Make background tranquility a configurable parameter

src/block/manager.rs

@@ -29,15 +29,13 @@ use garage_rpc::*;
 
 use garage_table::replication::{TableReplication, TableShardedReplication};
 
-use crate::metrics::*;
 use crate::block::*;
+use crate::metrics::*;
 use crate::rc::*;
 
 /// 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
@@ -82,8 +80,9 @@ pub struct BlockManager {
 	pub replication: TableShardedReplication,
 	/// Directory in which block are stored
 	pub data_dir: PathBuf,
-	/// Zstd compression level
+
 	compression_level: Option<i32>,
+	background_tranquility: u32,
 
 	mutation_lock: Mutex<BlockManagerLocked>,
 
@@ -109,6 +108,7 @@ impl BlockManager {
 		db: &sled::Db,
 		data_dir: PathBuf,
 		compression_level: Option<i32>,
+		background_tranquility: u32,
 		replication: TableShardedReplication,
 		system: Arc<System>,
 	) -> Arc<Self> {
@@ -139,6 +139,7 @@ impl BlockManager {
 			replication,
 			data_dir,
 			compression_level,
+			background_tranquility,
 			mutation_lock: Mutex::new(manager_locked),
 			rc,
 			resync_queue,
@@ -440,7 +441,7 @@ impl BlockManager {
 		while !*must_exit.borrow() {
 			match self.resync_iter(&mut must_exit).await {
 				Ok(true) => {
-					tranquilizer.tranquilize(BACKGROUND_TRANQUILITY).await;
+					tranquilizer.tranquilize(self.background_tranquility).await;
 				}
 				Ok(false) => {
 					tranquilizer.reset();

src/block/rc.rs

@@ -1,7 +1,7 @@
 use std::convert::TryInto;
 
-use garage_util::error::*;
 use garage_util::data::*;
+use garage_util::error::*;
 use garage_util::time::*;
 
 use crate::manager::BLOCK_GC_DELAY;
@@ -12,9 +12,7 @@ pub struct BlockRc {
 
 impl BlockRc {
 	pub(crate) fn new(rc: sled::Tree) -> Self {
-		Self {
-			rc
-		}
+		Self { rc }
 	}
 
 	/// Increment the reference counter associated to a hash.
@@ -34,7 +32,7 @@ impl BlockRc {
 			.rc
 			.update_and_fetch(&hash, |old| RcEntry::parse_opt(old).decrement().serialize())?;
 		let new_rc = RcEntry::parse_opt(new_rc);
-		Ok(matches!(new_rc, RcEntry::Deletable {..}))
+		Ok(matches!(new_rc, RcEntry::Deletable { .. }))
 	}
 
 	/// Read a block's reference count