unify peers snapshot logic

2 files changed, 17 insertions, 16 deletions

diff --git a/src/state/host.rs b/src/state/host.rs
index 9b149b8..fd40bf3 100644
--- a/src/state/host.rs
+++ b/src/state/host.rs
@@ -7,11 +7,11 @@ use std::time::Duration;
 
 use anyhow::Result;
 use automerge::{AutoCommit, ChangeHash};
-use tokio::sync::{Mutex, broadcast};
+use tokio::sync::broadcast;
 use tokio::time::Instant;
 use tracing::debug;
 
-use super::{AppState, HelloState, Liveness, NodeLifecycle, PeerState, StaleView, Standing};
+use super::{AppState, HelloState, Liveness, NodeLifecycle, StaleView, Standing};
 use crate::document::replica::Epoch;
 use crate::locks::MutexExt;
 use crate::remake::{Host, PeerSummary, RemakeState};
@@ -22,13 +22,7 @@ impl AppState {
     /// document, so start over with all of them. Peers still on the old epoch are
     /// skipped by the sync worker until they switch too.
     async fn after_epoch_switch(&self) {
-        let peers: Vec<(String, Arc<Mutex<PeerState>>)> = self
-            .peer_states
-            .read()
-            .await
-            .iter()
-            .map(|(id, peer)| (id.clone(), Arc::clone(peer)))
-            .collect();
+        let peers = self.peers_snapshot().await;
 
         // Sync states were reset under the document lock by the swap itself.
         self.publish_change();
@@ -126,13 +120,7 @@ impl Host for AppState {
     fn peer_summaries(&self) -> impl Future<Output = Vec<PeerSummary>> + Send {
         let state = self.clone();
         async move {
-            let peers: Vec<(String, Arc<Mutex<PeerState>>)> = state
-                .peer_states
-                .read()
-                .await
-                .iter()
-                .map(|(id, peer)| (id.clone(), Arc::clone(peer)))
-                .collect();
+            let peers = state.peers_snapshot().await;
 
             let mut summaries = Vec::with_capacity(peers.len());
             for (id, peer) in peers {
diff --git a/src/state/mod.rs b/src/state/mod.rs
index 3336b00..1c31c61 100644
--- a/src/state/mod.rs
+++ b/src/state/mod.rs
@@ -280,6 +280,19 @@ impl AppState {
         Ok(())
     }
 
+    /// Every known peer with its state, copied out of the peer map. Lock a peer's state
+    /// only from such a copy, never while holding the map's lock: the map would then
+    /// wait for the peer, and with it everything that only needs the map (a lookup, a
+    /// new peer).
+    pub(crate) async fn peers_snapshot(&self) -> Vec<(String, Arc<Mutex<PeerState>>)> {
+        self.peer_states
+            .read()
+            .await
+            .iter()
+            .map(|(peer, state)| (peer.clone(), Arc::clone(state)))
+            .collect()
+    }
+
     /// Looks up a peer without creating it. Background work (sync, retries,
     /// keepalives) must use this so a forgotten peer isn't resurrected.
     pub(crate) async fn get_peer_state(&self, pk: &str) -> Option<Arc<Mutex<PeerState>>> {