Configure structopt to report the right version

By default, structopt reports the value provided by
the env var CARGO_PKG_VERSION, feeded by Cargo when reading
Cargo.toml. However for Garage we use a versioning based on git,
so we often report a version that is behind the real version.
In this commit, we create garage_util::version::garage() that
reports the right version and configure all structopt subcommands
to call this function instead of using the env var.

.drone.yml

@@ -14,7 +14,7 @@ steps:
   - name: build
     image: nixpkgs/nix:nixos-22.05
     commands:
-      - nix-build --no-build-output --attr clippy.amd64 --argstr git_version ${DRONE_TAG:-$DRONE_COMMIT}
+      - nix-build --no-build-output --attr clippy.amd64 --argstr git_version $DRONE_COMMIT
 
   - name: unit + func tests
     image: nixpkgs/nix:nixos-22.05
@@ -34,7 +34,7 @@ steps:
   - name: integration tests
     image: nixpkgs/nix:nixos-22.05
     commands:
-      - nix-build --no-build-output --attr clippy.amd64 --argstr git_version ${DRONE_TAG:-$DRONE_COMMIT}
+      - nix-build --no-build-output --attr clippy.amd64 --argstr git_version $DRONE_COMMIT
       - nix-shell --attr integration --run ./script/test-smoke.sh || (cat /tmp/garage.log; false)
 
 trigger:
@@ -57,7 +57,7 @@ steps:
   - name: build
     image: nixpkgs/nix:nixos-22.05
     commands:
-      - nix-build --no-build-output --attr pkgs.amd64.release --argstr git_version ${DRONE_TAG:-$DRONE_COMMIT}
+      - nix-build --no-build-output --attr pkgs.amd64.release --argstr git_version $DRONE_COMMIT
       - nix-shell --attr rust --run "./script/not-dynamic.sh result/bin/garage"
 
   - name: integration
@@ -108,7 +108,7 @@ steps:
   - name: build
     image: nixpkgs/nix:nixos-22.05
     commands:
-      - nix-build --no-build-output --attr pkgs.i386.release --argstr git_version ${DRONE_TAG:-$DRONE_COMMIT}
+      - nix-build --no-build-output --attr pkgs.i386.release --argstr git_version $DRONE_COMMIT
       - nix-shell --attr rust --run "./script/not-dynamic.sh result/bin/garage"
 
   - name: integration
@@ -158,7 +158,7 @@ steps:
   - name: build
     image: nixpkgs/nix:nixos-22.05
     commands:
-      - nix-build --no-build-output --attr pkgs.arm64.release --argstr git_version ${DRONE_TAG:-$DRONE_COMMIT}
+      - nix-build --no-build-output --attr pkgs.arm64.release --argstr git_version $DRONE_COMMIT
       - nix-shell --attr rust --run "./script/not-dynamic.sh result/bin/garage"
 
   - name: push static binary
@@ -203,7 +203,7 @@ steps:
   - name: build
     image: nixpkgs/nix:nixos-22.05
     commands:
-      - nix-build --no-build-output --attr pkgs.arm.release --argstr git_version ${DRONE_TAG:-$DRONE_COMMIT}
+      - nix-build --no-build-output --attr pkgs.arm.release --argstr git_version $DRONE_COMMIT
       - nix-shell --attr rust --run "./script/not-dynamic.sh result/bin/garage"
 
   - name: push static binary
@@ -269,6 +269,6 @@ trigger:
 
 ---
 kind: signature
-hmac: 362639b4c9541ad9bd06ff7f72b5235b2b0216bcb16eececd25285b6fe94ba6f
+hmac: ccec0e06bf6676a705d6a4e63dc322691148bc72e72a4aaa54be6c5fd22652a2
 
 ...

doc/book/cookbook/reverse-proxy.md

@@ -280,25 +280,3 @@ Traefik's caching middleware is only available on [entreprise version](https://d
 [http.middlewares]
   [http.middlewares.gzip_compress.compress]
 ```
-
-## Caddy
-
-Your Caddy configuration can be as simple as:
-
-```caddy
-s3.garage.tld, *.s3.garage.tld {
-	reverse_proxy localhost:3900 192.168.1.2:3900 example.tld:3900
-}
-
-*.web.garage.tld {
-	reverse_proxy localhost:3902 192.168.1.2:3900 example.tld:3900
-}
-
-admin.garage.tld {
-	reverse_proxy localhost:3903
-}
-```
-
-But at the same time, the `reverse_proxy` is very flexible.
-For a production deployment, you should [read its documentation](https://caddyserver.com/docs/caddyfile/directives/reverse_proxy) as it supports features like DNS discovery of upstreams, load balancing with checks, streaming parameters, etc.
-

nix/compile.nix

@@ -118,7 +118,6 @@ let
      But we want to ship these additional features when we release Garage.
      In the end, we chose to exclude all features from debug builds while putting (all of) them in the release builds.
      Currently, the only feature of Garage is kubernetes-discovery from the garage_rpc crate.
-     The experimental feature k2v is also enabled here in all builds.
     */
     (pkgs.rustBuilder.rustLib.makeOverride {
       name = "garage";
@@ -132,7 +131,7 @@ let
       name = "garage_rpc";
       overrideAttrs = drv: { /* [1] */ setBuildEnv = (buildEnv drv); };
       overrideArgs = old: {
-        /* [4] */ features = if release then [ "kubernetes-discovery" "k2v" ] else [ "k2v" ];
+        /* [4] */ features = if release then [ "kubernetes-discovery" ] else [];
       };
     })
 

src/block/lib.rs

@@ -3,7 +3,6 @@ extern crate tracing;
 
 pub mod manager;
 pub mod repair;
-pub mod resync;
 
 mod block;
 mod metrics;

src/block/manager.rs

@@ -1,19 +1,32 @@
+use std::convert::TryInto;
 use std::path::PathBuf;
 use std::sync::Arc;
 use std::time::Duration;
 
+use arc_swap::ArcSwapOption;
 use async_trait::async_trait;
 use serde::{Deserialize, Serialize};
 
+use futures::future::*;
 use tokio::fs;
 use tokio::io::{AsyncReadExt, AsyncWriteExt};
-use tokio::sync::{mpsc, Mutex};
+use tokio::select;
+use tokio::sync::{mpsc, watch, Mutex, Notify};
+
+use opentelemetry::{
+	trace::{FutureExt as OtelFutureExt, TraceContextExt, Tracer},
+	Context, KeyValue,
+};
 
 use garage_db as db;
+use garage_db::counted_tree_hack::CountedTree;
 
+use garage_util::background::*;
 use garage_util::data::*;
 use garage_util::error::*;
 use garage_util::metrics::RecordDuration;
+use garage_util::time::*;
+use garage_util::tranquilizer::Tranquilizer;
 
 use garage_rpc::system::System;
 use garage_rpc::*;
@@ -24,13 +37,23 @@ use crate::block::*;
 use crate::metrics::*;
 use crate::rc::*;
 use crate::repair::*;
-use crate::resync::*;
 
 /// Size under which data will be stored inlined in database instead of as files
 pub const INLINE_THRESHOLD: usize = 3072;
 
 // Timeout for RPCs that read and write blocks to remote nodes
-pub(crate) const BLOCK_RW_TIMEOUT: Duration = Duration::from_secs(30);
+const BLOCK_RW_TIMEOUT: Duration = Duration::from_secs(30);
+// Timeout for RPCs that ask other nodes whether they need a copy
+// of a given block before we delete it locally
+const NEED_BLOCK_QUERY_TIMEOUT: Duration = Duration::from_secs(5);
+
+// The delay between the time where a resync operation fails
+// and the time when it is retried, with exponential backoff
+// (multiplied by 2, 4, 8, 16, etc. for every consecutive failure).
+const RESYNC_RETRY_DELAY: Duration = Duration::from_secs(60);
+// The minimum retry delay is 60 seconds = 1 minute
+// 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;
 
 // The delay between the moment when the reference counter
 // drops to zero, and the moment where we allow ourselves
@@ -67,18 +90,22 @@ pub struct BlockManager {
 	pub data_dir: PathBuf,
 
 	compression_level: Option<i32>,
+	background_tranquility: u32,
 
 	mutation_lock: Mutex<BlockManagerLocked>,
 
 	pub(crate) rc: BlockRc,
-	pub resync: BlockResyncManager,
+
+	resync_queue: CountedTree,
+	resync_notify: Notify,
+	resync_errors: CountedTree,
 
 	pub(crate) system: Arc<System>,
-	pub(crate) endpoint: Arc<Endpoint<BlockRpc, Self>>,
+	endpoint: Arc<Endpoint<BlockRpc, Self>>,
 
-	pub(crate) metrics: BlockManagerMetrics,
+	metrics: BlockManagerMetrics,
 
-	tx_scrub_command: mpsc::Sender<ScrubWorkerCommand>,
+	tx_scrub_command: ArcSwapOption<mpsc::Sender<ScrubWorkerCommand>>,
 }
 
 // This custom struct contains functions that must only be ran
@@ -86,11 +113,18 @@ pub struct BlockManager {
 // it INSIDE a Mutex.
 struct BlockManagerLocked();
 
+enum ResyncIterResult {
+	BusyDidSomething,
+	BusyDidNothing,
+	IdleFor(Duration),
+}
+
 impl BlockManager {
 	pub fn new(
 		db: &db::Db,
 		data_dir: PathBuf,
 		compression_level: Option<i32>,
+		background_tranquility: u32,
 		replication: TableShardedReplication,
 		system: Arc<System>,
 	) -> Arc<Self> {
@@ -99,7 +133,17 @@ impl BlockManager {
 			.expect("Unable to open block_local_rc tree");
 		let rc = BlockRc::new(rc);
 
-		let resync = BlockResyncManager::new(db, &system);
+		let resync_queue = db
+			.open_tree("block_local_resync_queue")
+			.expect("Unable to open block_local_resync_queue tree");
+		let resync_queue =
+			CountedTree::new(resync_queue).expect("Could not count block_local_resync_queue");
+
+		let resync_errors = db
+			.open_tree("block_local_resync_errors")
+			.expect("Unable to open block_local_resync_errors tree");
+		let resync_errors =
+			CountedTree::new(resync_errors).expect("Could not count block_local_resync_errors");
 
 		let endpoint = system
 			.netapp
@@ -107,39 +151,32 @@ impl BlockManager {
 
 		let manager_locked = BlockManagerLocked();
 
-		let metrics = BlockManagerMetrics::new(resync.queue.clone(), resync.errors.clone());
-
-		let (scrub_tx, scrub_rx) = mpsc::channel(1);
+		let metrics = BlockManagerMetrics::new(resync_queue.clone(), resync_errors.clone());
 
 		let block_manager = Arc::new(Self {
 			replication,
 			data_dir,
 			compression_level,
+			background_tranquility,
 			mutation_lock: Mutex::new(manager_locked),
 			rc,
-			resync,
+			resync_queue,
+			resync_notify: Notify::new(),
+			resync_errors,
 			system,
 			endpoint,
 			metrics,
-			tx_scrub_command: scrub_tx,
+			tx_scrub_command: ArcSwapOption::new(None),
 		});
 		block_manager.endpoint.set_handler(block_manager.clone());
 
-		// Spawn a bunch of resync workers
-		for index in 0..MAX_RESYNC_WORKERS {
-			let worker = ResyncWorker::new(index, block_manager.clone());
-			block_manager.system.background.spawn_worker(worker);
-		}
-
-		// Spawn scrub worker
-		let scrub_worker = ScrubWorker::new(block_manager.clone(), scrub_rx);
-		block_manager.system.background.spawn_worker(scrub_worker);
+		block_manager.clone().spawn_background_workers();
 
 		block_manager
 	}
 
 	/// Ask nodes that might have a (possibly compressed) block for it
-	pub(crate) async fn rpc_get_raw_block(&self, hash: &Hash) -> Result<DataBlock, Error> {
+	async fn rpc_get_raw_block(&self, hash: &Hash) -> Result<DataBlock, Error> {
 		let who = self.replication.read_nodes(hash);
 		let resps = self
 			.system
@@ -191,6 +228,20 @@ impl BlockManager {
 		Ok(())
 	}
 
+	/// Get lenght of resync queue
+	pub fn resync_queue_len(&self) -> Result<usize, Error> {
+		// This currently can't return an error because the CountedTree hack
+		// doesn't error on .len(), but this will change when we remove the hack
+		// (hopefully someday!)
+		Ok(self.resync_queue.len())
+	}
+
+	/// Get number of blocks that have an error
+	pub fn resync_errors_len(&self) -> Result<usize, Error> {
+		// (see resync_queue_len comment)
+		Ok(self.resync_errors.len())
+	}
+
 	/// Get number of items in the refcount table
 	pub fn rc_len(&self) -> Result<usize, Error> {
 		Ok(self.rc.rc.len()?)
@@ -198,7 +249,13 @@ impl BlockManager {
 
 	/// Send command to start/stop/manager scrub worker
 	pub async fn send_scrub_command(&self, cmd: ScrubWorkerCommand) {
-		let _ = self.tx_scrub_command.send(cmd).await;
+		let _ = self
+			.tx_scrub_command
+			.load()
+			.as_ref()
+			.unwrap()
+			.send(cmd)
+			.await;
 	}
 
 	//// ----- Managing the reference counter ----
@@ -219,7 +276,7 @@ impl BlockManager {
 			// we will fecth it from someone.
 			let this = self.clone();
 			tokio::spawn(async move {
-				if let Err(e) = this.resync.put_to_resync(&hash, 2 * BLOCK_RW_TIMEOUT) {
+				if let Err(e) = this.put_to_resync(&hash, 2 * BLOCK_RW_TIMEOUT) {
 					error!("Block {:?} could not be put in resync queue: {}.", hash, e);
 				}
 			});
@@ -241,9 +298,7 @@ impl BlockManager {
 			// after that delay has passed.
 			let this = self.clone();
 			tokio::spawn(async move {
-				if let Err(e) = this
-					.resync
-					.put_to_resync(&hash, BLOCK_GC_DELAY + Duration::from_secs(10))
+				if let Err(e) = this.put_to_resync(&hash, BLOCK_GC_DELAY + Duration::from_secs(10))
 				{
 					error!("Block {:?} could not be put in resync queue: {}.", hash, e);
 				}
@@ -255,11 +310,7 @@ impl BlockManager {
 	// ---- Reading and writing blocks locally ----
 
 	/// Write a block to disk
-	pub(crate) async fn write_block(
-		&self,
-		hash: &Hash,
-		data: &DataBlock,
-	) -> Result<BlockRpc, Error> {
+	async fn write_block(&self, hash: &Hash, data: &DataBlock) -> Result<BlockRpc, Error> {
 		let write_size = data.inner_buffer().len() as u64;
 
 		let res = self
@@ -295,7 +346,7 @@ impl BlockManager {
 			Ok(c) => c,
 			Err(e) => {
 				// Not found but maybe we should have had it ??
-				self.resync.put_to_resync(hash, 2 * BLOCK_RW_TIMEOUT)?;
+				self.put_to_resync(hash, 2 * BLOCK_RW_TIMEOUT)?;
 				return Err(Into::into(e));
 			}
 		};
@@ -322,37 +373,24 @@ impl BlockManager {
 				.await
 				.move_block_to_corrupted(hash, self)
 				.await?;
-			self.resync.put_to_resync(hash, Duration::from_millis(0))?;
+			self.put_to_resync(hash, Duration::from_millis(0))?;
 			return Err(Error::CorruptData(*hash));
 		}
 
 		Ok(data)
 	}
 
-	/// Check if this node has a block and whether it needs it
-	pub(crate) async fn check_block_status(&self, hash: &Hash) -> Result<BlockStatus, Error> {
-		self.mutation_lock
+	/// Check if this node should have a block, but don't actually have it
+	async fn need_block(&self, hash: &Hash) -> Result<bool, Error> {
+		let BlockStatus { exists, needed } = self
+			.mutation_lock
 			.lock()
 			.await
 			.check_block_status(hash, self)
-			.await
-	}
-
-	/// Check if this node should have a block, but don't actually have it
-	async fn need_block(&self, hash: &Hash) -> Result<bool, Error> {
-		let BlockStatus { exists, needed } = self.check_block_status(hash).await?;
+			.await?;
 		Ok(needed.is_nonzero() && !exists)
 	}
 
-	/// Delete block if it is not needed anymore
-	pub(crate) async fn delete_if_unneeded(&self, hash: &Hash) -> Result<(), Error> {
-		self.mutation_lock
-			.lock()
-			.await
-			.delete_if_unneeded(hash, self)
-			.await
-	}
-
 	/// Utility: gives the path of the directory in which a block should be found
 	fn block_dir(&self, hash: &Hash) -> PathBuf {
 		let mut path = self.data_dir.clone();
@@ -379,6 +417,305 @@ impl BlockManager {
 		path.set_extension("");
 		fs::metadata(&path).await.map(|_| false).map_err(Into::into)
 	}
+
+	// ---- Resync loop ----
+
+	// This part manages a queue of blocks that need to be
+	// "resynchronized", i.e. that need to have a check that
+	// they are at present if we need them, or that they are
+	// deleted once the garbage collection delay has passed.
+	//
+	// Here are some explanations on how the resync queue works.
+	// There are two Sled trees that are used to have information
+	// about the status of blocks that need to be resynchronized:
+	//
+	// - resync_queue: a tree that is ordered first by a timestamp
+	//   (in milliseconds since Unix epoch) that is the time at which
+	//   the resync must be done, and second by block hash.
+	//   The key in this tree is just:
+	//       concat(timestamp (8 bytes), hash (32 bytes))
+	//   The value is the same 32-byte hash.
+	//
+	// - resync_errors: a tree that indicates for each block
+	//   if the last resync resulted in an error, and if so,
+	//   the following two informations (see the ErrorCounter struct):
+	//   - how many consecutive resync errors for this block?
+	//   - when was the last try?
+	//   These two informations are used to implement an
+	//   exponential backoff retry strategy.
+	//   The key in this tree is the 32-byte hash of the block,
+	//   and the value is the encoded ErrorCounter value.
+	//
+	// We need to have these two trees, because the resync queue
+	// is not just a queue of items to process, but a set of items
+	// that are waiting a specific delay until we can process them
+	// (the delay being necessary both internally for the exponential
+	// backoff strategy, and exposed as a parameter when adding items
+	// to the queue, e.g. to wait until the GC delay has passed).
+	// This is why we need one tree ordered by time, and one
+	// ordered by identifier of item to be processed (block hash).
+	//
+	// When the worker wants to process an item it takes from
+	// resync_queue, it checks in resync_errors that if there is an
+	// exponential back-off delay to await, it has passed before we
+	// process the item. If not, the item in the queue is skipped
+	// (but added back for later processing after the time of the
+	// delay).
+	//
+	// An alternative that would have seemed natural is to
+	// only add items to resync_queue with a processing time that is
+	// after the delay, but there are several issues with this:
+	// - This requires to synchronize updates to resync_queue and
+	//   resync_errors (with the current model, there is only one thread,
+	//   the worker thread, that accesses resync_errors,
+	//   so no need to synchronize) by putting them both in a lock.
+	//   This would mean that block_incref might need to take a lock
+	//   before doing its thing, meaning it has much more chances of
+	//   not completing successfully if something bad happens to Garage.
+	//   Currently Garage is not able to recover from block_incref that
+	//   doesn't complete successfully, because it is necessary to ensure
+	//   the consistency between the state of the block manager and
+	//   information in the BlockRef table.
+	// - If a resync fails, we put that block in the resync_errors table,
+	//   and also add it back to resync_queue to be processed after
+	//   the exponential back-off delay,
+	//   but maybe the block is already scheduled to be resynced again
+	//   at another time that is before the exponential back-off delay,
+	//   and we have no way to check that easily. This means that
+	//   in all cases, we need to check the resync_errors table
+	//   in the resync loop at the time when a block is popped from
+	//   the resync_queue.
+	// Overall, the current design is therefore simpler and more robust
+	// because it tolerates inconsistencies between the resync_queue
+	// and resync_errors table (items being scheduled in resync_queue
+	// for times that are earlier than the exponential back-off delay
+	// is a natural condition that is handled properly).
+
+	fn spawn_background_workers(self: Arc<Self>) {
+		// Launch a background workers for background resync loop processing
+		let background = self.system.background.clone();
+		let worker = ResyncWorker::new(self.clone());
+		tokio::spawn(async move {
+			tokio::time::sleep(Duration::from_secs(10)).await;
+			background.spawn_worker(worker);
+		});
+
+		// Launch a background worker for data store scrubs
+		let (scrub_tx, scrub_rx) = mpsc::channel(1);
+		self.tx_scrub_command.store(Some(Arc::new(scrub_tx)));
+		let scrub_worker = ScrubWorker::new(self.clone(), scrub_rx);
+		self.system.background.spawn_worker(scrub_worker);
+	}
+
+	pub(crate) fn put_to_resync(&self, hash: &Hash, delay: Duration) -> db::Result<()> {
+		let when = now_msec() + delay.as_millis() as u64;
+		self.put_to_resync_at(hash, when)
+	}
+
+	fn put_to_resync_at(&self, hash: &Hash, when: u64) -> db::Result<()> {
+		trace!("Put resync_queue: {} {:?}", when, hash);
+		let mut key = u64::to_be_bytes(when).to_vec();
+		key.extend(hash.as_ref());
+		self.resync_queue.insert(key, hash.as_ref())?;
+		self.resync_notify.notify_waiters();
+		Ok(())
+	}
+
+	async fn resync_iter(&self) -> Result<ResyncIterResult, db::Error> {
+		if let Some((time_bytes, hash_bytes)) = self.resync_queue.first()? {
+			let time_msec = u64::from_be_bytes(time_bytes[0..8].try_into().unwrap());
+			let now = now_msec();
+
+			if now >= time_msec {
+				let hash = Hash::try_from(&hash_bytes[..]).unwrap();
+
+				if let Some(ec) = self.resync_errors.get(hash.as_slice())? {
+					let ec = ErrorCounter::decode(&ec);
+					if now < ec.next_try() {
+						// if next retry after an error is not yet,
+						// don't do resync and return early, but still
+						// make sure the item is still in queue at expected time
+						self.put_to_resync_at(&hash, ec.next_try())?;
+						// ec.next_try() > now >= time_msec, so this remove
+						// is not removing the one we added just above
+						// (we want to do the remove after the insert to ensure
+						// that the item is not lost if we crash in-between)
+						self.resync_queue.remove(time_bytes)?;
+						return Ok(ResyncIterResult::BusyDidNothing);
+					}
+				}
+
+				let tracer = opentelemetry::global::tracer("garage");
+				let trace_id = gen_uuid();
+				let span = tracer
+					.span_builder("Resync block")
+					.with_trace_id(
+						opentelemetry::trace::TraceId::from_hex(&hex::encode(
+							&trace_id.as_slice()[..16],
+						))
+						.unwrap(),
+					)
+					.with_attributes(vec![KeyValue::new("block", format!("{:?}", hash))])
+					.start(&tracer);
+
+				let res = self
+					.resync_block(&hash)
+					.with_context(Context::current_with_span(span))
+					.bound_record_duration(&self.metrics.resync_duration)
+					.await;
+
+				self.metrics.resync_counter.add(1);
+
+				if let Err(e) = &res {
+					self.metrics.resync_error_counter.add(1);
+					warn!("Error when resyncing {:?}: {}", hash, e);
+
+					let err_counter = match self.resync_errors.get(hash.as_slice())? {
+						Some(ec) => ErrorCounter::decode(&ec).add1(now + 1),
+						None => ErrorCounter::new(now + 1),
+					};
+
+					self.resync_errors
+						.insert(hash.as_slice(), err_counter.encode())?;
+
+					self.put_to_resync_at(&hash, err_counter.next_try())?;
+					// err_counter.next_try() >= now + 1 > now,
+					// the entry we remove from the queue is not
+					// the entry we inserted with put_to_resync_at
+					self.resync_queue.remove(time_bytes)?;
+				} else {
+					self.resync_errors.remove(hash.as_slice())?;
+					self.resync_queue.remove(time_bytes)?;
+				}
+
+				Ok(ResyncIterResult::BusyDidSomething)
+			} else {
+				Ok(ResyncIterResult::IdleFor(Duration::from_millis(
+					time_msec - now,
+				)))
+			}
+		} else {
+			// Here we wait either for a notification that an item has been
+			// added to the queue, or for a constant delay of 10 secs to expire.
+			// The delay avoids a race condition where the notification happens
+			// between the time we checked the queue and the first poll
+			// to resync_notify.notified(): if that happens, we'll just loop
+			// back 10 seconds later, which is fine.
+			Ok(ResyncIterResult::IdleFor(Duration::from_secs(10)))
+		}
+	}
+
+	async fn resync_block(&self, hash: &Hash) -> Result<(), Error> {
+		let BlockStatus { exists, needed } = self
+			.mutation_lock
+			.lock()
+			.await
+			.check_block_status(hash, self)
+			.await?;
+
+		if exists != needed.is_needed() || exists != needed.is_nonzero() {
+			debug!(
+				"Resync block {:?}: exists {}, nonzero rc {}, deletable {}",
+				hash,
+				exists,
+				needed.is_nonzero(),
+				needed.is_deletable(),
+			);
+		}
+
+		if exists && needed.is_deletable() {
+			info!("Resync block {:?}: offloading and deleting", hash);
+
+			let mut who = self.replication.write_nodes(hash);
+			if who.len() < self.replication.write_quorum() {
+				return Err(Error::Message("Not trying to offload block because we don't have a quorum of nodes to write to".to_string()));
+			}
+			who.retain(|id| *id != self.system.id);
+
+			let msg = Arc::new(BlockRpc::NeedBlockQuery(*hash));
+			let who_needs_fut = who.iter().map(|to| {
+				self.system.rpc.call_arc(
+					&self.endpoint,
+					*to,
+					msg.clone(),
+					RequestStrategy::with_priority(PRIO_BACKGROUND)
+						.with_timeout(NEED_BLOCK_QUERY_TIMEOUT),
+				)
+			});
+			let who_needs_resps = join_all(who_needs_fut).await;
+
+			let mut need_nodes = vec![];
+			for (node, needed) in who.iter().zip(who_needs_resps.into_iter()) {
+				match needed.err_context("NeedBlockQuery RPC")? {
+					BlockRpc::NeedBlockReply(needed) => {
+						if needed {
+							need_nodes.push(*node);
+						}
+					}
+					m => {
+						return Err(Error::unexpected_rpc_message(m));
+					}
+				}
+			}
+
+			if !need_nodes.is_empty() {
+				trace!(
+					"Block {:?} needed by {} nodes, sending",
+					hash,
+					need_nodes.len()
+				);
+
+				for node in need_nodes.iter() {
+					self.metrics
+						.resync_send_counter
+						.add(1, &[KeyValue::new("to", format!("{:?}", node))]);
+				}
+
+				let put_block_message = self.read_block(hash).await?;
+				self.system
+					.rpc
+					.try_call_many(
+						&self.endpoint,
+						&need_nodes[..],
+						put_block_message,
+						RequestStrategy::with_priority(PRIO_BACKGROUND)
+							.with_quorum(need_nodes.len())
+							.with_timeout(BLOCK_RW_TIMEOUT),
+					)
+					.await
+					.err_context("PutBlock RPC")?;
+			}
+			info!(
+				"Deleting unneeded block {:?}, offload finished ({} / {})",
+				hash,
+				need_nodes.len(),
+				who.len()
+			);
+
+			self.mutation_lock
+				.lock()
+				.await
+				.delete_if_unneeded(hash, self)
+				.await?;
+
+			self.rc.clear_deleted_block_rc(hash)?;
+		}
+
+		if needed.is_nonzero() && !exists {
+			info!(
+				"Resync block {:?}: fetching absent but needed block (refcount > 0)",
+				hash
+			);
+
+			let block_data = self.rpc_get_raw_block(hash).await?;
+
+			self.metrics.resync_recv_counter.add(1);
+
+			self.write_block(hash, &block_data).await?;
+		}
+
+		Ok(())
+	}
 }
 
 #[async_trait]
@@ -397,9 +734,80 @@ impl EndpointHandler<BlockRpc> for BlockManager {
 	}
 }
 
-pub(crate) struct BlockStatus {
-	pub(crate) exists: bool,
-	pub(crate) needed: RcEntry,
+struct ResyncWorker {
+	manager: Arc<BlockManager>,
+	tranquilizer: Tranquilizer,
+	next_delay: Duration,
+}
+
+impl ResyncWorker {
+	fn new(manager: Arc<BlockManager>) -> Self {
+		Self {
+			manager,
+			tranquilizer: Tranquilizer::new(30),
+			next_delay: Duration::from_secs(10),
+		}
+	}
+}
+
+#[async_trait]
+impl Worker for ResyncWorker {
+	fn name(&self) -> String {
+		"Block resync worker".into()
+	}
+
+	fn info(&self) -> Option<String> {
+		let mut ret = vec![];
+		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));
+		}
+		if elen > 0 {
+			ret.push(format!("{} blocks in error state", elen));
+		}
+		if !ret.is_empty() {
+			Some(ret.join(", "))
+		} else {
+			None
+		}
+	}
+
+	async fn work(&mut self, _must_exit: &mut watch::Receiver<bool>) -> Result<WorkerState, Error> {
+		self.tranquilizer.reset();
+		match self.manager.resync_iter().await {
+			Ok(ResyncIterResult::BusyDidSomething) => Ok(self
+				.tranquilizer
+				.tranquilize_worker(self.manager.background_tranquility)),
+			Ok(ResyncIterResult::BusyDidNothing) => Ok(WorkerState::Busy),
+			Ok(ResyncIterResult::IdleFor(delay)) => {
+				self.next_delay = delay;
+				Ok(WorkerState::Idle)
+			}
+			Err(e) => {
+				// The errors that we have here are only Sled errors
+				// We don't really know how to handle them so just ¯\_(ツ)_/¯
+				// (there is kind of an assumption that Sled won't error on us,
+				// if it does there is not much we can do -- TODO should we just panic?)
+				// Here we just give the error to the worker manager,
+				// it will print it to the logs and increment a counter
+				Err(e.into())
+			}
+		}
+	}
+
+	async fn wait_for_work(&mut self, _must_exit: &watch::Receiver<bool>) -> WorkerState {
+		select! {
+			_ = tokio::time::sleep(self.next_delay) => (),
+			_ = self.manager.resync_notify.notified() => (),
+		};
+		WorkerState::Busy
+	}
+}
+
+struct BlockStatus {
+	exists: bool,
+	needed: RcEntry,
 }
 
 impl BlockManagerLocked {
@@ -504,3 +912,50 @@ impl BlockManagerLocked {
 		Ok(())
 	}
 }
+
+/// Counts the number of errors when resyncing a block,
+/// and the time of the last try.
+/// Used to implement exponential backoff.
+#[derive(Clone, Copy, Debug)]
+struct ErrorCounter {
+	errors: u64,
+	last_try: u64,
+}
+
+impl ErrorCounter {
+	fn new(now: u64) -> Self {
+		Self {
+			errors: 1,
+			last_try: now,
+		}
+	}
+
+	fn decode(data: &[u8]) -> Self {
+		Self {
+			errors: u64::from_be_bytes(data[0..8].try_into().unwrap()),
+			last_try: u64::from_be_bytes(data[8..16].try_into().unwrap()),
+		}
+	}
+	fn encode(&self) -> Vec<u8> {
+		[
+			u64::to_be_bytes(self.errors),
+			u64::to_be_bytes(self.last_try),
+		]
+		.concat()
+	}
+
+	fn add1(self, now: u64) -> Self {
+		Self {
+			errors: self.errors + 1,
+			last_try: now,
+		}
+	}
+
+	fn delay_msec(&self) -> u64 {
+		(RESYNC_RETRY_DELAY.as_millis() as u64)
+			<< std::cmp::min(self.errors - 1, RESYNC_RETRY_DELAY_MAX_BACKOFF_POWER)
+	}
+	fn next_try(&self) -> u64 {
+		self.last_try + self.delay_msec()
+	}
+}

src/block/repair.rs

@@ -19,17 +19,7 @@ use garage_util::tranquilizer::Tranquilizer;
 
 use crate::manager::*;
 
-// Full scrub every 30 days
-const SCRUB_INTERVAL: Duration = Duration::from_secs(3600 * 24 * 30);
-// Scrub tranquility is initially set to 4, but can be changed in the CLI
-// and the updated version is persisted over Garage restarts
-const INITIAL_SCRUB_TRANQUILITY: u32 = 4;
-
-// ---- ---- ----
-// FIRST KIND OF REPAIR: FINDING MISSING BLOCKS/USELESS BLOCKS
-// This is a one-shot repair operation that can be launched,
-// checks everything, and then exits.
-// ---- ---- ----
+const SCRUB_INTERVAL: Duration = Duration::from_secs(3600 * 24 * 30); // full scrub every 30 days
 
 pub struct RepairWorker {
 	manager: Arc<BlockManager>,
@@ -112,9 +102,7 @@ impl Worker for RepairWorker {
 				}
 
 				for hash in batch_of_hashes.into_iter() {
-					self.manager
-						.resync
-						.put_to_resync(&hash, Duration::from_secs(0))?;
+					self.manager.put_to_resync(&hash, Duration::from_secs(0))?;
 					self.next_start = Some(hash)
 				}
 
@@ -126,9 +114,7 @@ impl Worker for RepairWorker {
 				// This allows us to find blocks we are storing but don't actually need,
 				// so that we can offload them if necessary and then delete them locally.
 				if let Some(hash) = bi.next().await? {
-					self.manager
-						.resync
-						.put_to_resync(&hash, Duration::from_secs(0))?;
+					self.manager.put_to_resync(&hash, Duration::from_secs(0))?;
 					Ok(WorkerState::Busy)
 				} else {
 					Ok(WorkerState::Done)
@@ -142,13 +128,7 @@ impl Worker for RepairWorker {
 	}
 }
 
-// ---- ---- ----
-// SECOND KIND OF REPAIR: SCRUBBING THE DATASTORE
-// This is significantly more complex than the process above,
-// as it is a continuously-running task that triggers automatically
-// every SCRUB_INTERVAL, but can also be triggered manually
-// and whose parameter (esp. speed) can be controlled at runtime.
-// ---- ---- ----
+// ----
 
 pub struct ScrubWorker {
 	manager: Arc<BlockManager>,
@@ -196,7 +176,7 @@ impl ScrubWorker {
 			Ok(v) => v,
 			Err(_) => ScrubWorkerPersisted {
 				time_last_complete_scrub: 0,
-				tranquility: INITIAL_SCRUB_TRANQUILITY,
+				tranquility: 4,
 				corruptions_detected: 0,
 			},
 		};
@@ -363,9 +343,7 @@ impl Worker for ScrubWorker {
 	}
 }
 
-// ---- ---- ----
-// UTILITY FOR ENUMERATING THE BLOCK STORE
-// ---- ---- ----
+// ----
 
 struct BlockStoreIterator {
 	path: Vec<ReadingDir>,

src/block/resync.rs

@@ -1,590 +0,0 @@
-use std::collections::HashSet;
-use std::convert::TryInto;
-use std::sync::{Arc, Mutex};
-use std::time::Duration;
-
-use arc_swap::ArcSwap;
-use async_trait::async_trait;
-use serde::{Deserialize, Serialize};
-
-use futures::future::*;
-use tokio::select;
-use tokio::sync::{watch, Notify};
-
-use opentelemetry::{
-	trace::{FutureExt as OtelFutureExt, TraceContextExt, Tracer},
-	Context, KeyValue,
-};
-
-use garage_db as db;
-use garage_db::counted_tree_hack::CountedTree;
-
-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;
-
-use garage_rpc::system::System;
-use garage_rpc::*;
-
-use garage_table::replication::TableReplication;
-
-use crate::manager::*;
-
-// Timeout for RPCs that ask other nodes whether they need a copy
-// of a given block before we delete it locally
-pub(crate) const NEED_BLOCK_QUERY_TIMEOUT: Duration = Duration::from_secs(5);
-
-// The delay between the time where a resync operation fails
-// and the time when it is retried, with exponential backoff
-// (multiplied by 2, 4, 8, 16, etc. for every consecutive failure).
-pub(crate) const RESYNC_RETRY_DELAY: Duration = Duration::from_secs(60);
-// The minimum retry delay is 60 seconds = 1 minute
-// The maximum retry delay is 60 seconds * 2^6 = 60 seconds << 6 = 64 minutes (~1 hour)
-pub(crate) const RESYNC_RETRY_DELAY_MAX_BACKOFF_POWER: u64 = 6;
-
-// No more than 4 resync workers can be running in the system
-pub(crate) const MAX_RESYNC_WORKERS: usize = 4;
-// 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;
-
-pub struct BlockResyncManager {
-	pub(crate) queue: CountedTree,
-	pub(crate) notify: Notify,
-	pub(crate) errors: CountedTree,
-
-	busy_set: BusySet,
-
-	persister: Persister<ResyncPersistedConfig>,
-	persisted: ArcSwap<ResyncPersistedConfig>,
-}
-
-#[derive(Serialize, Deserialize, Clone, Copy)]
-struct ResyncPersistedConfig {
-	n_workers: usize,
-	tranquility: u32,
-}
-
-enum ResyncIterResult {
-	BusyDidSomething,
-	BusyDidNothing,
-	IdleFor(Duration),
-}
-
-type BusySet = Arc<Mutex<HashSet<Vec<u8>>>>;
-
-struct BusyBlock {
-	time_bytes: Vec<u8>,
-	hash_bytes: Vec<u8>,
-	busy_set: BusySet,
-}
-
-impl BlockResyncManager {
-	pub(crate) fn new(db: &db::Db, system: &System) -> Self {
-		let queue = db
-			.open_tree("block_local_resync_queue")
-			.expect("Unable to open block_local_resync_queue tree");
-		let queue = CountedTree::new(queue).expect("Could not count block_local_resync_queue");
-
-		let errors = db
-			.open_tree("block_local_resync_errors")
-			.expect("Unable to open block_local_resync_errors tree");
-		let errors = CountedTree::new(errors).expect("Could not count block_local_resync_errors");
-
-		let persister = Persister::new(&system.metadata_dir, "resync_cfg");
-		let persisted = match persister.load() {
-			Ok(v) => v,
-			Err(_) => ResyncPersistedConfig {
-				n_workers: 1,
-				tranquility: INITIAL_RESYNC_TRANQUILITY,
-			},
-		};
-
-		Self {
-			queue,
-			notify: Notify::new(),
-			errors,
-			busy_set: Arc::new(Mutex::new(HashSet::new())),
-			persister,
-			persisted: ArcSwap::new(Arc::new(persisted)),
-		}
-	}
-
-	/// Get lenght of resync queue
-	pub fn queue_len(&self) -> Result<usize, Error> {
-		// This currently can't return an error because the CountedTree hack
-		// doesn't error on .len(), but this will change when we remove the hack
-		// (hopefully someday!)
-		Ok(self.queue.len())
-	}
-
-	/// Get number of blocks that have an error
-	pub fn errors_len(&self) -> Result<usize, Error> {
-		// (see queue_len comment)
-		Ok(self.errors.len())
-	}
-
-	// ---- Resync loop ----
-
-	// This part manages a queue of blocks that need to be
-	// "resynchronized", i.e. that need to have a check that
-	// they are at present if we need them, or that they are
-	// deleted once the garbage collection delay has passed.
-	//
-	// Here are some explanations on how the resync queue works.
-	// There are two Sled trees that are used to have information
-	// about the status of blocks that need to be resynchronized:
-	//
-	// - resync.queue: a tree that is ordered first by a timestamp
-	//   (in milliseconds since Unix epoch) that is the time at which
-	//   the resync must be done, and second by block hash.
-	//   The key in this tree is just:
-	//       concat(timestamp (8 bytes), hash (32 bytes))
-	//   The value is the same 32-byte hash.
-	//
-	// - resync.errors: a tree that indicates for each block
-	//   if the last resync resulted in an error, and if so,
-	//   the following two informations (see the ErrorCounter struct):
-	//   - how many consecutive resync errors for this block?
-	//   - when was the last try?
-	//   These two informations are used to implement an
-	//   exponential backoff retry strategy.
-	//   The key in this tree is the 32-byte hash of the block,
-	//   and the value is the encoded ErrorCounter value.
-	//
-	// We need to have these two trees, because the resync queue
-	// is not just a queue of items to process, but a set of items
-	// that are waiting a specific delay until we can process them
-	// (the delay being necessary both internally for the exponential
-	// backoff strategy, and exposed as a parameter when adding items
-	// to the queue, e.g. to wait until the GC delay has passed).
-	// This is why we need one tree ordered by time, and one
-	// ordered by identifier of item to be processed (block hash).
-	//
-	// When the worker wants to process an item it takes from
-	// resync.queue, it checks in resync.errors that if there is an
-	// exponential back-off delay to await, it has passed before we
-	// process the item. If not, the item in the queue is skipped
-	// (but added back for later processing after the time of the
-	// delay).
-	//
-	// An alternative that would have seemed natural is to
-	// only add items to resync.queue with a processing time that is
-	// after the delay, but there are several issues with this:
-	// - This requires to synchronize updates to resync.queue and
-	//   resync.errors (with the current model, there is only one thread,
-	//   the worker thread, that accesses resync.errors,
-	//   so no need to synchronize) by putting them both in a lock.
-	//   This would mean that block_incref might need to take a lock
-	//   before doing its thing, meaning it has much more chances of
-	//   not completing successfully if something bad happens to Garage.
-	//   Currently Garage is not able to recover from block_incref that
-	//   doesn't complete successfully, because it is necessary to ensure
-	//   the consistency between the state of the block manager and
-	//   information in the BlockRef table.
-	// - If a resync fails, we put that block in the resync.errors table,
-	//   and also add it back to resync.queue to be processed after
-	//   the exponential back-off delay,
-	//   but maybe the block is already scheduled to be resynced again
-	//   at another time that is before the exponential back-off delay,
-	//   and we have no way to check that easily. This means that
-	//   in all cases, we need to check the resync.errors table
-	//   in the resync loop at the time when a block is popped from
-	//   the resync.queue.
-	// Overall, the current design is therefore simpler and more robust
-	// because it tolerates inconsistencies between the resync.queue
-	// and resync.errors table (items being scheduled in resync.queue
-	// for times that are earlier than the exponential back-off delay
-	// is a natural condition that is handled properly).
-
-	pub(crate) fn put_to_resync(&self, hash: &Hash, delay: Duration) -> db::Result<()> {
-		let when = now_msec() + delay.as_millis() as u64;
-		self.put_to_resync_at(hash, when)
-	}
-
-	pub(crate) fn put_to_resync_at(&self, hash: &Hash, when: u64) -> db::Result<()> {
-		trace!("Put resync_queue: {} {:?}", when, hash);
-		let mut key = u64::to_be_bytes(when).to_vec();
-		key.extend(hash.as_ref());
-		self.queue.insert(key, hash.as_ref())?;
-		self.notify.notify_waiters();
-		Ok(())
-	}
-
-	async fn resync_iter(&self, manager: &BlockManager) -> Result<ResyncIterResult, db::Error> {
-		if let Some(block) = self.get_block_to_resync()? {
-			let time_msec = u64::from_be_bytes(block.time_bytes[0..8].try_into().unwrap());
-			let now = now_msec();
-
-			if now >= time_msec {
-				let hash = Hash::try_from(&block.hash_bytes[..]).unwrap();
-
-				if let Some(ec) = self.errors.get(hash.as_slice())? {
-					let ec = ErrorCounter::decode(&ec);
-					if now < ec.next_try() {
-						// if next retry after an error is not yet,
-						// don't do resync and return early, but still
-						// make sure the item is still in queue at expected time
-						self.put_to_resync_at(&hash, ec.next_try())?;
-						// ec.next_try() > now >= time_msec, so this remove
-						// is not removing the one we added just above
-						// (we want to do the remove after the insert to ensure
-						// that the item is not lost if we crash in-between)
-						self.queue.remove(&block.time_bytes)?;
-						return Ok(ResyncIterResult::BusyDidNothing);
-					}
-				}
-
-				let tracer = opentelemetry::global::tracer("garage");
-				let trace_id = gen_uuid();
-				let span = tracer
-					.span_builder("Resync block")
-					.with_trace_id(
-						opentelemetry::trace::TraceId::from_hex(&hex::encode(
-							&trace_id.as_slice()[..16],
-						))
-						.unwrap(),
-					)
-					.with_attributes(vec![KeyValue::new("block", format!("{:?}", hash))])
-					.start(&tracer);
-
-				let res = self
-					.resync_block(manager, &hash)
-					.with_context(Context::current_with_span(span))
-					.bound_record_duration(&manager.metrics.resync_duration)
-					.await;
-
-				manager.metrics.resync_counter.add(1);
-
-				if let Err(e) = &res {
-					manager.metrics.resync_error_counter.add(1);
-					warn!("Error when resyncing {:?}: {}", hash, e);
-
-					let err_counter = match self.errors.get(hash.as_slice())? {
-						Some(ec) => ErrorCounter::decode(&ec).add1(now + 1),
-						None => ErrorCounter::new(now + 1),
-					};
-
-					self.errors.insert(hash.as_slice(), err_counter.encode())?;
-
-					self.put_to_resync_at(&hash, err_counter.next_try())?;
-					// err_counter.next_try() >= now + 1 > now,
-					// the entry we remove from the queue is not
-					// the entry we inserted with put_to_resync_at
-					self.queue.remove(&block.time_bytes)?;
-				} else {
-					self.errors.remove(hash.as_slice())?;
-					self.queue.remove(&block.time_bytes)?;
-				}
-
-				Ok(ResyncIterResult::BusyDidSomething)
-			} else {
-				Ok(ResyncIterResult::IdleFor(Duration::from_millis(
-					time_msec - now,
-				)))
-			}
-		} else {
-			// Here we wait either for a notification that an item has been
-			// added to the queue, or for a constant delay of 10 secs to expire.
-			// The delay avoids a race condition where the notification happens
-			// between the time we checked the queue and the first poll
-			// to resync_notify.notified(): if that happens, we'll just loop
-			// back 10 seconds later, which is fine.
-			Ok(ResyncIterResult::IdleFor(Duration::from_secs(10)))
-		}
-	}
-
-	fn get_block_to_resync(&self) -> Result<Option<BusyBlock>, db::Error> {
-		let mut busy = self.busy_set.lock().unwrap();
-		for it in self.queue.iter()? {
-			let (time_bytes, hash_bytes) = it?;
-			if !busy.contains(&time_bytes) {
-				busy.insert(time_bytes.clone());
-				return Ok(Some(BusyBlock {
-					time_bytes,
-					hash_bytes,
-					busy_set: self.busy_set.clone(),
-				}));
-			}
-		}
-		Ok(None)
-	}
-
-	async fn resync_block(&self, manager: &BlockManager, hash: &Hash) -> Result<(), Error> {
-		let BlockStatus { exists, needed } = manager.check_block_status(hash).await?;
-
-		if exists != needed.is_needed() || exists != needed.is_nonzero() {
-			debug!(
-				"Resync block {:?}: exists {}, nonzero rc {}, deletable {}",
-				hash,
-				exists,
-				needed.is_nonzero(),
-				needed.is_deletable(),
-			);
-		}
-
-		if exists && needed.is_deletable() {
-			info!("Resync block {:?}: offloading and deleting", hash);
-
-			let mut who = manager.replication.write_nodes(hash);
-			if who.len() < manager.replication.write_quorum() {
-				return Err(Error::Message("Not trying to offload block because we don't have a quorum of nodes to write to".to_string()));
-			}
-			who.retain(|id| *id != manager.system.id);
-
-			let msg = Arc::new(BlockRpc::NeedBlockQuery(*hash));
-			let who_needs_fut = who.iter().map(|to| {
-				manager.system.rpc.call_arc(
-					&manager.endpoint,
-					*to,
-					msg.clone(),
-					RequestStrategy::with_priority(PRIO_BACKGROUND)
-						.with_timeout(NEED_BLOCK_QUERY_TIMEOUT),
-				)
-			});
-			let who_needs_resps = join_all(who_needs_fut).await;
-
-			let mut need_nodes = vec![];
-			for (node, needed) in who.iter().zip(who_needs_resps.into_iter()) {
-				match needed.err_context("NeedBlockQuery RPC")? {
-					BlockRpc::NeedBlockReply(needed) => {
-						if needed {
-							need_nodes.push(*node);
-						}
-					}
-					m => {
-						return Err(Error::unexpected_rpc_message(m));
-					}
-				}
-			}
-
-			if !need_nodes.is_empty() {
-				trace!(
-					"Block {:?} needed by {} nodes, sending",
-					hash,
-					need_nodes.len()
-				);
-
-				for node in need_nodes.iter() {
-					manager
-						.metrics
-						.resync_send_counter
-						.add(1, &[KeyValue::new("to", format!("{:?}", node))]);
-				}
-
-				let put_block_message = manager.read_block(hash).await?;
-				manager
-					.system
-					.rpc
-					.try_call_many(
-						&manager.endpoint,
-						&need_nodes[..],
-						put_block_message,
-						RequestStrategy::with_priority(PRIO_BACKGROUND)
-							.with_quorum(need_nodes.len())
-							.with_timeout(BLOCK_RW_TIMEOUT),
-					)
-					.await
-					.err_context("PutBlock RPC")?;
-			}
-			info!(
-				"Deleting unneeded block {:?}, offload finished ({} / {})",
-				hash,
-				need_nodes.len(),
-				who.len()
-			);
-
-			manager.delete_if_unneeded(hash).await?;
-
-			manager.rc.clear_deleted_block_rc(hash)?;
-		}
-
-		if needed.is_nonzero() && !exists {
-			info!(
-				"Resync block {:?}: fetching absent but needed block (refcount > 0)",
-				hash
-			);
-
-			let block_data = manager.rpc_get_raw_block(hash).await?;
-
-			manager.metrics.resync_recv_counter.add(1);
-
-			manager.write_block(hash, &block_data).await?;
-		}
-
-		Ok(())
-	}
-
-	async fn update_persisted(
-		&self,
-		update: impl Fn(&mut ResyncPersistedConfig),
-	) -> Result<(), Error> {
-		let mut cfg: ResyncPersistedConfig = *self.persisted.load().as_ref();
-		update(&mut cfg);
-		self.persister.save_async(&cfg).await?;
-		self.persisted.store(Arc::new(cfg));
-		self.notify.notify_waiters();
-		Ok(())
-	}
-
-	pub async fn set_n_workers(&self, n_workers: usize) -> Result<(), Error> {
-		if !(1..=MAX_RESYNC_WORKERS).contains(&n_workers) {
-			return Err(Error::Message(format!(
-				"Invalid number of resync workers, must be between 1 and {}",
-				MAX_RESYNC_WORKERS
-			)));
-		}
-		self.update_persisted(|cfg| cfg.n_workers = n_workers).await
-	}
-
-	pub async fn set_tranquility(&self, tranquility: u32) -> Result<(), Error> {
-		self.update_persisted(|cfg| cfg.tranquility = tranquility)
-			.await
-	}
-}
-
-impl Drop for BusyBlock {
-	fn drop(&mut self) {
-		let mut busy = self.busy_set.lock().unwrap();
-		busy.remove(&self.time_bytes);
-	}
-}
-
-pub(crate) struct ResyncWorker {
-	index: usize,
-	manager: Arc<BlockManager>,
-	tranquilizer: Tranquilizer,
-	next_delay: Duration,
-}
-
-impl ResyncWorker {
-	pub(crate) fn new(index: usize, manager: Arc<BlockManager>) -> Self {
-		Self {
-			index,
-			manager,
-			tranquilizer: Tranquilizer::new(30),
-			next_delay: Duration::from_secs(10),
-		}
-	}
-}
-
-#[async_trait]
-impl Worker for ResyncWorker {
-	fn name(&self) -> String {
-		format!("Block resync worker #{}", self.index + 1)
-	}
-
-	fn info(&self) -> Option<String> {
-		let persisted = self.manager.resync.persisted.load();
-
-		if self.index >= persisted.n_workers {
-			return Some("(unused)".into());
-		}
-
-		let mut ret = vec![];
-		ret.push(format!("tranquility = {}", persisted.tranquility));
-
-		let qlen = self.manager.resync.queue_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));
-		}
-
-		Some(ret.join(", "))
-	}
-
-	async fn work(&mut self, _must_exit: &mut watch::Receiver<bool>) -> Result<WorkerState, Error> {
-		if self.index >= self.manager.resync.persisted.load().n_workers {
-			return Ok(WorkerState::Idle);
-		}
-
-		self.tranquilizer.reset();
-		match self.manager.resync.resync_iter(&self.manager).await {
-			Ok(ResyncIterResult::BusyDidSomething) => Ok(self
-				.tranquilizer
-				.tranquilize_worker(self.manager.resync.persisted.load().tranquility)),
-			Ok(ResyncIterResult::BusyDidNothing) => Ok(WorkerState::Busy),
-			Ok(ResyncIterResult::IdleFor(delay)) => {
-				self.next_delay = delay;
-				Ok(WorkerState::Idle)
-			}
-			Err(e) => {
-				// The errors that we have here are only Sled errors
-				// We don't really know how to handle them so just ¯\_(ツ)_/¯
-				// (there is kind of an assumption that Sled won't error on us,
-				// if it does there is not much we can do -- TODO should we just panic?)
-				// Here we just give the error to the worker manager,
-				// it will print it to the logs and increment a counter
-				Err(e.into())
-			}
-		}
-	}
-
-	async fn wait_for_work(&mut self, _must_exit: &watch::Receiver<bool>) -> WorkerState {
-		while self.index >= self.manager.resync.persisted.load().n_workers {
-			self.manager.resync.notify.notified().await
-		}
-
-		select! {
-			_ = tokio::time::sleep(self.next_delay) => (),
-			_ = self.manager.resync.notify.notified() => (),
-		};
-
-		WorkerState::Busy
-	}
-}
-
-/// Counts the number of errors when resyncing a block,
-/// and the time of the last try.
-/// Used to implement exponential backoff.
-#[derive(Clone, Copy, Debug)]
-struct ErrorCounter {
-	errors: u64,
-	last_try: u64,
-}
-
-impl ErrorCounter {
-	fn new(now: u64) -> Self {
-		Self {
-			errors: 1,
-			last_try: now,
-		}
-	}
-
-	fn decode(data: &[u8]) -> Self {
-		Self {
-			errors: u64::from_be_bytes(data[0..8].try_into().unwrap()),
-			last_try: u64::from_be_bytes(data[8..16].try_into().unwrap()),
-		}
-	}
-	fn encode(&self) -> Vec<u8> {
-		[
-			u64::to_be_bytes(self.errors),
-			u64::to_be_bytes(self.last_try),
-		]
-		.concat()
-	}
-
-	fn add1(self, now: u64) -> Self {
-		Self {
-			errors: self.errors + 1,
-			last_try: now,
-		}
-	}
-
-	fn delay_msec(&self) -> u64 {
-		(RESYNC_RETRY_DELAY.as_millis() as u64)
-			<< std::cmp::min(self.errors - 1, RESYNC_RETRY_DELAY_MAX_BACKOFF_POWER)
-	}
-	fn next_try(&self) -> u64 {
-		self.last_try + self.delay_msec()
-	}
-}

src/garage/admin.rs

@@ -15,8 +15,6 @@ use garage_table::*;
 
 use garage_rpc::*;
 
-use garage_block::repair::ScrubWorkerCommand;
-
 use garage_model::bucket_alias_table::*;
 use garage_model::bucket_table::*;
 use garage_model::garage::Garage;
@@ -781,13 +779,13 @@ impl AdminRpcHandler {
 		writeln!(
 			&mut ret,
 			"  resync queue length: {}",
-			self.garage.block_manager.resync.queue_len()?
+			self.garage.block_manager.resync_queue_len()?
 		)
 		.unwrap();
 		writeln!(
 			&mut ret,
 			"  blocks with resync errors: {}",
-			self.garage.block_manager.resync.errors_len()?
+			self.garage.block_manager.resync_errors_len()?
 		)
 		.unwrap();
 
@@ -838,32 +836,6 @@ impl AdminRpcHandler {
 				let workers = self.garage.background.get_worker_info();
 				Ok(AdminRpc::WorkerList(workers, opt))
 			}
-			WorkerCmd::Set { opt } => match opt {
-				WorkerSetCmd::ScrubTranquility { tranquility } => {
-					let scrub_command = ScrubWorkerCommand::SetTranquility(tranquility);
-					self.garage
-						.block_manager
-						.send_scrub_command(scrub_command)
-						.await;
-					Ok(AdminRpc::Ok("Scrub tranquility updated".into()))
-				}
-				WorkerSetCmd::ResyncNWorkers { n_workers } => {
-					self.garage
-						.block_manager
-						.resync
-						.set_n_workers(n_workers)
-						.await?;
-					Ok(AdminRpc::Ok("Number of resync workers updated".into()))
-				}
-				WorkerSetCmd::ResyncTranquility { tranquility } => {
-					self.garage
-						.block_manager
-						.resync
-						.set_tranquility(tranquility)
-						.await?;
-					Ok(AdminRpc::Ok("Resync tranquility updated".into()))
-				}
-			},
 		}
 	}
 }

src/garage/cli/structs.rs

@@ -501,12 +501,6 @@ pub enum WorkerCmd {
 		#[structopt(flatten)]
 		opt: WorkerListOpt,
 	},
-	/// Set worker parameter
-	#[structopt(name = "set", version = version::garage())]
-	Set {
-		#[structopt(subcommand)]
-		opt: WorkerSetCmd,
-	},
 }
 
 #[derive(Serialize, Deserialize, StructOpt, Debug, Eq, PartialEq, Clone, Copy)]
@@ -518,16 +512,3 @@ pub struct WorkerListOpt {
 	#[structopt(short = "e", long = "errors")]
 	pub errors: bool,
 }
-
-#[derive(Serialize, Deserialize, StructOpt, Debug, Eq, PartialEq, Clone)]
-pub enum WorkerSetCmd {
-	/// Set tranquility of scrub operations
-	#[structopt(name = "scrub-tranquility", version = version::garage())]
-	ScrubTranquility { tranquility: u32 },
-	/// Set number of concurrent block resync workers
-	#[structopt(name = "resync-n-workers", version = version::garage())]
-	ResyncNWorkers { n_workers: usize },
-	/// Set tranquility of block resync operations
-	#[structopt(name = "resync-tranquility", version = version::garage())]
-	ResyncTranquility { tranquility: u32 },
-}

src/model/garage.rs

@@ -159,6 +159,7 @@ impl Garage {
 			&db,
 			config.data_dir.clone(),
 			config.compression_level,
+			config.block_manager_background_tranquility,
 			data_rep_param,
 			system.clone(),
 		);

src/util/config.rs

@@ -23,6 +23,10 @@ pub struct Config {
 	#[serde(default = "default_block_size")]
 	pub block_size: usize,
 
+	/// Size of data blocks to save to disk
+	#[serde(default = "default_block_manager_background_tranquility")]
+	pub block_manager_background_tranquility: u32,
+
 	/// Replication mode. Supported values:
 	/// - none, 1 -> no replication
 	/// - 2 -> 2-way replication
@@ -143,6 +147,9 @@ fn default_sled_flush_every_ms() -> u64 {
 fn default_block_size() -> usize {
 	1048576
 }
+fn default_block_manager_background_tranquility() -> u32 {
+	2
+}
 
 /// Read and parse configuration
 pub fn read_config(config_file: PathBuf) -> Result<Config, Error> {