add better comments, return helpful error messages over http and rpc

Author: eserilev

beacon_node/beacon_chain/src/light_client_server_cache.rs

@@ -399,6 +399,9 @@ impl<T: BeaconChainTypes> LightClientServerCache<T> {
         self.latest_optimistic_update.read().clone()
     }
 
+    /// Fetches a `sync_committee_branch` for a given `block_root`
+    ///
+    /// Note:
     pub fn get_sync_committee_branch(
         &self,
         store: &BeaconStore<T>,
@@ -410,9 +413,9 @@ impl<T: BeaconChainTypes> LightClientServerCache<T> {
             .hot_db
             .get_bytes(column.into(), &block_root.as_ssz_bytes())?
         {
-            // TODO unwrap
             let sync_committee_branch: FixedVector<Hash256, CurrentSyncCommitteeProofLen> =
-                FixedVector::from_ssz_bytes(&bytes).unwrap();
+                FixedVector::from_ssz_bytes(&bytes)
+                    .map_err(store::errors::Error::SszDecodeError)?;
 
             return Ok(Some(sync_committee_branch));
         }
@@ -432,13 +435,20 @@ impl<T: BeaconChainTypes> LightClientServerCache<T> {
             .get_bytes(column.into(), &sync_committee_period.as_ssz_bytes())?
         {
             let sync_committee: SyncCommittee<T::EthSpec> =
-                SyncCommittee::from_ssz_bytes(&bytes).unwrap();
+                SyncCommittee::from_ssz_bytes(&bytes)
+                    .map_err(store::errors::Error::SszDecodeError)?;
             return Ok(Some(sync_committee));
         }
 
         Ok(None)
     }
 
+    /// Fetches a light client bootstrap for a given finalized checkpoint `block_root`. We eagerly persist
+    /// `sync_committee_branch and `sync_committee` to allow for a more efficient bootstrap construction.
+    ///
+    /// Note: It should be the case that a `sync_committee_branch` and `sync_committee` exist in the db
+    /// for a finalized checkpoint block root. However, we currently have no backfill mechanism for these values.
+    /// Therefore, `sync_committee_branch` and `sync_committee` are only persisted while a node is synced.
     #[allow(clippy::type_complexity)]
     pub fn get_light_client_bootstrap(
         &self,

beacon_node/network/src/network_beacon_processor/rpc_methods.rs

@@ -328,7 +328,7 @@ impl<T: BeaconChainTypes> NetworkBeaconProcessor<T> {
                 Ok(Some((bootstrap, _))) => Ok(Arc::new(bootstrap)),
                 Ok(None) => Err((
                     RPCResponseErrorCode::ResourceUnavailable,
-                    "Bootstrap not available",
+                    "Bootstrap not available".to_string(),
                 )),
                 Err(e) => {
                     error!(self.log, "Error getting LightClientBootstrap instance";
@@ -338,7 +338,7 @@ impl<T: BeaconChainTypes> NetworkBeaconProcessor<T> {
                     );
                     Err((
                         RPCResponseErrorCode::ResourceUnavailable,
-                        "Bootstrap not available",
+                        format!("{:?}", e),
                     ))
                 }
             },
@@ -363,7 +363,7 @@ impl<T: BeaconChainTypes> NetworkBeaconProcessor<T> {
                 Some(update) => Ok(Arc::new(update)),
                 None => Err((
                     RPCResponseErrorCode::ResourceUnavailable,
-                    "Latest optimistic update not available",
+                    "Latest optimistic update not available".to_string(),
                 )),
             },
             Response::LightClientOptimisticUpdate,
@@ -387,7 +387,7 @@ impl<T: BeaconChainTypes> NetworkBeaconProcessor<T> {
                 Some(update) => Ok(Arc::new(update)),
                 None => Err((
                     RPCResponseErrorCode::ResourceUnavailable,
-                    "Latest finality update not available",
+                    "Latest finality update not available".to_string(),
                 )),
             },
             Response::LightClientFinalityUpdate,
@@ -821,7 +821,7 @@ impl<T: BeaconChainTypes> NetworkBeaconProcessor<T> {
         &self,
         peer_id: PeerId,
         request_id: PeerRequestId,
-        result: Result<R, (RPCResponseErrorCode, &'static str)>,
+        result: Result<R, (RPCResponseErrorCode, String)>,
         into_response: F,
     ) {
         match result {
@@ -836,7 +836,7 @@ impl<T: BeaconChainTypes> NetworkBeaconProcessor<T> {
                 });
             }
             Err((error_code, reason)) => {
-                self.send_error_response(peer_id, error_code, reason.into(), request_id);
+                self.send_error_response(peer_id, error_code, reason, request_id);
             }
         }
     }