consensus missed round metric

Author: Brindrajsinh-Chauhan

crates/malachite-app/METRICS.md

@@ -74,6 +74,13 @@ This application exposes Prometheus metrics on the `/metrics` endpoint. The foll
 - **`arc_malachite_app_height_restart_count`** (Counter)
   - **Description:** Number of times the consensus height has been restarted due to errors or recovery scenarios.
 
+- **`arc_malachite_app_consensus_round_missed`** (Counter)
+  - **Description:** Number of consensus rounds that failed to decide before advancing to the next round.
+  - **Labels:**
+    - `proposer`: Address of the validator that was proposer for the missed round.
+    - `height`: Current height of the chain.
+    - `round`: The round number that failed to decide.
+
 - **`arc_malachite_app_sync_fell_behind_count`** (Counter)
   - **Description:** Number of times the node fell behind and transitioned from InSync to CatchingUp.
 

crates/malachite-app/src/handlers/started_round.rs

@@ -97,6 +97,17 @@ async fn on_started_round(
     assert!(round != Round::Nil, "Round cannot be Nil");
     assert!(round >= state.current_round, "Round cannot go backwards");
 
+    if round.as_i64() > 0 {
+        let current_round = round.as_u32().expect("round is defined");
+        let missed_round = Round::new(current_round - 1);
+        let missed_proposer = state
+            .ctx
+            .proposer_selector
+            .select_proposer(state.validator_set(), height, missed_round)
+            .address;
+        state.metrics().inc_consensus_round_missed(missed_proposer, height, missed_round);
+    }
+
     state.current_round = round;
     state.current_proposer = Some(proposer);
 

crates/malachite-app/src/metrics/app.rs

@@ -23,7 +23,7 @@ use std::sync::RwLock;
 use std::time::{Duration, Instant};
 
 use arc_consensus_types::ConsensusParams;
-use arc_consensus_types::{Address, ValidatorSet};
+use arc_consensus_types::{Address, Height, Round, ValidatorSet};
 use malachitebft_app_channel::app::metrics::prometheus::encoding::{
     EncodeLabelSet, EncodeLabelValue, LabelValueEncoder,
 };
@@ -111,6 +111,9 @@ pub struct Inner {
     /// Number of blocks replayed from CL to EL during startup handshake
     handshake_replay_blocks: Gauge<u64, AtomicU64>,
 
+    /// Number of consensus rounds that failed to decide before advancing to the next round
+    consensus_round_missed: Family<RoundMissedLabel, Counter>,
+
     /// Internal state recording the previous validator set.
     /// Useful field to manage validators' metrics.
     /// This field is only accessible internally, and is not a metrics itself.
@@ -145,6 +148,7 @@ impl Inner {
             pending_proposal_parts_count: Gauge::default(),
             consensus_params: Family::default(),
             handshake_replay_blocks: Gauge::default(),
+            consensus_round_missed: Family::default(),
         }
     }
 }
@@ -280,6 +284,12 @@ impl AppMetrics {
                 metrics.handshake_replay_blocks.clone(),
             );
 
+            registry.register(
+                "consensus_round_missed",
+                "Number of consensus rounds that failed to decide before advancing to the next round",
+                metrics.consensus_round_missed.clone(),
+            );
+
             // Register version info as a separate Info metric
             let version_info = Info::new(VersionInfoLabel {
                 version: arc_version::SHORT_VERSION,
@@ -468,6 +478,21 @@ impl AppMetrics {
     pub fn get_handshake_replay_blocks(&self) -> u64 {
         self.handshake_replay_blocks.get()
     }
+
+    /// Record that a consensus round failed to decide before advancing.
+    pub fn inc_consensus_round_missed(&self, proposer: Address, height: Height, round: Round) {
+        self.consensus_round_missed
+            .get_or_create(&RoundMissedLabel::new(proposer, height, round))
+            .inc();
+    }
+
+    /// Total number of missed consensus rounds since start.
+    #[cfg(test)]
+    pub fn get_consensus_round_missed_count(&self, proposer: Address, height: Height, round: Round) -> u64 {
+        self.consensus_round_missed
+            .get_or_create(&RoundMissedLabel::new(proposer, height, round))
+            .get()
+    }
 }
 
 impl Default for AppMetrics {
@@ -505,6 +530,35 @@ impl AddressLabel {
     }
 }
 
+impl EncodeLabelValue for AsLabelValue<i64> {
+    fn encode(&self, encoder: &mut LabelValueEncoder) -> Result<(), std::fmt::Error> {
+        encoder.write_fmt(format_args!("{}", self.0))
+    }
+}
+
+impl EncodeLabelValue for AsLabelValue<u64> {
+    fn encode(&self, encoder: &mut LabelValueEncoder) -> Result<(), std::fmt::Error> {
+        encoder.write_fmt(format_args!("{}", self.0))
+    }
+}
+
+#[derive(Clone, Copy, Debug, Hash, PartialEq, Eq, EncodeLabelSet)]
+struct RoundMissedLabel {
+    proposer: AsLabelValue<Address>,
+    height: AsLabelValue<u64>,
+    round: AsLabelValue<i64>,
+}
+
+impl RoundMissedLabel {
+    fn new(proposer: Address, height: Height, round: Round) -> Self {
+        Self {
+            proposer: AsLabelValue(proposer),
+            height: AsLabelValue(height.as_u64()),
+            round: AsLabelValue(round.as_i64()),
+        }
+    }
+}
+
 #[derive(Clone, Debug, Hash, PartialEq, Eq, EncodeLabelSet)]
 struct ProcessMsgLabel {
     msg: &'static str,
@@ -641,4 +695,18 @@ mod tests {
             "Metrics should not contain 0x prefix: {buf}"
         );
     }
+
+    #[test]
+    fn test_consensus_round_missed_and_blocks_proposed_counters() {
+        let metrics = AppMetrics::new();
+        let proposer = Address::new([0xAA; 20]);
+
+        metrics.inc_consensus_round_missed(proposer, Height::new(1), Round::new(0));
+        metrics.inc_consensus_round_missed(proposer, Height::new(2), Round::new(0));
+        metrics.inc_consensus_round_missed(proposer, Height::new(2), Round::new(1));
+
+        assert_eq!(metrics.get_consensus_round_missed_count(proposer, Height::new(1), Round::new(0)), 1);
+        assert_eq!(metrics.get_consensus_round_missed_count(proposer, Height::new(2), Round::new(0)), 1);
+        assert_eq!(metrics.get_consensus_round_missed_count(proposer, Height::new(2), Round::new(1)), 1);
+    }
 }