1 files changed, 23 insertions, 2 deletions
diff --git a/src/transport.rs b/src/transport.rs
index 95d3046..9cfb026 100644
--- a/src/transport.rs
+++ b/src/transport.rs
@@ -5,11 +5,15 @@ use std::boxed::Box;
 use std::future::Future;
 use std::pin::Pin;
 
+pub use crate::replica::Epoch;
+
 pub type HeadsDigest = [u8; 32];
 
 #[derive(Debug, Clone)]
 pub struct Keepalive {
     pub heads_digest: HeadsDigest,
+    /// The digest is only comparable between nodes on the same epoch.
+    pub epoch: Epoch,
 }
 
 #[derive(Debug)]
@@ -21,18 +25,35 @@ pub enum ParsedMessage {
     Pong(Keepalive),
 }
 
-#[derive(Debug)]
-pub struct HelloRequest {}
+impl ParsedMessage {
+    /// Every message carries the sender's epoch.
+    pub fn epoch(&self) -> Epoch {
+        match self {
+            ParsedMessage::Hello(hello) => hello.epoch,
+            ParsedMessage::HelloReply(reply) => reply.epoch,
+            ParsedMessage::Sync(envelope) => envelope.epoch,
+            ParsedMessage::Ping(keepalive) | ParsedMessage::Pong(keepalive) => keepalive.epoch,
+        }
+    }
+}
+
+#[derive(Debug, Clone)]
+pub struct HelloRequest {
+    pub epoch: Epoch,
+}
 
 #[derive(Debug, Clone)]
 pub struct HelloReply {
     pub cluster_id: String,
     pub peers: Vec<String>,
+    pub epoch: Epoch,
 }
 
 #[derive(Debug, Clone)]
 pub struct SyncEnvelope {
     pub cluster_id: String,
+    /// Epoch of the document the message was generated from.
+    pub epoch: Epoch,
     pub message: Message,
 }