abstract service worker pattern; restart on panic.

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

src/service/services.rs

@@ -1,7 +1,13 @@
-use std::{collections::BTreeMap, fmt::Write, sync::Arc};
+use std::{collections::BTreeMap, fmt::Write, panic::AssertUnwindSafe, sync::Arc, time::Duration};
 
-use conduit::{debug, debug_info, info, trace, Result, Server};
+use conduit::{debug, debug_info, error, info, trace, utils::time, warn, Error, Result, Server};
 use database::Database;
+use futures_util::FutureExt;
+use tokio::{
+	sync::{Mutex, MutexGuard},
+	task::{JoinHandle, JoinSet},
+	time::sleep,
+};
 
 use crate::{
 	account_data, admin, appservice, globals, key_backups, media, presence, pusher, rooms, sending,
@@ -24,11 +30,19 @@ pub struct Services {
 	pub media: Arc<media::Service>,
 	pub sending: Arc<sending::Service>,
 
+	workers: Mutex<Workers>,
+	manager: Mutex<Option<JoinHandle<Result<()>>>>,
 	pub(crate) service: Map,
 	pub server: Arc<Server>,
 	pub db: Arc<Database>,
 }
 
+type Workers = JoinSet<WorkerResult>;
+type WorkerResult = (Arc<dyn Service>, Result<()>);
+type WorkersLocked<'a> = MutexGuard<'a, Workers>;
+
+const RESTART_DELAY_MS: u64 = 2500;
+
 impl Services {
 	pub fn build(server: Arc<Server>, db: Arc<Database>) -> Result<Self> {
 		let mut service: Map = BTreeMap::new();
@@ -79,12 +93,74 @@ impl Services {
 			media: build!(media::Service),
 			sending: build!(sending::Service),
 			globals: build!(globals::Service),
+			workers: Mutex::new(JoinSet::new()),
+			manager: Mutex::new(None),
 			service,
 			server,
 			db,
 		})
 	}
 
+	pub async fn start(&self) -> Result<()> {
+		debug_info!("Starting services...");
+
+		self.media.create_media_dir().await?;
+		globals::migrations::migrations(&self.db, &self.globals.config).await?;
+		globals::emerg_access::init_emergency_access();
+
+		let mut workers = self.workers.lock().await;
+		for service in self.service.values() {
+			self.start_worker(&mut workers, service).await?;
+		}
+
+		debug!("Starting service manager...");
+		let manager = async move { crate::services().manager().await };
+		let manager = self.server.runtime().spawn(manager);
+		_ = self.manager.lock().await.insert(manager);
+
+		if self.globals.allow_check_for_updates() {
+			let handle = globals::updates::start_check_for_updates_task();
+			_ = self.globals.updates_handle.lock().await.insert(handle);
+		}
+
+		debug_info!("Services startup complete.");
+		Ok(())
+	}
+
+	pub async fn stop(&self) {
+		info!("Shutting down services...");
+		self.interrupt();
+
+		debug!("Waiting for update worker...");
+		if let Some(updates_handle) = self.globals.updates_handle.lock().await.take() {
+			updates_handle.abort();
+			_ = updates_handle.await;
+		}
+
+		debug!("Stopping service manager...");
+		if let Some(manager) = self.manager.lock().await.take() {
+			if let Err(e) = manager.await {
+				error!("Manager shutdown error: {e:?}");
+			}
+		}
+
+		debug_info!("Services shutdown complete.");
+	}
+
+	pub async fn clear_cache(&self) {
+		for service in self.service.values() {
+			service.clear_cache();
+		}
+
+		//TODO
+		self.rooms
+			.spaces
+			.roomid_spacehierarchy_cache
+			.lock()
+			.await
+			.clear();
+	}
+
 	pub async fn memory_usage(&self) -> Result<String> {
 		let mut out = String::new();
 		for service in self.service.values() {
@@ -104,65 +180,97 @@ impl Services {
 		Ok(out)
 	}
 
-	pub async fn clear_cache(&self) {
-		for service in self.service.values() {
-			service.clear_cache();
-		}
-
-		//TODO
-		self.rooms
-			.spaces
-			.roomid_spacehierarchy_cache
-			.lock()
-			.await
-			.clear();
-	}
-
-	pub async fn start(&self) -> Result<()> {
-		debug_info!("Starting services");
-
-		self.media.create_media_dir().await?;
-		globals::migrations::migrations(&self.db, &self.globals.config).await?;
-		globals::emerg_access::init_emergency_access();
-
-		for (name, service) in &self.service {
-			debug!("Starting {name}");
-			service.clone().start().await?;
-		}
-
-		if self.globals.allow_check_for_updates() {
-			let handle = globals::updates::start_check_for_updates_task();
-			_ = self.globals.updates_handle.lock().await.insert(handle);
-		}
-
-		debug_info!("Services startup complete.");
-		Ok(())
-	}
-
-	pub fn interrupt(&self) {
+	fn interrupt(&self) {
 		debug!("Interrupting services...");
-
 		for (name, service) in &self.service {
 			trace!("Interrupting {name}");
 			service.interrupt();
 		}
 	}
 
-	pub async fn stop(&self) {
-		info!("Shutting down services");
-		self.interrupt();
-
-		debug!("Waiting for update worker...");
-		if let Some(updates_handle) = self.globals.updates_handle.lock().await.take() {
-			updates_handle.abort();
-			_ = updates_handle.await;
+	async fn manager(&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,
+				}
+			}
 		}
 
-		for (name, service) in &self.service {
-			debug!("Waiting for {name} ...");
-			service.stop().await;
+		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:?} worker error: {error}");
+
+		if !error.is_panic() {
+			return Ok(());
 		}
 
-		debug_info!("Services shutdown complete.");
+		if !self.server.running() {
+			return Ok(());
+		}
+
+		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))
+}