Ability to dynamically set resync tranquility

src/block/manager.rs

@@ -3,7 +3,7 @@ use std::path::PathBuf;
 use std::sync::Arc;
 use std::time::Duration;
 
-use arc_swap::ArcSwapOption;
+use arc_swap::{ArcSwap, ArcSwapOption};
 use async_trait::async_trait;
 use serde::{Deserialize, Serialize};
 
@@ -25,6 +25,7 @@ use garage_util::background::*;
 use garage_util::data::*;
 use garage_util::error::*;
 use garage_util::metrics::RecordDuration;
+use garage_util::persister::Persister;
 use garage_util::time::*;
 use garage_util::tranquilizer::Tranquilizer;
 
@@ -55,6 +56,10 @@ const RESYNC_RETRY_DELAY: Duration = Duration::from_secs(60);
 // The maximum retry delay is 60 seconds * 2^6 = 60 seconds << 6 = 64 minutes (~1 hour)
 const RESYNC_RETRY_DELAY_MAX_BACKOFF_POWER: u64 = 6;
 
+// Resync tranquility is initially set to 2, but can be changed in the CLI
+// and the updated version is persisted over Garage restarts
+const INITIAL_RESYNC_TRANQUILITY: u32 = 2;
+
 // The delay between the moment when the reference counter
 // drops to zero, and the moment where we allow ourselves
 // to delete the block locally.
@@ -90,7 +95,6 @@ pub struct BlockManager {
 	pub data_dir: PathBuf,
 
 	compression_level: Option<i32>,
-	background_tranquility: u32,
 
 	mutation_lock: Mutex<BlockManagerLocked>,
 
@@ -100,6 +104,9 @@ pub struct BlockManager {
 	resync_notify: Notify,
 	resync_errors: CountedTree,
 
+	resync_persister: Persister<ResyncPersistedConfig>,
+	resync_persisted: ArcSwap<ResyncPersistedConfig>,
+
 	pub(crate) system: Arc<System>,
 	endpoint: Arc<Endpoint<BlockRpc, Self>>,
 
@@ -124,7 +131,6 @@ impl BlockManager {
 		db: &db::Db,
 		data_dir: PathBuf,
 		compression_level: Option<i32>,
-		background_tranquility: u32,
 		replication: TableShardedReplication,
 		system: Arc<System>,
 	) -> Arc<Self> {
@@ -145,6 +151,14 @@ impl BlockManager {
 		let resync_errors =
 			CountedTree::new(resync_errors).expect("Could not count block_local_resync_errors");
 
+		let resync_persister = Persister::new(&system.metadata_dir, "resync_cfg");
+		let resync_persisted = match resync_persister.load() {
+			Ok(v) => v,
+			Err(_) => ResyncPersistedConfig {
+				tranquility: INITIAL_RESYNC_TRANQUILITY,
+			},
+		};
+
 		let endpoint = system
 			.netapp
 			.endpoint("garage_block/manager.rs/Rpc".to_string());
@@ -157,12 +171,13 @@ impl BlockManager {
 			replication,
 			data_dir,
 			compression_level,
-			background_tranquility,
 			mutation_lock: Mutex::new(manager_locked),
 			rc,
 			resync_queue,
 			resync_notify: Notify::new(),
 			resync_errors,
+			resync_persister,
+			resync_persisted: ArcSwap::new(Arc::new(resync_persisted)),
 			system,
 			endpoint,
 			metrics,
@@ -716,6 +731,23 @@ impl BlockManager {
 
 		Ok(())
 	}
+
+	async fn update_resync_persisted(
+		&self,
+		update: impl Fn(&mut ResyncPersistedConfig),
+	) -> Result<(), Error> {
+		let mut cfg: ResyncPersistedConfig = *self.resync_persisted.load().as_ref();
+		update(&mut cfg);
+		self.resync_persister.save_async(&cfg).await?;
+		self.resync_persisted.store(Arc::new(cfg));
+		self.resync_notify.notify_one();
+		Ok(())
+	}
+
+	pub async fn set_resync_tranquility(&self, tranquility: u32) -> Result<(), Error> {
+		self.update_resync_persisted(|cfg| cfg.tranquility = tranquility)
+			.await
+	}
 }
 
 #[async_trait]
@@ -734,6 +766,11 @@ impl EndpointHandler<BlockRpc> for BlockManager {
 	}
 }
 
+#[derive(Serialize, Deserialize, Clone, Copy)]
+struct ResyncPersistedConfig {
+	tranquility: u32,
+}
+
 struct ResyncWorker {
 	manager: Arc<BlockManager>,
 	tranquilizer: Tranquilizer,
@@ -758,19 +795,22 @@ impl Worker for ResyncWorker {
 
 	fn info(&self) -> Option<String> {
 		let mut ret = vec![];
+		ret.push(format!(
+			"tranquility = {}",
+			self.manager.resync_persisted.load().tranquility
+		));
+
 		let qlen = self.manager.resync_queue_len().unwrap_or(0);
-		let elen = self.manager.resync_errors_len().unwrap_or(0);
 		if qlen > 0 {
 			ret.push(format!("{} blocks in queue", qlen));
 		}
+
+		let elen = self.manager.resync_errors_len().unwrap_or(0);
 		if elen > 0 {
 			ret.push(format!("{} blocks in error state", elen));
 		}
-		if !ret.is_empty() {
-			Some(ret.join(", "))
-		} else {
-			None
-		}
+
+		Some(ret.join(", "))
 	}
 
 	async fn work(&mut self, _must_exit: &mut watch::Receiver<bool>) -> Result<WorkerState, Error> {
@@ -778,7 +818,7 @@ impl Worker for ResyncWorker {
 		match self.manager.resync_iter().await {
 			Ok(ResyncIterResult::BusyDidSomething) => Ok(self
 				.tranquilizer
-				.tranquilize_worker(self.manager.background_tranquility)),
+				.tranquilize_worker(self.manager.resync_persisted.load().tranquility)),
 			Ok(ResyncIterResult::BusyDidNothing) => Ok(WorkerState::Busy),
 			Ok(ResyncIterResult::IdleFor(delay)) => {
 				self.next_delay = delay;