Squash supermajority root on blockstore replay at startup (#11727)

ledger/src/blockstore_processor.rs

@@ -18,6 +18,7 @@ use solana_runtime::{
     bank::{Bank, TransactionBalancesSet, TransactionProcessResult, TransactionResults},
     bank_forks::BankForks,
     bank_utils,
+    commitment::VOTE_THRESHOLD_SIZE,
     transaction_batch::TransactionBatch,
     transaction_utils::OrderedIterator,
     vote_sender_types::ReplayVoteSender,
@@ -31,9 +32,10 @@ use solana_sdk::{
     timing::duration_as_ms,
     transaction::{Result, Transaction, TransactionError},
 };
+use solana_vote_program::vote_state::VoteState;
 use std::{
     cell::RefCell,
-    collections::HashMap,
+    collections::{BTreeMap, HashMap},
     path::PathBuf,
     result,
     sync::Arc,
@@ -454,6 +456,7 @@ pub fn verify_ticks(
 ) -> std::result::Result<(), BlockError> {
     let next_bank_tick_height = bank.tick_height() + entries.tick_count();
     let max_bank_tick_height = bank.max_tick_height();
+
     if next_bank_tick_height > max_bank_tick_height {
         warn!("Too many entry ticks found in slot: {}", bank.slot());
         return Err(BlockError::InvalidTickCount);
@@ -757,11 +760,18 @@ fn load_frozen_forks(
     transaction_status_sender: Option<TransactionStatusSender>,
 ) -> result::Result<Vec<Arc<Bank>>, BlockstoreProcessorError> {
     let mut initial_forks = HashMap::new();
+    let mut all_banks = HashMap::new();
     let mut last_status_report = Instant::now();
     let mut pending_slots = vec![];
     let mut last_root_slot = root_bank.slot();
     let mut slots_elapsed = 0;
     let mut txs = 0;
+    let blockstore_max_root = blockstore.max_root();
+    let max_root = std::cmp::max(root_bank.slot(), blockstore_max_root);
+    info!(
+        "load_frozen_forks() latest root from blockstore: {}, max_root: {}",
+        blockstore_max_root, max_root,
+    );
     process_next_slots(
         root_bank,
         root_meta,
@@ -810,14 +820,49 @@ fn load_frozen_forks(
         }
         txs += progress.num_txs;
 
-        if blockstore.is_root(slot) {
+        // Block must be frozen by this point, otherwise `process_single_slot` would
-            *root = slot;
+        // have errored above
-            leader_schedule_cache.set_root(&bank);
+        assert!(bank.is_frozen());
-            bank.squash();
+        all_banks.insert(bank.slot(), bank.clone());
-            pending_slots.clear();
+
-            initial_forks.clear();
+        // If we've reached the last known root in blockstore, start looking
-            last_root_slot = slot;
+        // for newer cluster confirmed roots
+        let new_root_bank = {
+            if *root == max_root {
+                supermajority_root_from_bank(&bank).and_then(|supermajority_root| {
+                    if supermajority_root > *root {
+                        // If there's a cluster confirmed root greater than our last
+                        // replayed root, then beccause the cluster confirmed root should
+                        // be descended from our last root, it must exist in `all_banks`
+                        let cluster_root_bank = all_banks.get(&supermajority_root).unwrap();
+
+                        // cluster root must be a descendant of our root, otherwise something
+                        // is drastically wrong
+                        assert!(cluster_root_bank.ancestors.contains_key(root));
+                        info!("blockstore processor found new cluster confirmed root: {}, observed in bank: {}", cluster_root_bank.slot(), bank.slot());
+                        Some(cluster_root_bank)
+                    } else {
+                        None
                     }
+                })
+            } else if blockstore.is_root(slot) {
+                Some(&bank)
+            } else {
+                None
+            }
+        };
+
+        if let Some(new_root_bank) = new_root_bank {
+            *root = new_root_bank.slot();
+            last_root_slot = new_root_bank.slot();
+            leader_schedule_cache.set_root(&new_root_bank);
+            new_root_bank.squash();
+
+            // Filter out all non descendants of the new root
+            pending_slots.retain(|(_, pending_bank, _)| pending_bank.ancestors.contains_key(root));
+            initial_forks.retain(|_, fork_tip_bank| fork_tip_bank.ancestors.contains_key(root));
+        }
+
         slots_elapsed += 1;
 
         trace!(
@@ -844,6 +889,51 @@ fn load_frozen_forks(
     Ok(initial_forks.values().cloned().collect::<Vec<_>>())
 }
 
+fn supermajority_root(roots: &BTreeMap<Slot, u64>, total_epoch_stake: u64) -> Option<Slot> {
+    // Find latest root
+    let mut total = 0;
+    for (root, stake) in roots.iter().rev() {
+        total += stake;
+        if total as f64 / total_epoch_stake as f64 > VOTE_THRESHOLD_SIZE {
+            return Some(*root);
+        }
+    }
+
+    None
+}
+
+fn supermajority_root_from_bank(bank: &Bank) -> Option<Slot> {
+    let roots: BTreeMap<Slot, u64> = bank
+        .vote_accounts()
+        .into_iter()
+        .filter_map(|(key, (stake, account))| {
+            if stake == 0 {
+                return None;
+            }
+
+            let vote_state = VoteState::from(&account);
+            if vote_state.is_none() {
+                warn!(
+                    "Unable to get vote_state from account {} in bank: {}",
+                    key,
+                    bank.slot()
+                );
+                return None;
+            }
+
+            vote_state
+                .unwrap()
+                .root_slot
+                .map(|root_slot| (root_slot, stake))
+        })
+        .collect();
+
+    let total_epoch_stake = bank.total_epoch_stake();
+
+    // Find latest root
+    supermajority_root(&roots, total_epoch_stake)
+}
+
 // Processes and replays the contents of a single slot, returns Error
 // if failed to play the slot
 fn process_single_slot(
@@ -871,6 +961,7 @@ fn process_single_slot(
     })?;
 
     bank.freeze(); // all banks handled by this routine are created from complete slots
+
     Ok(())
 }
 
@@ -951,7 +1042,7 @@ pub mod tests {
     use matches::assert_matches;
     use rand::{thread_rng, Rng};
     use solana_runtime::genesis_utils::{
-        create_genesis_config_with_vote_accounts, ValidatorVoteKeypairs,
+        self, create_genesis_config_with_vote_accounts, ValidatorVoteKeypairs,
     };
     use solana_sdk::account::Account;
     use solana_sdk::{
@@ -963,8 +1054,9 @@ pub mod tests {
         system_transaction,
         transaction::{Transaction, TransactionError},
     };
-    use solana_vote_program::vote_transaction;
+    use solana_vote_program::{vote_state::MAX_LOCKOUT_HISTORY, vote_transaction};
     use std::{collections::BTreeSet, sync::RwLock};
+    use trees::tr;
 
     #[test]
     fn test_process_blockstore_with_missing_hashes() {
@@ -1535,11 +1627,11 @@ pub mod tests {
         let blockstore =
             Blockstore::open(&ledger_path).expect("Expected to successfully open database ledger");
 
-        // Let last_slot be the number of slots in the first two epochs
+        // Let `last_slot` be the number of slots in the first two epochs
         let epoch_schedule = get_epoch_schedule(&genesis_config, Vec::new());
         let last_slot = epoch_schedule.get_last_slot_in_epoch(1);
 
-        // Create a single chain of slots with all indexes in the range [0, last_slot + 1]
+        // Create a single chain of slots with all indexes in the range [0, v + 1]
         for i in 1..=last_slot + 1 {
             last_entry_hash = fill_blockstore_slot_with_ticks(
                 &blockstore,
@@ -2824,4 +2916,153 @@ pub mod tests {
             .collect();
         assert_eq!(successes, expected_successful_voter_pubkeys);
     }
+
+    fn make_slot_with_vote_tx(
+        blockstore: &Blockstore,
+        ticks_per_slot: u64,
+        tx_landed_slot: Slot,
+        parent_slot: Slot,
+        parent_blockhash: &Hash,
+        vote_tx: Transaction,
+        slot_leader_keypair: &Arc<Keypair>,
+    ) {
+        // Add votes to `last_slot` so that `root` will be confirmed
+        let vote_entry = next_entry(&parent_blockhash, 1, vec![vote_tx]);
+        let mut entries = create_ticks(ticks_per_slot, 0, vote_entry.hash);
+        entries.insert(0, vote_entry);
+        blockstore
+            .write_entries(
+                tx_landed_slot,
+                0,
+                0,
+                ticks_per_slot,
+                Some(parent_slot),
+                true,
+                &slot_leader_keypair,
+                entries,
+                0,
+            )
+            .unwrap();
+    }
+
+    fn run_test_process_blockstore_with_supermajority_root(blockstore_root: Option<Slot>) {
+        solana_logger::setup();
+        /*
+            Build fork structure:
+                 slot 0
+                   |
+                 slot 1 <- (blockstore root)
+                 /    \
+            slot 2    |
+               |      |
+            slot 4    |
+                    slot 5
+                      |
+                `expected_root_slot`
+                     /    \
+                  ...    minor fork
+                  /
+            `last_slot`
+        */
+        let starting_fork_slot = 5;
+        let mut main_fork = tr(starting_fork_slot);
+        let mut main_fork_ref = main_fork.root_mut();
+
+        // Make enough slots to make a root slot > blockstore_root
+        let expected_root_slot = starting_fork_slot + blockstore_root.unwrap_or(0);
+        let last_main_fork_slot = expected_root_slot + MAX_LOCKOUT_HISTORY as u64 + 1;
+
+        // Make `minor_fork`
+        let last_minor_fork_slot = last_main_fork_slot + 1;
+        let minor_fork = tr(last_minor_fork_slot);
+
+        // Make 'main_fork`
+        for slot in starting_fork_slot + 1..last_main_fork_slot {
+            if slot - 1 == expected_root_slot {
+                main_fork_ref.push_front(minor_fork.clone());
+            }
+            main_fork_ref.push_front(tr(slot));
+            main_fork_ref = main_fork_ref.first_mut().unwrap();
+        }
+        let forks = tr(0) / (tr(1) / (tr(2) / (tr(4))) / main_fork);
+        let validator_keypairs = ValidatorVoteKeypairs::new_rand();
+        let GenesisConfigInfo { genesis_config, .. } =
+            genesis_utils::create_genesis_config_with_vote_accounts(
+                10_000,
+                &[&validator_keypairs],
+                vec![100],
+            );
+        let ticks_per_slot = genesis_config.ticks_per_slot();
+        let ledger_path = get_tmp_ledger_path!();
+        let blockstore = Blockstore::open(&ledger_path).unwrap();
+        blockstore.add_tree(forks, false, true, ticks_per_slot, genesis_config.hash());
+
+        if let Some(blockstore_root) = blockstore_root {
+            blockstore.set_roots(&[blockstore_root]).unwrap();
+        }
+
+        let opts = ProcessOptions {
+            poh_verify: true,
+            ..ProcessOptions::default()
+        };
+        let (bank_forks, _leader_schedule) =
+            process_blockstore(&genesis_config, &blockstore, Vec::new(), opts.clone()).unwrap();
+
+        let last_vote_bank_hash = bank_forks.get(last_main_fork_slot - 1).unwrap().hash();
+        let last_vote_blockhash = bank_forks
+            .get(last_main_fork_slot - 1)
+            .unwrap()
+            .last_blockhash();
+        let slots: Vec<_> = (expected_root_slot..last_main_fork_slot).collect();
+        let vote_tx = vote_transaction::new_vote_transaction(
+            slots,
+            last_vote_bank_hash,
+            last_vote_blockhash,
+            &validator_keypairs.node_keypair,
+            &validator_keypairs.vote_keypair,
+            &validator_keypairs.vote_keypair,
+            None,
+        );
+
+        // Add votes to `last_slot` so that `root` will be confirmed
+        let leader_keypair = Arc::new(validator_keypairs.node_keypair);
+        make_slot_with_vote_tx(
+            &blockstore,
+            ticks_per_slot,
+            last_main_fork_slot,
+            last_main_fork_slot - 1,
+            &last_vote_blockhash,
+            vote_tx,
+            &leader_keypair,
+        );
+
+        let (bank_forks, _leader_schedule) =
+            process_blockstore(&genesis_config, &blockstore, Vec::new(), opts).unwrap();
+
+        assert_eq!(bank_forks.root(), expected_root_slot);
+        assert_eq!(
+            bank_forks.frozen_banks().len() as u64,
+            last_minor_fork_slot - expected_root_slot + 1
+        );
+
+        // Minor fork at `last_main_fork_slot + 1` was above the `expected_root_slot`
+        // so should not have been purged
+        //
+        // Fork at slot 2 was purged because it was below the `expected_root_slot`
+        for slot in 0..=last_minor_fork_slot {
+            if slot >= expected_root_slot {
+                let bank = bank_forks.get(slot).unwrap();
+                assert_eq!(bank.slot(), slot);
+                assert!(bank.is_frozen());
+            } else {
+                assert!(bank_forks.get(slot).is_none());
+            }
+        }
+    }
+
+    #[test]
+    fn test_process_blockstore_with_supermajority_root() {
+        run_test_process_blockstore_with_supermajority_root(None);
+        run_test_process_blockstore_with_supermajority_root(Some(1))
+    }
 }