fix(sync): avoid unnecessary block hash fetching during block sync

chain/chain/src/chain.rs

@@ -15,8 +15,7 @@ use crate::lightclient::get_epoch_block_producers_view;
 use crate::store::{ChainStore, ChainStoreAccess, ChainStoreUpdate, GCMode};
 use crate::types::{
     AcceptedBlock, ApplyTransactionResult, Block, BlockEconomicsConfig, BlockHeader,
-    BlockHeaderInfo, BlockStatus, BlockSyncResponse, ChainGenesis, Provenance, ReceiptList,
-    RuntimeAdapter,
+    BlockHeaderInfo, BlockStatus, ChainGenesis, Provenance, ReceiptList, RuntimeAdapter,
 };
 use crate::validate::{
     validate_challenge, validate_chunk_proofs, validate_chunk_with_chunk_extra,
@@ -827,57 +826,8 @@ impl Chain {
         chain_update.commit()
     }
 
-    /// Check if state download is required, otherwise return hashes of blocks to fetch.
-    /// Hashes are sorted increasingly by height.
-    pub fn check_state_needed(
-        &mut self,
-        block_fetch_horizon: BlockHeightDelta,
-        force_block_sync: bool,
-    ) -> Result<BlockSyncResponse, Error> {
-        let block_head = self.head()?;
-        let header_head = self.header_head()?;
-        let mut hashes = vec![];
-
-        // If latest block is up to date return early.
-        // No state download is required, neither any blocks need to be fetched.
-        if block_head.height >= header_head.height {
-            return Ok(BlockSyncResponse::None);
-        }
-
-        let next_epoch_id =
-            self.get_block_header(&block_head.last_block_hash)?.next_epoch_id().clone();
-
-        // Don't run State Sync if header head is not more than one epoch ahead.
-        if block_head.epoch_id != header_head.epoch_id && next_epoch_id != header_head.epoch_id {
-            if block_head.height < header_head.height.saturating_sub(block_fetch_horizon)
-                && !force_block_sync
-            {
-                // Epochs are different and we are too far from horizon, State Sync is needed
-                return Ok(BlockSyncResponse::StateNeeded);
-            }
-        }
-
-        // Find hashes of blocks to sync
-        let mut current = self.get_block_header(&header_head.last_block_hash).map(|h| h.clone());
-        while let Ok(header) = current {
-            if header.height() <= block_head.height {
-                if self.is_on_current_chain(&header).is_ok() {
-                    break;
-                }
-            }
-
-            hashes.push(*header.hash());
-            current = self.get_previous_header(&header).map(|h| h.clone());
-        }
-
-        // Sort hashes by height
-        hashes.reverse();
-
-        Ok(BlockSyncResponse::BlocksNeeded(hashes))
-    }
-
     /// Returns if given block header is on the current chain.
-    fn is_on_current_chain(&mut self, header: &BlockHeader) -> Result<(), Error> {
+    pub fn is_on_current_chain(&mut self, header: &BlockHeader) -> Result<(), Error> {
         let chain_header = self.get_header_by_height(header.height())?;
         if chain_header.hash() == header.hash() {
             Ok(())

chain/chain/src/types.rs

@@ -584,17 +584,6 @@ pub struct LatestKnown {
     pub seen: u64,
 }
 
-/// When running block sync response to know if the node needs to sync state,
-/// or the hashes from the blocks that are needed.
-pub enum BlockSyncResponse {
-    /// State is needed before we start fetching recent blocks.
-    StateNeeded,
-    /// We are up to date with state, list of block hashes that need to be fetched.
-    BlocksNeeded(Vec<CryptoHash>),
-    /// We are up to date, nothing is required.
-    None,
-}
-
 #[cfg(test)]
 mod tests {
     use chrono::Utc;

chain/client/Cargo.toml

@@ -22,6 +22,7 @@ lazy_static = "1.4"
 borsh = "0.7.1"
 reed-solomon-erasure = "4"
 num-rational = "0.2.4"
+linked-hash-map = "0.5.3"
 
 near-crypto = { path = "../../core/crypto" }
 near-primitives = { path = "../../core/primitives" }