fix(sync-v2): Fix issues caused by concurrent syncing peers

hathor/p2p/sync_v2/agent.py

@@ -494,11 +494,12 @@ def start_blockchain_streaming(self,
                                    start_block: _HeightInfo,
                                    end_block: _HeightInfo) -> Deferred[StreamEnd]:
         """Request peer to start streaming blocks to us."""
-        self.log.info('requesting blocks streaming',
-                      start_block=start_block,
-                      end_block=end_block)
         self._blk_streaming_client = BlockchainStreamingClient(self, start_block, end_block)
         quantity = self._blk_streaming_client._blk_max_quantity
+        self.log.info('requesting blocks streaming',
+                      start_block=start_block,
+                      end_block=end_block,
+                      quantity=quantity)
         self.send_get_next_blocks(start_block.id, end_block.id, quantity)
         return self._blk_streaming_client.wait()
 
@@ -579,11 +580,14 @@ def find_best_common_block(self,
     @inlineCallbacks
     def on_block_complete(self, blk: Block, vertex_list: list[BaseTransaction]) -> Generator[Any, Any, None]:
         """This method is called when a block and its transactions are downloaded."""
+        # Note: Any vertex and block could have already been added by another concurrent syncing peer.
         for tx in vertex_list:
-            self.manager.on_new_tx(tx, propagate_to_peers=False, fails_silently=False)
+            if not self.tx_storage.transaction_exists(tx.hash):
+                self.manager.on_new_tx(tx, propagate_to_peers=False, fails_silently=False)
             yield deferLater(self.reactor, 0, lambda: None)
 
-        self.manager.on_new_tx(blk, propagate_to_peers=False, fails_silently=False)
+        if not self.tx_storage.transaction_exists(blk.hash):
+            self.manager.on_new_tx(blk, propagate_to_peers=False, fails_silently=False)
 
     def get_peer_block_hashes(self, heights: list[int]) -> Deferred[list[_HeightInfo]]:
         """ Returns the peer's block hashes in the given heights.

hathor/p2p/sync_v2/streamers.py

@@ -180,22 +180,14 @@ def send_next(self) -> None:
         if cur.hash == self.end_hash:
             # only send the last when not reverse
             if not self.reverse:
-                self.log.debug('send next block', blk_id=cur.hash.hex())
+                self.log.debug('send next block', height=cur.get_height(), blk_id=cur.hash.hex())
                 self.sync_agent.send_blocks(cur)
             self.sync_agent.stop_blk_streaming_server(StreamEnd.END_HASH_REACHED)
             return
 
-        if self.counter >= self.limit:
-            # only send the last when not reverse
-            if not self.reverse:
-                self.log.debug('send next block', blk_id=cur.hash.hex())
-                self.sync_agent.send_blocks(cur)
-            self.sync_agent.stop_blk_streaming_server(StreamEnd.LIMIT_EXCEEDED)
-            return
-
         self.counter += 1
 
-        self.log.debug('send next block', blk_id=cur.hash.hex())
+        self.log.debug('send next block', height=cur.get_height(), blk_id=cur.hash.hex())
         self.sync_agent.send_blocks(cur)
 
         if self.reverse:
@@ -208,6 +200,10 @@ def send_next(self) -> None:
             self.sync_agent.stop_blk_streaming_server(StreamEnd.NO_MORE_BLOCKS)
             return
 
+        if self.counter >= self.limit:
+            self.sync_agent.stop_blk_streaming_server(StreamEnd.LIMIT_EXCEEDED)
+            return
+
 
 class TransactionsStreamingServer(_StreamingServerBase):
     """Streams all transactions confirmed by the given block, from right to left (decreasing timestamp).

hathor/p2p/sync_v2/transaction_streaming_client.py

@@ -116,9 +116,9 @@ def handle_transaction(self, tx: BaseTransaction) -> None:
 
         assert tx.hash is not None
         self.log.debug('tx received', tx_id=tx.hash.hex())
-
         self._queue.append(tx)
         assert len(self._queue) <= self._tx_max_quantity
+
         if not self._is_processing:
             self.reactor.callLater(0, self.process_queue)
 
@@ -135,6 +135,7 @@ def process_queue(self) -> Generator[Any, Any, None]:
         self._is_processing = True
         try:
             tx = self._queue.popleft()
+            self.log.debug('processing tx', tx_id=tx.hash.hex())
             yield self._process_transaction(tx)
         finally:
             self._is_processing = False
@@ -160,18 +161,18 @@ def _process_transaction(self, tx: BaseTransaction) -> Generator[Any, Any, None]
             if tx.hash in self._db:
                 # This case might happen during a resume, so we just log and keep syncing.
                 self.log.debug('duplicated vertex received', tx_id=tx.hash.hex())
+                self.update_dependencies(tx)
             elif tx.hash in self._existing_deps:
                 # This case might happen if we already have the transaction from another sync.
                 self.log.debug('existing vertex received', tx_id=tx.hash.hex())
+                self.update_dependencies(tx)
             else:
                 self.log.info('unexpected vertex received', tx_id=tx.hash.hex())
                 self.fails(UnexpectedVertex(tx.hash.hex()))
             return
         self._waiting_for.remove(tx.hash)
 
-        for dep in self.get_missing_deps(tx):
-            self.log.debug('adding dependency', tx_id=tx.hash.hex(), dep=dep.hex())
-            self._waiting_for.add(dep)
+        self.update_dependencies(tx)
 
         self._db[tx.hash] = tx
 
@@ -187,15 +188,13 @@ def _process_transaction(self, tx: BaseTransaction) -> Generator[Any, Any, None]
         if self._tx_received % 100 == 0:
             self.log.debug('tx streaming in progress', txs_received=self._tx_received)
 
-    def get_missing_deps(self, tx: BaseTransaction) -> Iterator[bytes]:
-        """Return missing dependencies."""
+    def update_dependencies(self, tx: BaseTransaction) -> Iterator[bytes]:
+        """Update _existing_deps and _waiting_for with the dependencies."""
         for dep in tx.get_all_dependencies():
-            if self.tx_storage.transaction_exists(dep):
+            if self.tx_storage.transaction_exists(dep) or dep in self._db:
                 self._existing_deps.add(dep)
-                continue
-            if dep in self._db:
-                continue
-            yield dep
+            else:
+                self._waiting_for.add(dep)
 
     def handle_transactions_end(self, response_code: StreamEnd) -> None:
         """This method is called by the sync agent when a TRANSACTIONS-END message is received."""