attempt at documenting model crate

src/model/block.rs

@@ -24,6 +24,7 @@ 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_WORKERS: u64 = 1;
@@ -33,28 +34,41 @@ const BLOCK_GC_TIMEOUT: Duration = Duration::from_secs(60);
 const NEED_BLOCK_QUERY_TIMEOUT: Duration = Duration::from_secs(5);
 const RESYNC_RETRY_TIMEOUT: Duration = Duration::from_secs(10);
 
+/// RPC messages used to share blocks of data between nodes
 #[derive(Debug, Serialize, Deserialize)]
 pub enum Message {
 	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(PutBlockMessage),
+	/// 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),
 }
 
+/// Structure used to send a block
 #[derive(Debug, Serialize, Deserialize)]
 pub struct PutBlockMessage {
+	/// Hash of the block
 	pub hash: Hash,
 
+	/// Content of the block
 	#[serde(with = "serde_bytes")]
 	pub data: Vec<u8>,
 }
 
 impl RpcMessage for Message {}
 
+/// 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,
+	/// Lock to prevent concurrent edition of the directory
 	pub data_dir_lock: Mutex<()>,
 
 	rc: sled::Tree,
@@ -128,7 +142,8 @@ impl BlockManager {
 	}
 
 	pub fn spawn_background_worker(self: Arc<Self>) {
-		// Launch 2 simultaneous workers for background resync loop preprocessing
+		// Launch 2 simultaneous workers for background resync loop preprocessing <= TODO actually this
+		// launches only one worker with current value of BACKGROUND_WORKERS
 		for i in 0..BACKGROUND_WORKERS {
 			let bm2 = self.clone();
 			let background = self.system.background.clone();
@@ -141,6 +156,7 @@ impl BlockManager {
 		}
 	}
 
+	/// Write a block to disk
 	pub async fn write_block(&self, hash: &Hash, data: &[u8]) -> Result<Message, Error> {
 		let _lock = self.data_dir_lock.lock().await;
 
@@ -159,6 +175,7 @@ impl BlockManager {
 		Ok(Message::Ok)
 	}
 
+	/// Read block from disk, verifying it's integrity
 	pub async fn read_block(&self, hash: &Hash) -> Result<Message, Error> {
 		let path = self.block_path(hash);
 
@@ -190,6 +207,7 @@ impl BlockManager {
 		Ok(Message::PutBlock(PutBlockMessage { hash: *hash, data }))
 	}
 
+	/// Check if this node should have a block, but don't actually have it
 	pub async fn need_block(&self, hash: &Hash) -> Result<bool, Error> {
 		let needed = self
 			.rc
@@ -217,6 +235,8 @@ impl BlockManager {
 		path
 	}
 
+	/// 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| {
 			let old_v = old.map(u64_from_be_bytes).unwrap_or(0);
@@ -229,6 +249,8 @@ impl BlockManager {
 		Ok(())
 	}
 
+	/// Decrement the number of time a block is used
+	// when counter reach 0, it seems not put to resync which I assume put it to gc?
 	pub fn block_decref(&self, hash: &Hash) -> Result<(), Error> {
 		let new_rc = self.rc.update_and_fetch(&hash, |old| {
 			let old_v = old.map(u64_from_be_bytes).unwrap_or(0);
@@ -388,6 +410,7 @@ impl BlockManager {
 		Ok(())
 	}
 
+	/// Ask nodes that might have a block for it
 	pub async fn rpc_get_block(&self, hash: &Hash) -> Result<Vec<u8>, Error> {
 		let who = self.replication.read_nodes(&hash);
 		let resps = self
@@ -412,6 +435,7 @@ impl BlockManager {
 		)))
 	}
 
+	/// 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);
 		self.rpc_client
@@ -498,6 +522,7 @@ impl BlockManager {
 		.boxed()
 	}
 
+	/// Get lenght of resync queue
 	pub fn resync_queue_len(&self) -> usize {
 		self.resync_queue.len()
 	}