Speed up getLeaderSchedule RPC call by reducing pubkey duplication

book/src/api-reference/jsonrpc-api.md

@@ -384,7 +384,9 @@ Returns the leader schedule for an epoch
 
 #### Results:
 
-The result field will be an array of leader public keys \(as base-58 encoded strings\) for each slot in the epoch
+The result field will be a dictionary of leader public keys \(as base-58 encoded
+strings\) and their corresponding leader slot indices as values (indices are to
+the first slot in the requested epoch)
 
 #### Example:
 
@@ -393,7 +395,7 @@ The result field will be an array of leader public keys \(as base-58 encoded str
 curl -X POST -H "Content-Type: application/json" -d '{"jsonrpc":"2.0","id":1, "method":"getLeaderSchedule"}' http://localhost:8899
 
 // Result
-{"jsonrpc":"2.0","result":[...],"id":1}
+{"jsonrpc":"2.0","result":{"4Qkev8aNZcqFNSRhQzwyLMFSsi94jHqE8WNVTJzTP99F":[0,1,2,3,4,5,6,7,8,9,10,11,12,13,14,15,16,17,18,19,20,21,22,23,24,25,26,27,28,29,30,31,32,33,34,35,36,37,38,39,40,41,42,43,44,45,46,47,48,49,50,51,52,53,54,55,56,57,58,59,60,61,62,63]},"id":1}
 ```
 
 ### getMinimumBalanceForRentExemption

client/src/rpc_client.rs

@@ -4,7 +4,10 @@ use crate::{
     generic_rpc_client_request::GenericRpcClientRequest,
     mock_rpc_client_request::MockRpcClientRequest,
     rpc_client_request::RpcClientRequest,
-    rpc_request::{RpcContactInfo, RpcEpochInfo, RpcRequest, RpcVersionInfo, RpcVoteAccountStatus},
+    rpc_request::{
+        RpcContactInfo, RpcEpochInfo, RpcLeaderSchedule, RpcRequest, RpcVersionInfo,
+        RpcVoteAccountStatus,
+    },
 };
 use bincode::serialize;
 use log::*;
@@ -248,15 +251,15 @@ impl RpcClient {
         })
     }
 
-    pub fn get_leader_schedule(&self, slot: Option<Slot>) -> io::Result<Option<Vec<String>>> {
+    pub fn get_leader_schedule(&self, slot: Option<Slot>) -> io::Result<Option<RpcLeaderSchedule>> {
         self.get_leader_schedule_with_commitment(slot, CommitmentConfig::default())
     }
 
     pub fn get_leader_schedule_with_commitment(
         &self,
         slot: Option<Slot>,
         commitment_config: CommitmentConfig,
-    ) -> io::Result<Option<Vec<String>>> {
+    ) -> io::Result<Option<RpcLeaderSchedule>> {
         let params = slot.map(|slot| json!(slot));
         let response = self
             .client

client/src/rpc_request.rs

@@ -6,7 +6,7 @@ use solana_sdk::{
     hash::Hash,
     transaction::{Result, Transaction},
 };
-use std::{error, fmt, io, net::SocketAddr};
+use std::{collections::HashMap, error, fmt, io, net::SocketAddr};
 
 pub type RpcResponseIn<T> = JsonResult<Response<T>>;
 pub type RpcResponse<T> = io::Result<Response<T>>;
@@ -52,6 +52,9 @@ pub struct RpcContactInfo {
     pub rpc: Option<SocketAddr>,
 }
 
+/// Map of leader base58 identity pubkeys to the slot indices relative to the first epoch slot
+pub type RpcLeaderSchedule = HashMap<String, Vec<usize>>;
+
 #[derive(Serialize, Deserialize, Clone, Debug)]
 #[serde(rename_all = "camelCase")]
 pub struct RpcEpochInfo {

core/src/rpc.rs

@@ -12,8 +12,8 @@ use bincode::serialize;
 use jsonrpc_core::{Error, Metadata, Result};
 use jsonrpc_derive::rpc;
 use solana_client::rpc_request::{
-    Response, RpcConfirmedBlock, RpcContactInfo, RpcEpochInfo, RpcResponseContext, RpcVersionInfo,
-    RpcVoteAccountInfo, RpcVoteAccountStatus,
+    Response, RpcConfirmedBlock, RpcContactInfo, RpcEpochInfo, RpcLeaderSchedule,
+    RpcResponseContext, RpcVersionInfo, RpcVoteAccountInfo, RpcVoteAccountStatus,
 };
 use solana_faucet::faucet::request_airdrop_transaction;
 use solana_ledger::{bank_forks::BankForks, blocktree::Blocktree};
@@ -431,7 +431,7 @@ pub trait RpcSol {
         meta: Self::Metadata,
         slot: Option<Slot>,
         commitment: Option<CommitmentConfig>,
-    ) -> Result<Option<Vec<String>>>;
+    ) -> Result<Option<RpcLeaderSchedule>>;
 
     #[rpc(meta, name = "getRecentBlockhash")]
     fn get_recent_blockhash(
@@ -713,18 +713,23 @@ impl RpcSol for RpcSolImpl {
         meta: Self::Metadata,
         slot: Option<Slot>,
         commitment: Option<CommitmentConfig>,
-    ) -> Result<Option<Vec<String>>> {
+    ) -> Result<Option<RpcLeaderSchedule>> {
         let bank = meta.request_processor.read().unwrap().bank(commitment);
         let slot = slot.unwrap_or_else(|| bank.slot());
         let epoch = bank.epoch_schedule().get_epoch(slot);
+
         Ok(
             solana_ledger::leader_schedule_utils::leader_schedule(epoch, &bank).map(
                 |leader_schedule| {
-                    leader_schedule
-                        .get_slot_leaders()
-                        .iter()
-                        .map(|pubkey| pubkey.to_string())
-                        .collect()
+                    let mut map = HashMap::new();
+
+                    for (slot_index, pubkey) in
+                        leader_schedule.get_slot_leaders().iter().enumerate()
+                    {
+                        let pubkey = pubkey.to_string();
+                        map.entry(pubkey).or_insert_with(|| vec![]).push(slot_index);
+                    }
+                    map
                 },
             ),
         )
@@ -1394,7 +1399,7 @@ pub mod tests {
             let res: Response = serde_json::from_str(&rep.expect("actual response"))
                 .expect("actual response deserialization");
 
-            let schedule: Option<Vec<String>> = if let Response::Single(res) = res {
+            let schedule: Option<RpcLeaderSchedule> = if let Response::Single(res) = res {
                 if let Output::Success(res) = res {
                     serde_json::from_value(res.result).unwrap()
                 } else {
@@ -1403,9 +1408,14 @@ pub mod tests {
             } else {
                 panic!("Expected single response");
             };
+            let schedule = schedule.expect("leader schedule");
+
+            let bob_schedule = schedule
+                .get(&bank.collector_id().to_string())
+                .expect("leader not in the leader schedule");
 
             assert_eq!(
-                schedule.unwrap().len(),
+                bob_schedule.len(),
                 solana_ledger::leader_schedule_utils::leader_schedule(bank.epoch(), &bank)
                     .unwrap()
                     .get_slot_leaders()
@@ -1418,7 +1428,7 @@ pub mod tests {
         let res: Response = serde_json::from_str(&rep.expect("actual response"))
             .expect("actual response deserialization");
 
-        let schedule: Option<Vec<String>> = if let Response::Single(res) = res {
+        let schedule: Option<RpcLeaderSchedule> = if let Response::Single(res) = res {
             if let Output::Success(res) = res {
                 serde_json::from_value(res.result).unwrap()
             } else {