optimize write_meta

Author: iwanbk

src/cas/fjall_store.rs

@@ -221,29 +221,28 @@ impl MetaStore for FjallStore {
         block_hash: BlockID,
         data_len: usize,
         key_has_block: bool,
-    ) -> Result<bool, MetaError> {
+    ) -> Result<(bool, Block), MetaError> {
         let blocks = self.block_partition.clone();
         let paths = self.path_partition.clone();
 
         let mut tx = self.keyspace.write_tx();
-        let should_write = match tx.get(&blocks, block_hash) {
+        let res = match tx.get(&blocks, block_hash) {
             Ok(Some(block_data)) => {
                 // Block already exists
 
+                let mut block =
+                    Block::try_from(&*block_data).expect("Only valid blocks are stored");
+
                 // if the key already has this block, the block doesn't got more references
                 // and we don't need to write it back.
                 if !key_has_block {
                     // bump refcount on the block
-                    let mut block =
-                        Block::try_from(&*block_data).expect("Only valid blocks are stored");
-
                     block.increment_refcount();
                     // write block back
                     // TODO: this could be done in an `update_and_fetch`
                     tx.insert(&blocks, block_hash, block.to_vec());
                 }
-
-                Ok(false)
+                Ok((false, block))
             }
             Ok(None) => {
                 let mut idx = 0;
@@ -267,12 +266,12 @@ impl MetaStore for FjallStore {
                 let block = Block::new(data_len, block_hash[..idx].to_vec());
 
                 tx.insert(&blocks, block_hash, block.to_vec());
-                Ok(true)
+                Ok((true, block))
             }
             Err(e) => Err(MetaError::OtherDBError(e.to_string())),
         };
         self.commit_persist(tx)?;
-        should_write
+        res
     }
 }
 

src/cas/fs.rs

@@ -243,7 +243,6 @@ impl CasFS {
             Err(_) => None,
         };
         let old_obj_meta = Arc::new(old_obj_meta);
-        let block_map = Arc::new(self.meta_store.get_block_tree()?);
 
         let (tx, rx) = unbounded();
         let mut content_hash = Md5::new();
@@ -262,11 +261,11 @@ impl CasFS {
                 self.metrics.bytes_received(bytes.len());
             }
         })
-        .zip(stream::repeat((tx, block_map, old_obj_meta)))
+        .zip(stream::repeat((tx, old_obj_meta)))
         .enumerate()
         .for_each_concurrent(
             5,
-            |(idx, (maybe_chunk, (mut tx, block_map, old_obj_meta)))| async move {
+            |(idx, (maybe_chunk, (mut tx, old_obj_meta)))| async move {
                 if let Err(e) = maybe_chunk {
                     if let Err(e) = tx
                         .send(Err(std::io::Error::new(e.kind(), e.to_string())))
@@ -290,41 +289,33 @@ impl CasFS {
                     false
                 };
 
-                let should_write = self
-                    .meta_store
-                    .write_block(block_hash, data_len, key_has_block);
+                let write_meta_result =
+                    self.meta_store
+                        .write_block(block_hash, data_len, key_has_block);
 
                 let mut pm = PendingMarker::new(self.metrics.clone());
-                match should_write {
+
+                let block = match write_meta_result {
                     Err(e) => {
                         if let Err(e) = tx.send(Err(e.into())).await {
                             error!("Could not send transaction error: {}", e);
                         }
                         return;
                     }
-                    Ok(false) => {
+                    Ok((false, _)) => {
                         pm.block_ignored();
                         if let Err(e) = tx.send(Ok((idx, block_hash))).await {
                             error!("Could not send block id: {}", e);
                         }
                         return;
                     }
-                    Ok(true) => pm.block_pending(),
-                };
-
-                // write the actual block
-                // first load the block again from the DB
-                let block = match block_map.get_block(&block_hash) {
-                    Ok(block) => block,
-                    Err(e) => {
-                        if let Err(e) = tx.send(Err(e.into())).await {
-                            pm.block_write_error();
-                            error!("Could not send db error: {}", e);
-                        }
-                        return;
+                    Ok((true, block)) => {
+                        pm.block_pending();
+                        block
                     }
                 };
 
+                // write the actual block to disk
                 let block_path = block.disk_path(self.root.clone());
                 if let Err(e) = async_fs::create_dir_all(block_path.parent().unwrap()).await {
                     if let Err(e) = tx.send(Err(e)).await {

src/cas/meta_store.rs

@@ -66,6 +66,10 @@ pub trait MetaStore: Send + Sync + Debug + 'static {
     // data_len is the length of the block data.
     // key_has_block is true if the coresponding key already has the block
     //
+    // It returns a tuple of bool and Block:
+    // - bool is true if the block is new, hence need to be written to the disk
+    // - Block is the block object
+    //
     // It should do at least the following:
     // - Check if the hash is present in the block map
     //    - if exists and key_has_block is false: increment the refcount
@@ -81,7 +85,7 @@ pub trait MetaStore: Send + Sync + Debug + 'static {
         block_hash: BlockID,
         data_len: usize,
         key_has_block: bool,
-    ) -> Result<bool, MetaError>;
+    ) -> Result<(bool, Block), MetaError>;
 }
 
 pub trait BaseMetaTree: Send + Sync {