Add metric for duplicate retransmit (#20129)

core/src/retransmit_stage.rs

@@ -65,6 +65,7 @@ struct RetransmitStats {
     epoch_cache_update: AtomicU64,
     repair_total: AtomicU64,
     discard_total: AtomicU64,
+    duplicate_retransmit: AtomicU64,
     retransmit_total: AtomicU64,
     last_ts: AtomicInterval,
     compute_turbine_peers_total: AtomicU64,
@@ -81,6 +82,7 @@ fn update_retransmit_stats(
     retransmit_total: u64,
     discard_total: u64,
     repair_total: u64,
+    duplicate_retransmit: u64,
     compute_turbine_peers_total: u64,
     peers_len: usize,
     packets_by_slot: HashMap<Slot, usize>,
@@ -102,6 +104,9 @@ fn update_retransmit_stats(
     stats
         .discard_total
         .fetch_add(discard_total, Ordering::Relaxed);
+    stats
+        .duplicate_retransmit
+        .fetch_add(duplicate_retransmit, Ordering::Relaxed);
     stats
         .compute_turbine_peers_total
         .fetch_add(compute_turbine_peers_total, Ordering::Relaxed);
@@ -180,6 +185,11 @@ fn update_retransmit_stats(
                 stats.discard_total.swap(0, Ordering::Relaxed) as i64,
                 i64
             ),
+            (
+                "duplicate_retransmit",
+                stats.duplicate_retransmit.swap(0, Ordering::Relaxed) as i64,
+                i64
+            ),
         );
         let mut packets_by_slot = stats.packets_by_slot.lock().unwrap();
         let old_packets_by_slot = std::mem::take(&mut *packets_by_slot);
@@ -334,6 +344,7 @@ fn retransmit(
     let socket_addr_space = cluster_info.socket_addr_space();
     let mut discard_total = 0;
     let mut repair_total = 0;
+    let mut duplicate_retransmit = 0;
     let mut retransmit_total = 0;
     let mut compute_turbine_peers_total = 0;
     let mut retransmit_tree_mismatch = 0;
@@ -354,7 +365,11 @@ fn retransmit(
         }
         let shred_slot = match check_if_already_received(packet, shreds_received) {
             Some(slot) => slot,
-            None => continue,
+            None => {
+                total_packets -= 1;
+                duplicate_retransmit += 1;
+                continue;
+            }
         };
         max_slot = max_slot.max(shred_slot);
 
@@ -429,6 +444,7 @@ fn retransmit(
         retransmit_total,
         discard_total,
         repair_total,
+        duplicate_retransmit,
         compute_turbine_peers_total,
         peers_len,
         packets_by_slot,