test: add binary e2e test for joining with an outdated checkpoint (#86)

Changes:
- Adds a route to the RPC server that returns the current epoch
- Adds another binary e2e test (similar to stake-and-checkpoint), where a node joins with an outdated checkpoint (2 epochs old). Since the nodes keep track of 4 peer sets by default, a node should be able to join with a checkpoint that contains an outdated peer set, as long as it is not older than 4 epochs.

Author: matthias-wright

finalizer/src/actor.rs

@@ -767,6 +767,10 @@ impl<
                 let height = self.canonical_state.get_latest_height();
                 let _ = sender.send(ConsensusStateResponse::LatestHeight(height));
             }
+            ConsensusStateRequest::GetLatestEpoch => {
+                let epoch = self.canonical_state.get_epoch();
+                let _ = sender.send(ConsensusStateResponse::LatestEpoch(epoch));
+            }
             ConsensusStateRequest::GetValidatorBalance(public_key) => {
                 let mut key_bytes = [0u8; 32];
                 key_bytes.copy_from_slice(&public_key);

finalizer/src/ingress.rs

@@ -150,6 +150,24 @@ impl<S: Scheme, B: ConsensusBlock + Committable> FinalizerMailbox<S, B> {
         height
     }
 
+    pub async fn get_latest_epoch(&self) -> u64 {
+        let (response, rx) = oneshot::channel();
+        let request = ConsensusStateRequest::GetLatestEpoch;
+        let _ = self
+            .sender
+            .clone()
+            .send(FinalizerMessage::QueryState { request, response })
+            .await;
+
+        let res = rx
+            .await
+            .expect("consensus state query response sender dropped");
+        let ConsensusStateResponse::LatestEpoch(epoch) = res else {
+            unreachable!("request and response variants must match");
+        };
+        epoch
+    }
+
     pub async fn get_validator_balance(&self, public_key: PublicKey) -> Option<u64> {
         let (response, rx) = oneshot::channel();
         let request = ConsensusStateRequest::GetValidatorBalance(public_key);

node/Cargo.toml

@@ -16,6 +16,11 @@ name = "stake-and-checkpoint"
 path = "src/bin/stake_and_checkpoint.rs"
 required-features = ["e2e"]
 
+[[bin]]
+name = "stake-and-join-with-outdated-checkpoint"
+path = "src/bin/stake_and_join_with_outdated_ckpt.rs"
+required-features = ["e2e"]
+
 [[bin]]
 name = "withdraw-and-exit"
 path = "src/bin/withdraw_and_exit.rs"