1 files changed, 311 insertions, 630 deletions

diff --git a/src/block/manager.rs b/src/block/manager.rs
index 1c04a335..7f439b96 100644
--- a/src/block/manager.rs
+++ b/src/block/manager.rs
@@ -1,29 +1,32 @@
-use std::convert::TryInto;
-use std::path::{Path, PathBuf};
+use std::path::PathBuf;
+use std::pin::Pin;
 use std::sync::Arc;
 use std::time::Duration;
 
 use async_trait::async_trait;
+use bytes::Bytes;
 use serde::{Deserialize, Serialize};
 
-use futures::future::*;
-use futures::select;
+use futures::Stream;
+use futures_util::stream::StreamExt;
 use tokio::fs;
-use tokio::io::{AsyncReadExt, AsyncWriteExt};
-use tokio::sync::{watch, Mutex, Notify};
+use tokio::io::{AsyncReadExt, AsyncWriteExt, BufReader};
+use tokio::sync::{mpsc, Mutex, MutexGuard};
 
 use opentelemetry::{
 	trace::{FutureExt as OtelFutureExt, TraceContextExt, Tracer},
-	Context, KeyValue,
+	Context,
 };
 
+use garage_rpc::rpc_helper::netapp::stream::{stream_asyncread, ByteStream};
+
+use garage_db as db;
+
 use garage_util::data::*;
 use garage_util::error::*;
 use garage_util::metrics::RecordDuration;
-use garage_util::sled_counter::SledCountedTree;
-use garage_util::time::*;
-use garage_util::tranquilizer::Tranquilizer;
 
+use garage_rpc::rpc_helper::OrderTag;
 use garage_rpc::system::System;
 use garage_rpc::*;
 
@@ -32,24 +35,12 @@ use garage_table::replication::{TableReplication, TableShardedReplication};
 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
-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
 // to delete the block locally.
@@ -60,12 +51,12 @@ pub(crate) const BLOCK_GC_DELAY: Duration = Duration::from_secs(600);
 pub enum BlockRpc {
 	Ok,
 	/// Message to ask for a block of data, by hash
-	GetBlock(Hash),
+	GetBlock(Hash, Option<OrderTag>),
 	/// Message to send a block of data, either because requested, of for first delivery of new
 	/// block
 	PutBlock {
 		hash: Hash,
-		data: DataBlock,
+		header: DataBlockHeader,
 	},
 	/// Ask other node if they should have this block, but don't actually have it
 	NeedBlockQuery(Hash),
@@ -85,20 +76,18 @@ pub struct BlockManager {
 	pub data_dir: PathBuf,
 
 	compression_level: Option<i32>,
-	background_tranquility: u32,
 
-	mutation_lock: Mutex<BlockManagerLocked>,
+	mutation_lock: [Mutex<BlockManagerLocked>; 256],
 
-	rc: BlockRc,
+	pub(crate) rc: BlockRc,
+	pub resync: BlockResyncManager,
 
-	resync_queue: SledCountedTree,
-	resync_notify: Notify,
-	resync_errors: SledCountedTree,
+	pub(crate) system: Arc<System>,
+	pub(crate) endpoint: Arc<Endpoint<BlockRpc, Self>>,
 
-	system: Arc<System>,
-	endpoint: Arc<Endpoint<BlockRpc, Self>>,
+	pub(crate) metrics: BlockManagerMetrics,
 
-	metrics: BlockManagerMetrics,
+	tx_scrub_command: mpsc::Sender<ScrubWorkerCommand>,
 }
 
 // This custom struct contains functions that must only be ran
@@ -108,10 +97,9 @@ struct BlockManagerLocked();
 
 impl BlockManager {
 	pub fn new(
-		db: &sled::Db,
+		db: &db::Db,
 		data_dir: PathBuf,
 		compression_level: Option<i32>,
-		background_tranquility: u32,
 		replication: TableShardedReplication,
 		system: Arc<System>,
 	) -> Arc<Self> {
@@ -120,215 +108,323 @@ impl BlockManager {
 			.expect("Unable to open block_local_rc tree");
 		let rc = BlockRc::new(rc);
 
-		let resync_queue = db
-			.open_tree("block_local_resync_queue")
-			.expect("Unable to open block_local_resync_queue tree");
-		let resync_queue = SledCountedTree::new(resync_queue);
-
-		let resync_errors = db
-			.open_tree("block_local_resync_errors")
-			.expect("Unable to open block_local_resync_errors tree");
-		let resync_errors = SledCountedTree::new(resync_errors);
+		let resync = BlockResyncManager::new(db, &system);
 
 		let endpoint = system
 			.netapp
-			.endpoint("garage_model/block.rs/Rpc".to_string());
+			.endpoint("garage_block/manager.rs/Rpc".to_string());
 
-		let manager_locked = BlockManagerLocked();
+		let metrics = BlockManagerMetrics::new(resync.queue.clone(), resync.errors.clone());
 
-		let metrics = BlockManagerMetrics::new(resync_queue.clone(), resync_errors.clone());
+		let (scrub_tx, scrub_rx) = mpsc::channel(1);
 
 		let block_manager = Arc::new(Self {
 			replication,
 			data_dir,
 			compression_level,
-			background_tranquility,
-			mutation_lock: Mutex::new(manager_locked),
+			mutation_lock: [(); 256].map(|_| Mutex::new(BlockManagerLocked())),
 			rc,
-			resync_queue,
-			resync_notify: Notify::new(),
-			resync_errors,
+			resync,
 			system,
 			endpoint,
 			metrics,
+			tx_scrub_command: scrub_tx,
 		});
 		block_manager.endpoint.set_handler(block_manager.clone());
 
-		block_manager.clone().spawn_background_worker();
+		// 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
 	}
 
 	/// Ask nodes that might have a (possibly compressed) block for it
-	async fn rpc_get_raw_block(&self, hash: &Hash) -> Result<DataBlock, Error> {
+	/// Return it as a stream with a header
+	async fn rpc_get_raw_block_streaming(
+		&self,
+		hash: &Hash,
+		order_tag: Option<OrderTag>,
+	) -> Result<(DataBlockHeader, ByteStream), Error> {
 		let who = self.replication.read_nodes(hash);
-		let resps = self
-			.system
-			.rpc
-			.try_call_many(
-				&self.endpoint,
-				&who[..],
-				BlockRpc::GetBlock(*hash),
-				RequestStrategy::with_priority(PRIO_NORMAL)
-					.with_quorum(1)
-					.with_timeout(BLOCK_RW_TIMEOUT)
-					.interrupt_after_quorum(true),
-			)
-			.await?;
+		let who = self.system.rpc.request_order(&who);
+
+		for node in who.iter() {
+			let node_id = NodeID::from(*node);
+			let rpc = self.endpoint.call_streaming(
+				&node_id,
+				BlockRpc::GetBlock(*hash, order_tag),
+				PRIO_NORMAL | PRIO_SECONDARY,
+			);
+			tokio::select! {
+				res = rpc => {
+					let res = match res {
+						Ok(res) => res,
+						Err(e) => {
+							debug!("Node {:?} returned error: {}", node, e);
+							continue;
+						}
+					};
+					let (header, stream) = match res.into_parts() {
+						(Ok(BlockRpc::PutBlock { hash: _, header }), Some(stream)) => (header, stream),
+						_ => {
+							debug!("Node {:?} returned a malformed response", node);
+							continue;
+						}
+					};
+					return Ok((header, stream));
+				}
+				_ = tokio::time::sleep(self.system.rpc.rpc_timeout()) => {
+					debug!("Node {:?} didn't return block in time, trying next.", node);
+				}
+			};
+		}
 
-		for resp in resps {
-			if let BlockRpc::PutBlock { data, .. } = resp {
-				return Ok(data);
-			}
+		Err(Error::Message(format!(
+			"Unable to read block {:?}: no node returned a valid block",
+			hash
+		)))
+	}
+
+	/// Ask nodes that might have a (possibly compressed) block for it
+	/// Return its entire body
+	pub(crate) async fn rpc_get_raw_block(
+		&self,
+		hash: &Hash,
+		order_tag: Option<OrderTag>,
+	) -> Result<DataBlock, Error> {
+		let who = self.replication.read_nodes(hash);
+		let who = self.system.rpc.request_order(&who);
+
+		for node in who.iter() {
+			let node_id = NodeID::from(*node);
+			let rpc = self.endpoint.call_streaming(
+				&node_id,
+				BlockRpc::GetBlock(*hash, order_tag),
+				PRIO_NORMAL | PRIO_SECONDARY,
+			);
+			tokio::select! {
+				res = rpc => {
+					let res = match res {
+						Ok(res) => res,
+						Err(e) => {
+							debug!("Node {:?} returned error: {}", node, e);
+							continue;
+						}
+					};
+					let (header, stream) = match res.into_parts() {
+						(Ok(BlockRpc::PutBlock { hash: _, header }), Some(stream)) => (header, stream),
+						_ => {
+							debug!("Node {:?} returned a malformed response", node);
+							continue;
+						}
+					};
+					match read_stream_to_end(stream).await {
+						Ok(bytes) => return Ok(DataBlock::from_parts(header, bytes)),
+						Err(e) => {
+							debug!("Error reading stream from node {:?}: {}", node, e);
+						}
+					}
+				}
+				_ = tokio::time::sleep(self.system.rpc.rpc_timeout()) => {
+					debug!("Node {:?} didn't return block in time, trying next.", node);
+				}
+			};
 		}
+
 		Err(Error::Message(format!(
-			"Unable to read block {:?}: no valid blocks returned",
+			"Unable to read block {:?}: no node returned a valid block",
 			hash
 		)))
 	}
 
 	// ---- Public interface ----
 
+	/// Ask nodes that might have a block for it,
+	/// return it as a stream
+	pub async fn rpc_get_block_streaming(
+		&self,
+		hash: &Hash,
+		order_tag: Option<OrderTag>,
+	) -> Result<
+		Pin<Box<dyn Stream<Item = Result<Bytes, std::io::Error>> + Send + Sync + 'static>>,
+		Error,
+	> {
+		let (header, stream) = self.rpc_get_raw_block_streaming(hash, order_tag).await?;
+		match header {
+			DataBlockHeader::Plain => Ok(stream),
+			DataBlockHeader::Compressed => {
+				// Too many things, I hate it.
+				let reader = stream_asyncread(stream);
+				let reader = BufReader::new(reader);
+				let reader = async_compression::tokio::bufread::ZstdDecoder::new(reader);
+				Ok(Box::pin(tokio_util::io::ReaderStream::new(reader)))
+			}
+		}
+	}
+
 	/// Ask nodes that might have a block for it
-	pub async fn rpc_get_block(&self, hash: &Hash) -> Result<Vec<u8>, Error> {
-		self.rpc_get_raw_block(hash).await?.verify_get(*hash)
+	pub async fn rpc_get_block(
+		&self,
+		hash: &Hash,
+		order_tag: Option<OrderTag>,
+	) -> Result<Bytes, Error> {
+		self.rpc_get_raw_block(hash, order_tag)
+			.await?
+			.verify_get(*hash)
 	}
 
 	/// Send block to nodes that should have it
-	pub async fn rpc_put_block(&self, hash: Hash, data: Vec<u8>) -> Result<(), Error> {
+	pub async fn rpc_put_block(&self, hash: Hash, data: Bytes) -> Result<(), Error> {
 		let who = self.replication.write_nodes(&hash);
-		let data = DataBlock::from_buffer(data, self.compression_level);
+
+		let (header, bytes) = DataBlock::from_buffer(data, self.compression_level)
+			.await
+			.into_parts();
+		let put_block_rpc =
+			Req::new(BlockRpc::PutBlock { hash, header })?.with_stream_from_buffer(bytes);
+
 		self.system
 			.rpc
 			.try_call_many(
 				&self.endpoint,
 				&who[..],
-				BlockRpc::PutBlock { hash, data },
-				RequestStrategy::with_priority(PRIO_NORMAL)
-					.with_quorum(self.replication.write_quorum())
-					.with_timeout(BLOCK_RW_TIMEOUT),
+				put_block_rpc,
+				RequestStrategy::with_priority(PRIO_NORMAL | PRIO_SECONDARY)
+					.with_quorum(self.replication.write_quorum()),
 			)
 			.await?;
-		Ok(())
-	}
 
-	/// Launch the repair procedure on the data store
-	///
-	/// This will list all blocks locally present, as well as those
-	/// that are required because of refcount > 0, and will try
-	/// to fix any mismatch between the two.
-	pub async fn repair_data_store(&self, must_exit: &watch::Receiver<bool>) -> Result<(), Error> {
-		// 1. Repair blocks from RC table.
-		for (i, entry) in self.rc.rc.iter().enumerate() {
-			let (hash, _) = entry?;
-			let hash = Hash::try_from(&hash[..]).unwrap();
-			self.put_to_resync(&hash, Duration::from_secs(0))?;
-			if i & 0xFF == 0 && *must_exit.borrow() {
-				return Ok(());
-			}
-		}
-
-		// 2. Repair blocks actually on disk
-		// Lists all blocks on disk and adds them to the resync queue.
-		// 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.
-		self.for_each_file(
-			(),
-			move |_, hash| async move {
-				self.put_to_resync(&hash, Duration::from_secs(0))
-					.map_err(Into::into)
-			},
-			must_exit,
-		)
-		.await
-	}
-
-	/// Verify integrity of each block on disk. Use `speed_limit` to limit the load generated by
-	/// this function.
-	pub async fn scrub_data_store(
-		&self,
-		must_exit: &watch::Receiver<bool>,
-		tranquility: u32,
-	) -> Result<(), Error> {
-		let tranquilizer = Tranquilizer::new(30);
-		self.for_each_file(
-			tranquilizer,
-			move |mut tranquilizer, hash| async move {
-				let _ = self.read_block(&hash).await;
-				tranquilizer.tranquilize(tranquility).await;
-				Ok(tranquilizer)
-			},
-			must_exit,
-		)
-		.await
-	}
-
-	/// Get lenght of resync queue
-	pub fn resync_queue_len(&self) -> usize {
-		self.resync_queue.len()
+		Ok(())
 	}
 
-	/// Get number of blocks that have an error
-	pub fn resync_errors_len(&self) -> usize {
-		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()?)
 	}
 
-	/// Get number of items in the refcount table
-	pub fn rc_len(&self) -> usize {
-		self.rc.rc.len()
+	/// 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;
 	}
 
 	//// ----- Managing the reference counter ----
 
 	/// Increment the number of time a block is used, putting it to resynchronization if it is
 	/// required, but not known
-	pub fn block_incref(&self, hash: &Hash) -> Result<(), Error> {
-		if self.rc.block_incref(hash)? {
+	pub fn block_incref(
+		self: &Arc<Self>,
+		tx: &mut db::Transaction,
+		hash: Hash,
+	) -> db::TxOpResult<()> {
+		if self.rc.block_incref(tx, &hash)? {
 			// When the reference counter is incremented, there is
 			// normally a node that is responsible for sending us the
 			// data of the block. However that operation may fail,
 			// so in all cases we add the block here to the todo list
 			// to check later that it arrived correctly, and if not
 			// we will fecth it from someone.
-			self.put_to_resync(hash, 2 * BLOCK_RW_TIMEOUT)?;
+			let this = self.clone();
+			tokio::spawn(async move {
+				if let Err(e) = this
+					.resync
+					.put_to_resync(&hash, 2 * this.system.rpc.rpc_timeout())
+				{
+					error!("Block {:?} could not be put in resync queue: {}.", hash, e);
+				}
+			});
 		}
 		Ok(())
 	}
 
 	/// Decrement the number of time a block is used
-	pub fn block_decref(&self, hash: &Hash) -> Result<(), Error> {
-		if self.rc.block_decref(hash)? {
+	pub fn block_decref(
+		self: &Arc<Self>,
+		tx: &mut db::Transaction,
+		hash: Hash,
+	) -> db::TxOpResult<()> {
+		if self.rc.block_decref(tx, &hash)? {
 			// When the RC is decremented, it might drop to zero,
 			// indicating that we don't need the block.
 			// There is a delay before we garbage collect it;
 			// make sure that it is handled in the resync loop
 			// after that delay has passed.
-			self.put_to_resync(hash, BLOCK_GC_DELAY + Duration::from_secs(10))?;
+			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))
+				{
+					error!("Block {:?} could not be put in resync queue: {}.", hash, e);
+				}
+			});
 		}
 		Ok(())
 	}
 
 	// ---- Reading and writing blocks locally ----
 
+	async fn handle_put_block(
+		&self,
+		hash: Hash,
+		header: DataBlockHeader,
+		stream: Option<ByteStream>,
+	) -> Result<(), Error> {
+		let stream = stream.ok_or_message("missing stream")?;
+		let bytes = read_stream_to_end(stream).await?;
+		let data = DataBlock::from_parts(header, bytes);
+		self.write_block(&hash, &data).await
+	}
+
 	/// Write a block to disk
-	async fn write_block(&self, hash: &Hash, data: &DataBlock) -> Result<BlockRpc, Error> {
+	pub(crate) async fn write_block(&self, hash: &Hash, data: &DataBlock) -> Result<(), Error> {
+		let tracer = opentelemetry::global::tracer("garage");
+
 		let write_size = data.inner_buffer().len() as u64;
 
-		let res = self
-			.mutation_lock
-			.lock()
+		self.lock_mutate(hash)
 			.await
 			.write_block(hash, data, self)
 			.bound_record_duration(&self.metrics.block_write_duration)
+			.with_context(Context::current_with_span(
+				tracer.start("BlockManagerLocked::write_block"),
+			))
 			.await?;
 
 		self.metrics.bytes_written.add(write_size);
 
-		Ok(res)
+		Ok(())
+	}
+
+	async fn handle_get_block(&self, hash: &Hash, order_tag: Option<OrderTag>) -> Resp<BlockRpc> {
+		let block = match self.read_block(hash).await {
+			Ok(data) => data,
+			Err(e) => return Resp::new(Err(e)),
+		};
+
+		let (header, data) = block.into_parts();
+
+		let resp = Resp::new(Ok(BlockRpc::PutBlock {
+			hash: *hash,
+			header,
+		}))
+		.with_stream_from_buffer(data);
+
+		if let Some(order_tag) = order_tag {
+			resp.with_order_tag(order_tag)
+		} else {
+			resp
+		}
 	}
 
 	/// Read block from disk, verifying it's integrity
-	async fn read_block(&self, hash: &Hash) -> Result<BlockRpc, Error> {
+	pub(crate) async fn read_block(&self, hash: &Hash) -> Result<DataBlock, Error> {
 		let data = self
 			.read_block_internal(hash)
 			.bound_record_duration(&self.metrics.block_read_duration)
@@ -338,7 +434,7 @@ impl BlockManager {
 			.bytes_read
 			.add(data.inner_buffer().len() as u64);
 
-		Ok(BlockRpc::PutBlock { hash: *hash, data })
+		Ok(data)
 	}
 
 	async fn read_block_internal(&self, hash: &Hash) -> Result<DataBlock, Error> {
@@ -347,7 +443,8 @@ impl BlockManager {
 			Ok(c) => c,
 			Err(e) => {
 				// Not found but maybe we should have had it ??
-				self.put_to_resync(hash, 2 * BLOCK_RW_TIMEOUT)?;
+				self.resync
+					.put_to_resync(hash, 2 * self.system.rpc.rpc_timeout())?;
 				return Err(Into::into(e));
 			}
 		};
@@ -361,37 +458,47 @@ impl BlockManager {
 		drop(f);
 
 		let data = if compressed {
-			DataBlock::Compressed(data)
+			DataBlock::Compressed(data.into())
 		} else {
-			DataBlock::Plain(data)
+			DataBlock::Plain(data.into())
 		};
 
 		if data.verify(*hash).is_err() {
 			self.metrics.corruption_counter.add(1);
 
-			self.mutation_lock
-				.lock()
+			self.lock_mutate(hash)
 				.await
 				.move_block_to_corrupted(hash, self)
 				.await?;
-			self.put_to_resync(hash, Duration::from_millis(0))?;
+			self.resync.put_to_resync(hash, Duration::from_millis(0))?;
 			return Err(Error::CorruptData(*hash));
 		}
 
 		Ok(data)
 	}
 
-	/// 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()
+	/// 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.lock_mutate(hash)
 			.await
 			.check_block_status(hash, self)
-			.await?;
+			.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?;
 		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.lock_mutate(hash)
+			.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();
@@ -419,431 +526,38 @@ impl BlockManager {
 		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_worker(self: Arc<Self>) {
-		// Launch a background workers for background resync loop processing
-		let background = self.system.background.clone();
-		tokio::spawn(async move {
-			tokio::time::sleep(Duration::from_secs(10)).await;
-			background.spawn_worker("block resync worker".into(), move |must_exit| {
-				self.resync_loop(must_exit)
-			});
-		});
-	}
-
-	fn put_to_resync(&self, hash: &Hash, delay: Duration) -> Result<(), sled::Error> {
-		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) -> Result<(), sled::Error> {
-		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_loop(self: Arc<Self>, mut must_exit: watch::Receiver<bool>) {
-		let mut tranquilizer = Tranquilizer::new(30);
-
-		while !*must_exit.borrow() {
-			match self.resync_iter(&mut must_exit).await {
-				Ok(true) => {
-					tranquilizer.tranquilize(self.background_tranquility).await;
-				}
-				Ok(false) => {
-					tranquilizer.reset();
-				}
-				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?)
-					error!(
-						"Could not do a resync iteration: {} (this is a very bad error)",
-						e
-					);
-					tranquilizer.reset();
-				}
-			}
-		}
-	}
-
-	// The result of resync_iter is:
-	// - Ok(true) -> a block was processed (successfully or not)
-	// - Ok(false) -> no block was processed, but we are ready for the next iteration
-	// - Err(_) -> a Sled error occurred when reading/writing from resync_queue/resync_errors
-	async fn resync_iter(
-		&self,
-		must_exit: &mut watch::Receiver<bool>,
-	) -> Result<bool, sled::Error> {
-		if let Some(first_pair_res) = self.resync_queue.iter().next() {
-			let (time_bytes, hash_bytes) = first_pair_res?;
-
-			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(false);
-					}
-				}
-
-				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(true)
-			} else {
-				let delay = tokio::time::sleep(Duration::from_millis(time_msec - now));
-				select! {
-					_ = delay.fuse() => {},
-					_ = self.resync_notify.notified().fuse() => {},
-					_ = must_exit.changed().fuse() => {},
-				}
-				Ok(false)
-			}
-		} 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.
-			let delay = tokio::time::sleep(Duration::from_secs(10));
-			select! {
-				_ = delay.fuse() => {},
-				_ = self.resync_notify.notified().fuse() => {},
-				_ = must_exit.changed().fuse() => {},
-			}
-			Ok(false)
-		}
-	}
-
-	async fn resync_block(&self, hash: &Hash) -> Result<(), Error> {
-		let BlockStatus { exists, needed } = self
-			.mutation_lock
+	async fn lock_mutate(&self, hash: &Hash) -> MutexGuard<'_, BlockManagerLocked> {
+		let tracer = opentelemetry::global::tracer("garage");
+		self.mutation_lock[hash.as_slice()[0] as usize]
 			.lock()
+			.with_context(Context::current_with_span(
+				tracer.start("Acquire mutation_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(())
-	}
-
-	// ---- Utility: iteration on files in the data directory ----
-
-	async fn for_each_file<F, Fut, State>(
-		&self,
-		state: State,
-		mut f: F,
-		must_exit: &watch::Receiver<bool>,
-	) -> Result<(), Error>
-	where
-		F: FnMut(State, Hash) -> Fut + Send,
-		Fut: Future<Output = Result<State, Error>> + Send,
-		State: Send,
-	{
-		self.for_each_file_rec(&self.data_dir, state, &mut f, must_exit)
-			.await
-			.map(|_| ())
-	}
-
-	fn for_each_file_rec<'a, F, Fut, State>(
-		&'a self,
-		path: &'a Path,
-		mut state: State,
-		f: &'a mut F,
-		must_exit: &'a watch::Receiver<bool>,
-	) -> BoxFuture<'a, Result<State, Error>>
-	where
-		F: FnMut(State, Hash) -> Fut + Send,
-		Fut: Future<Output = Result<State, Error>> + Send,
-		State: Send + 'a,
-	{
-		async move {
-			let mut ls_data_dir = fs::read_dir(path).await?;
-			while let Some(data_dir_ent) = ls_data_dir.next_entry().await? {
-				if *must_exit.borrow() {
-					break;
-				}
-
-				let name = data_dir_ent.file_name();
-				let name = if let Ok(n) = name.into_string() {
-					n
-				} else {
-					continue;
-				};
-				let ent_type = data_dir_ent.file_type().await?;
-
-				let name = name.strip_suffix(".zst").unwrap_or(&name);
-				if name.len() == 2 && hex::decode(&name).is_ok() && ent_type.is_dir() {
-					state = self
-						.for_each_file_rec(&data_dir_ent.path(), state, f, must_exit)
-						.await?;
-				} else if name.len() == 64 {
-					let hash_bytes = if let Ok(h) = hex::decode(&name) {
-						h
-					} else {
-						continue;
-					};
-					let mut hash = [0u8; 32];
-					hash.copy_from_slice(&hash_bytes[..]);
-					state = f(state, hash.into()).await?;
-				}
-			}
-			Ok(state)
-		}
-		.boxed()
 	}
 }
 
 #[async_trait]
-impl EndpointHandler<BlockRpc> for BlockManager {
-	async fn handle(
-		self: &Arc<Self>,
-		message: &BlockRpc,
-		_from: NodeID,
-	) -> Result<BlockRpc, Error> {
-		match message {
-			BlockRpc::PutBlock { hash, data } => self.write_block(hash, data).await,
-			BlockRpc::GetBlock(h) => self.read_block(h).await,
-			BlockRpc::NeedBlockQuery(h) => self.need_block(h).await.map(BlockRpc::NeedBlockReply),
-			m => Err(Error::unexpected_rpc_message(m)),
+impl StreamingEndpointHandler<BlockRpc> for BlockManager {
+	async fn handle(self: &Arc<Self>, mut message: Req<BlockRpc>, _from: NodeID) -> Resp<BlockRpc> {
+		match message.msg() {
+			BlockRpc::PutBlock { hash, header } => Resp::new(
+				self.handle_put_block(*hash, *header, message.take_stream())
+					.await
+					.map(|_| BlockRpc::Ok),
+			),
+			BlockRpc::GetBlock(h, order_tag) => self.handle_get_block(h, *order_tag).await,
+			BlockRpc::NeedBlockQuery(h) => {
+				Resp::new(self.need_block(h).await.map(BlockRpc::NeedBlockReply))
+			}
+			m => Resp::new(Err(Error::unexpected_rpc_message(m))),
 		}
 	}
 }
 
-struct BlockStatus {
-	exists: bool,
-	needed: RcEntry,
+pub(crate) struct BlockStatus {
+	pub(crate) exists: bool,
+	pub(crate) needed: RcEntry,
 }
 
 impl BlockManagerLocked {
@@ -863,7 +577,7 @@ impl BlockManagerLocked {
 		hash: &Hash,
 		data: &DataBlock,
 		mgr: &BlockManager,
-	) -> Result<BlockRpc, Error> {
+	) -> Result<(), Error> {
 		let compressed = data.is_compressed();
 		let data = data.inner_buffer();
 
@@ -874,8 +588,8 @@ impl BlockManagerLocked {
 		fs::create_dir_all(&directory).await?;
 
 		let to_delete = match (mgr.is_block_compressed(hash).await, compressed) {
-			(Ok(true), _) => return Ok(BlockRpc::Ok),
-			(Ok(false), false) => return Ok(BlockRpc::Ok),
+			(Ok(true), _) => return Ok(()),
+			(Ok(false), false) => return Ok(()),
 			(Ok(false), true) => {
 				let path_to_delete = path.clone();
 				path.set_extension("zst");
@@ -914,7 +628,7 @@ impl BlockManagerLocked {
 		dir.sync_all().await?;
 		drop(dir);
 
-		Ok(BlockRpc::Ok)
+		Ok(())
 	}
 
 	async fn move_block_to_corrupted(&self, hash: &Hash, mgr: &BlockManager) -> Result<(), Error> {
@@ -949,49 +663,16 @@ impl BlockManagerLocked {
 	}
 }
 
-/// 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,
-		}
+async fn read_stream_to_end(mut stream: ByteStream) -> Result<Bytes, Error> {
+	let mut parts: Vec<Bytes> = vec![];
+	while let Some(part) = stream.next().await {
+		parts.push(part.ok_or_message("error in stream")?);
 	}
 
-	fn decode(data: sled::IVec) -> 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),
-		]
+	Ok(parts
+		.iter()
+		.map(|x| &x[..])
+		.collect::<Vec<_>>()
 		.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()
-	}
+		.into())
 }