fix:(drand): SizeTrackingCache cache name per drand network name

CHANGELOG.md

@@ -35,6 +35,8 @@
 
 ### Fixed
 
+- [#7414](https://github.com/ChainSafe/forest/issues/7414): The drand entry cache metrics are now named per drand network (`cache_verified_beacons_quicknet_*` and so on). They previously all shared the name `cache_verified_beacons_*`, so a network with more than one drand point (such as mainnet) exported duplicate metric families in a single scrape.
+
 - [#5795](https://github.com/ChainSafe/forest/issues/5795): `Filecoin.ChainNotify` now closes the subscription channel when a client falls too far behind instead of silently dropping head changes, matching Lotus, so clients can detect the gap and resubscribe.
 
 ## Forest v0.36.0 "bafy2bzacedpdckv7nsqfjwqnqwtgu7ipqbox4tfuuhwxhdox27uuznfyv3o2g"

src/beacon/drand.rs

@@ -37,7 +37,8 @@ pub static IGNORE_DRAND: LazyLock<bool> = LazyLock::new(|| is_env_truthy(IGNORE_
 
 /// Type of the `drand` network. `mainnet` is chained and `quicknet` is unchained.
 /// For the details, see <https://github.com/filecoin-project/FIPs/blob/1bd887028ac1b50b6f2f94913e07ede73583da5b/FIPS/fip-0063.md#specification>
-#[derive(PartialEq, Eq, Copy, Clone, Debug, SerdeSerialize, SerdeDeserialize)]
+#[derive(PartialEq, Eq, Copy, Clone, Debug, SerdeSerialize, SerdeDeserialize, strum::Display)]
+#[strum(serialize_all = "snake_case")]
 pub enum DrandNetwork {
     Mainnet,
     Quicknet,
@@ -271,7 +272,10 @@ impl DrandBeacon {
             drand_gen_time: config.chain_info.genesis_time as u64,
             fil_round_time: interval,
             fil_gen_time: genesis_ts,
-            verified_beacons: SizeTrackingCache::new_with_metrics("verified_beacons", CACHE_SIZE),
+            verified_beacons: SizeTrackingCache::new_with_metrics(
+                format!("verified_beacons_{}", config.network_type),
+                CACHE_SIZE,
+            ),
         }
     }
 

src/beacon/tests/drand.rs

@@ -308,3 +308,36 @@ async fn beacon_entries_for_block_covers_null_rounds_quicknet() {
         );
     }
 }
+
+#[test]
+#[serial_test::serial]
+fn verified_beacons_cache_metrics_are_uniquely_named() {
+    use crate::networks::ChainConfig;
+
+    crate::metrics::reset_collector_registry();
+    // Mainnet has three drand points: Incentinet, Mainnet and Quicknet.
+    let schedule = ChainConfig::mainnet().get_beacon_schedule(1598306400);
+    assert_eq!(schedule.0.len(), 3);
+
+    let mut encoded = String::new();
+    prometheus_client::encoding::text::encode_registry(
+        &mut encoded,
+        &crate::metrics::collector_registry(),
+    )
+    .unwrap();
+
+    let families: Vec<_> = encoded
+        .lines()
+        .filter_map(|line| line.strip_prefix("# HELP "))
+        .filter(|line| line.starts_with("cache_verified_beacons"))
+        .map(|line| line.split_whitespace().next().unwrap_or_default())
+        .collect();
+
+    // Five metrics (size/len/cap/hits/misses) for each of the three beacons.
+    assert_eq!(families.len(), 15);
+    assert_eq!(
+        families.iter().unique().count(),
+        families.len(),
+        "duplicate cache metric families: {families:?}"
+    );
+}