ME Coverage Ratio in API + as Draining Factor

src/api/model.rs

@@ -237,6 +237,7 @@ pub(super) struct MeWritersSummary {
     pub(super) available_pct: f64,
     pub(super) required_writers: usize,
     pub(super) alive_writers: usize,
+    pub(super) coverage_ratio: f64,
     pub(super) coverage_pct: f64,
     pub(super) fresh_alive_writers: usize,
     pub(super) fresh_coverage_pct: f64,
@@ -285,6 +286,7 @@ pub(super) struct DcStatus {
     pub(super) floor_max: usize,
     pub(super) floor_capped: bool,
     pub(super) alive_writers: usize,
+    pub(super) coverage_ratio: f64,
     pub(super) coverage_pct: f64,
     pub(super) fresh_alive_writers: usize,
     pub(super) fresh_coverage_pct: f64,

src/api/runtime_min.rs

@@ -113,6 +113,7 @@ pub(super) struct RuntimeMeQualityDcRttData {
     pub(super) rtt_ema_ms: Option<f64>,
     pub(super) alive_writers: usize,
     pub(super) required_writers: usize,
+    pub(super) coverage_ratio: f64,
     pub(super) coverage_pct: f64,
 }
 
@@ -388,6 +389,7 @@ pub(super) async fn build_runtime_me_quality_data(shared: &ApiShared) -> Runtime
                     rtt_ema_ms: dc.rtt_ms,
                     alive_writers: dc.alive_writers,
                     required_writers: dc.required_writers,
+                    coverage_ratio: dc.coverage_ratio,
                     coverage_pct: dc.coverage_pct,
                 })
                 .collect(),

src/api/runtime_stats.rs

@@ -315,6 +315,7 @@ async fn get_minimal_payload_cached(
             available_pct: status.available_pct,
             required_writers: status.required_writers,
             alive_writers: status.alive_writers,
+            coverage_ratio: status.coverage_ratio,
             coverage_pct: status.coverage_pct,
             fresh_alive_writers: status.fresh_alive_writers,
             fresh_coverage_pct: status.fresh_coverage_pct,
@@ -372,6 +373,7 @@ async fn get_minimal_payload_cached(
                 floor_max: entry.floor_max,
                 floor_capped: entry.floor_capped,
                 alive_writers: entry.alive_writers,
+                coverage_ratio: entry.coverage_ratio,
                 coverage_pct: entry.coverage_pct,
                 fresh_alive_writers: entry.fresh_alive_writers,
                 fresh_coverage_pct: entry.fresh_coverage_pct,
@@ -502,6 +504,7 @@ fn disabled_me_writers(now_epoch_secs: u64, reason: &'static str) -> MeWritersDa
             available_pct: 0.0,
             required_writers: 0,
             alive_writers: 0,
+            coverage_ratio: 0.0,
             coverage_pct: 0.0,
             fresh_alive_writers: 0,
             fresh_coverage_pct: 0.0,

src/transport/middle_proxy/pool_reinit.rs

@@ -70,10 +70,12 @@ impl MePool {
 
         let mut missing_dc = Vec::<i32>::new();
         let mut covered = 0usize;
+        let mut total = 0usize;
         for (dc, endpoints) in desired_by_dc {
             if endpoints.is_empty() {
                 continue;
             }
+            total += 1;
             if endpoints
                 .iter()
                 .any(|addr| active_writer_addrs.contains(&(*dc, *addr)))
@@ -85,7 +87,9 @@ impl MePool {
         }
 
         missing_dc.sort_unstable();
-        let total = desired_by_dc.len().max(1);
+        if total == 0 {
+            return (1.0, missing_dc);
+        }
         let ratio = (covered as f32) / (total as f32);
         (ratio, missing_dc)
     }
@@ -399,29 +403,21 @@ impl MePool {
         }
 
         if hardswap {
-            let mut fresh_missing_dc = Vec::<(i32, usize, usize)>::new();
+            let fresh_writer_addrs: HashSet<(i32, SocketAddr)> = writers
-            for (dc, endpoints) in &desired_by_dc {
-                if endpoints.is_empty() {
-                    continue;
-                }
-                let required = self.required_writers_for_dc(endpoints.len());
-                let fresh_count = writers
                 .iter()
                 .filter(|w| !w.draining.load(Ordering::Relaxed))
                 .filter(|w| w.generation == generation)
-                    .filter(|w| w.writer_dc == *dc)
+                .map(|w| (w.writer_dc, w.addr))
-                    .filter(|w| endpoints.contains(&w.addr))
+                .collect();
-                    .count();
+            let (fresh_coverage_ratio, fresh_missing_dc) =
-                if fresh_count < required {
+                Self::coverage_ratio(&desired_by_dc, &fresh_writer_addrs);
-                    fresh_missing_dc.push((*dc, fresh_count, required));
-                }
-            }
             if !fresh_missing_dc.is_empty() {
                 warn!(
                     previous_generation,
                     generation,
+                    fresh_coverage_ratio = format_args!("{fresh_coverage_ratio:.3}"),
                     missing_dc = ?fresh_missing_dc,
-                    "ME hardswap pending: fresh generation coverage incomplete"
+                    "ME hardswap pending: fresh generation DC coverage incomplete"
                 );
                 return;
             }
@@ -491,3 +487,61 @@ impl MePool {
         self.zero_downtime_reinit_after_map_change(rng).await;
     }
 }
+
+#[cfg(test)]
+mod tests {
+    use std::collections::{HashMap, HashSet};
+    use std::net::{IpAddr, Ipv4Addr, SocketAddr};
+
+    use super::MePool;
+
+    fn addr(octet: u8, port: u16) -> SocketAddr {
+        SocketAddr::new(IpAddr::V4(Ipv4Addr::new(127, 0, 0, octet)), port)
+    }
+
+    #[test]
+    fn coverage_ratio_counts_dc_coverage_not_floor() {
+        let dc1 = addr(1, 2001);
+        let dc2 = addr(2, 2002);
+
+        let mut desired_by_dc = HashMap::<i32, HashSet<SocketAddr>>::new();
+        desired_by_dc.insert(1, HashSet::from([dc1]));
+        desired_by_dc.insert(2, HashSet::from([dc2]));
+
+        let active_writer_addrs = HashSet::from([(1, dc1)]);
+        let (ratio, missing_dc) = MePool::coverage_ratio(&desired_by_dc, &active_writer_addrs);
+
+        assert_eq!(ratio, 0.5);
+        assert_eq!(missing_dc, vec![2]);
+    }
+
+    #[test]
+    fn coverage_ratio_ignores_empty_dc_groups() {
+        let dc1 = addr(1, 2001);
+
+        let mut desired_by_dc = HashMap::<i32, HashSet<SocketAddr>>::new();
+        desired_by_dc.insert(1, HashSet::from([dc1]));
+        desired_by_dc.insert(2, HashSet::new());
+
+        let active_writer_addrs = HashSet::from([(1, dc1)]);
+        let (ratio, missing_dc) = MePool::coverage_ratio(&desired_by_dc, &active_writer_addrs);
+
+        assert_eq!(ratio, 1.0);
+        assert!(missing_dc.is_empty());
+    }
+
+    #[test]
+    fn coverage_ratio_reports_missing_dcs_sorted() {
+        let dc1 = addr(1, 2001);
+        let dc2 = addr(2, 2002);
+
+        let mut desired_by_dc = HashMap::<i32, HashSet<SocketAddr>>::new();
+        desired_by_dc.insert(2, HashSet::from([dc2]));
+        desired_by_dc.insert(1, HashSet::from([dc1]));
+
+        let (ratio, missing_dc) = MePool::coverage_ratio(&desired_by_dc, &HashSet::new());
+
+        assert_eq!(ratio, 0.0);
+        assert_eq!(missing_dc, vec![1, 2]);
+    }
+}

src/transport/middle_proxy/pool_status.rs

@@ -40,6 +40,7 @@ pub(crate) struct MeApiDcStatusSnapshot {
     pub floor_max: usize,
     pub floor_capped: bool,
     pub alive_writers: usize,
+    pub coverage_ratio: f64,
     pub coverage_pct: f64,
     pub fresh_alive_writers: usize,
     pub fresh_coverage_pct: f64,
@@ -62,6 +63,7 @@ pub(crate) struct MeApiStatusSnapshot {
     pub available_pct: f64,
     pub required_writers: usize,
     pub alive_writers: usize,
+    pub coverage_ratio: f64,
     pub coverage_pct: f64,
     pub fresh_alive_writers: usize,
     pub fresh_coverage_pct: f64,
@@ -342,6 +344,8 @@ impl MePool {
         let mut available_endpoints = 0usize;
         let mut alive_writers = 0usize;
         let mut fresh_alive_writers = 0usize;
+        let mut coverage_ratio_dcs_total = 0usize;
+        let mut coverage_ratio_dcs_covered = 0usize;
         let floor_mode = self.floor_mode();
         let adaptive_cpu_cores = (self
             .me_adaptive_floor_cpu_cores_effective
@@ -393,6 +397,12 @@ impl MePool {
             available_endpoints += dc_available_endpoints;
             alive_writers += dc_alive_writers;
             fresh_alive_writers += dc_fresh_alive_writers;
+            if endpoint_count > 0 {
+                coverage_ratio_dcs_total += 1;
+                if dc_alive_writers > 0 {
+                    coverage_ratio_dcs_covered += 1;
+                }
+            }
 
             dcs.push(MeApiDcStatusSnapshot {
                 dc,
@@ -415,6 +425,11 @@ impl MePool {
                 floor_max,
                 floor_capped,
                 alive_writers: dc_alive_writers,
+                coverage_ratio: if endpoint_count > 0 && dc_alive_writers > 0 {
+                    100.0
+                } else {
+                    0.0
+                },
                 coverage_pct: ratio_pct(dc_alive_writers, dc_required_writers),
                 fresh_alive_writers: dc_fresh_alive_writers,
                 fresh_coverage_pct: ratio_pct(dc_fresh_alive_writers, dc_required_writers),
@@ -431,6 +446,7 @@ impl MePool {
             available_pct: ratio_pct(available_endpoints, configured_endpoints),
             required_writers,
             alive_writers,
+            coverage_ratio: ratio_pct(coverage_ratio_dcs_covered, coverage_ratio_dcs_total),
             coverage_pct: ratio_pct(alive_writers, required_writers),
             fresh_alive_writers,
             fresh_coverage_pct: ratio_pct(fresh_alive_writers, required_writers),