feat: stub for instant resharding state root creation

chain/chain/src/chain.rs

@@ -92,13 +92,15 @@ use near_primitives::views::{
 };
 use near_store::config::StateSnapshotType;
 use near_store::flat::{store_helper, FlatStorageReadyStatus, FlatStorageStatus};
-use near_store::get_genesis_state_roots;
+use near_store::trie::mem::resharding::RetainMode;
 use near_store::DBCol;
+use near_store::{get_genesis_state_roots, PartialStorage};
 use node_runtime::bootstrap_congestion_info;
 use rayon::iter::{IntoParallelIterator, ParallelIterator};
 use std::collections::{BTreeMap, HashMap, HashSet};
 use std::fmt::{Debug, Formatter};
 use std::num::NonZeroUsize;
+use std::str::FromStr;
 use std::sync::Arc;
 use time::ext::InstantExt as _;
 use tracing::{debug, debug_span, error, info, warn, Span};
@@ -1847,6 +1849,77 @@ impl Chain {
         });
     }
 
+    /// If shard layout changes after the given block, creates temporary
+    /// memtries for new shards to be able to process them in the next epoch.
+    /// Note this doesn't complete resharding, proper memtries are to be
+    /// created later.
+    fn process_instant_resharding_storage_update(
+        &mut self,
+        block: &Block,
+        shard_uid: ShardUId,
+    ) -> Result<(), Error> {
+        let block_hash = block.hash();
+        let block_height = block.header().height();
+        let prev_hash = block.header().prev_hash();
+        if !self.epoch_manager.will_shard_layout_change(prev_hash)? {
+            return Ok(());
+        }
+
+        let next_epoch_id = self.epoch_manager.get_next_epoch_id_from_prev_block(prev_hash)?;
+        let next_shard_layout = self.epoch_manager.get_shard_layout(&next_epoch_id)?;
+        let children_shard_uids =
+            next_shard_layout.get_children_shards_uids(shard_uid.shard_id()).unwrap();
+
+        // Hack to ensure this logic is not applied before ReshardingV3.
+        // TODO(#12019): proper logic.
+        if next_shard_layout.version() < 3 || children_shard_uids.len() == 1 {
+            return Ok(());
+        }
+        assert_eq!(children_shard_uids.len(), 2);
+
+        let chunk_extra = self.get_chunk_extra(block_hash, &shard_uid)?;
+        let tries = self.runtime_adapter.get_tries();
+        let Some(mem_tries) = tries.get_mem_tries(shard_uid) else {
+            // TODO(#12019): what if node doesn't have memtrie? just pause
+            // processing?
+            return Ok(());
+        };
+        let boundary_account = AccountId::from_str("boundary.near").unwrap();
+
+        // TODO(#12019): leave only tracked shards.
+        for (new_shard_uid, retain_mode) in [
+            (children_shard_uids[0], RetainMode::Left),
+            (children_shard_uids[1], RetainMode::Right),
+        ] {
+            let mut mem_tries = mem_tries.write().unwrap();
+            let mut mem_trie_update = mem_tries.update(*chunk_extra.state_root(), false)?;
+
+            let (trie_changes, partial_state) =
+                mem_trie_update.cut(boundary_account.clone(), retain_mode);
+            let partial_storage = PartialStorage { nodes: partial_state };
+            let mem_changes = trie_changes.mem_trie_changes.as_ref().unwrap();
+            let new_state_root = mem_tries.apply_memtrie_changes(block_height, mem_changes);
+            let mut new_chunk_extra = ChunkExtra::clone(&chunk_extra);
+            *new_chunk_extra.state_root_mut() = new_state_root;
+
+            let mut chain_store_update = ChainStoreUpdate::new(&mut self.chain_store);
+            chain_store_update.save_chunk_extra(block_hash, &new_shard_uid, new_chunk_extra);
+            chain_store_update.save_state_transition_data(
+                *block_hash,
+                new_shard_uid.shard_id(),
+                Some(partial_storage),
+                CryptoHash::default(),
+            );
+            chain_store_update.commit()?;
+
+            let mut store_update = self.chain_store.store().store_update();
+            tries.apply_insertions(&trie_changes, new_shard_uid, &mut store_update);
+            store_update.commit()?;
+        }
+
+        Ok(())
+    }
+
     #[tracing::instrument(level = "debug", target = "chain", "postprocess_block_only", skip_all)]
     fn postprocess_block_only(
         &mut self,
@@ -1867,6 +1940,7 @@ impl Chain {
             should_save_state_transition_data,
         )?;
         chain_update.commit()?;
+
         Ok(new_head)
     }
 
@@ -1936,30 +2010,33 @@ impl Chain {
                 true,
             );
             let care_about_shard_this_or_next_epoch = care_about_shard || will_care_about_shard;
+            let shard_uid = self.epoch_manager.shard_id_to_uid(shard_id, &epoch_id).unwrap();
             if care_about_shard_this_or_next_epoch {
-                let shard_uid = self.epoch_manager.shard_id_to_uid(shard_id, &epoch_id).unwrap();
                 shards_cares_this_or_next_epoch.push(shard_uid);
             }
 
-            // Update flat storage head to be the last final block. Note that this update happens
-            // in a separate db transaction from the update from block processing. This is intentional
-            // because flat_storage need to be locked during the update of flat head, otherwise
-            // flat_storage is in an inconsistent state that could be accessed by the other
-            // apply chunks processes. This means, the flat head is not always the same as
-            // the last final block on chain, which is OK, because in the flat storage implementation
-            // we don't assume that.
-            let need_flat_storage_update = if is_caught_up {
-                // If we already caught up this epoch, then flat storage exists for both shards which we already track
+            let need_storage_update = if is_caught_up {
+                // If we already caught up this epoch, then storage exists for both shards which we already track
                 // and shards which will be tracked in next epoch, so we can update them.
                 care_about_shard_this_or_next_epoch
             } else {
                 // If we didn't catch up, we can update only shards tracked right now. Remaining shards will be updated
                 // during catchup of this block.
                 care_about_shard
             };
-            tracing::debug!(target: "chain", shard_id, need_flat_storage_update, "Updating flat storage");
-
-            if need_flat_storage_update {
+            tracing::debug!(target: "chain", shard_id, need_storage_update, "Updating storage");
+
+            if need_storage_update {
+                // TODO(#12019): consider adding to catchup flow.
+                self.process_instant_resharding_storage_update(&block, shard_uid)?;
+
+                // Update flat storage head to be the last final block. Note that this update happens
+                // in a separate db transaction from the update from block processing. This is intentional
+                // because flat_storage need to be locked during the update of flat head, otherwise
+                // flat_storage is in an inconsistent state that could be accessed by the other
+                // apply chunks processes. This means, the flat head is not always the same as
+                // the last final block on chain, which is OK, because in the flat storage implementation
+                // we don't assume that.
                 self.update_flat_storage_and_memtrie(&block, shard_id)?;
             }
         }

core/store/src/trie/mem/mod.rs

@@ -9,6 +9,7 @@ pub mod mem_tries;
 pub mod metrics;
 pub mod node;
 mod parallel_loader;
+pub mod resharding;
 pub mod updating;
 
 /// Check this, because in the code we conveniently assume usize is 8 bytes.