Move block manager to separate module

1 files changed, 0 insertions, 1107 deletions

diff --git a/src/model/block.rs b/src/model/block.rs
deleted file mode 100644
index a41daa64..00000000
--- a/src/model/block.rs
+++ /dev/null
@@ -1,1107 +0,0 @@
-use std::convert::TryInto;
-use std::path::{Path, PathBuf};
-use std::sync::Arc;
-use std::time::Duration;
-
-use arc_swap::ArcSwapOption;
-use async_trait::async_trait;
-use serde::{Deserialize, Serialize};
-use zstd::stream::{decode_all as zstd_decode, Encoder};
-
-use futures::future::*;
-use futures::select;
-use tokio::fs;
-use tokio::io::{AsyncReadExt, AsyncWriteExt};
-use tokio::sync::{watch, Mutex, Notify};
-
-use opentelemetry::{
-	trace::{FutureExt as OtelFutureExt, TraceContextExt, Tracer},
-	Context, KeyValue,
-};
-
-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::system::System;
-use garage_rpc::*;
-
-use garage_table::replication::{TableReplication, TableShardedReplication};
-
-use crate::block_metrics::*;
-use crate::block_ref_table::*;
-use crate::garage::Garage;
-
-/// Size under which data will be stored inlined in database instead of as files
-pub const INLINE_THRESHOLD: usize = 3072;
-
-pub const BACKGROUND_TRANQUILITY: u32 = 2;
-
-// 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 delay between the moment when the reference counter
-// drops to zero, and the moment where we allow ourselves
-// to delete the block locally.
-const BLOCK_GC_DELAY: Duration = Duration::from_secs(600);
-
-/// RPC messages used to share blocks of data between nodes
-#[derive(Debug, Serialize, Deserialize)]
-pub enum BlockRpc {
-	Ok,
-	/// Message to ask for a block of data, by hash
-	GetBlock(Hash),
-	/// Message to send a block of data, either because requested, of for first delivery of new
-	/// block
-	PutBlock {
-		hash: Hash,
-		data: DataBlock,
-	},
-	/// Ask other node if they should have this block, but don't actually have it
-	NeedBlockQuery(Hash),
-	/// Response : whether the node do require that block
-	NeedBlockReply(bool),
-}
-
-/// A possibly compressed block of data
-#[derive(Debug, Serialize, Deserialize)]
-pub enum DataBlock {
-	/// Uncompressed data
-	Plain(#[serde(with = "serde_bytes")] Vec<u8>),
-	/// Data compressed with zstd
-	Compressed(#[serde(with = "serde_bytes")] Vec<u8>),
-}
-
-impl DataBlock {
-	/// Query whether this block is compressed
-	pub fn is_compressed(&self) -> bool {
-		matches!(self, DataBlock::Compressed(_))
-	}
-
-	/// Get the inner, possibly compressed buffer. You should probably use [`DataBlock::verify_get`]
-	/// instead
-	pub fn inner_buffer(&self) -> &[u8] {
-		use DataBlock::*;
-		let (Plain(ref res) | Compressed(ref res)) = self;
-		res
-	}
-
-	/// Get the buffer, possibly decompressing it, and verify it's integrity.
-	/// For Plain block, data is compared to hash, for Compressed block, zstd checksumming system
-	/// is used instead.
-	pub fn verify_get(self, hash: Hash) -> Result<Vec<u8>, Error> {
-		match self {
-			DataBlock::Plain(data) => {
-				if blake2sum(&data) == hash {
-					Ok(data)
-				} else {
-					Err(Error::CorruptData(hash))
-				}
-			}
-			DataBlock::Compressed(data) => {
-				zstd_decode(&data[..]).map_err(|_| Error::CorruptData(hash))
-			}
-		}
-	}
-
-	/// Verify data integrity. Allocate less than [`DataBlock::verify_get`] and don't consume self, but
-	/// does not return the buffer content.
-	pub fn verify(&self, hash: Hash) -> Result<(), Error> {
-		match self {
-			DataBlock::Plain(data) => {
-				if blake2sum(data) == hash {
-					Ok(())
-				} else {
-					Err(Error::CorruptData(hash))
-				}
-			}
-			DataBlock::Compressed(data) => zstd::stream::copy_decode(&data[..], std::io::sink())
-				.map_err(|_| Error::CorruptData(hash)),
-		}
-	}
-
-	pub fn from_buffer(data: Vec<u8>, level: Option<i32>) -> DataBlock {
-		if let Some(level) = level {
-			if let Ok(data) = zstd_encode(&data[..], level) {
-				return DataBlock::Compressed(data);
-			}
-		}
-		DataBlock::Plain(data)
-	}
-}
-
-impl Rpc for BlockRpc {
-	type Response = Result<BlockRpc, Error>;
-}
-
-/// The block manager, handling block exchange between nodes, and block storage on local node
-pub struct BlockManager {
-	/// Replication strategy, allowing to find on which node blocks should be located
-	pub replication: TableShardedReplication,
-	/// Directory in which block are stored
-	pub data_dir: PathBuf,
-
-	mutation_lock: Mutex<BlockManagerLocked>,
-
-	rc: sled::Tree,
-
-	resync_queue: SledCountedTree,
-	resync_notify: Notify,
-	resync_errors: SledCountedTree,
-
-	system: Arc<System>,
-	endpoint: Arc<Endpoint<BlockRpc, Self>>,
-	pub(crate) garage: ArcSwapOption<Garage>,
-
-	metrics: BlockManagerMetrics,
-}
-
-// This custom struct contains functions that must only be ran
-// when the lock is held. We ensure that it is the case by storing
-// it INSIDE a Mutex.
-struct BlockManagerLocked();
-
-impl BlockManager {
-	pub fn new(
-		db: &sled::Db,
-		data_dir: PathBuf,
-		replication: TableShardedReplication,
-		system: Arc<System>,
-	) -> Arc<Self> {
-		let rc = db
-			.open_tree("block_local_rc")
-			.expect("Unable to open block_local_rc tree");
-
-		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 endpoint = system
-			.netapp
-			.endpoint("garage_model/block.rs/Rpc".to_string());
-
-		let manager_locked = BlockManagerLocked();
-
-		let metrics = BlockManagerMetrics::new(resync_queue.clone(), resync_errors.clone());
-
-		let block_manager = Arc::new(Self {
-			replication,
-			data_dir,
-			mutation_lock: Mutex::new(manager_locked),
-			rc,
-			resync_queue,
-			resync_notify: Notify::new(),
-			resync_errors,
-			system,
-			endpoint,
-			garage: ArcSwapOption::from(None),
-			metrics,
-		});
-		block_manager.endpoint.set_handler(block_manager.clone());
-
-		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> {
-		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?;
-
-		for resp in resps {
-			if let BlockRpc::PutBlock { data, .. } = resp {
-				return Ok(data);
-			}
-		}
-		Err(Error::Message(format!(
-			"Unable to read block {:?}: no valid blocks returned",
-			hash
-		)))
-	}
-
-	// ---- Public interface ----
-
-	/// 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)
-	}
-
-	/// Send block to nodes that should have it
-	pub async fn rpc_put_block(&self, hash: Hash, data: Vec<u8>) -> Result<(), Error> {
-		let who = self.replication.write_nodes(&hash);
-		let compression_level = self
-			.garage
-			.load()
-			.as_ref()
-			.unwrap()
-			.config
-			.compression_level;
-		let data = DataBlock::from_buffer(data, compression_level);
-		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),
-			)
-			.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.
-		let garage = self.garage.load_full().unwrap();
-		let mut last_hash = None;
-		for (i, entry) in garage.block_ref_table.data.store.iter().enumerate() {
-			let (_k, v_bytes) = entry?;
-			let block_ref = rmp_serde::decode::from_read_ref::<_, BlockRef>(v_bytes.as_ref())?;
-			if Some(&block_ref.block) == last_hash.as_ref() {
-				continue;
-			}
-			if !block_ref.deleted.get() {
-				last_hash = Some(block_ref.block);
-				self.put_to_resync(&block_ref.block, 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)) },
-			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()
-	}
-
-	/// Get number of items in the refcount table
-	pub fn rc_len(&self) -> usize {
-		self.rc.len()
-	}
-
-	//// ----- 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> {
-		let old_rc = self
-			.rc
-			.fetch_and_update(&hash, |old| RcEntry::parse_opt(old).increment().serialize())?;
-		let old_rc = RcEntry::parse_opt(old_rc);
-		if old_rc.is_zero() {
-			// 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)?;
-		}
-		Ok(())
-	}
-
-	/// Decrement the number of time a block is used
-	pub fn block_decref(&self, hash: &Hash) -> Result<(), Error> {
-		let new_rc = self
-			.rc
-			.update_and_fetch(&hash, |old| RcEntry::parse_opt(old).decrement().serialize())?;
-		let new_rc = RcEntry::parse_opt(new_rc);
-		if let RcEntry::Deletable { .. } = new_rc {
-			self.put_to_resync(hash, BLOCK_GC_DELAY + Duration::from_secs(10))?;
-		}
-		Ok(())
-	}
-
-	/// Read a block's reference count
-	fn get_block_rc(&self, hash: &Hash) -> Result<RcEntry, Error> {
-		Ok(RcEntry::parse_opt(self.rc.get(hash.as_ref())?))
-	}
-
-	/// Delete an entry in the RC table if it is deletable and the
-	/// deletion time has passed
-	fn clear_deleted_block_rc(&self, hash: &Hash) -> Result<(), Error> {
-		let now = now_msec();
-		self.rc.update_and_fetch(&hash, |rcval| {
-			let updated = match RcEntry::parse_opt(rcval) {
-				RcEntry::Deletable { at_time } if now > at_time => RcEntry::Absent,
-				v => v,
-			};
-			updated.serialize()
-		})?;
-		Ok(())
-	}
-
-	// ---- Reading and writing blocks locally ----
-
-	/// Write a block to disk
-	async fn write_block(&self, hash: &Hash, data: &DataBlock) -> Result<BlockRpc, Error> {
-		let write_size = data.inner_buffer().len() as u64;
-
-		let res = self
-			.mutation_lock
-			.lock()
-			.await
-			.write_block(hash, data, self)
-			.bound_record_duration(&self.metrics.block_write_duration)
-			.await?;
-
-		self.metrics.bytes_written.add(write_size);
-
-		Ok(res)
-	}
-
-	/// Read block from disk, verifying it's integrity
-	async fn read_block(&self, hash: &Hash) -> Result<BlockRpc, Error> {
-		let data = self
-			.read_block_internal(hash)
-			.bound_record_duration(&self.metrics.block_read_duration)
-			.await?;
-
-		self.metrics
-			.bytes_read
-			.add(data.inner_buffer().len() as u64);
-
-		Ok(BlockRpc::PutBlock { hash: *hash, data })
-	}
-
-	async fn read_block_internal(&self, hash: &Hash) -> Result<DataBlock, Error> {
-		let mut path = self.block_path(hash);
-		let compressed = match self.is_block_compressed(hash).await {
-			Ok(c) => c,
-			Err(e) => {
-				// Not found but maybe we should have had it ??
-				self.put_to_resync(hash, 2 * BLOCK_RW_TIMEOUT)?;
-				return Err(Into::into(e));
-			}
-		};
-		if compressed {
-			path.set_extension("zst");
-		}
-		let mut f = fs::File::open(&path).await?;
-
-		let mut data = vec![];
-		f.read_to_end(&mut data).await?;
-		drop(f);
-
-		let data = if compressed {
-			DataBlock::Compressed(data)
-		} else {
-			DataBlock::Plain(data)
-		};
-
-		if data.verify(*hash).is_err() {
-			self.metrics.corruption_counter.add(1);
-
-			self.mutation_lock
-				.lock()
-				.await
-				.move_block_to_corrupted(hash, self)
-				.await?;
-			self.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()
-			.await
-			.check_block_status(hash, self)
-			.await?;
-		Ok(needed.is_nonzero() && !exists)
-	}
-
-	/// 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();
-		path.push(hex::encode(&hash.as_slice()[0..1]));
-		path.push(hex::encode(&hash.as_slice()[1..2]));
-		path
-	}
-
-	/// Utility: give the full path where a block should be found, minus extension if block is
-	/// compressed
-	fn block_path(&self, hash: &Hash) -> PathBuf {
-		let mut path = self.block_dir(hash);
-		path.push(hex::encode(hash.as_ref()));
-		path
-	}
-
-	/// Utility: check if block is stored compressed. Error if block is not stored
-	async fn is_block_compressed(&self, hash: &Hash) -> Result<bool, Error> {
-		let mut path = self.block_path(hash);
-		path.set_extension("zst");
-		if fs::metadata(&path).await.is_ok() {
-			return Ok(true);
-		}
-		path.set_extension("");
-		fs::metadata(&path).await.map(|_| false).map_err(Into::into)
-	}
-
-	// ---- Resync loop ----
-
-	pub 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<(), 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<(), 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(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();
-				}
-			}
-		}
-	}
-
-	async fn resync_iter(&self, must_exit: &mut watch::Receiver<bool>) -> Result<bool, 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
-						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 {
-			select! {
-				_ = 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
-			.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.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)),
-		}
-	}
-}
-
-struct BlockStatus {
-	exists: bool,
-	needed: RcEntry,
-}
-
-impl BlockManagerLocked {
-	async fn check_block_status(
-		&self,
-		hash: &Hash,
-		mgr: &BlockManager,
-	) -> Result<BlockStatus, Error> {
-		let exists = mgr.is_block_compressed(hash).await.is_ok();
-		let needed = mgr.get_block_rc(hash)?;
-
-		Ok(BlockStatus { exists, needed })
-	}
-
-	async fn write_block(
-		&self,
-		hash: &Hash,
-		data: &DataBlock,
-		mgr: &BlockManager,
-	) -> Result<BlockRpc, Error> {
-		let compressed = data.is_compressed();
-		let data = data.inner_buffer();
-
-		let mut path = mgr.block_dir(hash);
-		let directory = path.clone();
-		path.push(hex::encode(hash));
-
-		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(false), true) => {
-				let path_to_delete = path.clone();
-				path.set_extension("zst");
-				Some(path_to_delete)
-			}
-			(Err(_), compressed) => {
-				if compressed {
-					path.set_extension("zst");
-				}
-				None
-			}
-		};
-
-		let mut path2 = path.clone();
-		path2.set_extension("tmp");
-		let mut f = fs::File::create(&path2).await?;
-		f.write_all(data).await?;
-		f.sync_all().await?;
-		drop(f);
-
-		fs::rename(path2, path).await?;
-		if let Some(to_delete) = to_delete {
-			fs::remove_file(to_delete).await?;
-		}
-
-		// We want to ensure that when this function returns, data is properly persisted
-		// to disk. The first step is the sync_all above that does an fsync on the data file.
-		// Now, we do an fsync on the containing directory, to ensure that the rename
-		// is persisted properly. See:
-		// http://thedjbway.b0llix.net/qmail/syncdir.html
-		let dir = fs::OpenOptions::new()
-			.read(true)
-			.mode(0)
-			.open(directory)
-			.await?;
-		dir.sync_all().await?;
-		drop(dir);
-
-		Ok(BlockRpc::Ok)
-	}
-
-	async fn move_block_to_corrupted(&self, hash: &Hash, mgr: &BlockManager) -> Result<(), Error> {
-		warn!(
-			"Block {:?} is corrupted. Renaming to .corrupted and resyncing.",
-			hash
-		);
-		let mut path = mgr.block_path(hash);
-		let mut path2 = path.clone();
-		if mgr.is_block_compressed(hash).await? {
-			path.set_extension("zst");
-			path2.set_extension("zst.corrupted");
-		} else {
-			path2.set_extension("corrupted");
-		}
-		fs::rename(path, path2).await?;
-		Ok(())
-	}
-
-	async fn delete_if_unneeded(&self, hash: &Hash, mgr: &BlockManager) -> Result<(), Error> {
-		let BlockStatus { exists, needed } = self.check_block_status(hash, mgr).await?;
-
-		if exists && needed.is_deletable() {
-			let mut path = mgr.block_path(hash);
-			if mgr.is_block_compressed(hash).await? {
-				path.set_extension("zst");
-			}
-			fs::remove_file(path).await?;
-			mgr.metrics.delete_counter.add(1);
-		}
-		Ok(())
-	}
-}
-
-/// Describes the state of the reference counter for a block
-#[derive(Clone, Copy, Debug)]
-enum RcEntry {
-	/// Present: the block has `count` references, with `count` > 0.
-	///
-	/// This is stored as u64::to_be_bytes(count)
-	Present { count: u64 },
-
-	/// Deletable: the block has zero references, and can be deleted
-	/// once time (returned by now_msec) is larger than at_time
-	/// (in millis since Unix epoch)
-	///
-	/// This is stored as [0u8; 8] followed by u64::to_be_bytes(at_time),
-	/// (this allows for the data format to be backwards compatible with
-	/// previous Garage versions that didn't have this intermediate state)
-	Deletable { at_time: u64 },
-
-	/// Absent: the block has zero references, and can be deleted
-	/// immediately
-	Absent,
-}
-
-impl RcEntry {
-	fn parse(bytes: &[u8]) -> Self {
-		if bytes.len() == 8 {
-			RcEntry::Present {
-				count: u64::from_be_bytes(bytes.try_into().unwrap()),
-			}
-		} else if bytes.len() == 16 {
-			RcEntry::Deletable {
-				at_time: u64::from_be_bytes(bytes[8..16].try_into().unwrap()),
-			}
-		} else {
-			panic!("Invalid RC entry: {:?}, database is corrupted. This is an error Garage is currently unable to recover from. Sorry, and also please report a bug.",
-				bytes
-			)
-		}
-	}
-
-	fn parse_opt<V: AsRef<[u8]>>(bytes: Option<V>) -> Self {
-		bytes
-			.map(|b| Self::parse(b.as_ref()))
-			.unwrap_or(Self::Absent)
-	}
-
-	fn serialize(self) -> Option<Vec<u8>> {
-		match self {
-			RcEntry::Present { count } => Some(u64::to_be_bytes(count).to_vec()),
-			RcEntry::Deletable { at_time } => {
-				Some([u64::to_be_bytes(0), u64::to_be_bytes(at_time)].concat())
-			}
-			RcEntry::Absent => None,
-		}
-	}
-
-	fn increment(self) -> Self {
-		let old_count = match self {
-			RcEntry::Present { count } => count,
-			_ => 0,
-		};
-		RcEntry::Present {
-			count: old_count + 1,
-		}
-	}
-
-	fn decrement(self) -> Self {
-		match self {
-			RcEntry::Present { count } => {
-				if count > 1 {
-					RcEntry::Present { count: count - 1 }
-				} else {
-					RcEntry::Deletable {
-						at_time: now_msec() + BLOCK_GC_DELAY.as_millis() as u64,
-					}
-				}
-			}
-			del => del,
-		}
-	}
-
-	fn is_zero(&self) -> bool {
-		matches!(self, RcEntry::Deletable { .. } | RcEntry::Absent)
-	}
-
-	fn is_nonzero(&self) -> bool {
-		!self.is_zero()
-	}
-
-	fn is_deletable(&self) -> bool {
-		match self {
-			RcEntry::Present { .. } => false,
-			RcEntry::Deletable { at_time } => now_msec() > *at_time,
-			RcEntry::Absent => true,
-		}
-	}
-
-	fn is_needed(&self) -> bool {
-		!self.is_deletable()
-	}
-}
-
-/// 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: 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),
-		]
-		.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, 10)
-	}
-	fn next_try(&self) -> u64 {
-		self.last_try + self.delay_msec()
-	}
-}
-
-fn zstd_encode<R: std::io::Read>(mut source: R, level: i32) -> std::io::Result<Vec<u8>> {
-	let mut result = Vec::<u8>::new();
-	let mut encoder = Encoder::new(&mut result, level)?;
-	encoder.include_checksum(true)?;
-	std::io::copy(&mut source, &mut encoder)?;
-	encoder.finish()?;
-	Ok(result)
-}