Enable multi node attestation consensus for the VC

book/src/help_vc.md

@@ -205,6 +205,13 @@ Flags:
       --distributed
           Enables functionality required for running the validator in a
           distributed validator cluster.
+      --enable-beacon-head-monitor
+          Enable the beacon head monitor so fallback head updates trigger duties
+          when a lagging        primary is detected. This keeps the attestation
+          service responsive when using multiple beacon nodes, but it relies on
+          the fallback service streaming head events which may increase network
+          usage. When not enabled (default), duties are only triggered on slot
+          boundaries and ignore fallback head changes.
       --enable-doppelganger-protection
           If this flag is set, Lighthouse will delay startup for three epochs
           and monitor for messages on the network by any of the validators

common/eth2/src/lib.rs

@@ -152,6 +152,7 @@ pub struct BeaconNodeHttpClient {
     client: reqwest::Client,
     server: SensitiveUrl,
     timeouts: Timeouts,
+    index: usize,
 }
 
 impl Eq for BeaconNodeHttpClient {}
@@ -168,18 +169,34 @@ impl BeaconNodeHttpClient {
             client: reqwest::Client::new(),
             server,
             timeouts,
+            index: 0,
+        }
+    }
+
+    pub fn index(&self) -> usize {
+        self.index
+    }
+
+    pub fn new_with_index(server: SensitiveUrl, timeouts: Timeouts, index: usize) -> Self {
+        Self {
+            client: reqwest::Client::new(),
+            server,
+            timeouts,
+            index,
         }
     }
 
     pub fn from_components(
         server: SensitiveUrl,
         client: reqwest::Client,
         timeouts: Timeouts,
+        index: usize,
     ) -> Self {
         Self {
             client,
             server,
             timeouts,
+            index,
         }
     }
     // Returns a reference to the `SensitiveUrl` of the server.

consensus/types/src/core/slot_epoch.rs

@@ -59,6 +59,10 @@ impl Slot {
     pub fn max_value() -> Slot {
         Slot(u64::MAX)
     }
+
+    pub fn is_start_slot_in_epoch(&self, slots_per_epoch: u64) -> bool {
+        self.0.is_multiple_of(slots_per_epoch)
+    }
 }
 
 impl Epoch {

testing/node_test_rig/src/lib.rs

@@ -89,6 +89,7 @@ impl<E: EthSpec> LocalBeaconNode<E> {
             beacon_node_url,
             beacon_node_http_client,
             Timeouts::set_all(HTTP_TIMEOUT),
+            0,
         ))
     }
 }

testing/validator_test_rig/src/mock_beacon_node.rs

@@ -18,12 +18,13 @@ pub struct MockBeaconNode<E: EthSpec> {
 }
 
 impl<E: EthSpec> MockBeaconNode<E> {
-    pub async fn new() -> Self {
+    pub async fn new(index: usize) -> Self {
         // mock server logging
         let server = Server::new_async().await;
-        let beacon_api_client = BeaconNodeHttpClient::new(
+        let beacon_api_client = BeaconNodeHttpClient::new_with_index(
             SensitiveUrl::from_str(&server.url()).unwrap(),
             Timeouts::set_all(Duration::from_secs(1)),
+            index,
         );
         Self {
             server,