Drop overflow cache (#5891)

* Drop overflow cache

* Update docs

* Update beacon_node/store/src/lib.rs

* Update data_availability_checker.rs

* Lint

beacon_node/beacon_chain/src/beacon_chain.rs

@@ -723,13 +723,6 @@ impl<T: BeaconChainTypes> BeaconChain<T> {
         Ok(())
     }
 
-    pub fn persist_data_availability_checker(&self) -> Result<(), Error> {
-        let _timer = metrics::start_timer(&metrics::PERSIST_DATA_AVAILABILITY_CHECKER);
-        self.data_availability_checker.persist_all()?;
-
-        Ok(())
-    }
-
     /// Returns the slot _right now_ according to `self.slot_clock`. Returns `Err` if the slot is
     /// unavailable.
     ///
@@ -6753,7 +6746,6 @@ impl<T: BeaconChainTypes> Drop for BeaconChain<T> {
         let drop = || -> Result<(), Error> {
             self.persist_head_and_fork_choice()?;
             self.persist_op_pool()?;
-            self.persist_data_availability_checker()?;
             self.persist_eth1_cache()
         };
 

beacon_node/beacon_chain/src/data_availability_checker.rs

@@ -2,7 +2,7 @@ use crate::blob_verification::{verify_kzg_for_blob_list, GossipVerifiedBlob, Kzg
 use crate::block_verification_types::{
     AvailabilityPendingExecutedBlock, AvailableExecutedBlock, RpcBlock,
 };
-use crate::data_availability_checker::overflow_lru_cache::OverflowLRUCache;
+use crate::data_availability_checker::overflow_lru_cache::DataAvailabilityCheckerInner;
 use crate::{BeaconChain, BeaconChainTypes, BeaconStore};
 use kzg::Kzg;
 use slog::{debug, error, Logger};
@@ -33,12 +33,32 @@ pub const OVERFLOW_LRU_CAPACITY: NonZeroUsize = new_non_zero_usize(1024);
 pub const STATE_LRU_CAPACITY_NON_ZERO: NonZeroUsize = new_non_zero_usize(2);
 pub const STATE_LRU_CAPACITY: usize = STATE_LRU_CAPACITY_NON_ZERO.get();
 
-/// This includes a cache for any blocks or blobs that have been received over gossip or RPC
+/// Cache to hold fully valid data that can't be imported to fork-choice yet. After Dencun hard-fork
-/// and are awaiting more components before they can be imported. Additionally the
+/// blocks have a sidecar of data that is received separately from the network. We call the concept
-/// `DataAvailabilityChecker` is responsible for KZG verification of block components as well as
+/// of a block "becoming available" when all of its import dependencies are inserted into this
-/// checking whether a "availability check" is required at all.
+/// cache.
+///
+/// Usually a block becomes available on its slot within a second of receiving its first component
+/// over gossip. However, a block may never become available if a malicious proposer does not
+/// publish its data, or there are network issues that prevent us from receiving it. If the block
+/// does not become available after some time we can safely forget about it. Consider these two
+/// cases:
+///
+/// - Global unavailability: If nobody has received the block components it's likely that the
+///   proposer never made the block available. So we can safely forget about the block as it will
+///   never become available.
+/// - Local unavailability: Some fraction of the network has received all block components, but not us.
+///   Some of our peers will eventually attest to a descendant of that block and lookup sync will
+///   fetch its components. Therefore it's not strictly necessary to hold to the partially available
+///   block for too long as we can recover from other peers.
+///
+/// Even in periods of non-finality, the proposer is expected to publish the block's data
+/// immediately. Because this cache only holds fully valid data, its capacity is bound to 1 block
+/// per slot and fork: before inserting into this cache we check the proposer signature and correct
+/// proposer. Having a capacity > 1 is an optimization to prevent sync lookup from having re-fetch
+/// data during moments of unstable network conditions.
 pub struct DataAvailabilityChecker<T: BeaconChainTypes> {
-    availability_cache: Arc<OverflowLRUCache<T>>,
+    availability_cache: Arc<DataAvailabilityCheckerInner<T>>,
     slot_clock: T::SlotClock,
     kzg: Option<Arc<Kzg>>,
     log: Logger,
@@ -74,7 +94,8 @@ impl<T: BeaconChainTypes> DataAvailabilityChecker<T> {
         log: &Logger,
         spec: ChainSpec,
     ) -> Result<Self, AvailabilityCheckError> {
-        let overflow_cache = OverflowLRUCache::new(OVERFLOW_LRU_CAPACITY, store, spec.clone())?;
+        let overflow_cache =
+            DataAvailabilityCheckerInner::new(OVERFLOW_LRU_CAPACITY, store, spec.clone())?;
         Ok(Self {
             availability_cache: Arc::new(overflow_cache),
             slot_clock,
@@ -329,15 +350,9 @@ impl<T: BeaconChainTypes> DataAvailabilityChecker<T> {
         })
     }
 
-    /// Persist all in memory components to disk
-    pub fn persist_all(&self) -> Result<(), AvailabilityCheckError> {
-        self.availability_cache.write_all_to_disk()
-    }
-
     /// Collects metrics from the data availability checker.
     pub fn metrics(&self) -> DataAvailabilityCheckerMetrics {
         DataAvailabilityCheckerMetrics {
-            num_store_entries: self.availability_cache.num_store_entries(),
             state_cache_size: self.availability_cache.state_cache_size(),
             block_cache_size: self.availability_cache.block_cache_size(),
         }
@@ -346,7 +361,6 @@ impl<T: BeaconChainTypes> DataAvailabilityChecker<T> {
 
 /// Helper struct to group data availability checker metrics.
 pub struct DataAvailabilityCheckerMetrics {
-    pub num_store_entries: usize,
     pub state_cache_size: usize,
     pub block_cache_size: usize,
 }
@@ -372,7 +386,7 @@ pub fn start_availability_cache_maintenance_service<T: BeaconChainTypes>(
 
 async fn availability_cache_maintenance_service<T: BeaconChainTypes>(
     chain: Arc<BeaconChain<T>>,
-    overflow_cache: Arc<OverflowLRUCache<T>>,
+    overflow_cache: Arc<DataAvailabilityCheckerInner<T>>,
 ) {
     let epoch_duration = chain.slot_clock.slot_duration() * T::EthSpec::slots_per_epoch() as u32;
     loop {

beacon_node/beacon_chain/src/data_availability_checker/state_lru_cache.rs

@@ -114,38 +114,12 @@ impl<T: BeaconChainTypes> StateLRUCache<T> {
         &self,
         diet_executed_block: DietAvailabilityPendingExecutedBlock<T::EthSpec>,
     ) -> Result<AvailabilityPendingExecutedBlock<T::EthSpec>, AvailabilityCheckError> {
-        let maybe_state = self.states.write().pop(&diet_executed_block.state_root);
+        let state = if let Some(state) = self.states.write().pop(&diet_executed_block.state_root) {
-        if let Some(state) = maybe_state {
+            state
-            let block_root = diet_executed_block.block.canonical_root();
-            Ok(AvailabilityPendingExecutedBlock {
-                block: diet_executed_block.block,
-                import_data: BlockImportData {
-                    block_root,
-                    state,
-                    parent_block: diet_executed_block.parent_block,
-                    parent_eth1_finalization_data: diet_executed_block
-                        .parent_eth1_finalization_data,
-                    confirmed_state_roots: diet_executed_block.confirmed_state_roots,
-                    consensus_context: diet_executed_block
-                        .consensus_context
-                        .into_consensus_context(),
-                },
-                payload_verification_outcome: diet_executed_block.payload_verification_outcome,
-            })
         } else {
-            self.reconstruct_pending_executed_block(diet_executed_block)
+            self.reconstruct_state(&diet_executed_block)?
-        }
+        };
-    }
-
-    /// Reconstruct the `AvailabilityPendingExecutedBlock` by loading the parent
-    /// state from disk and replaying the block. This function does NOT check the
-    /// LRU cache.
-    pub fn reconstruct_pending_executed_block(
-        &self,
-        diet_executed_block: DietAvailabilityPendingExecutedBlock<T::EthSpec>,
-    ) -> Result<AvailabilityPendingExecutedBlock<T::EthSpec>, AvailabilityCheckError> {
         let block_root = diet_executed_block.block.canonical_root();
-        let state = self.reconstruct_state(&diet_executed_block)?;
         Ok(AvailabilityPendingExecutedBlock {
             block: diet_executed_block.block,
             import_data: BlockImportData {

beacon_node/beacon_chain/src/metrics.rs

@@ -401,8 +401,6 @@ lazy_static! {
         try_create_histogram("beacon_persist_eth1_cache", "Time taken to persist the eth1 caches");
     pub static ref PERSIST_FORK_CHOICE: Result<Histogram> =
         try_create_histogram("beacon_persist_fork_choice", "Time taken to persist the fork choice struct");
-    pub static ref PERSIST_DATA_AVAILABILITY_CHECKER: Result<Histogram> =
-        try_create_histogram("beacon_persist_data_availability_checker", "Time taken to persist the data availability checker");
 
     /*
      * Eth1
@@ -1213,10 +1211,6 @@ pub fn scrape_for_metrics<T: BeaconChainTypes>(beacon_chain: &BeaconChain<T>) {
         &DATA_AVAILABILITY_OVERFLOW_MEMORY_STATE_CACHE_SIZE,
         da_checker_metrics.state_cache_size,
     );
-    set_gauge_by_usize(
-        &DATA_AVAILABILITY_OVERFLOW_STORE_CACHE_SIZE,
-        da_checker_metrics.num_store_entries,
-    );
 
     if let Some((size, num_lookups)) = beacon_chain.pre_finalization_block_cache.metrics() {
         set_gauge_by_usize(&PRE_FINALIZATION_BLOCK_CACHE_SIZE, size);

beacon_node/store/src/lib.rs

@@ -289,7 +289,7 @@ impl DBColumn {
     /// This function returns the number of bytes used by keys in a given column.
     pub fn key_size(self) -> usize {
         match self {
-            Self::OverflowLRUCache => 33, // See `OverflowKey` encode impl.
+            Self::OverflowLRUCache => 33, // DEPRECATED
             Self::BeaconMeta
             | Self::BeaconBlock
             | Self::BeaconState