Use dedicated cache for HTTP API route

beacon_node/client/src/builder.rs

@@ -36,6 +36,7 @@ use rand::SeedableRng;
 use rand::rngs::{OsRng, StdRng};
 use slasher::Slasher;
 use slasher_service::SlasherService;
+use std::num::NonZeroUsize;
 use std::path::{Path, PathBuf};
 use std::sync::Arc;
 use std::time::Duration;
@@ -639,6 +640,10 @@ where
                 network_globals: self.network_globals.clone(),
                 beacon_processor_send: Some(beacon_processor_channels.beacon_processor_tx.clone()),
                 sse_logging_components: runtime_context.sse_logging_components.clone(),
+                historical_committee_cache: Arc::new(http_api::HistoricalCommitteeCache::new(
+                    NonZeroUsize::new(self.http_api_config.historical_committee_cache_size)
+                        .unwrap_or(NonZeroUsize::MIN),
+                )),
             });
 
             let exit = runtime_context.executor.exit();

beacon_node/http_api/src/beacon/states.rs

@@ -1,4 +1,5 @@
 use crate::StateId;
+use crate::caches::{HistoricalCommitteeCache, HistoricalShufflingId};
 use crate::task_spawner::{Priority, TaskSpawner};
 use crate::utils::ResponseFilter;
 use crate::validator::pubkey_to_validator_index;
@@ -13,7 +14,10 @@ use eth2::types::{
 };
 use ssz::Encode;
 use std::sync::Arc;
-use types::{AttestationShufflingId, BeaconStateError, CommitteeCache, EthSpec, RelativeEpoch};
+use types::{
+    AttestationShufflingId, BeaconStateError, CommitteeCache, EthSpec, RelativeEpoch,
+    RelativeEpochError,
+};
 use warp::filters::BoxedFilter;
 use warp::http::Response;
 use warp::hyper::Body;
@@ -26,6 +30,8 @@ type BeaconStatesPath<T> = BoxedFilter<(
     Arc<BeaconChain<T>>,
 )>;
 
+type BeaconStatesCommitteesFilter = BoxedFilter<(Arc<HistoricalCommitteeCache>,)>;
+
 // GET beacon/states/{state_id}/pending_consolidations
 pub fn get_beacon_state_pending_consolidations<T: BeaconChainTypes>(
     beacon_states_path: BeaconStatesPath<T>,
@@ -337,17 +343,20 @@ pub fn get_beacon_state_sync_committees<T: BeaconChainTypes>(
 // GET beacon/states/{state_id}/committees?slot,index,epoch
 pub fn get_beacon_state_committees<T: BeaconChainTypes>(
     beacon_states_path: BeaconStatesPath<T>,
+    beacon_states_committees_filter: BeaconStatesCommitteesFilter,
 ) -> ResponseFilter {
     beacon_states_path
         .clone()
         .and(warp::path("committees"))
         .and(warp::query::<eth2::types::CommitteesQuery>())
+        .and(beacon_states_committees_filter)
         .and(warp::path::end())
         .then(
             |state_id: StateId,
              task_spawner: TaskSpawner<T::EthSpec>,
              chain: Arc<BeaconChain<T>>,
-             query: eth2::types::CommitteesQuery| {
+             query: eth2::types::CommitteesQuery,
+             historical_committee_cache: Arc<HistoricalCommitteeCache>| {
                 task_spawner.blocking_json_task(Priority::P1, move || {
                     let (data, execution_optimistic, finalized) = state_id
                         .map_state_and_execution_optimistic_and_finalized(
@@ -364,33 +373,33 @@ pub fn get_beacon_state_committees<T: BeaconChainTypes>(
                                 let shuffling_id = if let Ok(Some(shuffling_decision_block)) =
                                     chain.block_root_at_slot(decision_slot, WhenSlotSkipped::Prev)
                                 {
-                                    Some(AttestationShufflingId {
-                                        shuffling_epoch: epoch,
-                                        shuffling_decision_block,
-                                    })
+                                    Some(HistoricalShufflingId::ShufflingId(
+                                        AttestationShufflingId {
+                                            shuffling_epoch: epoch,
+                                            shuffling_decision_block,
+                                        },
+                                    ))
+                                } else if epoch < chain.head().finalized_checkpoint().epoch {
+                                    // Use the case for finalized epochs
+                                    Some(HistoricalShufflingId::FinalizedEpoch(epoch))
                                 } else {
                                     None
                                 };
 
                                 // Attempt to read from the chain cache if there exists a
                                 // shuffling_id
-                                let maybe_cached_shuffling = if let Some(shuffling_id) =
-                                    shuffling_id.as_ref()
-                                {
-                                    chain
-                                        .shuffling_cache
-                                        .try_write_for(std::time::Duration::from_secs(1))
-                                        .and_then(|mut cache_write| cache_write.get(shuffling_id))
-                                        .and_then(|cache_item| cache_item.wait().ok())
-                                } else {
-                                    None
-                                };
+                                let maybe_cached_shuffling =
+                                    if let Some(shuffling_id) = shuffling_id.as_ref() {
+                                        historical_committee_cache.get(shuffling_id)
+                                    } else {
+                                        None
+                                    };
 
                                 let committee_cache =
                                     if let Some(shuffling) = maybe_cached_shuffling {
                                         shuffling
                                     } else {
-                                        let possibly_built_cache = match RelativeEpoch::from_epoch(
+                                        let committee_cache = match RelativeEpoch::from_epoch(
                                             current_epoch,
                                             epoch,
                                         ) {
@@ -401,11 +410,19 @@ pub fn get_beacon_state_committees<T: BeaconChainTypes>(
                                             {
                                                 state.committee_cache(relative_epoch).cloned()
                                             }
-                                            _ => CommitteeCache::initialized(
-                                                state,
-                                                epoch,
-                                                &chain.spec,
-                                            ),
+                                            Ok(_) | Err(RelativeEpochError::EpochTooLow { .. }) => {
+                                                CommitteeCache::initialized(
+                                                    state,
+                                                    epoch,
+                                                    &chain.spec,
+                                                )
+                                            }
+                                            Err(RelativeEpochError::EpochTooHigh { .. }) => {
+                                                Err(BeaconStateError::EpochOutOfBounds)
+                                            }
+                                            Err(RelativeEpochError::ArithError(e)) => {
+                                                Err(BeaconStateError::ArithError(e))
+                                            }
                                         }
                                         .map_err(|e| match e {
                                             BeaconStateError::EpochOutOfBounds => {
@@ -419,22 +436,12 @@ pub fn get_beacon_state_committees<T: BeaconChainTypes>(
                                             ),
                                         })?;
 
-                                        // Attempt to write to the beacon cache (only if the cache
-                                        // size is not the default value).
-                                        if chain.config.shuffling_cache_size
-                                            != beacon_chain::shuffling_cache::DEFAULT_CACHE_SIZE
-                                            && let Some(shuffling_id) = shuffling_id
-                                            && let Some(mut cache_write) = chain
-                                                .shuffling_cache
-                                                .try_write_for(std::time::Duration::from_secs(1))
-                                        {
-                                            cache_write.insert_committee_cache(
-                                                shuffling_id,
-                                                &possibly_built_cache,
-                                            );
+                                        if let Some(shuffling_id) = shuffling_id {
+                                            historical_committee_cache
+                                                .insert(shuffling_id, committee_cache.clone());
                                         }
 
-                                        possibly_built_cache
+                                        committee_cache
                                     };
 
                                 // Use either the supplied slot or all slots in the epoch.

beacon_node/http_api/src/caches.rs

@@ -0,0 +1,43 @@
+use lru::LruCache;
+use parking_lot::Mutex;
+use std::num::NonZeroUsize;
+use std::sync::Arc;
+use types::{AttestationShufflingId, CommitteeCache, Epoch};
+
+/// See `shuffling_cache::DEFAULT_CACHE_SIZE` for rationale
+pub const DEFAULT_HISTORICAL_COMMITTEE_CACHE_SIZE: usize = 16;
+
+/// Indexes the `HistoricalCommitteeCache`. We can compute committees for very old epochs, and we
+/// can't retrieve the decision root cheaply from a state. For those cases we allow the cache to
+/// key those committees by finalized epoch.
+#[derive(Eq, Hash, PartialEq)]
+pub enum HistoricalShufflingId {
+    FinalizedEpoch(Epoch),
+    ShufflingId(AttestationShufflingId),
+}
+
+/// Dedicated cache for attestation committees, used exclusively by the HTTP API.
+///
+/// This may contain committees for finalized and unfinalized epochs. The name is slightly
+/// missleading :)
+pub struct HistoricalCommitteeCache {
+    committees: Mutex<LruCache<HistoricalShufflingId, Arc<CommitteeCache>>>,
+}
+
+impl HistoricalCommitteeCache {
+    pub fn new(size: NonZeroUsize) -> Self {
+        Self {
+            committees: Mutex::new(LruCache::new(size)),
+        }
+    }
+}
+
+impl HistoricalCommitteeCache {
+    pub fn get(&self, id: &HistoricalShufflingId) -> Option<Arc<CommitteeCache>> {
+        self.committees.lock().get(id).cloned()
+    }
+
+    pub fn insert(&self, id: HistoricalShufflingId, cache: Arc<CommitteeCache>) {
+        self.committees.lock().put(id, cache);
+    }
+}

beacon_node/http_api/src/lib.rs

@@ -12,6 +12,7 @@ mod beacon;
 mod block_id;
 mod build_block_contents;
 mod builder_states;
+mod caches;
 mod custody;
 mod database;
 mod light_client;
@@ -40,6 +41,8 @@ use crate::beacon::execution_payload_envelope::{
     post_beacon_execution_payload_envelope_ssz,
 };
 use crate::beacon::pool::*;
+use crate::caches::DEFAULT_HISTORICAL_COMMITTEE_CACHE_SIZE;
+pub use crate::caches::HistoricalCommitteeCache;
 use crate::light_client::{get_light_client_bootstrap, get_light_client_updates};
 use crate::utils::{AnyVersionFilter, EthV1Filter};
 use crate::validator::post_validator_liveness_epoch;
@@ -132,6 +135,7 @@ pub struct Context<T: BeaconChainTypes> {
     pub network_globals: Option<Arc<NetworkGlobals<T::EthSpec>>>,
     pub beacon_processor_send: Option<BeaconProcessorSend<T::EthSpec>>,
     pub sse_logging_components: Option<SSELoggingComponents>,
+    pub historical_committee_cache: Arc<HistoricalCommitteeCache>,
 }
 
 /// Configuration for the HTTP server.
@@ -148,6 +152,7 @@ pub struct Config {
     #[serde(with = "eth2::types::serde_status_code")]
     pub duplicate_block_status_code: StatusCode,
     pub target_peers: usize,
+    pub historical_committee_cache_size: usize,
 }
 
 impl Default for Config {
@@ -163,6 +168,7 @@ impl Default for Config {
             enable_beacon_processor: true,
             duplicate_block_status_code: StatusCode::ACCEPTED,
             target_peers: 100,
+            historical_committee_cache_size: DEFAULT_HISTORICAL_COMMITTEE_CACHE_SIZE,
         }
     }
 }
@@ -416,6 +422,11 @@ pub fn serve<T: BeaconChainTypes>(
         })
         .boxed();
 
+    let historical_committee_cache = ctx.historical_committee_cache.clone();
+    let beacon_states_committees_filter = warp::any()
+        .map(move || historical_committee_cache.clone())
+        .boxed();
+
     // Create a `warp` filter that provides access to the network sender channel.
     let network_tx = ctx
         .network_senders
@@ -628,8 +639,10 @@ pub fn serve<T: BeaconChainTypes>(
         states::get_beacon_state_validators_id(beacon_states_path.clone());
 
     // GET beacon/states/{state_id}/committees?slot,index,epoch
-    let get_beacon_state_committees =
-        states::get_beacon_state_committees(beacon_states_path.clone());
+    let get_beacon_state_committees = states::get_beacon_state_committees(
+        beacon_states_path.clone(),
+        beacon_states_committees_filter,
+    );
 
     // GET beacon/states/{state_id}/sync_committees?epoch
     let get_beacon_state_sync_committees =

beacon_node/http_api/src/test_utils.rs

@@ -1,4 +1,4 @@
-use crate::{Config, Context};
+use crate::{Config, Context, caches::HistoricalCommitteeCache};
 use beacon_chain::{
     BeaconChain, BeaconChainTypes,
     custody_context::NodeCustodyType,
@@ -22,10 +22,10 @@ use lighthouse_network::{
 };
 use network::{NetworkReceivers, NetworkSenders};
 use sensitive_url::SensitiveUrl;
-use std::future::Future;
 use std::net::SocketAddr;
 use std::sync::Arc;
 use std::time::Duration;
+use std::{future::Future, num::NonZeroUsize};
 use store::MemoryStore;
 use task_executor::test_utils::TestRuntime;
 use types::{ChainSpec, EthSpec};
@@ -293,6 +293,9 @@ pub async fn create_api_server_with_config<T: BeaconChainTypes>(
         network_globals: Some(network_globals),
         beacon_processor_send: Some(beacon_processor_send),
         sse_logging_components: None,
+        historical_committee_cache: Arc::new(HistoricalCommitteeCache::new(
+            NonZeroUsize::new(http_config.historical_committee_cache_size).unwrap(),
+        )),
     });
 
     let (listening_socket, server) =

beacon_node/src/config.rs

@@ -215,6 +215,9 @@ pub fn get_config<E: EthSpec>(
 
     if let Some(cache_size) = clap_utils::parse_optional(cli_args, "shuffling-cache-size")? {
         client_config.chain.shuffling_cache_size = cache_size;
+        // Mantain backwards compatibility with users customizing `shuffling_cache_size` to tweak
+        // the behaviour of the HTTP API route `beacon/states/committees`
+        client_config.http_api.historical_committee_cache_size = cache_size;
     }
 
     if let Some(batches) = clap_utils::parse_optional(cli_args, "blob-publication-batches")? {