read stamps sync and lock free

1 files changed, 8 insertions, 5 deletions

diff --git a/src/state/mod.rs b/src/state/mod.rs
index a51339c..962d62a 100644
--- a/src/state/mod.rs
+++ b/src/state/mod.rs
@@ -29,7 +29,7 @@ use tokio::sync::{Mutex, RwLock, broadcast, mpsc, watch};
 use tokio::time::Instant;
 use tracing::{debug, error, warn};
 
-use crate::document::replica::{Epoch, Replica};
+use crate::document::replica::{Epoch, Replica, Stamp};
 use crate::locks::MutexExt;
 use crate::remake::{Host, RemakeState};
 use crate::swarm::sync::{ChangeSet, SyncEvent};
@@ -52,6 +52,8 @@ pub(crate) struct AppState {
     /// Copy of `doc.epoch` for cheap, lock-free reads (handshakes, keepalives, /peers).
     /// Only ever changed while holding `doc`'s write lock, together with `doc.epoch`.
     pub(crate) epoch_tx: watch::Sender<Epoch>,
+    /// `doc`'s epoch label and heads, readable without its lock (`Replica::stamps`).
+    pub(crate) stamp: watch::Receiver<Stamp>,
 
     pub(crate) lifecycle: Arc<RwLock<NodeLifecycle>>,
 
@@ -186,10 +188,11 @@ impl AppState {
         *self.epoch_tx.borrow()
     }
 
-    /// The local epoch and `Replica::epoch_seq`, read together.
-    pub(crate) async fn epoch_stamp(&self) -> (Epoch, u32) {
-        let replica = self.doc.read().await;
-        (replica.epoch, replica.epoch_seq)
+    /// The local epoch and `Replica::epoch_seq`, read together, without waiting for the
+    /// document's lock.
+    pub(crate) fn epoch_stamp(&self) -> (Epoch, u32) {
+        let stamp = self.stamp.borrow();
+        (stamp.epoch, stamp.epoch_seq)
     }
 
     pub(crate) async fn is_ready(&self) -> bool {