the accept loop, drained by the synchronous simulation thread.
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events: crossbeam_channel::Receiver<ServerEvent>,
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/// Shutdown signal. Dropping this sender resolves the accept loop's receiver and breaks the loop.
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shutdown: Option<tokio::sync::oneshot::Sender<()>>,
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/// Join handle for the network thread, awaited on drop for an orderly shutdown.
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thread: Option<thread::JoinHandle<()>>,
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}
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impl NetworkServer {
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/// Spawns a dedicated network thread, builds a current-thread `tokio` runtime on it, binds a QUIC server endpoint on `bind`, and runs the accept loop.
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///
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/// # Errors
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///
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/// Returns [`NetError::Io`] if the runtime cannot be built, the network thread cannot be spawned, or the thread exits before reporting a bound address, and any error from [`server_endpoint`] if the endpoint cannot be constructed or bound.
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pub fn spawn(
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bind: SocketAddr,
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server_build: String,
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tick_rate_hint: u16,
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) -> Result<(Self, SocketAddr), NetError> {
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let (events_tx, events_rx) = crossbeam_channel::unbounded();
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let (shutdown_tx, shutdown_rx) = tokio::sync::oneshot::channel();
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// Reports the bound address (or the error that prevented binding) back to this thread, so `spawn` can surface it synchronously.
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let (ready_tx, ready_rx) = crossbeam_channel::bounded::<Result<SocketAddr, NetError>>(1);
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let thread = thread::Builder::new()
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.name("net-server".to_owned())
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.spawn(move || {
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let runtime = match tokio::runtime::Builder::new_current_thread()
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.enable_all()
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.build()
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{
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Ok(runtime) => runtime,
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Err(error) => {
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let _ = ready_tx.send(Err(NetError::Io(error)));
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return;
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}
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};
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runtime.block_on(async move {
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// The endpoint is constructed inside the runtime context because `quinn` binds its driver task onto the current runtime.
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let endpoint = match server_endpoint(bind) {
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Ok(endpoint) => endpoint,
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Err(error) => {
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let _ = ready_tx.send(Err(error));
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return;
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}
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};
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let local_addr = match endpoint.local_addr() {
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Ok(addr) => addr,
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Err(error) => {
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let _ = ready_tx.send(Err(NetError::Io(error)));
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return;
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}
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};
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// If the caller has already given up, there is nothing to serve.
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if ready_tx.send(Ok(local_addr)).is_err() {
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return;
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}
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accept_loop(
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endpoint,
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events_tx,
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shutdown_rx,
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server_build,
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tick_rate_hint,
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)
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.await;
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});
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})
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.map_err(NetError::Io)?;
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let local_addr = match ready_rx.recv() {
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Ok(Ok(addr)) => addr,
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Ok(Err(error)) => return Err(error),
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Err(_) => {
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return Err(NetError::Io(std::io::Error::other(
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"network thread exited before reporting a bound address",
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)));
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}
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};
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Ok((
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Self {
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events: events_rx,
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shutdown: Some(shutdown_tx),
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thread: Some(thread),
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},
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local_addr,
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))
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}
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/// Drains every [`ServerEvent`] currently queued, without blocking.
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pub fn poll_events(&self) -> impl Iterator<Item = ServerEvent> + '_ {
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self.events.try_iter()
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}
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}
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impl Drop for NetworkServer {
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fn drop(&mut self) {
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// Dropping the sender resolves the accept loop's shutdown receiver, breaking the loop and letting `block_on` return so the thread unwinds and the runtime is dropped.
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self.shutdown.take();
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if let Some(thread) = self.thread.take() {
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let _ = thread.join();
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}
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}
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}
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/// Accepts incoming QUIC connections until the endpoint stops yielding them or a shutdown is signalled, spawning one handshake task per connection.
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async fn accept_loop(
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endpoint: quinn::Endpoint,
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events: crossbeam_channel::Sender<ServerEvent>,
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mut shutdown: tokio::sync::oneshot::Receiver<()>,
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server_build: String,
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tick_rate_hint: u16,
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) {
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// Session ids are handed out sequentially; the accept loop is the sole assigner, so a plain counter suffices.
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let mut next_id: u64 = 0;
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loop {
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tokio::select! {
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incoming = endpoint.accept() => {
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let Some(incoming) = incoming else { break };
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let id = next_id;
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next_id += 1;
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tokio::spawn(handle_connection(
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incoming,
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id,
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events.clone(),
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server_build.clone(),
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tick_rate_hint,
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));
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}
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// Resolves when the `NetworkServer` handle is dropped (sender gone) or an explicit signal is sent.
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_ = &mut shutdown => break,
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}
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}
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info!("network accept loop shutting down");
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}
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/// Performs the handshake for one incoming connection and, on success, reports connect and disconnect events for its session.
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async fn handle_connection(
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incoming: quinn::Incoming,
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id: u64,
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events: crossbeam_channel::Sender<ServerEvent>,
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server_build: String,
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tick_rate_hint: u16,
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) {
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match accept_connection(incoming, server_build, tick_rate_hint).await {
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Ok(ServerConnection {
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connection, hello, ..
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}) => {
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// The outbound chunk channel bridges the sync simulation loop to this connection's chunk-stream task; the sink is handed to the loop via the connect event.
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let (chunk_tx, chunk_rx) = tokio::sync::mpsc::unbounded_channel();
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// If the receiver is gone the server is shutting down; drop the connection silently.
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if events
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.send(ServerEvent::ClientConnected {
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id,
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hello,
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chunks: ChunkSink::new(chunk_tx),
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})
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.is_err()
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{
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return;
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}
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// The chunk pump runs on its own task so the connection-close wait below does not block it.
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tokio::spawn(chunk_stream_task(
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connection.clone(),
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id,
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events.clone(),
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chunk_rx,
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));
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let reason = connection.closed().await;
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let _ = events.send(ServerEvent::ClientDisconnected {
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id,
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reason: reason.to_string(),
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});
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}
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Err(error) => {
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warn!(%error, id, "connection handshake failed");
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}
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}
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}
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/// Runs a connect and Synvael handshake against `server_addr` on a background `tokio` thread, then pumps the chunk stream, returning the handles the UI thread uses to observe and drive the connection.
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///
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/// The returned [`ClientLink`] is available immediately; its channels buffer until the handshake completes and the chunk task starts. A handshake failure is reported on `handshake` and leaves the subscribe and chunk channels inert.
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#[must_use]
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pub fn connect_in_background(server_addr: SocketAddr, hello: ClientHello) -> ClientLink {
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let (outcome_tx, outcome_rx) = crossbeam_channel::bounded(1);
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// Retained so a failure to spawn the thread can still be reported to the caller.
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let spawn_err_tx = outcome_tx.clone();
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// Published by the network thread once the handshake succeeds, so the UI thread can read `quinn`'s own connection statistics without owning the connection.
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let connection = Arc::new(OnceLock::new());
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let task_connection = Arc::clone(&connection);
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let counters = Arc::new(NetCounters::default());
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let task_counters = Arc::clone(&counters);
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// Subscription updates flow UI -> network (sync send, async recv); chunk deliveries flow network -> UI (async send, sync try_recv).
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let (subscribe_tx, subscribe_rx) = tokio::sync::mpsc::unbounded_channel::<ChunkSubscribe>();
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// The delivery channel is bounded so a slow (e.g. debug-build) UI thread applies backpressure to the network task instead of letting undelivered chunks accumulate without limit.
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let (chunks_tx, chunks_rx) =
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tokio::sync::mpsc::channel::<ChunkMessage>(CHUNK_DELIVERY_CAPACITY);
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let spawned = thread::Builder::new()
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.name("net-client".to_owned())
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.spawn(move || {
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let runtime = match tokio::runtime::Builder::new_current_thread()
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.enable_all()
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.build()
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{
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Ok(runtime) => runtime,
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Err(error) => {
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let _ = outcome_tx.send(Err(format!("failed to build tokio runtime: {error}")));
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return;
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}
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};
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runtime.block_on(async move {
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let endpoint = match client_endpoint() {
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Ok(endpoint) => endpoint,
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Err(error) => {
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let _ = outcome_tx.send(Err(error.to_string()));
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return;
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}
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};
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// The server name matches the self-signed certificate's subject; the current verifier accepts any certificate regardless.
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match connect(&endpoint, server_addr, "localhost", hello).await {
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Ok(connected) => {
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if outcome_tx.send(Ok(connected.ack.clone())).is_err() {
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return;
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}
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// The cell is written exactly once, here; a failure would mean a second handshake on one link, which cannot occur.
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let _ = task_connection.set(connected.connection.clone());
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// Pump the chunk stream on this thread until the UI drops its handles or the server closes the connection.
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client_chunk_task(
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connected.connection,
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subscribe_rx,
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chunks_tx,
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&task_counters,
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)
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.await;
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warn!("server connection closed");
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}
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Err(error) => {
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let _ = outcome_tx.send(Err(error.to_string()));
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}
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}
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});
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});
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if let Err(error) = spawned {
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let _ = spawn_err_tx.send(Err(format!("failed to spawn network thread: {error}")));
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}
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ClientLink {
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handshake: outcome_rx,
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subscribe: ChunkSubscriber::new(subscribe_tx),
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chunks: chunks_rx,
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connection,
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counters,
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}
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}
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