Implement validator_identities Beacon API endpoint (#7462)

* #7442

beacon_node/http_api/src/lib.rs

@@ -48,7 +48,8 @@ use directory::DEFAULT_ROOT_DIR;
 use eth2::types::{
     self as api_types, BroadcastValidation, ContextDeserialize, EndpointVersion, ForkChoice,
     ForkChoiceNode, LightClientUpdatesQuery, PublishBlockRequest, StateId as CoreStateId,
-    ValidatorBalancesRequestBody, ValidatorId, ValidatorStatus, ValidatorsRequestBody,
+    ValidatorBalancesRequestBody, ValidatorId, ValidatorIdentitiesRequestBody, ValidatorStatus,
+    ValidatorsRequestBody,
 };
 use eth2::{CONSENSUS_VERSION_HEADER, CONTENT_TYPE_HEADER, SSZ_CONTENT_TYPE_HEADER};
 use health_metrics::observe::Observe;
@@ -702,6 +703,34 @@ pub fn serve<T: BeaconChainTypes>(
             },
         );
 
+    // POST beacon/states/{state_id}/validator_identities
+    let post_beacon_state_validator_identities = beacon_states_path
+        .clone()
+        .and(warp::path("validator_identities"))
+        .and(warp::path::end())
+        .and(warp_utils::json::json_no_body())
+        .then(
+            |state_id: StateId,
+             task_spawner: TaskSpawner<T::EthSpec>,
+             chain: Arc<BeaconChain<T>>,
+             query: ValidatorIdentitiesRequestBody| {
+                // Prioritise requests for validators at the head. These should be fast to service
+                // and could be required by the validator client.
+                let priority = if let StateId(eth2::types::StateId::Head) = state_id {
+                    Priority::P0
+                } else {
+                    Priority::P1
+                };
+                task_spawner.blocking_json_task(priority, move || {
+                    crate::validators::get_beacon_state_validator_identities(
+                        state_id,
+                        chain,
+                        Some(&query.ids),
+                    )
+                })
+            },
+        );
+
     // GET beacon/states/{state_id}/validators?id,status
     let get_beacon_state_validators = beacon_states_path
         .clone()
@@ -4852,6 +4881,7 @@ pub fn serve<T: BeaconChainTypes>(
                     .uor(post_beacon_pool_bls_to_execution_changes)
                     .uor(post_beacon_state_validators)
                     .uor(post_beacon_state_validator_balances)
+                    .uor(post_beacon_state_validator_identities)
                     .uor(post_beacon_rewards_attestations)
                     .uor(post_beacon_rewards_sync_committee)
                     .uor(post_validator_duties_attester)