Persist light client bootstrap

beacon_node/beacon_chain/src/beacon_chain.rs

@@ -6789,32 +6789,18 @@ impl<T: BeaconChainTypes> BeaconChain<T> {
         &self,
         block_root: &Hash256,
     ) -> Result<Option<(LightClientBootstrap<T::EthSpec>, ForkName)>, Error> {
-        let Some(block) = self.get_blinded_block(block_root)? else {
-            return Ok(None);
-        };
-
-        let (state_root, slot) = (block.state_root(), block.slot());
-
-        let Some(mut state) = self.get_state(&state_root, Some(slot))? else {
-            return Ok(None);
-        };
+        let head_state = &self.head().snapshot.beacon_state;
+        let finalized_period = head_state
+            .finalized_checkpoint()
+            .epoch
+            .sync_committee_period(&self.spec)?;
 
-        let fork_name = state
-            .fork_name(&self.spec)
-            .map_err(Error::InconsistentFork)?;
-
-        match fork_name {
-            ForkName::Altair
-            | ForkName::Bellatrix
-            | ForkName::Capella
-            | ForkName::Deneb
-            | ForkName::Electra => {
-                LightClientBootstrap::from_beacon_state(&mut state, &block, &self.spec)
-                    .map(|bootstrap| Some((bootstrap, fork_name)))
-                    .map_err(Error::LightClientError)
-            }
-            ForkName::Base => Err(Error::UnsupportedFork),
-        }
+        self.light_client_server_cache.get_light_client_bootstrap(
+            &self.store,
+            block_root,
+            finalized_period,
+            &self.spec,
+        )
     }
 
     pub fn metrics(&self) -> BeaconChainMetrics {

beacon_node/beacon_chain/src/errors.rs

@@ -217,7 +217,8 @@ pub enum BeaconChainError {
     ProposerHeadForkChoiceError(fork_choice::Error<proto_array::Error>),
     UnableToPublish,
     AvailabilityCheckError(AvailabilityCheckError),
-    LightClientError(LightClientError),
+    LightClientUpdateError(LightClientUpdateError),
+    LightClientBootstrapError(String),
     UnsupportedFork,
     MilhouseError(MilhouseError),
     AttestationError(AttestationError),
@@ -250,7 +251,7 @@ easy_from_to!(BlockReplayError, BeaconChainError);
 easy_from_to!(InconsistentFork, BeaconChainError);
 easy_from_to!(AvailabilityCheckError, BeaconChainError);
 easy_from_to!(EpochCacheError, BeaconChainError);
-easy_from_to!(LightClientError, BeaconChainError);
+easy_from_to!(LightClientUpdateError, BeaconChainError);
 easy_from_to!(MilhouseError, BeaconChainError);
 easy_from_to!(AttestationError, BeaconChainError);
 

beacon_node/beacon_chain/src/light_client_server_cache.rs

@@ -1,5 +1,6 @@
 use crate::errors::BeaconChainError;
 use crate::{metrics, BeaconChainTypes, BeaconStore};
+use eth2::types::light_client_update::CurrentSyncCommitteeProofLen;
 use parking_lot::{Mutex, RwLock};
 use safe_arith::SafeArith;
 use slog::{debug, Logger};
@@ -10,14 +11,16 @@ use std::num::NonZeroUsize;
 use std::sync::Arc;
 use store::DBColumn;
 use store::KeyValueStore;
+use tree_hash::TreeHash;
 use types::light_client_update::{
-    FinalizedRootProofLen, NextSyncCommitteeProofLen, FINALIZED_ROOT_INDEX,
-    NEXT_SYNC_COMMITTEE_INDEX,
+    FinalizedRootProofLen, NextSyncCommitteeProofLen, CURRENT_SYNC_COMMITTEE_INDEX,
+    FINALIZED_ROOT_INDEX, NEXT_SYNC_COMMITTEE_INDEX,
 };
 use types::non_zero_usize::new_non_zero_usize;
 use types::{
-    BeaconBlockRef, BeaconState, ChainSpec, EthSpec, ForkName, Hash256, LightClientFinalityUpdate,
-    LightClientOptimisticUpdate, LightClientUpdate, Slot, SyncAggregate, SyncCommittee,
+    BeaconBlockRef, BeaconState, ChainSpec, Checkpoint, EthSpec, ForkName, Hash256,
+    LightClientBootstrap, LightClientFinalityUpdate, LightClientOptimisticUpdate,
+    LightClientUpdate, Slot, SyncAggregate, SyncCommittee,
 };
 
 /// A prev block cache miss requires to re-generate the state of the post-parent block. Items in the
@@ -28,7 +31,6 @@ const PREV_BLOCK_CACHE_SIZE: NonZeroUsize = new_non_zero_usize(32);
 /// This cache computes light client messages ahead of time, required to satisfy p2p and API
 /// requests. These messages include proofs on historical states, so on-demand computation is
 /// expensive.
-///
 pub struct LightClientServerCache<T: BeaconChainTypes> {
     /// Tracks a single global latest finality update out of all imported blocks.
     ///
@@ -41,6 +43,8 @@ pub struct LightClientServerCache<T: BeaconChainTypes> {
     latest_optimistic_update: RwLock<Option<LightClientOptimisticUpdate<T::EthSpec>>>,
     /// Caches the most recent light client update
     latest_light_client_update: RwLock<Option<LightClientUpdate<T::EthSpec>>>,
+    /// Caches the current sync committee,
+    latest_written_current_sync_committee: RwLock<Option<Arc<SyncCommittee<T::EthSpec>>>>,
     /// Caches state proofs by block root
     prev_block_cache: Mutex<lru::LruCache<Hash256, LightClientCachedData<T::EthSpec>>>,
 }
@@ -51,6 +55,7 @@ impl<T: BeaconChainTypes> LightClientServerCache<T> {
             latest_finality_update: None.into(),
             latest_optimistic_update: None.into(),
             latest_light_client_update: None.into(),
+            latest_written_current_sync_committee: None.into(),
             prev_block_cache: lru::LruCache::new(PREV_BLOCK_CACHE_SIZE).into(),
         }
     }
@@ -96,6 +101,10 @@ impl<T: BeaconChainTypes> LightClientServerCache<T> {
         let signature_slot = block_slot;
         let attested_block_root = block_parent_root;
 
+        let sync_period = block_slot
+            .epoch(T::EthSpec::slots_per_epoch())
+            .sync_committee_period(chain_spec)?;
+
         let attested_block = store.get_blinded_block(attested_block_root)?.ok_or(
             BeaconChainError::DBInconsistent(format!(
                 "Block not available {:?}",
@@ -110,6 +119,19 @@ impl<T: BeaconChainTypes> LightClientServerCache<T> {
             attested_block.slot(),
         )?;
 
+        let finalized_period = cached_parts
+            .finalized_checkpoint
+            .epoch
+            .sync_committee_period(chain_spec)?;
+
+        self.store_current_sync_committee_branch(
+            &store,
+            &cached_parts,
+            attested_block.message().tree_hash_root(),
+        )?;
+
+        self.store_sync_committee(&store, &cached_parts, sync_period, finalized_period)?;
+
         let attested_slot = attested_block.slot();
 
         let maybe_finalized_block = store.get_blinded_block(&cached_parts.finalized_block_root)?;
@@ -178,24 +200,13 @@ impl<T: BeaconChainTypes> LightClientServerCache<T> {
 
         // Spec: Full nodes SHOULD provide the best derivable LightClientUpdate (according to is_better_update)
         // for each sync committee period
-        let prev_light_client_update = match &self.latest_light_client_update.read().clone() {
-            Some(prev_light_client_update) => Some(prev_light_client_update.clone()),
-            None => self.get_light_client_update(&store, sync_period, chain_spec)?,
-        };
+        let prev_light_client_update =
+            self.get_light_client_update(&store, sync_period, chain_spec)?;
 
         let should_persist_light_client_update =
             if let Some(prev_light_client_update) = prev_light_client_update {
-                let prev_sync_period = prev_light_client_update
-                    .signature_slot()
-                    .epoch(T::EthSpec::slots_per_epoch())
-                    .sync_committee_period(chain_spec)?;
-
-                if sync_period != prev_sync_period {
-                    true
-                } else {
-                    prev_light_client_update
-                        .is_better_light_client_update(&new_light_client_update, chain_spec)?
-                }
+                prev_light_client_update
+                    .is_better_light_client_update(&new_light_client_update, chain_spec)?
             } else {
                 true
             };
@@ -207,7 +218,52 @@ impl<T: BeaconChainTypes> LightClientServerCache<T> {
         Ok(())
     }
 
-    fn store_light_client_update(
+    fn store_current_sync_committee_branch(
+        &self,
+        store: &BeaconStore<T>,
+        cached_parts: &LightClientCachedData<T::EthSpec>,
+        block_root: Hash256,
+    ) -> Result<(), BeaconChainError> {
+        let column = DBColumn::SyncCommitteeBranch;
+        store.hot_db.put_bytes(
+            column.into(),
+            &block_root.as_ssz_bytes(),
+            &cached_parts.current_sync_committee_branch.as_ssz_bytes(),
+        )?;
+        Ok(())
+    }
+
+    fn store_sync_committee(
+        &self,
+        store: &BeaconStore<T>,
+        cached_parts: &LightClientCachedData<T::EthSpec>,
+        sync_committee_period: u64,
+        finalized_period: u64,
+    ) -> Result<(), BeaconChainError> {
+        if let Some(latest_sync_committee) =
+            self.latest_written_current_sync_committee.read().clone()
+        {
+            if latest_sync_committee == cached_parts.current_sync_committee {
+                return Ok(());
+            }
+        };
+
+        let column = DBColumn::SyncCommittee;
+
+        if finalized_period >= sync_committee_period - 1 {
+            store.hot_db.put_bytes(
+                column.into(),
+                &sync_committee_period.to_le_bytes(),
+                &cached_parts.current_sync_committee.as_ssz_bytes(),
+            )?;
+            *self.latest_written_current_sync_committee.write() =
+                Some(cached_parts.current_sync_committee.clone());
+        }
+
+        Ok(())
+    }
+
+    pub fn store_light_client_update(
         &self,
         store: &BeaconStore<T>,
         sync_committee_period: u64,
@@ -226,9 +282,11 @@ impl<T: BeaconChainTypes> LightClientServerCache<T> {
         Ok(())
     }
 
-    // Used to fetch the most recently persisted "best" light client update.
-    // Should not be used outside the light client server, as it also caches the fetched
-    // light client update.
+    /// Used to fetch the most recently persisted light client update for the given `sync_committee_period`.
+    /// It first checks the `latest_light_client_update` cache before querying the db.
+    ///
+    /// Note: Should not be used outside the light client server, as it also caches the fetched
+    /// light client update.
     fn get_light_client_update(
         &self,
         store: &BeaconStore<T>,
@@ -340,6 +398,111 @@ impl<T: BeaconChainTypes> LightClientServerCache<T> {
     pub fn get_latest_optimistic_update(&self) -> Option<LightClientOptimisticUpdate<T::EthSpec>> {
         self.latest_optimistic_update.read().clone()
     }
+
+    /// Fetches a `sync_committee_branch` for a given `block_root`
+    ///
+    /// Note:
+    pub fn get_sync_committee_branch(
+        &self,
+        store: &BeaconStore<T>,
+        block_root: &Hash256,
+    ) -> Result<Option<FixedVector<Hash256, CurrentSyncCommitteeProofLen>>, BeaconChainError> {
+        let column = DBColumn::SyncCommitteeBranch;
+
+        if let Some(bytes) = store
+            .hot_db
+            .get_bytes(column.into(), &block_root.as_ssz_bytes())?
+        {
+            let sync_committee_branch: FixedVector<Hash256, CurrentSyncCommitteeProofLen> =
+                FixedVector::from_ssz_bytes(&bytes)
+                    .map_err(store::errors::Error::SszDecodeError)?;
+
+            return Ok(Some(sync_committee_branch));
+        }
+
+        Ok(None)
+    }
+
+    pub fn get_sync_committee(
+        &self,
+        store: &BeaconStore<T>,
+        sync_committee_period: u64,
+    ) -> Result<Option<SyncCommittee<T::EthSpec>>, BeaconChainError> {
+        let column = DBColumn::SyncCommittee;
+
+        if let Some(bytes) = store
+            .hot_db
+            .get_bytes(column.into(), &sync_committee_period.as_ssz_bytes())?
+        {
+            let sync_committee: SyncCommittee<T::EthSpec> =
+                SyncCommittee::from_ssz_bytes(&bytes)
+                    .map_err(store::errors::Error::SszDecodeError)?;
+            return Ok(Some(sync_committee));
+        }
+
+        Ok(None)
+    }
+
+    /// Fetches a light client bootstrap for a given finalized checkpoint `block_root`. We eagerly persist
+    /// `sync_committee_branch and `sync_committee` to allow for a more efficient bootstrap construction.
+    ///
+    /// Note: It should be the case that a `sync_committee_branch` and `sync_committee` exist in the db
+    /// for a finalized checkpoint block root. However, we currently have no backfill mechanism for these values.
+    /// Therefore, `sync_committee_branch` and `sync_committee` are only persisted while a node is synced.
+    #[allow(clippy::type_complexity)]
+    pub fn get_light_client_bootstrap(
+        &self,
+        store: &BeaconStore<T>,
+        block_root: &Hash256,
+        finalized_period: u64,
+        chain_spec: &ChainSpec,
+    ) -> Result<Option<(LightClientBootstrap<T::EthSpec>, ForkName)>, BeaconChainError> {
+        let Some(block) = store.get_blinded_block(block_root)? else {
+            return Err(BeaconChainError::LightClientBootstrapError(format!(
+                "Block root {block_root} not found"
+            )));
+        };
+
+        let (_, slot) = (block.state_root(), block.slot());
+
+        let fork_name = chain_spec.fork_name_at_slot::<T::EthSpec>(slot);
+
+        let sync_committee_period = block
+            .slot()
+            .epoch(T::EthSpec::slots_per_epoch())
+            .sync_committee_period(chain_spec)?;
+
+        let Some(current_sync_committee_branch) =
+            self.get_sync_committee_branch(store, block_root)?
+        else {
+            return Err(BeaconChainError::LightClientBootstrapError(format!(
+                "Sync committee branch for block root {:?} not found",
+                block_root
+            )));
+        };
+
+        if sync_committee_period > finalized_period {
+            return Err(BeaconChainError::LightClientBootstrapError(
+                format!("The blocks sync committee period {sync_committee_period} is greater than the current finalized period {finalized_period}"),
+            ));
+        }
+
+        let Some(current_sync_committee) = self.get_sync_committee(store, sync_committee_period)?
+        else {
+            return Err(BeaconChainError::LightClientBootstrapError(format!(
+                "Sync committee for block root {block_root} not found"
+            )));
+        };
+
+        let light_client_bootstrap = LightClientBootstrap::new(
+            &block,
+            Arc::new(current_sync_committee),
+            current_sync_committee_branch,
+            chain_spec,
+        )?;
+
+        Ok(Some((light_client_bootstrap, fork_name)))
+    }
 }
 
 impl<T: BeaconChainTypes> Default for LightClientServerCache<T> {
@@ -350,23 +513,32 @@ impl<T: BeaconChainTypes> Default for LightClientServerCache<T> {
 
 type FinalityBranch = FixedVector<Hash256, FinalizedRootProofLen>;
 type NextSyncCommitteeBranch = FixedVector<Hash256, NextSyncCommitteeProofLen>;
+type CurrentSyncCommitteeBranch = FixedVector<Hash256, CurrentSyncCommitteeProofLen>;
 
 #[derive(Clone)]
 struct LightClientCachedData<E: EthSpec> {
+    finalized_checkpoint: Checkpoint,
     finality_branch: FinalityBranch,
     next_sync_committee_branch: NextSyncCommitteeBranch,
+    current_sync_committee_branch: CurrentSyncCommitteeBranch,
     next_sync_committee: Arc<SyncCommittee<E>>,
+    current_sync_committee: Arc<SyncCommittee<E>>,
     finalized_block_root: Hash256,
 }
 
 impl<E: EthSpec> LightClientCachedData<E> {
     fn from_state(state: &mut BeaconState<E>) -> Result<Self, BeaconChainError> {
         Ok(Self {
+            finalized_checkpoint: state.finalized_checkpoint(),
             finality_branch: state.compute_merkle_proof(FINALIZED_ROOT_INDEX)?.into(),
             next_sync_committee: state.next_sync_committee()?.clone(),
+            current_sync_committee: state.current_sync_committee()?.clone(),
             next_sync_committee_branch: state
                 .compute_merkle_proof(NEXT_SYNC_COMMITTEE_INDEX)?
                 .into(),
+            current_sync_committee_branch: state
+                .compute_merkle_proof(CURRENT_SYNC_COMMITTEE_INDEX)?
+                .into(),
             finalized_block_root: state.finalized_checkpoint().root,
         })
     }

beacon_node/beacon_chain/src/migrate.rs

@@ -676,6 +676,7 @@ impl<E: EthSpec, Hot: ItemStore<E>, Cold: ItemStore<E>> BackgroundMigrator<E, Ho
                     StoreOp::DeleteBlock(block_root),
                     StoreOp::DeleteExecutionPayload(block_root),
                     StoreOp::DeleteBlobs(block_root),
+                    StoreOp::DeleteSyncCommitteeBranch(block_root),
                 ]
             })
             .chain(