add propagation stats

1 files changed, 15 insertions, 0 deletions

diff --git a/src/swarm/sync.rs b/src/swarm/sync.rs
index adf8146..09e10f4 100644
--- a/src/swarm/sync.rs
+++ b/src/swarm/sync.rs
@@ -307,6 +307,8 @@ pub(crate) async fn handle_sync(
         let peer_state_mutex = Arc::clone(&peer_state_mutex);
         let stats = Arc::clone(&state.stats);
         let check_caught_up = !state.initial_sync_done.load(Ordering::Acquire);
+        // While catching up, everything arrives late; that says nothing about propagation.
+        let measure_propagation = !check_caught_up;
         let epoch = envelope.epoch;
         let message = envelope.message;
         let peer = peer.to_owned();
@@ -338,6 +340,19 @@ pub(crate) async fn handle_sync(
             let heads_after = replica.doc.get_heads();
             stats.heads_seen(heads_after.len());
             let changed = heads_after != heads_before;
+            if changed && measure_propagation {
+                let now_ms = crate::state::unix_millis() as i64;
+                // Time 0: not stamped (snapshots, older nodes).
+                let delays: Vec<i64> = replica
+                    .doc
+                    .get_changes(&heads_before)
+                    .iter()
+                    .map(|change| change.timestamp())
+                    .filter(|&time| time > 0)
+                    .map(|time| now_ms - time)
+                    .collect();
+                stats.propagated(delays);
+            }
 
             Ok(Some((
                 // Only from a ready peer: a peer still catching up has empty heads, which