From 23c2e55cbf00ee339380e5b28c3b1a7629cd927b Mon Sep 17 00:00:00 2001
From: Greg Fitzgerald <greg@solana.com>
Date: Mon, 20 Jul 2020 17:03:40 -0600
Subject: [PATCH] Use BlockCommitmentCache for RPC slots, take 2 (#11137)

* Use BlockCommitmentCache for RPC slots (#11103)

* Add BankForks::highest_descendant(slot)

* Update debug messages

* Update core/src/rpc.rs

Co-authored-by: Tyera Eulberg <teulberg@gmail.com>

* cargo fmt

* Remove highest_descendant

* Fix test

Co-authored-by: Tyera Eulberg <teulberg@gmail.com>

* Fix crossed-in-flight compilation error

Co-authored-by: Tyera Eulberg <teulberg@gmail.com>
---
 core/src/rpc.rs           | 48 ++++++++++++++++++++++++---------------
 runtime/src/commitment.rs | 18 ++++++++++++++-
 2 files changed, 47 insertions(+), 19 deletions(-)

diff --git a/core/src/rpc.rs b/core/src/rpc.rs
index 63f0e1b56d..31ee28f13d 100644
--- a/core/src/rpc.rs
+++ b/core/src/rpc.rs
@@ -112,36 +112,27 @@ impl JsonRpcRequestProcessor {
             Some(config) => config.commitment,
         };
 
-        let slot = match commitment_level {
+        let slot = self
+            .block_commitment_cache
+            .read()
+            .unwrap()
+            .slot_with_commitment(commitment_level);
+
+        match commitment_level {
             CommitmentLevel::Recent => {
-                let slot = r_bank_forks.highest_slot();
-                debug!("RPC using working_bank: {:?}", slot);
-                slot
+                debug!("RPC using the heaviest slot: {:?}", slot);
             }
             CommitmentLevel::Root => {
-                let slot = r_bank_forks.root();
                 debug!("RPC using node root: {:?}", slot);
-                slot
             }
             CommitmentLevel::Single | CommitmentLevel::SingleGossip => {
-                let slot = self
-                    .block_commitment_cache
-                    .read()
-                    .unwrap()
-                    .highest_confirmed_slot();
                 debug!("RPC using confirmed slot: {:?}", slot);
-                slot
             }
             CommitmentLevel::Max => {
-                let slot = self
-                    .block_commitment_cache
-                    .read()
-                    .unwrap()
-                    .highest_confirmed_root();
                 debug!("RPC using block: {:?}", slot);
-                slot
             }
         };
+
         r_bank_forks.get(slot).cloned().unwrap()
     }
 
@@ -3674,6 +3665,24 @@ pub mod tests {
         assert_eq!(expected, result);
     }
 
+    fn advance_block_commitment_cache(
+        block_commitment_cache: &Arc<RwLock<BlockCommitmentCache>>,
+        bank_forks: &Arc<RwLock<BankForks>>,
+    ) {
+        let mut new_block_commitment = BlockCommitmentCache::new(
+            HashMap::new(),
+            0,
+            CommitmentSlots {
+                root: 0,
+                slot: bank_forks.read().unwrap().highest_slot(),
+                highest_confirmed_slot: 0,
+                highest_confirmed_root: 0,
+            },
+        );
+        let mut w_block_commitment_cache = block_commitment_cache.write().unwrap();
+        std::mem::swap(&mut *w_block_commitment_cache, &mut new_block_commitment);
+    }
+
     #[test]
     fn test_get_vote_accounts() {
         let RpcHandler {
@@ -3683,6 +3692,7 @@ pub mod tests {
             bank_forks,
             alice,
             leader_vote_keypair,
+            block_commitment_cache,
             ..
         } = start_rpc_handler_with_tx(&Pubkey::new_rand());
 
@@ -3761,6 +3771,7 @@ pub mod tests {
                 &Pubkey::default(),
                 bank.slot() + 1,
             ));
+            advance_block_commitment_cache(&block_commitment_cache, &bank_forks);
 
             let transaction = Transaction::new_signed_with_payer(
                 &instructions,
@@ -3814,6 +3825,7 @@ pub mod tests {
             &Pubkey::default(),
             bank.slot() + TEST_SLOTS_PER_EPOCH,
         ));
+        advance_block_commitment_cache(&block_commitment_cache, &bank_forks);
 
         // The leader vote account should now be delinquent, and the other vote account disappears
         // because it's inactive with no stake
diff --git a/runtime/src/commitment.rs b/runtime/src/commitment.rs
index 7ad0cddd5d..47a00feb77 100644
--- a/runtime/src/commitment.rs
+++ b/runtime/src/commitment.rs
@@ -1,4 +1,4 @@
-use solana_sdk::clock::Slot;
+use solana_sdk::{clock::Slot, commitment_config::CommitmentLevel};
 use solana_vote_program::vote_state::MAX_LOCKOUT_HISTORY;
 use std::collections::HashMap;
 
@@ -103,6 +103,22 @@ impl BlockCommitmentCache {
         self.commitment_slots
     }
 
+    pub fn highest_gossip_confirmed_slot(&self) -> Slot {
+        // TODO: see solana_core::RpcSubscriptions:
+        //self.last_checked_slots.get(&CommitmentLevel::SingleGossip).unwrap_or(&0)
+        self.highest_confirmed_slot()
+    }
+
+    pub fn slot_with_commitment(&self, commitment_level: CommitmentLevel) -> Slot {
+        match commitment_level {
+            CommitmentLevel::Recent => self.slot(),
+            CommitmentLevel::Root => self.root(),
+            CommitmentLevel::Single => self.highest_confirmed_slot(),
+            CommitmentLevel::SingleGossip => self.highest_gossip_confirmed_slot(),
+            CommitmentLevel::Max => self.highest_confirmed_root(),
+        }
+    }
+
     fn highest_slot_with_confirmation_count(&self, confirmation_count: usize) -> Slot {
         assert!(confirmation_count > 0 && confirmation_count <= MAX_LOCKOUT_HISTORY);
         for slot in (self.root()..self.slot()).rev() {