Do timeout lock for beacon state metrics

beacon_node/beacon_chain/src/canonical_head.rs

@@ -35,6 +35,10 @@ impl<T> CanonicalHeadRwLock<T> {
         self.0.read()
     }
 
+    pub fn try_read_for(&self, timeout: Duration) -> Option<RwLockReadGuard<T>> {
+        self.0.try_read_for(timeout)
+    }
+
     pub fn write(&self) -> RwLockWriteGuard<T> {
         self.0.write()
     }

beacon_node/beacon_chain/src/metrics.rs

@@ -1,6 +1,6 @@
 use crate::observed_attesters::SlotSubcommitteeIndex;
 use crate::types::consts::altair::SYNC_COMMITTEE_SUBNET_COUNT;
-use crate::{BeaconChain, BeaconChainError, BeaconChainTypes};
+use crate::{BeaconChain, BeaconChainTypes};
 use lazy_static::lazy_static;
 pub use lighthouse_metrics::*;
 use slot_clock::SlotClock;
@@ -10,6 +10,9 @@ use types::{BeaconState, Epoch, EthSpec, Hash256, Slot};
 /// The maximum time to wait for the snapshot cache lock during a metrics scrape.
 const SNAPSHOT_CACHE_TIMEOUT: Duration = Duration::from_millis(100);
 
+/// The time to wait for the canonical head lock before just proceeding with other metrics.
+const CANONICAL_HEAD_LOCK_TIMEOUT: Duration = Duration::from_secs(1);
+
 lazy_static! {
     /*
      * Block Processing
@@ -927,10 +930,13 @@ lazy_static! {
 /// Scrape the `beacon_chain` for metrics that are not constantly updated (e.g., the present slot,
 /// head state info, etc) and update the Prometheus `DEFAULT_REGISTRY`.
 pub fn scrape_for_metrics<T: BeaconChainTypes>(beacon_chain: &BeaconChain<T>) {
-    let _ = beacon_chain.with_head(|head| {
+    if let Some(canonical_head) = beacon_chain
+        .canonical_head
+        .try_read_for(CANONICAL_HEAD_LOCK_TIMEOUT)
+    {
+        let head = &canonical_head.head_snapshot;
         scrape_head_state(&head.beacon_state, head.beacon_state_root());
-        Ok::<_, BeaconChainError>(())
-    });
+    }
 
     if let Some(slot) = beacon_chain.slot_clock.now() {
         scrape_attestation_observation(slot, beacon_chain);