newly added neighbour get a sync attempt

1 files changed, 12 insertions, 3 deletions

diff --git a/src/swarm/peer.rs b/src/swarm/peer.rs
index 238194c..fc37ec2 100644
--- a/src/swarm/peer.rs
+++ b/src/swarm/peer.rs
@@ -406,15 +406,24 @@ async fn discover_peers(state: &AppState, from_peer: &str, advertised_peers: &[S
 }
 
 /// New neighbours get our HELLO (we may not have known them before: the member list is
-/// how a partial mesh discovers them). Former neighbours get no more HELLOs, keepalives
-/// or sync openings from us; their session is reset, so we don't keep pushing changes
-/// to them either. They are still answered if they contact us.
+/// how a partial mesh discovers them) and a sync opening. The opening matters for a
+/// neighbour whose handshake is already complete, e.g. one that returned from dormancy
+/// while it wasn't our neighbour: it was only answered then, and with no HELLO to send,
+/// nothing else would open sync until the keepalive heal (`resync_after`). Former
+/// neighbours get no more HELLOs, keepalives or sync openings from us; their session is
+/// reset, so we don't keep pushing changes to them either. They are still answered if
+/// they contact us.
 async fn apply_neighbour_change(state: &AppState, change: topology::NeighbourChange) {
     for peer in &change.added {
         remember_peer(state, peer).await;
         if let Err(error) = send_hello_once(state, peer).await {
             warn!(peer = %peer, error = %format!("{error:#}"), "HELLO to new neighbour failed; will retry");
         }
+        // Skipped there unless the handshake is complete; otherwise its reply restarts
+        // sync anyway.
+        let _ = state
+            .sync_events
+            .send(SyncEvent::PeerNeedsSync(peer.clone()));
     }
     for peer in &change.removed {
         if let Some(peer_state) = state.get_peer_state(peer).await {