GetLeaderSchedule RPC API can now return a schedule for arbitrary epoches

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

@@ -373,15 +373,16 @@ curl -X POST -H "Content-Type: application/json" -d '{"jsonrpc":"2.0","id":1, "m
 
 ### getLeaderSchedule
 
-Returns the leader schedule for the current epoch
+Returns the leader schedule for an epoch
 
 #### Parameters:
 
+* `slot` - (optional) Fetch the leader schedule for the epoch that corresponds to the provided slot.  If unspecified, the leader schedule for the current epoch is fetch
 * `object` - (optional) [Commitment](jsonrpc-api.md#configuring-state-commitment)
 
 #### Results:
 
-The result field will be an array of leader public keys \(as base-58 encoded strings\) for each slot in the current epoch
+The result field will be an array of leader public keys \(as base-58 encoded strings\) for each slot in the epoch
 
 #### Example:
 

client/src/rpc_client.rs

@@ -248,6 +248,39 @@ impl RpcClient {
         })
     }
 
+    pub fn get_leader_schedule(&self, slot: Option<Slot>) -> io::Result<Option<Vec<String>>> {
+        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>>> {
+        let params = slot.map(|slot| json!(slot));
+        let response = self
+            .client
+            .send(
+                &RpcRequest::GetLeaderSchedule,
+                params,
+                0,
+                commitment_config.ok(),
+            )
+            .map_err(|err| {
+                io::Error::new(
+                    io::ErrorKind::Other,
+                    format!("GetLeaderSchedule request failure: {:?}", err),
+                )
+            })?;
+
+        serde_json::from_value(response).map_err(|err| {
+            io::Error::new(
+                io::ErrorKind::Other,
+                format!("GetLeaderSchedule failure: {}", err),
+            )
+        })
+    }
+
     pub fn get_epoch_schedule(&self) -> io::Result<EpochSchedule> {
         let response = self
             .client

client/src/rpc_request.rs

@@ -121,6 +121,7 @@ pub enum RpcRequest {
     GetEpochSchedule,
     GetGenesisHash,
     GetInflation,
+    GetLeaderSchedule,
     GetNumBlocksSinceSignatureConfirmation,
     GetProgramAccounts,
     GetRecentBlockhash,
@@ -161,6 +162,7 @@ impl RpcRequest {
             RpcRequest::GetEpochSchedule => "getEpochSchedule",
             RpcRequest::GetGenesisHash => "getGenesisHash",
             RpcRequest::GetInflation => "getInflation",
+            RpcRequest::GetLeaderSchedule => "getLeaderSchedule",
             RpcRequest::GetNumBlocksSinceSignatureConfirmation => {
                 "getNumBlocksSinceSignatureConfirmation"
             }

core/src/rpc.rs

@@ -419,7 +419,7 @@ pub trait RpcSol {
     fn get_block_commitment(
         &self,
         meta: Self::Metadata,
-        block: u64,
+        block: Slot,
     ) -> Result<(Option<BlockCommitment>, u64)>;
 
     #[rpc(meta, name = "getGenesisHash")]
@@ -429,6 +429,7 @@ pub trait RpcSol {
     fn get_leader_schedule(
         &self,
         meta: Self::Metadata,
+        slot: Option<Slot>,
         commitment: Option<CommitmentConfig>,
     ) -> Result<Option<Vec<String>>>;
 
@@ -679,8 +680,9 @@ impl RpcSol for RpcSolImpl {
     ) -> Result<RpcEpochInfo> {
         let bank = meta.request_processor.read().unwrap().bank(commitment);
         let epoch_schedule = bank.epoch_schedule();
-        let (epoch, slot_index) = epoch_schedule.get_epoch_and_slot_index(bank.slot());
+
         let slot = bank.slot();
+        let (epoch, slot_index) = epoch_schedule.get_epoch_and_slot_index(slot);
         Ok(RpcEpochInfo {
             epoch,
             slot_index,
@@ -709,11 +711,14 @@ impl RpcSol for RpcSolImpl {
     fn get_leader_schedule(
         &self,
         meta: Self::Metadata,
+        slot: Option<Slot>,
         commitment: Option<CommitmentConfig>,
     ) -> Result<Option<Vec<String>>> {
         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(bank.epoch(), &bank).map(
+            solana_ledger::leader_schedule_utils::leader_schedule(epoch, &bank).map(
                 |leader_schedule| {
                     leader_schedule
                         .get_slot_leaders()
@@ -1374,6 +1379,57 @@ pub mod tests {
         assert_eq!(epoch_schedule, *bank.epoch_schedule());
     }
 
+    #[test]
+    fn test_rpc_get_leader_schedule() {
+        let bob_pubkey = Pubkey::new_rand();
+        let RpcHandler { io, meta, bank, .. } = start_rpc_handler_with_tx(&bob_pubkey);
+
+        for req in [
+            r#"{"jsonrpc":"2.0","id":1,"method":"getLeaderSchedule", "params": [0]}"#,
+            r#"{"jsonrpc":"2.0","id":1,"method":"getLeaderSchedule"}"#,
+        ]
+        .iter()
+        {
+            let rep = io.handle_request_sync(&req, meta.clone());
+            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 {
+                if let Output::Success(res) = res {
+                    serde_json::from_value(res.result).unwrap()
+                } else {
+                    panic!("Expected success for {}", req);
+                }
+            } else {
+                panic!("Expected single response");
+            };
+
+            assert_eq!(
+                schedule.unwrap().len(),
+                solana_ledger::leader_schedule_utils::leader_schedule(bank.epoch(), &bank)
+                    .unwrap()
+                    .get_slot_leaders()
+                    .len()
+            );
+        }
+
+        let req = r#"{"jsonrpc":"2.0","id":1,"method":"getLeaderSchedule", "params": [42424242]}"#;
+        let rep = io.handle_request_sync(&req, meta);
+        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 {
+            if let Output::Success(res) = res {
+                serde_json::from_value(res.result).unwrap()
+            } else {
+                panic!("Expected success");
+            }
+        } else {
+            panic!("Expected single response");
+        };
+        assert_eq!(schedule, None);
+    }
+
     #[test]
     fn test_rpc_get_account_info() {
         let bob_pubkey = Pubkey::new_rand();