announcements answered only if heads differ

1 files changed, 6 insertions, 5 deletions

diff --git a/src/swarm/relay.rs b/src/swarm/relay.rs
index 1393d50..a4a4034 100644
--- a/src/swarm/relay.rs
+++ b/src/swarm/relay.rs
@@ -2,8 +2,9 @@
 //!
 //! A node pushes its own changes to its neighbours, but nothing it receives goes any
 //! further by itself. So after applying changes from one neighbour, a node *announces*
-//! its new heads to its other neighbours with a STATUS (a keepalive: heads, about 100
-//! bytes, not the changes). A neighbour that sees heads it lacks *pulls*: it enters the
+//! its new heads to its other neighbours with a STATUS (heads, about 100 bytes, not the
+//! changes; no keepalive, and answered only by a neighbour whose heads differ). A
+//! neighbour that sees heads it lacks *pulls*: it enters the
 //! announced heads as the peer's heads in its sync state, Automerge asks for what's
 //! missing (`need`), and the announcer answers with exactly those changes. Each node
 //! receives a change about once; the rest is announcements. Regular keepalives work the
@@ -11,7 +12,7 @@
 //!
 //! Announcements are coalesced: the first applied change schedules one announcement
 //! round `ANNOUNCE_DELAY` later, and every change applied until then rides along. A
-//! round costs one STATUS and one STATUS_REPLY per neighbour (plus the pulls), whatever the
+//! round costs one STATUS per neighbour (plus the pulls and their replies), whatever the
 //! write rate; the delay is the price per hop. Without coalescing, every applied sync
 //! message would announce to every neighbour, and announcements would outnumber the
 //! data they announce (about 15 to 1 at 250 nodes).
@@ -31,7 +32,7 @@ use tracing::debug;
 
 use crate::locks::MutexExt;
 use crate::state::{AppState, Standing};
-use crate::swarm::peer::send_status;
+use crate::swarm::peer::announce_heads;
 use crate::swarm::topology;
 use crate::transport::{self, HeadsSummary};
 
@@ -86,7 +87,7 @@ async fn announce_now(state: &AppState, senders: &HashSet<String>) {
     }
     state.stats.announce_round();
     for peer in neighbours {
-        if let Err(error) = send_status(state, &peer).await {
+        if let Err(error) = announce_heads(state, &peer).await {
             debug!(peer = %peer, error = %format!("{error:#}"), "Announcing our heads failed");
         }
     }