follow and download from ready members only

2 files changed, 23 insertions, 1 deletions

diff --git a/src/remake/catchup.rs b/src/remake/catchup.rs
index 39b9550..56aeee1 100644
--- a/src/remake/catchup.rs
+++ b/src/remake/catchup.rs
@@ -71,11 +71,13 @@ pub(super) async fn check<H: Host>(host: &H) {
     }
 
     let local = host.current_epoch();
+    // Only ready members count: a rejoining peer advertises an epoch it doesn't hold
+    // yet, and a node of another swarm (or a stranger) advertises one that isn't ours.
     let mut ahead: Vec<(String, Epoch)> = host
         .peer_summaries()
         .await
         .into_iter()
-        .filter(|peer| peer.active)
+        .filter(|peer| peer.serves())
         .filter_map(|peer| peer.epoch.map(|epoch| (peer.id, epoch)))
         .filter(|(_, epoch)| epoch.generation > local.generation)
         .collect();
diff --git a/src/remake/mod.rs b/src/remake/mod.rs
index dacd1db..ca17956 100644
--- a/src/remake/mod.rs
+++ b/src/remake/mod.rs
@@ -141,10 +141,30 @@ pub(crate) struct PeerSummary {
     pub(crate) id: String,
     /// Not dormant.
     pub(crate) active: bool,
+    /// Completed the handshake and belongs to our swarm. A peer that merely sent us
+    /// something (a node of another swarm on the same network, a stranger before
+    /// admission) is not one, and nothing it advertises is followed.
+    pub(crate) member: bool,
+    /// What it last said about being ready; None before it said anything.
+    pub(crate) ready: Option<bool>,
     /// The epoch the peer last advertised.
     pub(crate) epoch: Option<Epoch>,
 }
 
+impl PeerSummary {
+    /// A peer whose epoch can be followed and downloaded from: an active member that
+    /// holds the document it advertises. A rejoining peer advertises its target epoch
+    /// with an empty document and `ready: false`.
+    pub(crate) fn serves_epoch(&self, epoch: Epoch) -> bool {
+        self.serves() && self.epoch == Some(epoch)
+    }
+
+    /// An active, ready member.
+    pub(crate) fn serves(&self) -> bool {
+        self.active && self.member && self.ready == Some(true)
+    }
+}
+
 /// Admin routes. Merged into the authenticated part of the node's router.
 /// Largest remake request (bytes). The proposal carries the new document to every
 /// node in one sync message, which Mycelium must deliver within its deadline, so