split service manager into unit

Signed-off-by: Jason Volk <jason@zemos.net>

src/service/manager.rs

@@ -0,0 +1,159 @@
+use std::{panic::AssertUnwindSafe, sync::Arc, time::Duration};
+
+use conduit::{debug, debug_warn, error, trace, utils::time, warn, Error, Result, Server};
+use futures_util::FutureExt;
+use tokio::{
+	sync::{Mutex, MutexGuard},
+	task::{JoinHandle, JoinSet},
+	time::sleep,
+};
+
+use crate::{service::Service, Services};
+
+pub(crate) struct Manager {
+	manager: Mutex<Option<JoinHandle<Result<()>>>>,
+	workers: Mutex<Workers>,
+	server: Arc<Server>,
+	services: &'static Services,
+}
+
+type Workers = JoinSet<WorkerResult>;
+type WorkerResult = (Arc<dyn Service>, Result<()>);
+type WorkersLocked<'a> = MutexGuard<'a, Workers>;
+
+const RESTART_DELAY_MS: u64 = 2500;
+
+impl Manager {
+	pub(super) fn new(services: &Services) -> Arc<Self> {
+		Arc::new(Self {
+			manager: Mutex::new(None),
+			workers: Mutex::new(JoinSet::new()),
+			server: services.server.clone(),
+			services: crate::services(),
+		})
+	}
+
+	pub(super) async fn poll(&self) -> Result<()> {
+		if let Some(manager) = &mut *self.manager.lock().await {
+			trace!("Polling service manager...");
+			return manager.await?;
+		}
+
+		Ok(())
+	}
+
+	pub(super) async fn start(self: Arc<Self>) -> Result<()> {
+		let mut workers = self.workers.lock().await;
+
+		debug!("Starting service manager...");
+		let self_ = self.clone();
+		_ = self.manager.lock().await.insert(
+			self.server
+				.runtime()
+				.spawn(async move { self_.worker().await }),
+		);
+
+		debug!("Starting service workers...");
+		for service in self.services.service.values() {
+			self.start_worker(&mut workers, service).await?;
+		}
+
+		Ok(())
+	}
+
+	pub(super) async fn stop(&self) {
+		if let Some(manager) = self.manager.lock().await.take() {
+			debug!("Waiting for service manager...");
+			if let Err(e) = manager.await {
+				error!("Manager shutdown error: {e:?}");
+			}
+		}
+	}
+
+	async fn worker(&self) -> Result<()> {
+		loop {
+			let mut workers = self.workers.lock().await;
+			tokio::select! {
+				result = workers.join_next() => match result {
+					Some(Ok(result)) => self.handle_result(&mut workers, result).await?,
+					Some(Err(error)) => self.handle_abort(&mut workers, Error::from(error)).await?,
+					None => break,
+				}
+			}
+		}
+
+		debug!("Worker manager finished");
+		Ok(())
+	}
+
+	async fn handle_abort(&self, _workers: &mut WorkersLocked<'_>, error: Error) -> Result<()> {
+		// not supported until service can be associated with abort
+		unimplemented!("unexpected worker task abort {error:?}");
+	}
+
+	async fn handle_result(&self, workers: &mut WorkersLocked<'_>, result: WorkerResult) -> Result<()> {
+		let (service, result) = result;
+		match result {
+			Ok(()) => self.handle_finished(workers, &service).await,
+			Err(error) => self.handle_error(workers, &service, error).await,
+		}
+	}
+
+	async fn handle_finished(&self, _workers: &mut WorkersLocked<'_>, service: &Arc<dyn Service>) -> Result<()> {
+		debug!("service {:?} worker finished", service.name());
+		Ok(())
+	}
+
+	async fn handle_error(
+		&self, workers: &mut WorkersLocked<'_>, service: &Arc<dyn Service>, error: Error,
+	) -> Result<()> {
+		let name = service.name();
+		error!("service {name:?} aborted: {error}");
+
+		if !self.server.running() {
+			debug_warn!("service {name:?} error ignored on shutdown.");
+			return Ok(());
+		}
+
+		if !error.is_panic() {
+			return Err(error);
+		}
+
+		let delay = Duration::from_millis(RESTART_DELAY_MS);
+		warn!("service {name:?} worker restarting after {} delay", time::pretty(delay));
+		sleep(delay).await;
+
+		self.start_worker(workers, service).await
+	}
+
+	/// Start the worker in a task for the service.
+	async fn start_worker(&self, workers: &mut WorkersLocked<'_>, service: &Arc<dyn Service>) -> Result<()> {
+		if !self.server.running() {
+			return Err(Error::Err(format!(
+				"Service {:?} worker not starting during server shutdown.",
+				service.name()
+			)));
+		}
+
+		debug!("Service {:?} worker starting...", service.name());
+		workers.spawn_on(worker(service.clone()), self.server.runtime());
+
+		Ok(())
+	}
+}
+
+/// Base frame for service worker. This runs in a tokio::task. All errors and
+/// panics from the worker are caught and returned cleanly. The JoinHandle
+/// should never error with a panic, and if so it should propagate, but it may
+/// error with an Abort which the manager should handle along with results to
+/// determine if the worker should be restarted.
+async fn worker(service: Arc<dyn Service>) -> WorkerResult {
+	let service_ = Arc::clone(&service);
+	let result = AssertUnwindSafe(service_.worker())
+		.catch_unwind()
+		.await
+		.map_err(Error::from_panic);
+
+	// flattens JoinError for panic into worker's Error
+	(service, result.unwrap_or_else(Err))
+}