cache heads

To reduce the number of write locks, heads are now cached.

1 files changed, 4 insertions, 4 deletions

diff --git a/src/swarm/peer.rs b/src/swarm/peer.rs
index dd70bbb..3d7da32 100644
--- a/src/swarm/peer.rs
+++ b/src/swarm/peer.rs
@@ -108,12 +108,12 @@ pub(crate) async fn send_ping(state: &AppState, peer: &str) -> Result<()> {
 
 /// Our keepalive for `peer`.
 pub(crate) async fn local_keepalive(state: &AppState, peer: &str) -> transport::Keepalive {
-    // AutoCommit::get_heads takes &mut self (it closes the pending transaction).
-    // Heads and epoch come from the same locked replica, so they always match.
+    // Heads and epoch come from the same locked replica, so they always match. The heads
+    // are cached (`Replica`), so the read lock is enough.
     let (heads, epoch) = {
-        let mut replica = state.doc.write().await;
+        let replica = state.doc.read().await;
         (
-            transport::HeadsSummary::of(replica.doc.get_heads()),
+            transport::HeadsSummary::of(replica.heads().to_vec()),
             replica.epoch,
         )
     };