Add a cli option for the snapshot cache size (#5270)

* Add a cli option for snapshot cache size

* Remove junk

* Make snapshot_cache module public

* lint

* Update docs

beacon_node/beacon_chain/src/builder.rs

@@ -12,7 +12,7 @@ use crate::light_client_server_cache::LightClientServerCache;
 use crate::migrate::{BackgroundMigrator, MigratorConfig};
 use crate::persisted_beacon_chain::PersistedBeaconChain;
 use crate::shuffling_cache::{BlockShufflingIds, ShufflingCache};
-use crate::snapshot_cache::{SnapshotCache, DEFAULT_SNAPSHOT_CACHE_SIZE};
+use crate::snapshot_cache::SnapshotCache;
 use crate::timeout_rw_lock::TimeoutRwLock;
 use crate::validator_monitor::{ValidatorMonitor, ValidatorMonitorConfig};
 use crate::validator_pubkey_cache::ValidatorPubkeyCache;
@@ -870,6 +870,7 @@ where
         let head_for_snapshot_cache = head_snapshot.clone();
         let canonical_head = CanonicalHead::new(fork_choice, Arc::new(head_snapshot));
         let shuffling_cache_size = self.chain_config.shuffling_cache_size;
+        let snapshot_cache_size = self.chain_config.snapshot_cache_size;
 
         // Calculate the weak subjectivity point in which to backfill blocks to.
         let genesis_backfill_slot = if self.chain_config.genesis_backfill {
@@ -946,7 +947,7 @@ where
             event_handler: self.event_handler,
             head_tracker,
             snapshot_cache: TimeoutRwLock::new(SnapshotCache::new(
-                DEFAULT_SNAPSHOT_CACHE_SIZE,
+                snapshot_cache_size,
                 head_for_snapshot_cache,
             )),
             shuffling_cache: TimeoutRwLock::new(ShufflingCache::new(

beacon_node/beacon_chain/src/chain_config.rs

@@ -72,6 +72,8 @@ pub struct ChainConfig {
     pub optimistic_finalized_sync: bool,
     /// The size of the shuffling cache,
     pub shuffling_cache_size: usize,
+    /// The size of the snapshot cache.
+    pub snapshot_cache_size: usize,
     /// If using a weak-subjectivity sync, whether we should download blocks all the way back to
     /// genesis.
     pub genesis_backfill: bool,
@@ -112,6 +114,7 @@ impl Default for ChainConfig {
             // This value isn't actually read except in tests.
             optimistic_finalized_sync: true,
             shuffling_cache_size: crate::shuffling_cache::DEFAULT_CACHE_SIZE,
+            snapshot_cache_size: crate::snapshot_cache::DEFAULT_SNAPSHOT_CACHE_SIZE,
             genesis_backfill: false,
             always_prepare_payload: false,
             progressive_balances_mode: ProgressiveBalancesMode::Fast,

beacon_node/beacon_chain/src/lib.rs

@@ -50,7 +50,7 @@ mod pre_finalization_cache;
 pub mod proposer_prep_service;
 pub mod schema_change;
 pub mod shuffling_cache;
-mod snapshot_cache;
+pub mod snapshot_cache;
 pub mod state_advance_timer;
 pub mod sync_committee_rewards;
 pub mod sync_committee_verification;

beacon_node/beacon_chain/src/snapshot_cache.rs

@@ -9,7 +9,7 @@ use types::{
 };
 
 /// The default size of the cache.
-pub const DEFAULT_SNAPSHOT_CACHE_SIZE: usize = 4;
+pub const DEFAULT_SNAPSHOT_CACHE_SIZE: usize = 3;
 
 /// The minimum block delay to clone the state in the cache instead of removing it.
 /// This helps keep block processing fast during re-orgs from late blocks.
@@ -174,6 +174,7 @@ impl<T: EthSpec> SnapshotCache<T> {
         self.snapshots.iter().map(|s| s.beacon_block_root).collect()
     }
 
+    #[allow(clippy::len_without_is_empty)]
     /// The number of snapshots contained in `self`.
     pub fn len(&self) -> usize {
         self.snapshots.len()

beacon_node/src/cli.rs

@@ -622,6 +622,13 @@ pub fn cli_app<'a, 'b>() -> App<'a, 'b> {
                 .help("Specifies how many states from the freezer database should cache in memory [default: 1]")
                 .takes_value(true)
         )
+        .arg(
+            Arg::with_name("state-cache-size")
+                .long("state-cache-size")
+                .value_name("STATE_CACHE_SIZE")
+                .help("Specifies the size of the snapshot cache [default: 3]")
+                .takes_value(true)
+        )
         /*
          * Execution Layer Integration
          */

beacon_node/src/config.rs

@@ -170,6 +170,9 @@ 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;
     }
+    if let Some(cache_size) = clap_utils::parse_optional(cli_args, "state-cache-size")? {
+        client_config.chain.snapshot_cache_size = cache_size;
+    }
 
     /*
      * Prometheus metrics HTTP server