New worker semantics applied to garage_table

src/table/gc.rs

@@ -8,12 +8,11 @@ use serde::{Deserialize, Serialize};
 use serde_bytes::ByteBuf;
 
 use futures::future::join_all;
-use futures::select;
-use futures_util::future::*;
 use tokio::sync::watch;
 
 use garage_db::counted_tree_hack::CountedTree;
 
+use garage_util::background::*;
 use garage_util::data::*;
 use garage_util::error::*;
 use garage_util::time::*;
@@ -69,35 +68,11 @@ where
 
 		gc.endpoint.set_handler(gc.clone());
 
-		let gc1 = gc.clone();
+		system.background.spawn_worker(GcWorker::new(gc.clone()));
-		system.background.spawn_worker(
-			format!("GC loop for {}", F::TABLE_NAME),
-			move |must_exit: watch::Receiver<bool>| gc1.gc_loop(must_exit),
-		);
 
 		gc
 	}
 
-	async fn gc_loop(self: Arc<Self>, mut must_exit: watch::Receiver<bool>) {
-		while !*must_exit.borrow() {
-			match self.gc_loop_iter().await {
-				Ok(None) => {
-					// Stuff was done, loop immediately
-				}
-				Ok(Some(wait_delay)) => {
-					// Nothing was done, wait specified delay.
-					select! {
-						_ = tokio::time::sleep(wait_delay).fuse() => {},
-						_ = must_exit.changed().fuse() => {},
-					}
-				}
-				Err(e) => {
-					warn!("({}) Error doing GC: {}", F::TABLE_NAME, e);
-				}
-			}
-		}
-	}
-
 	async fn gc_loop_iter(&self) -> Result<Option<Duration>, Error> {
 		let now = now_msec();
 
@@ -328,6 +303,57 @@ where
 	}
 }
 
+struct GcWorker<F, R>
+where
+	F: TableSchema + 'static,
+	R: TableReplication + 'static,
+{
+	gc: Arc<TableGc<F, R>>,
+	wait_delay: Duration,
+}
+
+impl<F, R> GcWorker<F, R>
+where
+	F: TableSchema + 'static,
+	R: TableReplication + 'static,
+{
+	fn new(gc: Arc<TableGc<F, R>>) -> Self {
+		Self {
+			gc,
+			wait_delay: Duration::from_secs(0),
+		}
+	}
+}
+
+#[async_trait]
+impl<F, R> Worker for GcWorker<F, R>
+where
+	F: TableSchema + 'static,
+	R: TableReplication + 'static,
+{
+	fn name(&self) -> String {
+		format!("Table GC: {}", F::TABLE_NAME)
+	}
+
+	async fn work(
+		&mut self,
+		_must_exit: &mut watch::Receiver<bool>,
+	) -> Result<WorkerStatus, Error> {
+		match self.gc.gc_loop_iter().await? {
+			None => Ok(WorkerStatus::Busy),
+			Some(delay) => {
+				self.wait_delay = delay;
+				Ok(WorkerStatus::Idle)
+			}
+		}
+	}
+
+	async fn wait_for_work(&mut self, _must_exit: &watch::Receiver<bool>) -> WorkerStatus {
+		tokio::time::sleep(self.wait_delay).await;
+		WorkerStatus::Busy
+	}
+}
+
 /// An entry stored in the gc_todo Sled tree associated with the table
 /// Contains helper function for parsing, saving, and removing
 /// such entry in Sled

src/table/merkle.rs

@@ -1,14 +1,13 @@
 use std::sync::Arc;
 use std::time::Duration;
 
-use futures::select;
+use async_trait::async_trait;
-use futures_util::future::*;
 use serde::{Deserialize, Serialize};
 use tokio::sync::watch;
 
 use garage_db as db;
 
-use garage_util::background::BackgroundRunner;
+use garage_util::background::*;
 use garage_util::data::*;
 use garage_util::error::Error;
 
@@ -78,43 +77,17 @@ where
 			empty_node_hash,
 		});
 
-		let ret2 = ret.clone();
+		background.spawn_worker(MerkleWorker(ret.clone()));
-		background.spawn_worker(
-			format!("Merkle tree updater for {}", F::TABLE_NAME),
-			|must_exit: watch::Receiver<bool>| ret2.updater_loop(must_exit),
-		);
 
 		ret
 	}
 
-	async fn updater_loop(self: Arc<Self>, mut must_exit: watch::Receiver<bool>) {
+	fn updater_loop_iter(&self) -> Result<WorkerStatus, Error> {
-		while !*must_exit.borrow() {
-			match self.updater_loop_iter() {
-				Ok(true) => (),
-				Ok(false) => {
-					select! {
-						_ = self.data.merkle_todo_notify.notified().fuse() => {},
-						_ = must_exit.changed().fuse() => {},
-					}
-				}
-				Err(e) => {
-					warn!(
-						"({}) Error while updating Merkle tree item: {}",
-						F::TABLE_NAME,
-						e
-					);
-					tokio::time::sleep(Duration::from_secs(10)).await;
-				}
-			}
-		}
-	}
-
-	fn updater_loop_iter(&self) -> Result<bool, Error> {
 		if let Some((key, valhash)) = self.data.merkle_todo.first()? {
 			self.update_item(&key, &valhash)?;
-			Ok(true)
+			Ok(WorkerStatus::Busy)
 		} else {
-			Ok(false)
+			Ok(WorkerStatus::Idle)
 		}
 	}
 
@@ -325,6 +298,34 @@ where
 	}
 }
 
+struct MerkleWorker<F, R>(Arc<MerkleUpdater<F, R>>)
+where
+	F: TableSchema + 'static,
+	R: TableReplication + 'static;
+
+#[async_trait]
+impl<F, R> Worker for MerkleWorker<F, R>
+where
+	F: TableSchema + 'static,
+	R: TableReplication + 'static,
+{
+	fn name(&self) -> String {
+		format!("Merkle tree updater: {}", F::TABLE_NAME)
+	}
+
+	async fn work(
+		&mut self,
+		_must_exit: &mut watch::Receiver<bool>,
+	) -> Result<WorkerStatus, Error> {
+		self.0.updater_loop_iter()
+	}
+
+	async fn wait_for_work(&mut self, _must_exit: &watch::Receiver<bool>) -> WorkerStatus {
+		tokio::time::sleep(Duration::from_secs(10)).await;
+		WorkerStatus::Busy
+	}
+}
+
 impl MerkleNodeKey {
 	fn encode(&self) -> Vec<u8> {
 		let mut ret = Vec::with_capacity(2 + self.prefix.len());

src/table/sync.rs

@@ -1,17 +1,17 @@
 use std::collections::VecDeque;
-use std::sync::{Arc, Mutex};
+use std::sync::Arc;
 use std::time::{Duration, Instant};
 
 use async_trait::async_trait;
-use futures::select;
-use futures_util::future::*;
 use futures_util::stream::*;
 use opentelemetry::KeyValue;
 use rand::Rng;
 use serde::{Deserialize, Serialize};
 use serde_bytes::ByteBuf;
+use tokio::select;
 use tokio::sync::{mpsc, watch};
 
+use garage_util::background::*;
 use garage_util::data::*;
 use garage_util::error::Error;
 
@@ -34,7 +34,7 @@ pub struct TableSyncer<F: TableSchema + 'static, R: TableReplication + 'static>
 	data: Arc<TableData<F, R>>,
 	merkle: Arc<MerkleUpdater<F, R>>,
 
-	todo: Mutex<SyncTodo>,
+	add_full_sync_tx: mpsc::UnboundedSender<()>,
 	endpoint: Arc<Endpoint<SyncRpc, Self>>,
 }
 
@@ -52,10 +52,6 @@ impl Rpc for SyncRpc {
 	type Response = Result<SyncRpc, Error>;
 }
 
-struct SyncTodo {
-	todo: Vec<TodoPartition>,
-}
-
 #[derive(Debug, Clone)]
 struct TodoPartition {
 	partition: Partition,
@@ -80,118 +76,40 @@ where
 			.netapp
 			.endpoint(format!("garage_table/sync.rs/Rpc:{}", F::TABLE_NAME));
 
-		let todo = SyncTodo { todo: vec![] };
+		let (add_full_sync_tx, add_full_sync_rx) = mpsc::unbounded_channel();
 
 		let syncer = Arc::new(Self {
 			system: system.clone(),
 			data,
 			merkle,
-			todo: Mutex::new(todo),
+			add_full_sync_tx,
 			endpoint,
 		});
 
 		syncer.endpoint.set_handler(syncer.clone());
 
-		let (busy_tx, busy_rx) = mpsc::unbounded_channel();
+		system.background.spawn_worker(SyncWorker {
-
+			syncer: syncer.clone(),
-		let s1 = syncer.clone();
+			ring_recv: system.ring.clone(),
-		system.background.spawn_worker(
+			ring: system.ring.borrow().clone(),
-			format!("table sync watcher for {}", F::TABLE_NAME),
+			add_full_sync_rx,
-			move |must_exit: watch::Receiver<bool>| s1.watcher_task(must_exit, busy_rx),
+			todo: vec![],
-		);
+			next_full_sync: Instant::now() + Duration::from_secs(20),
-
-		let s2 = syncer.clone();
-		system.background.spawn_worker(
-			format!("table syncer for {}", F::TABLE_NAME),
-			move |must_exit: watch::Receiver<bool>| s2.syncer_task(must_exit, busy_tx),
-		);
-
-		let s3 = syncer.clone();
-		tokio::spawn(async move {
-			tokio::time::sleep(Duration::from_secs(20)).await;
-			s3.add_full_sync();
 		});
 
 		syncer
 	}
 
-	async fn watcher_task(
-		self: Arc<Self>,
-		mut must_exit: watch::Receiver<bool>,
-		mut busy_rx: mpsc::UnboundedReceiver<bool>,
-	) {
-		let mut prev_ring: Arc<Ring> = self.system.ring.borrow().clone();
-		let mut ring_recv: watch::Receiver<Arc<Ring>> = self.system.ring.clone();
-		let mut nothing_to_do_since = Some(Instant::now());
-
-		while !*must_exit.borrow() {
-			select! {
-				_ = ring_recv.changed().fuse() => {
-					let new_ring = ring_recv.borrow();
-					if !Arc::ptr_eq(&new_ring, &prev_ring) {
-						debug!("({}) Ring changed, adding full sync to syncer todo list", F::TABLE_NAME);
-						self.add_full_sync();
-						prev_ring = new_ring.clone();
-					}
-				}
-				busy_opt = busy_rx.recv().fuse() => {
-					if let Some(busy) = busy_opt {
-						if busy {
-							nothing_to_do_since = None;
-						} else if nothing_to_do_since.is_none() {
-							nothing_to_do_since = Some(Instant::now());
-						}
-					}
-				}
-				_ = must_exit.changed().fuse() => {},
-				_ = tokio::time::sleep(Duration::from_secs(1)).fuse() => {
-					if nothing_to_do_since.map(|t| Instant::now() - t >= ANTI_ENTROPY_INTERVAL).unwrap_or(false) {
-						nothing_to_do_since = None;
-						debug!("({}) Interval passed, adding full sync to syncer todo list", F::TABLE_NAME);
-						self.add_full_sync();
-					}
-				}
-			}
-		}
-	}
-
 	pub fn add_full_sync(&self) {
-		self.todo
+		if self.add_full_sync_tx.send(()).is_err() {
-			.lock()
+			error!("({}) Could not add full sync", F::TABLE_NAME);
-			.unwrap()
-			.add_full_sync(&self.data, &self.system);
-	}
-
-	async fn syncer_task(
-		self: Arc<Self>,
-		mut must_exit: watch::Receiver<bool>,
-		busy_tx: mpsc::UnboundedSender<bool>,
-	) {
-		while !*must_exit.borrow() {
-			let task = self.todo.lock().unwrap().pop_task();
-			if let Some(partition) = task {
-				busy_tx.send(true).unwrap();
-				let res = self
-					.clone()
-					.sync_partition(&partition, &mut must_exit)
-					.await;
-				if let Err(e) = res {
-					warn!(
-						"({}) Error while syncing {:?}: {}",
-						F::TABLE_NAME,
-						partition,
-						e
-					);
-				}
-			} else {
-				busy_tx.send(false).unwrap();
-				tokio::time::sleep(Duration::from_secs(1)).await;
-			}
 		}
 	}
 
+	// ----
+
 	async fn sync_partition(
-		self: Arc<Self>,
+		self: &Arc<Self>,
 		partition: &TodoPartition,
 		must_exit: &mut watch::Receiver<bool>,
 	) -> Result<(), Error> {
@@ -577,12 +495,22 @@ where
 	}
 }
 
-impl SyncTodo {
+// -------- Sync Worker ---------
-	fn add_full_sync<F: TableSchema, R: TableReplication>(
+
-		&mut self,
+struct SyncWorker<F: TableSchema + 'static, R: TableReplication + 'static> {
-		data: &TableData<F, R>,
+	syncer: Arc<TableSyncer<F, R>>,
-		system: &System,
+	ring_recv: watch::Receiver<Arc<Ring>>,
-	) {
+	ring: Arc<Ring>,
+	add_full_sync_rx: mpsc::UnboundedReceiver<()>,
+	todo: Vec<TodoPartition>,
+	next_full_sync: Instant,
+}
+
+impl<F: TableSchema + 'static, R: TableReplication + 'static> SyncWorker<F, R> {
+	fn add_full_sync(&mut self) {
+		let system = &self.syncer.system;
+		let data = &self.syncer.data;
+
 		let my_id = system.id;
 
 		self.todo.clear();
@@ -623,6 +551,8 @@ impl SyncTodo {
 				retain,
 			});
 		}
+
+		self.next_full_sync = Instant::now() + ANTI_ENTROPY_INTERVAL;
 	}
 
 	fn pop_task(&mut self) -> Option<TodoPartition> {
@@ -641,6 +571,51 @@ impl SyncTodo {
 	}
 }
 
+#[async_trait]
+impl<F: TableSchema + 'static, R: TableReplication + 'static> Worker for SyncWorker<F, R> {
+	fn name(&self) -> String {
+		format!("Table sync worker for {}", F::TABLE_NAME)
+	}
+
+	async fn work(&mut self, must_exit: &mut watch::Receiver<bool>) -> Result<WorkerStatus, Error> {
+		if let Some(partition) = self.pop_task() {
+			self.syncer.sync_partition(&partition, must_exit).await?;
+			Ok(WorkerStatus::Busy)
+		} else {
+			Ok(WorkerStatus::Idle)
+		}
+	}
+
+	async fn wait_for_work(&mut self, _must_exit: &watch::Receiver<bool>) -> WorkerStatus {
+		select! {
+			s = self.add_full_sync_rx.recv() => match s {
+				Some(()) => {
+					self.add_full_sync();
+				}
+				None => (),
+			},
+			_ = self.ring_recv.changed() => {
+				let new_ring = self.ring_recv.borrow();
+				if !Arc::ptr_eq(&new_ring, &self.ring) {
+					self.ring = new_ring.clone();
+					drop(new_ring);
+					debug!("({}) Ring changed, adding full sync to syncer todo list", F::TABLE_NAME);
+					self.add_full_sync();
+				}
+			},
+			_ = tokio::time::sleep(self.next_full_sync - Instant::now()) => {
+				self.add_full_sync();
+			}
+		}
+		match self.todo.is_empty() {
+			false => WorkerStatus::Busy,
+			true => WorkerStatus::Idle,
+		}
+	}
+}
+
+// ---- UTIL ----
+
 fn hash_of<T: Serialize>(x: &T) -> Result<Hash, Error> {
 	Ok(blake2sum(&rmp_to_vec_all_named(x)?[..]))
 }

src/util/background/job_worker.rs

@@ -34,16 +34,15 @@ impl Worker for JobWorker {
 		}
 	}
 
-	async fn wait_for_work(&mut self, must_exit: &mut watch::Receiver<bool>) -> WorkerStatus {
+	async fn wait_for_work(&mut self, must_exit: &watch::Receiver<bool>) -> WorkerStatus {
 		loop {
 			match self.job_chan.lock().await.recv().await {
 				Some((job, cancellable)) => {
 					if cancellable && *must_exit.borrow() {
-						// skip job
 						continue;
 					}
 					self.next_job = Some(job);
-					return WorkerStatus::Busy
+					return WorkerStatus::Busy;
 				}
 				None => return WorkerStatus::Done,
 			}

src/util/background/mod.rs

@@ -10,7 +10,8 @@ use std::sync::Arc;
 use tokio::sync::{mpsc, watch, Mutex};
 
 use crate::error::Error;
-use worker::{Worker, WorkerProcessor};
+use worker::WorkerProcessor;
+pub use worker::{Worker, WorkerStatus};
 
 pub(crate) type JobOutput = Result<(), Error>;
 pub(crate) type Job = Pin<Box<dyn Future<Output = JobOutput> + Send>>;
@@ -30,9 +31,7 @@ impl BackgroundRunner {
 		let (send_worker, worker_out) = mpsc::unbounded_channel::<Box<dyn Worker>>();
 
 		let await_all_done =
-			tokio::spawn(
+			tokio::spawn(async move { WorkerProcessor::new(worker_out, stop_signal).run().await });
-				async move { WorkerProcessor::new(worker_out, stop_signal).run().await },
-			);
 
 		let (send_job, queue_out) = mpsc::unbounded_channel();
 		let queue_out = Arc::new(Mutex::new(queue_out));
@@ -40,11 +39,14 @@ impl BackgroundRunner {
 		for i in 0..n_runners {
 			let queue_out = queue_out.clone();
 
-			send_worker.send(Box::new(job_worker::JobWorker {
+			send_worker
-				index: i,
+				.send(Box::new(job_worker::JobWorker {
-				job_chan: queue_out.clone(),
+					index: i,
-				next_job: None,
+					job_chan: queue_out.clone(),
-			})).ok().unwrap();
+					next_job: None,
+				}))
+				.ok()
+				.unwrap();
 		}
 
 		let bgrunner = Arc::new(Self {

src/util/background/worker.rs

@@ -1,16 +1,16 @@
 use std::time::{Duration, Instant};
 
-use tracing::*;
 use async_trait::async_trait;
 use futures::future::*;
-use tokio::select;
 use futures::stream::FuturesUnordered;
 use futures::StreamExt;
+use tokio::select;
 use tokio::sync::{mpsc, watch};
+use tracing::*;
 
 use crate::error::Error;
 
-#[derive(PartialEq, Copy, Clone)]
+#[derive(PartialEq, Copy, Clone, Debug)]
 pub enum WorkerStatus {
 	Busy,
 	Idle,
@@ -20,8 +20,20 @@ pub enum WorkerStatus {
 #[async_trait]
 pub trait Worker: Send {
 	fn name(&self) -> String;
+
+	/// Work: do a basic unit of work, if one is available (otherwise, should return
+	/// WorkerStatus::Idle immediately).  We will do our best to not interrupt this future in the
+	/// middle of processing, it will only be interrupted at the last minute when Garage is trying
+	/// to exit and this hasn't returned yet. This function may return an error to indicate that
+	/// its unit of work could not be processed due to an error: the error will be logged and
+	/// .work() will be called again immediately.
 	async fn work(&mut self, must_exit: &mut watch::Receiver<bool>) -> Result<WorkerStatus, Error>;
-	async fn wait_for_work(&mut self, must_exit: &mut watch::Receiver<bool>) -> WorkerStatus;
+
+	/// Wait for work: await for some task to become available.  This future can be interrupted in
+	/// the middle for any reason.  This future doesn't have to await on must_exit.changed(), we
+	/// are doing it for you.  Therefore it only receives a read refernce to must_exit which allows
+	/// it to check if we are exiting.
+	async fn wait_for_work(&mut self, must_exit: &watch::Receiver<bool>) -> WorkerStatus;
 }
 
 pub(crate) struct WorkerProcessor {
@@ -58,10 +70,12 @@ impl WorkerProcessor {
 						let task_id = next_task_id;
 						next_task_id += 1;
 						let stop_signal = self.stop_signal.clone();
+						let stop_signal_worker = self.stop_signal.clone();
 						workers.push(async move {
 							let mut worker = WorkerHandler {
 								task_id,
 								stop_signal,
+								stop_signal_worker,
 								worker: new_worker,
 								status: WorkerStatus::Busy,
 							};
@@ -91,15 +105,22 @@ impl WorkerProcessor {
 		let drain_half_time = Instant::now() + Duration::from_secs(5);
 		let drain_everything = async move {
 			while let Some(mut worker) = workers.next().await {
-				if worker.status == WorkerStatus::Busy
+				if worker.status == WorkerStatus::Done {
-					|| (worker.status == WorkerStatus::Idle && Instant::now() < drain_half_time)
+					info!(
-				{
+						"Worker {} (TID {}) exited",
-					workers.push(async move {
+						worker.worker.name(),
-						worker.step().await;
+						worker.task_id
-						worker
+					);
-					}.boxed());
+				} else if Instant::now() > drain_half_time {
+					warn!("Worker {} (TID {}) interrupted between two iterations in state {:?} (this should be fine)", worker.worker.name(), worker.task_id, worker.status);
 				} else {
-					info!("Worker {} (TID {}) exited", worker.worker.name(), worker.task_id);
+					workers.push(
+						async move {
+							worker.step().await;
+							worker
+						}
+						.boxed(),
+					);
 				}
 			}
 		};
@@ -109,7 +130,7 @@ impl WorkerProcessor {
 				info!("All workers exited in time \\o/");
 			}
 			_ = tokio::time::sleep(Duration::from_secs(9)) => {
-				warn!("Some workers could not exit in time, we are cancelling some things in the middle.");
+				error!("Some workers could not exit in time, we are cancelling some things in the middle");
 			}
 		}
 	}
@@ -119,27 +140,49 @@ impl WorkerProcessor {
 struct WorkerHandler {
 	task_id: usize,
 	stop_signal: watch::Receiver<bool>,
+	stop_signal_worker: watch::Receiver<bool>,
 	worker: Box<dyn Worker>,
 	status: WorkerStatus,
 }
 
 impl WorkerHandler {
-	async fn step(&mut self) { 
+	async fn step(&mut self) {
 		match self.status {
-			WorkerStatus::Busy => {
+			WorkerStatus::Busy => match self.worker.work(&mut self.stop_signal).await {
-				match self.worker.work(&mut self.stop_signal).await {
+				Ok(s) => {
-					Ok(s) => {
+					self.status = s;
-						self.status = s;
+				}
+				Err(e) => {
+					error!(
+						"Error in worker {} (TID {}): {}",
+						self.worker.name(),
+						self.task_id,
+						e
+					);
+				}
+			},
+			WorkerStatus::Idle => {
+				if *self.stop_signal.borrow() {
+					select! {
+						new_st = self.worker.wait_for_work(&mut self.stop_signal_worker) => {
+							self.status = new_st;
+						}
+						_ = tokio::time::sleep(Duration::from_secs(1)) => {
+							// stay in Idle state
+						}
 					}
-					Err(e) => {
+				} else {
-						error!("Error in worker {}: {}", self.worker.name(), e);
+					select! {
+						new_st = self.worker.wait_for_work(&mut self.stop_signal_worker) => {
+							self.status = new_st;
+						}
+						_ = self.stop_signal.changed() => {
+							// stay in Idle state
+						}
 					}
 				}
 			}
-			WorkerStatus::Idle => {
+			WorkerStatus::Done => unreachable!(),
-				self.status = self.worker.wait_for_work(&mut self.stop_signal).await;
-			}
-			WorkerStatus::Done => unreachable!()
 		}
 	}
 }