Add minimumLedgerSlot RPC API

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

@@ -40,6 +40,7 @@ To interact with a Solana node inside a JavaScript application, use the [solana-
 * [getTotalSupply](jsonrpc-api.md#gettotalsupply)
 * [getVersion](jsonrpc-api.md#getversion)
 * [getVoteAccounts](jsonrpc-api.md#getvoteaccounts)
+* [minimumLedgerSlot](jsonrpc-api.md#minimumledgerslot)
 * [requestAirdrop](jsonrpc-api.md#requestairdrop)
 * [sendTransaction](jsonrpc-api.md#sendtransaction)
 * [startSubscriptionChannel](jsonrpc-api.md#startsubscriptionchannel)
@@ -585,7 +586,7 @@ Returns the current slot the node is processing
 curl -X POST -H "Content-Type: application/json" -d '{"jsonrpc":"2.0","id":1, "method":"getSlot"}' http://localhost:8899
 
 // Result
-{"jsonrpc":"2.0","result":"1234","id":1}
+{"jsonrpc":"2.0","result":1234,"id":1}
 ```
 
 ### getSlotLeader
@@ -628,7 +629,7 @@ Returns the current storage segment size in terms of slots
 // Request
 curl -X POST -H "Content-Type: application/json" -d '{"jsonrpc":"2.0","id":1, "method":"getSlotsPerSegment"}' http://localhost:8899
 // Result
-{"jsonrpc":"2.0","result":"1024","id":1}
+{"jsonrpc":"2.0","result":1024,"id":1}
 ```
 
 ### getStorageTurn
@@ -772,6 +773,29 @@ curl -X POST -H "Content-Type: application/json" -d '{"jsonrpc":"2.0","id":1, "m
 {"jsonrpc":"2.0","result":{"current":[{"commission":0,"epochVoteAccount":true,"nodePubkey":"B97CCUW3AEZFGy6uUg6zUdnNYvnVq5VG8PUtb2HayTDD","lastVote":147,"activatedStake":42,"votePubkey":"3ZT31jkAGhUaw8jsy4bTknwBMP8i4Eueh52By4zXcsVw"}],"delinquent":[{"commission":127,"epochVoteAccount":false,"nodePubkey":"6ZPxeQaDo4bkZLRsdNrCzchNQr5LN9QMc9sipXv9Kw8f","lastVote":0,"activatedStake":0,"votePubkey":"CmgCk4aMS7KW1SHX3s9K5tBJ6Yng2LBaC8MFov4wx9sm"}]},"id":1}
 ```
 
+### minimumLedgerSlot
+
+Returns the lowest slot that the node has information about in its ledger.  This
+value may increase over time if the node is configured to purge older ledger data
+
+#### Parameters:
+
+None
+
+#### Results:
+
+* `u64` - Minimum ledger slot
+
+#### Example:
+
+```bash
+// Request
+curl -X POST -H "Content-Type: application/json" -d '{"jsonrpc":"2.0","id":1, "method":"minimumLedgerSlot"}' http://localhost:8899
+
+// Result
+{"jsonrpc":"2.0","result":1234,"id":1}
+```
+
 ### requestAirdrop
 
 Requests an airdrop of lamports to a Pubkey

client/src/rpc_client.rs

@@ -386,6 +386,25 @@ impl RpcClient {
         })
     }
 
+    pub fn minimum_ledger_slot(&self) -> io::Result<Slot> {
+        let response = self
+            .client
+            .send(&RpcRequest::MinimumLedgerSlot, Value::Null, 0)
+            .map_err(|err| {
+                io::Error::new(
+                    io::ErrorKind::Other,
+                    format!("MinimumLedgerSlot request failure: {:?}", err),
+                )
+            })?;
+
+        serde_json::from_value(response).map_err(|err| {
+            io::Error::new(
+                io::ErrorKind::Other,
+                format!("MinimumLedgerSlot parse failure: {}", err),
+            )
+        })
+    }
+
     pub fn send_and_confirm_transaction<T: KeypairUtil>(
         &self,
         transaction: &mut Transaction,

client/src/rpc_request.rs

@@ -35,6 +35,7 @@ pub enum RpcRequest {
     SendTransaction,
     SignVote,
     GetMinimumBalanceForRentExemption,
+    MinimumLedgerSlot,
 }
 
 impl RpcRequest {
@@ -75,6 +76,7 @@ impl RpcRequest {
             RpcRequest::SendTransaction => "sendTransaction",
             RpcRequest::SignVote => "signVote",
             RpcRequest::GetMinimumBalanceForRentExemption => "getMinimumBalanceForRentExemption",
+            RpcRequest::MinimumLedgerSlot => "minimumLedgerSlot",
         };
         json!({
            "jsonrpc": jsonrpc,

core/src/rpc.rs

@@ -229,6 +229,19 @@ impl JsonRpcRequestProcessor {
         Ok(self.bank(commitment).collector_id().to_string())
     }
 
+    fn minimum_ledger_slot(&self) -> Result<Slot> {
+        match self.blockstore.slot_meta_iterator(0) {
+            Ok(mut metas) => match metas.next() {
+                Some((slot, _meta)) => Ok(slot),
+                None => Err(Error::invalid_request()),
+            },
+            Err(err) => {
+                warn!("slot_meta_iterator failed: {:?}", err);
+                Err(Error::invalid_request())
+            }
+        }
+    }
+
     fn get_transaction_count(&self, commitment: Option<CommitmentConfig>) -> Result<u64> {
         Ok(self.bank(commitment).transaction_count() as u64)
     }
@@ -530,6 +543,9 @@ pub trait RpcSol {
         commitment: Option<CommitmentConfig>,
     ) -> Result<String>;
 
+    #[rpc(meta, name = "minimumLedgerSlot")]
+    fn minimum_ledger_slot(&self, meta: Self::Metadata) -> Result<Slot>;
+
     #[rpc(meta, name = "getVoteAccounts")]
     fn get_vote_accounts(
         &self,
@@ -990,6 +1006,10 @@ impl RpcSol for RpcSolImpl {
             .get_slot_leader(commitment)
     }
 
+    fn minimum_ledger_slot(&self, meta: Self::Metadata) -> Result<Slot> {
+        meta.request_processor.read().unwrap().minimum_ledger_slot()
+    }
+
     fn get_vote_accounts(
         &self,
         meta: Self::Metadata,
@@ -1379,6 +1399,21 @@ pub mod tests {
         assert_eq!(expected, result);
     }
 
+    #[test]
+    fn test_rpc_minimum_ledger_slot() {
+        let bob_pubkey = Pubkey::new_rand();
+        let RpcHandler { io, meta, .. } = start_rpc_handler_with_tx(&bob_pubkey);
+
+        let req = format!(r#"{{"jsonrpc":"2.0","id":1,"method":"minimumLedgerSlot"}}"#);
+        let res = io.handle_request_sync(&req, meta);
+        let expected = r#"{"jsonrpc":"2.0","result":0,"id":1}"#;
+        let expected: Response =
+            serde_json::from_str(&expected).expect("expected response deserialization");
+        let result: Response = serde_json::from_str(&res.expect("actual response"))
+            .expect("actual response deserialization");
+        assert_eq!(expected, result);
+    }
+
     #[test]
     fn test_rpc_get_total_supply() {
         let bob_pubkey = Pubkey::new_rand();