Use sync_tolerance_epochs flag to control the proposer prep routines (#7044)

Replace the `2 + 2 == 5` hacks from `holesky-rescue` and use the existing `sync_tolerance_epochs` flag to control the proposer prep routines.

Author: jimmygchen

beacon_node/beacon_chain/src/beacon_chain.rs

@@ -144,11 +144,6 @@ pub const FORK_CHOICE_DB_KEY: Hash256 = Hash256::ZERO;
 /// Defines how old a block can be before it's no longer a candidate for the early attester cache.
 const EARLY_ATTESTER_CACHE_HISTORIC_SLOTS: u64 = 4;
 
-/// Defines a distance between the head block slot and the current slot.
-///
-/// If the head block is older than this value, don't bother preparing beacon proposers.
-const PREPARE_PROPOSER_HISTORIC_EPOCHS: u64 = 4;
-
 /// If the head is more than `MAX_PER_SLOT_FORK_CHOICE_DISTANCE` slots behind the wall-clock slot, DO NOT
 /// run the per-slot tasks (primarily fork choice).
 ///
@@ -4848,7 +4843,7 @@ impl<T: BeaconChainTypes> BeaconChain<T> {
         let proposer_index = if let Some(proposer) = cached_proposer {
             proposer.index as u64
         } else {
-            if head_epoch + 2 < proposal_epoch {
+            if head_epoch + self.config.sync_tolerance_epochs < proposal_epoch {
                 warn!(
                     self.log,
                     "Skipping proposer preparation";
@@ -6079,19 +6074,18 @@ impl<T: BeaconChainTypes> BeaconChain<T> {
         // Use a blocking task since blocking the core executor on the canonical head read lock can
         // block the core tokio executor.
         let chain = self.clone();
+        let tolerance_slots = self.config.sync_tolerance_epochs * T::EthSpec::slots_per_epoch();
         let maybe_prep_data = self
             .spawn_blocking_handle(
                 move || {
                     let cached_head = chain.canonical_head.cached_head();
 
                     // Don't bother with proposer prep if the head is more than
-                    // `PREPARE_PROPOSER_HISTORIC_EPOCHS` prior to the current slot.
+                    // `sync_tolerance_epochs` prior to the current slot.
                     //
                     // This prevents the routine from running during sync.
                     let head_slot = cached_head.head_slot();
-                    if head_slot + T::EthSpec::slots_per_epoch() * PREPARE_PROPOSER_HISTORIC_EPOCHS
-                        < current_slot
-                    {
+                    if head_slot + tolerance_slots < current_slot {
                         debug!(
                             chain.log,
                             "Head too old for proposer prep";

beacon_node/beacon_chain/src/chain_config.rs

@@ -16,6 +16,9 @@ pub const DEFAULT_PREPARE_PAYLOAD_LOOKAHEAD_FACTOR: u32 = 3;
 /// Fraction of a slot lookahead for fork choice in the state advance timer (500ms on mainnet).
 pub const FORK_CHOICE_LOOKAHEAD_FACTOR: u32 = 24;
 
+/// Default sync tolerance epochs.
+pub const DEFAULT_SYNC_TOLERANCE_EPOCHS: u64 = 2;
+
 #[derive(Debug, PartialEq, Eq, Clone, Deserialize, Serialize)]
 pub struct ChainConfig {
     /// Maximum number of slots to skip when importing an attestation.
@@ -94,6 +97,9 @@ pub struct ChainConfig {
     /// The delay in milliseconds applied by the node between sending each blob or data column batch.
     /// This doesn't apply if the node is the block proposer.
     pub blob_publication_batch_interval: Duration,
+    /// The max distance between the head block and the current slot at which Lighthouse will
+    /// consider itself synced and still serve validator-related requests.
+    pub sync_tolerance_epochs: u64,
 }
 
 impl Default for ChainConfig {
@@ -129,6 +135,7 @@ impl Default for ChainConfig {
             enable_sampling: false,
             blob_publication_batches: 4,
             blob_publication_batch_interval: Duration::from_millis(300),
+            sync_tolerance_epochs: DEFAULT_SYNC_TOLERANCE_EPOCHS,
         }
     }
 }

beacon_node/http_api/src/lib.rs

@@ -107,13 +107,6 @@ use warp_utils::{query::multi_key_query, reject::convert_rejection, uor::Unifyin
 
 const API_PREFIX: &str = "eth";
 
-/// If the node is within this many epochs from the head, we declare it to be synced regardless of
-/// the network sync state.
-///
-/// This helps prevent attacks where nodes can convince us that we're syncing some non-existent
-/// finalized head.
-const DEFAULT_SYNC_TOLERANCE_EPOCHS: u64 = 8;
-
 /// A custom type which allows for both unsecured and TLS-enabled HTTP servers.
 type HttpServer = (SocketAddr, Pin<Box<dyn Future<Output = ()> + Send>>);
 
@@ -157,7 +150,6 @@ pub struct Config {
     pub duplicate_block_status_code: StatusCode,
     pub enable_light_client_server: bool,
     pub target_peers: usize,
-    pub sync_tolerance_epochs: Option<u64>,
 }
 
 impl Default for Config {
@@ -174,7 +166,6 @@ impl Default for Config {
             duplicate_block_status_code: StatusCode::ACCEPTED,
             enable_light_client_server: true,
             target_peers: 100,
-            sync_tolerance_epochs: None,
         }
     }
 }
@@ -475,10 +466,8 @@ pub fn serve<T: BeaconChainTypes>(
                                     )
                                 })?;
 
-                            let sync_tolerance_epochs = config
-                                .sync_tolerance_epochs
-                                .unwrap_or(DEFAULT_SYNC_TOLERANCE_EPOCHS);
-                            let tolerance = sync_tolerance_epochs * T::EthSpec::slots_per_epoch();
+                            let tolerance =
+                                chain.config.sync_tolerance_epochs * T::EthSpec::slots_per_epoch();
 
                             if head_slot + tolerance >= current_slot {
                                 Ok(())

beacon_node/src/config.rs

@@ -8,7 +8,7 @@ use beacon_chain::graffiti_calculator::GraffitiOrigin;
 use beacon_chain::TrustedSetup;
 use clap::{parser::ValueSource, ArgMatches, Id};
 use clap_utils::flags::DISABLE_MALLOC_TUNING_FLAG;
-use clap_utils::{parse_flag, parse_optional, parse_required};
+use clap_utils::{parse_flag, parse_required};
 use client::{ClientConfig, ClientGenesis};
 use directory::{DEFAULT_BEACON_NODE_DIR, DEFAULT_NETWORK_DIR, DEFAULT_ROOT_DIR};
 use environment::RuntimeContext;
@@ -177,9 +177,6 @@ pub fn get_config<E: EthSpec>(
 
         client_config.http_api.enable_light_client_server =
             !cli_args.get_flag("disable-light-client-server");
-
-        client_config.http_api.sync_tolerance_epochs =
-            parse_optional(cli_args, "sync-tolerance-epochs")?;
     }
 
     if cli_args.get_flag("light-client-server") {
@@ -194,6 +191,12 @@ pub fn get_config<E: EthSpec>(
         client_config.chain.enable_light_client_server = false;
     }
 
+    if let Some(sync_tolerance_epochs) =
+        clap_utils::parse_optional(cli_args, "sync-tolerance-epochs")?
+    {
+        client_config.chain.sync_tolerance_epochs = sync_tolerance_epochs;
+    }
+
     if let Some(cache_size) = clap_utils::parse_optional(cli_args, "shuffling-cache-size")? {
         client_config.chain.shuffling_cache_size = cache_size;
     }

lighthouse/tests/beacon_node.rs

@@ -1,7 +1,7 @@
 use crate::exec::{CommandLineTestExec, CompletedTest};
 use beacon_node::beacon_chain::chain_config::{
     DisallowedReOrgOffsets, DEFAULT_RE_ORG_CUTOFF_DENOMINATOR, DEFAULT_RE_ORG_HEAD_THRESHOLD,
-    DEFAULT_RE_ORG_MAX_EPOCHS_SINCE_FINALIZATION,
+    DEFAULT_RE_ORG_MAX_EPOCHS_SINCE_FINALIZATION, DEFAULT_SYNC_TOLERANCE_EPOCHS,
 };
 use beacon_node::{
     beacon_chain::graffiti_calculator::GraffitiOrigin,
@@ -2586,7 +2586,20 @@ fn sync_tolerance_epochs() {
         .flag("sync-tolerance-epochs", Some("0"))
         .run_with_zero_port()
         .with_config(|config| {
-            assert_eq!(config.http_api.sync_tolerance_epochs, Some(0));
+            assert_eq!(config.chain.sync_tolerance_epochs, 0);
+        });
+}
+
+#[test]
+fn sync_tolerance_epochs_default() {
+    CommandLineTest::new()
+        .flag("http", None)
+        .run_with_zero_port()
+        .with_config(|config| {
+            assert_eq!(
+                config.chain.sync_tolerance_epochs,
+                DEFAULT_SYNC_TOLERANCE_EPOCHS
+            );
         });
 }