Rename total_score to nonce in sync message

remagpie · remagpie · commit f03b60c1286f · 2019-11-18T13:47:04.000+09:00
When CodeChain is synchronized by snapshot sync, `total_score`
doesn't mean the accumulated score from the genesis block.
To handle this, the sync extension is updated to not rely on
`total_score` for deciding whether a peer is leading or not, and
use the value only as a monotonically increasing nonce.
diff --git a/core/src/lib.rs b/core/src/lib.rs
@@ -99,4 +99,4 @@ pub use crate::service::ClientService;
 pub use crate::transaction::{
     LocalizedTransaction, PendingSignedTransactions, SignedTransaction, UnverifiedTransaction,
 };
-pub use crate::types::{BlockId, TransactionId};
+pub use crate::types::{BlockId, BlockStatus, TransactionId};
diff --git a/spec/Block-Synchronization-Extension.md b/spec/Block-Synchronization-Extension.md
@@ -19,13 +19,14 @@ Message :=
 ### Status
 
 ```
-Status(total_score, best_hash, genesis_hash)
+Status(nonce, best_hash, genesis_hash)
 ```
 
 Send current chain status to peer.
 
 * Identifier: 0x01
-* Restriction: None
+* Restriction:
+  * `nonce` SHOULD be monotonically increasing every time the message is sent.
 
 ## Request messages
 
diff --git a/sync/src/block/downloader/header.rs b/sync/src/block/downloader/header.rs
@@ -20,7 +20,7 @@ use std::sync::Arc;
 use std::time::Instant;
 
 use ccore::encoded::Header;
-use ccore::{BlockChainClient, BlockId};
+use ccore::{BlockChainClient, BlockId, BlockStatus};
 use ctypes::BlockHash;
 use primitives::U256;
 
@@ -31,65 +31,46 @@ const MAX_HEADER_QUEUE_LENGTH: usize = 1024;
 const MAX_RETRY: usize = 3;
 const MAX_WAIT: u64 = 15;
 
-#[derive(Clone)]
-struct Pivot {
-    hash: BlockHash,
-    total_score: U256,
-}
-
 #[derive(Clone)]
 pub struct HeaderDownloader {
     // NOTE: Use this member as minimum as possible.
     client: Arc<dyn BlockChainClient>,
 
-    total_score: U256,
+    nonce: U256,
     best_hash: BlockHash,
-
-    pivot: Pivot,
+    pivot: BlockHash,
     request_time: Option<Instant>,
     downloaded: HashMap<BlockHash, Header>,
     queued: HashMap<BlockHash, Header>,
     trial: usize,
 }
 
 impl HeaderDownloader {
-    pub fn total_score(&self) -> U256 {
-        self.total_score
-    }
-
-    pub fn new(client: Arc<dyn BlockChainClient>, total_score: U256, best_hash: BlockHash) -> Self {
+    pub fn new(client: Arc<dyn BlockChainClient>, nonce: U256, best_hash: BlockHash) -> Self {
         let best_header_hash = client.best_block_header().hash();
-        let best_score = client.block_total_score(&BlockId::Latest).expect("Best block always exist");
 
         Self {
             client,
 
-            total_score,
+            nonce,
             best_hash,
-
-            pivot: Pivot {
-                hash: best_header_hash,
-                total_score: best_score,
-            },
+            pivot: best_header_hash,
             request_time: None,
             downloaded: HashMap::new(),
             queued: HashMap::new(),
             trial: 0,
         }
     }
 
-    pub fn update(&mut self, total_score: U256, best_hash: BlockHash) -> bool {
-        match self.total_score.cmp(&total_score) {
+    pub fn update(&mut self, nonce: U256, best_hash: BlockHash) -> bool {
+        match self.nonce.cmp(&nonce) {
             Ordering::Equal => true,
             Ordering::Less => {
-                self.total_score = total_score;
+                self.nonce = nonce;
                 self.best_hash = best_hash;
 
                 if self.client.block_header(&BlockId::Hash(best_hash)).is_some() {
-                    self.pivot = Pivot {
-                        hash: best_hash,
-                        total_score,
-                    }
+                    self.pivot = best_hash;
                 }
                 true
             }
@@ -108,25 +89,28 @@ impl HeaderDownloader {
     /// Find header from queued headers, downloaded cache and then from blockchain
     /// Panics if header dosn't exist
     fn pivot_header(&self) -> Header {
-        match self.queued.get(&self.pivot.hash) {
+        match self.queued.get(&self.pivot) {
             Some(header) => header.clone(),
-            None => match self.downloaded.get(&self.pivot.hash) {
+            None => match self.downloaded.get(&self.pivot) {
                 Some(header) => header.clone(),
-                None => self.client.block_header(&BlockId::Hash(self.pivot.hash)).unwrap(),
+                None => self.client.block_header(&BlockId::Hash(self.pivot)).unwrap(),
             },
         }
     }
 
-    pub fn pivot_score(&self) -> U256 {
-        self.pivot.total_score
-    }
-
     pub fn is_idle(&self) -> bool {
-        let can_request = self.request_time.is_none() && self.total_score > self.pivot.total_score;
+        let can_request = self.request_time.is_none() && self.best_hash != self.pivot;
 
         self.is_valid() && (can_request || self.is_expired())
     }
 
+    pub fn is_lagging(&self) -> bool {
+        let peer_status = self.client.block_status(&BlockId::Hash(self.best_hash));
+        let best_hash = self.client.block_hash(&BlockId::Latest).expect("Best hash always exists");
+
+        peer_status == BlockStatus::InChain && self.best_hash != best_hash
+    }
+
     pub fn create_request(&mut self) -> Option<RequestMessage> {
         if !self.is_idle() {
             return None
@@ -154,37 +138,30 @@ impl HeaderDownloader {
         let pivot_header = self.pivot_header();
 
         // This happens when best_hash is imported by other peer.
-        if self.best_hash == self.pivot.hash {
+        if self.best_hash == self.pivot {
             ctrace!(SYNC, "Ignore received headers, pivot already reached the best hash");
-        } else if first_header_hash == self.pivot.hash {
+        } else if first_header_hash == self.pivot {
             for header in headers.iter() {
                 self.downloaded.insert(header.hash(), header.clone());
             }
 
             // FIXME: skip known headers
-            let new_scores = headers[1..].iter().fold(U256::zero(), |acc, header| acc + header.score());
-            self.pivot = Pivot {
-                hash: headers.last().expect("Last downloaded header must exist").hash(),
-                total_score: self.pivot.total_score + new_scores,
-            }
+            self.pivot = headers.last().expect("Last downloaded header must exist").hash();
         } else if first_header_number < pivot_header.number() {
             ctrace!(
                 SYNC,
                 "Ignore received headers, pivot is already updated since headers are imported by other peers"
             );
         } else if first_header_number == pivot_header.number() {
             if pivot_header.number() != 0 {
-                self.pivot = Pivot {
-                    hash: pivot_header.parent_hash(),
-                    total_score: self.pivot.total_score - pivot_header.score(),
-                }
+                self.pivot = pivot_header.parent_hash();
             }
         } else {
             cerror!(
                 SYNC,
-                "Invalid header update state. best_hash: {}, self.pivot.hash: {}, first_header_hash: {}",
+                "Invalid header update state. best_hash: {}, self.pivot: {}, first_header_hash: {}",
                 self.best_hash,
-                self.pivot.hash,
+                self.pivot,
                 first_header_hash
             );
         }
@@ -203,10 +180,7 @@ impl HeaderDownloader {
             self.downloaded.remove(&hash);
 
             if self.best_hash == hash {
-                self.pivot = Pivot {
-                    hash,
-                    total_score: self.total_score,
-                }
+                self.pivot = hash;
             }
         }
         self.queued.shrink_to_fit();
diff --git a/sync/src/block/extension.rs b/sync/src/block/extension.rs
@@ -76,6 +76,7 @@ pub struct Extension {
     client: Arc<Client>,
     api: Box<dyn Api>,
     last_request: u64,
+    nonce: u64,
 }
 
 impl Extension {
@@ -126,6 +127,7 @@ impl Extension {
             client,
             api,
             last_request: Default::default(),
+            nonce: Default::default(),
         }
     }
 
@@ -243,14 +245,15 @@ impl NetworkExtension<Event> for Extension {
             id,
             Arc::new(
                 Message::Status {
-                    total_score: chain_info.best_proposal_score,
+                    nonce: U256::from(self.nonce),
                     best_hash: chain_info.best_proposal_block_hash,
                     genesis_hash: chain_info.genesis_hash,
                 }
                 .rlp_bytes()
                 .into_vec(),
             ),
         );
+        self.nonce += 1;
         let t = self.connected_nodes.insert(*id);
         debug_assert!(t, "{} is already added to peer list", id);
 
@@ -299,10 +302,10 @@ impl NetworkExtension<Event> for Extension {
         if let Ok(received_message) = UntrustedRlp::new(data).as_val() {
             match received_message {
                 Message::Status {
-                    total_score,
+                    nonce,
                     best_hash,
                     genesis_hash,
-                } => self.on_peer_status(id, total_score, best_hash, genesis_hash),
+                } => self.on_peer_status(id, nonce, best_hash, genesis_hash),
                 Message::Request(request_id, request) => self.on_peer_request(id, request_id, request),
                 Message::Response(request_id, response) => self.on_peer_response(id, request_id, response),
             }
@@ -328,7 +331,6 @@ impl NetworkExtension<Event> for Extension {
                     }
                     State::SnapshotChunk(..) => unimplemented!(),
                     State::Full => {
-                        let best_proposal_score = self.client.chain_info().best_proposal_score;
                         for id in &peer_ids {
                             let request =
                                 self.header_downloaders.get_mut(id).and_then(HeaderDownloader::create_request);
@@ -339,13 +341,7 @@ impl NetworkExtension<Event> for Extension {
                         }
 
                         for id in peer_ids {
-                            let peer_score = if let Some(peer) = self.header_downloaders.get(&id) {
-                                peer.total_score()
-                            } else {
-                                U256::zero()
-                            };
-
-                            if peer_score > best_proposal_score {
+                            if self.header_downloaders.get(&id).map_or(false, |d| !d.is_lagging()) {
                                 self.send_body_request(&id);
                             }
                         }
@@ -501,20 +497,21 @@ impl Extension {
                 id,
                 Arc::new(
                     Message::Status {
-                        total_score: chain_info.best_proposal_score,
+                        nonce: U256::from(self.nonce),
                         best_hash: chain_info.best_proposal_block_hash,
                         genesis_hash: chain_info.genesis_hash,
                     }
                     .rlp_bytes()
                     .into_vec(),
                 ),
             );
+            self.nonce += 1;
         }
     }
 }
 
 impl Extension {
-    fn on_peer_status(&mut self, from: &NodeId, total_score: U256, best_hash: BlockHash, genesis_hash: BlockHash) {
+    fn on_peer_status(&mut self, from: &NodeId, nonce: U256, best_hash: BlockHash, genesis_hash: BlockHash) {
         // Validity check
         if genesis_hash != self.client.chain_info().genesis_hash {
             cinfo!(SYNC, "Genesis hash mismatch with peer {}", from);
@@ -523,17 +520,17 @@ impl Extension {
 
         match self.header_downloaders.entry(*from) {
             Entry::Occupied(mut peer) => {
-                if !peer.get_mut().update(total_score, best_hash) {
+                if !peer.get_mut().update(nonce, best_hash) {
                     // FIXME: It should be an error level if the consensus is PoW.
                     cdebug!(SYNC, "Peer #{} status updated but score is less than before", from);
                     return
                 }
             }
             Entry::Vacant(e) => {
-                e.insert(HeaderDownloader::new(self.client.clone(), total_score, best_hash));
+                e.insert(HeaderDownloader::new(self.client.clone(), nonce, best_hash));
             }
         }
-        cinfo!(SYNC, "Peer #{} status update: total_score: {}, best_hash: {}", from, total_score, best_hash);
+        cinfo!(SYNC, "Peer #{} status update: nonce: {}, best_hash: {}", from, nonce, best_hash);
     }
 
     fn on_peer_request(&self, from: &NodeId, id: u64, request: RequestMessage) {
@@ -759,14 +756,12 @@ impl Extension {
             }
             State::SnapshotChunk(..) => {}
             State::Full => {
-                let (mut completed, pivot_score_changed) = if let Some(peer) = self.header_downloaders.get_mut(from) {
-                    let before_pivot_score = peer.pivot_score();
+                let (mut completed, is_lagging) = if let Some(peer) = self.header_downloaders.get_mut(from) {
                     let encoded: Vec<_> = headers.iter().map(|h| EncodedHeader::new(h.rlp_bytes().to_vec())).collect();
                     peer.import_headers(&encoded);
-                    let after_pivot_score = peer.pivot_score();
-                    (peer.downloaded(), before_pivot_score != after_pivot_score)
+                    (peer.downloaded(), peer.is_lagging())
                 } else {
-                    (Vec::new(), false)
+                    (Vec::new(), true)
                 };
                 completed.sort_unstable_by_key(EncodedHeader::number);
 
@@ -792,7 +787,7 @@ impl Extension {
                     peer.mark_as_imported(exists);
                     peer.create_request()
                 });
-                if pivot_score_changed {
+                if !is_lagging {
                     if let Some(request) = request {
                         self.send_header_request(from, request);
                     }
@@ -834,18 +829,11 @@ impl Extension {
             }
         }
 
-        let total_score = self.client.chain_info().best_proposal_score;
         let mut peer_ids: Vec<_> = self.header_downloaders.keys().cloned().collect();
         peer_ids.shuffle(&mut thread_rng());
 
         for id in peer_ids {
-            let peer_score = if let Some(peer) = self.header_downloaders.get(&id) {
-                peer.total_score()
-            } else {
-                U256::zero()
-            };
-
-            if peer_score > total_score {
+            if self.header_downloaders.get(&id).map_or(false, |d| !d.is_lagging()) {
                 self.send_body_request(&id);
             }
         }
diff --git a/sync/src/block/message/mod.rs b/sync/src/block/message/mod.rs
diff --git a/test/src/helper/mock/blockSyncMessage.ts b/test/src/helper/mock/blockSyncMessage.ts
