solana-rpc 4.3.0-beta.0

//! The `optimistically_confirmed_bank_tracker` module implements a threaded service to track the
//! most recent optimistically confirmed bank for use in rpc services, and triggers gossip
//! subscription notifications.
//! This module also supports notifying of slot status for subscribers using the SlotNotificationSender.
//! It receives the BankNotification events, transforms them into SlotNotification and sends them via
//! SlotNotificationSender in the following way:
//! BankNotification::OptimisticallyConfirmed --> SlotNotification::OptimisticallyConfirmed
//! BankNotification::Frozen --> SlotNotification::Frozen
//! BankNotification::NewRootedChain --> SlotNotification::Root for the roots in the chain.

use {
    crate::rpc_subscriptions::RpcSubscriptions,
    crossbeam_channel::{Receiver, RecvTimeoutError, Sender},
    solana_clock::{BankId, Slot},
    solana_hash::Hash,
    solana_rpc_client_api::response::{SlotTransactionStats, SlotUpdate},
    solana_runtime::{
        bank::Bank, bank_forks::BankForks, dependency_tracker::DependencyTracker,
        prioritization_fee_cache::PrioritizationFeeCache,
    },
    solana_time_utils::timestamp,
    std::{
        collections::HashSet,
        sync::{
            Arc, RwLock,
            atomic::{AtomicBool, Ordering},
        },
        thread::{self, Builder, JoinHandle},
        time::Duration,
    },
};

pub struct OptimisticallyConfirmedBank {
    pub bank: Arc<Bank>,
}

impl OptimisticallyConfirmedBank {
    pub fn locked_from_bank_forks_root(bank_forks: &RwLock<BankForks>) -> Arc<RwLock<Self>> {
        Arc::new(RwLock::new(Self {
            bank: bank_forks.read().unwrap().root_bank(),
        }))
    }
}

#[derive(Clone)]
pub enum BankNotification {
    OptimisticallyConfirmed(Slot, Hash),
    Frozen(Arc<Bank>),
    NewRootBank(Arc<Bank>),
    /// The newly rooted slot chain with bank ids and the parent slot of the oldest bank in the rooted chain.
    NewRootedChain(Vec<(Slot, BankId)>, Slot),
}

#[derive(Clone, Debug)]
pub enum SlotNotification {
    OptimisticallyConfirmed(Slot, BankId),
    /// The (Slot, Parent Slot, Bank Id) tuple for the slot frozen
    Frozen((Slot, Slot, BankId)),
    /// The (Slot, Parent Slot, Bank Id) tuple for the root slot
    Root((Slot, Slot, BankId)),
}

impl std::fmt::Debug for BankNotification {
    fn fmt(&self, f: &mut std::fmt::Formatter) -> std::fmt::Result {
        match self {
            BankNotification::OptimisticallyConfirmed(slot, hash) => {
                write!(f, "OptimisticallyConfirmed({slot:?}, {hash:?})")
            }
            BankNotification::Frozen(bank) => write!(f, "Frozen({})", bank.slot()),
            BankNotification::NewRootBank(bank) => write!(f, "Root({})", bank.slot()),
            BankNotification::NewRootedChain(chain, parent) => {
                write!(f, "RootedChain({chain:?}, parent: {parent})")
            }
        }
    }
}

pub type BankNotificationWithDependencyWork = (
    BankNotification,
    Option<u64>, // dependency work id
);

pub type BankNotificationReceiver = Receiver<BankNotificationWithDependencyWork>;
pub type BankNotificationSender = Sender<BankNotificationWithDependencyWork>;

#[derive(Clone)]
pub struct BankNotificationSenderConfig {
    pub sender: BankNotificationSender,
    pub should_send_parents: bool,
    pub dependency_tracker: Option<Arc<DependencyTracker>>,
}

pub type SlotNotificationReceiver = Receiver<SlotNotification>;
pub type SlotNotificationSender = Sender<SlotNotification>;
type PendingOptimisticallyConfirmedBanks = HashSet<(Slot, Hash)>;

pub struct OptimisticallyConfirmedBankTracker {
    thread_hdl: JoinHandle<()>,
}

impl OptimisticallyConfirmedBankTracker {
    pub fn new(
        receiver: BankNotificationReceiver,
        exit: Arc<AtomicBool>,
        bank_forks: Arc<RwLock<BankForks>>,
        optimistically_confirmed_bank: Arc<RwLock<OptimisticallyConfirmedBank>>,
        subscriptions: Arc<RpcSubscriptions>,
        slot_notification_subscribers: Option<Arc<RwLock<Vec<SlotNotificationSender>>>>,
        prioritization_fee_cache: Option<Arc<PrioritizationFeeCache>>,
        dependency_tracker: Option<Arc<DependencyTracker>>,
    ) -> Self {
        let mut pending_optimistically_confirmed_banks = HashSet::new();
        let mut last_notified_confirmed_slot: Slot = 0;
        let mut highest_confirmed_slot: Slot = 0;
        let mut newest_root_slot: Slot = 0;
        let thread_hdl = Builder::new()
            .name("solOpConfBnkTrk".to_string())
            .spawn(move || {
                loop {
                    if exit.load(Ordering::Relaxed) {
                        break;
                    }

                    if let Err(RecvTimeoutError::Disconnected) = Self::recv_notification(
                        &receiver,
                        &bank_forks,
                        &optimistically_confirmed_bank,
                        &subscriptions,
                        &mut pending_optimistically_confirmed_banks,
                        &mut last_notified_confirmed_slot,
                        &mut highest_confirmed_slot,
                        &mut newest_root_slot,
                        &slot_notification_subscribers,
                        prioritization_fee_cache.as_deref(),
                        &dependency_tracker,
                    ) {
                        break;
                    }
                }
            })
            .unwrap();
        Self { thread_hdl }
    }

    #[allow(clippy::too_many_arguments)]
    fn recv_notification(
        receiver: &Receiver<BankNotificationWithDependencyWork>,
        bank_forks: &RwLock<BankForks>,
        optimistically_confirmed_bank: &RwLock<OptimisticallyConfirmedBank>,
        subscriptions: &RpcSubscriptions,
        pending_optimistically_confirmed_banks: &mut PendingOptimisticallyConfirmedBanks,
        last_notified_confirmed_slot: &mut Slot,
        highest_confirmed_slot: &mut Slot,
        newest_root_slot: &mut Slot,
        slot_notification_subscribers: &Option<Arc<RwLock<Vec<SlotNotificationSender>>>>,
        prioritization_fee_cache: Option<&PrioritizationFeeCache>,
        dependency_tracker: &Option<Arc<DependencyTracker>>,
    ) -> Result<(), RecvTimeoutError> {
        let notification = receiver.recv_timeout(Duration::from_secs(1))?;
        Self::process_notification(
            notification,
            bank_forks,
            optimistically_confirmed_bank,
            subscriptions,
            pending_optimistically_confirmed_banks,
            last_notified_confirmed_slot,
            highest_confirmed_slot,
            newest_root_slot,
            slot_notification_subscribers,
            prioritization_fee_cache,
            dependency_tracker,
        );
        Ok(())
    }

    fn notify_slot_status(
        slot_notification_subscribers: &Option<Arc<RwLock<Vec<SlotNotificationSender>>>>,
        notification: SlotNotification,
    ) {
        if let Some(slot_notification_subscribers) = slot_notification_subscribers {
            for sender in slot_notification_subscribers.read().unwrap().iter() {
                match sender.send(notification.clone()) {
                    Ok(_) => {}
                    Err(err) => {
                        info!("Failed to send notification {notification:?}, error: {err:?}");
                    }
                }
            }
        }
    }

    fn notify_or_defer(
        subscriptions: &RpcSubscriptions,
        bank_forks: &RwLock<BankForks>,
        bank: &Bank,
        pending_confirmation: Option<(Slot, Hash)>,
        last_notified_confirmed_slot: &mut Slot,
        pending_optimistically_confirmed_banks: &mut PendingOptimisticallyConfirmedBanks,
        slot_notification_subscribers: &Option<Arc<RwLock<Vec<SlotNotificationSender>>>>,
        prioritization_fee_cache: Option<&PrioritizationFeeCache>,
    ) {
        if bank.is_frozen() {
            if bank.slot() > *last_notified_confirmed_slot {
                debug!(
                    "notify_or_defer notifying via notify_gossip_subscribers for slot {:?}",
                    bank.slot()
                );
                subscriptions.notify_gossip_subscribers(bank.slot());
                *last_notified_confirmed_slot = bank.slot();
                Self::notify_slot_status(
                    slot_notification_subscribers,
                    SlotNotification::OptimisticallyConfirmed(bank.slot(), bank.bank_id()),
                );

                // finalize block's minimum prioritization fee cache for this bank
                if let Some(prioritization_fee_cache) = prioritization_fee_cache {
                    prioritization_fee_cache.finalize_priority_fee(bank.slot(), bank.bank_id());
                }
            }
        } else if let Some((slot, hash)) = pending_confirmation
            && bank.slot() == slot
            && bank.slot() > bank_forks.read().unwrap().root()
        {
            pending_optimistically_confirmed_banks.insert((slot, hash));
            debug!("notify_or_defer defer notifying for slot {slot:?}");
        }
    }

    fn notify_or_defer_confirmed_banks(
        subscriptions: &RpcSubscriptions,
        bank_forks: &RwLock<BankForks>,
        bank: Arc<Bank>,
        slot_threshold: Slot,
        pending_confirmation: Option<(Slot, Hash)>,
        last_notified_confirmed_slot: &mut Slot,
        pending_optimistically_confirmed_banks: &mut PendingOptimisticallyConfirmedBanks,
        slot_notification_subscribers: &Option<Arc<RwLock<Vec<SlotNotificationSender>>>>,
        prioritization_fee_cache: Option<&PrioritizationFeeCache>,
    ) {
        for confirmed_bank in bank.parents_inclusive().iter().rev() {
            if confirmed_bank.slot() > slot_threshold {
                debug!(
                    "Calling notify_or_defer for confirmed_bank {:?}",
                    confirmed_bank.slot()
                );
                Self::notify_or_defer(
                    subscriptions,
                    bank_forks,
                    confirmed_bank,
                    pending_confirmation,
                    last_notified_confirmed_slot,
                    pending_optimistically_confirmed_banks,
                    slot_notification_subscribers,
                    prioritization_fee_cache,
                );
            }
        }
    }

    fn notify_new_root_slots(
        roots: &mut [(Slot, BankId)],
        oldest_parent: Slot,
        newest_root_slot: &mut Slot,
        slot_notification_subscribers: &Option<Arc<RwLock<Vec<SlotNotificationSender>>>>,
    ) {
        if slot_notification_subscribers.is_none() {
            return;
        }
        roots.sort_unstable_by_key(|(root, _bank_id)| *root);
        assert!(!roots.is_empty());
        let mut parent = oldest_parent;
        for (root, bank_id) in roots.iter() {
            if *root > *newest_root_slot {
                debug!("Doing SlotNotification::Root for root {root}, parent: {parent}");
                Self::notify_slot_status(
                    slot_notification_subscribers,
                    SlotNotification::Root((*root, parent, *bank_id)),
                );
                *newest_root_slot = *root;
            }
            parent = *root;
        }
    }

    #[allow(clippy::too_many_arguments)]
    pub fn process_notification(
        (notification, dependency_work): BankNotificationWithDependencyWork,
        bank_forks: &RwLock<BankForks>,
        optimistically_confirmed_bank: &RwLock<OptimisticallyConfirmedBank>,
        subscriptions: &RpcSubscriptions,
        pending_optimistically_confirmed_banks: &mut PendingOptimisticallyConfirmedBanks,
        last_notified_confirmed_slot: &mut Slot,
        highest_confirmed_slot: &mut Slot,
        newest_root_slot: &mut Slot,
        slot_notification_subscribers: &Option<Arc<RwLock<Vec<SlotNotificationSender>>>>,
        prioritization_fee_cache: Option<&PrioritizationFeeCache>,
        dependency_tracker: &Option<Arc<DependencyTracker>>,
    ) {
        debug!("received bank notification: {notification:?} event: {dependency_work:?}");

        if let Some(tracker) = dependency_tracker.as_ref()
            && let Some(dependency_work) = dependency_work
        {
            tracker.wait_for_dependency(dependency_work);
        }
        match notification {
            BankNotification::OptimisticallyConfirmed(slot, hash) => {
                let bank = bank_forks.read().unwrap().get(slot);
                if let Some(bank) = bank {
                    if bank.is_frozen() {
                        if bank.hash() != hash {
                            if slot > bank_forks.read().unwrap().root() {
                                pending_optimistically_confirmed_banks.insert((slot, hash));
                                debug!(
                                    "defer notifying optimistic confirmation for slot {slot}: \
                                     local bank hash {} does not match optimistic confirmation \
                                     hash {hash}",
                                    bank.hash()
                                );
                            }
                        } else {
                            let mut w_optimistically_confirmed_bank =
                                optimistically_confirmed_bank.write().unwrap();

                            if bank.slot() > w_optimistically_confirmed_bank.bank.slot() {
                                w_optimistically_confirmed_bank.bank = bank.clone();
                            }

                            if slot > *highest_confirmed_slot {
                                Self::notify_or_defer_confirmed_banks(
                                    subscriptions,
                                    bank_forks,
                                    bank,
                                    *highest_confirmed_slot,
                                    None,
                                    last_notified_confirmed_slot,
                                    pending_optimistically_confirmed_banks,
                                    slot_notification_subscribers,
                                    prioritization_fee_cache,
                                );

                                *highest_confirmed_slot = slot;
                            }
                            drop(w_optimistically_confirmed_bank);
                        }
                    } else if slot > bank_forks.read().unwrap().root() {
                        pending_optimistically_confirmed_banks.insert((slot, hash));
                        debug!("defer notifying optimistic confirmation for slot {slot}");
                    } else {
                        inc_new_counter_info!(
                            "dropped-already-rooted-optimistic-bank-notification",
                            1
                        );
                    }
                } else if slot > bank_forks.read().unwrap().root() {
                    pending_optimistically_confirmed_banks.insert((slot, hash));
                } else {
                    inc_new_counter_info!("dropped-already-rooted-optimistic-bank-notification", 1);
                }

                // Send slot notification regardless of whether the bank is replayed
                subscriptions.notify_slot_update(SlotUpdate::OptimisticConfirmation {
                    slot,
                    timestamp: timestamp(),
                });
                // NOTE: replay of `slot` may or may not be complete. Therefore, most new
                // functionality to be triggered on optimistic confirmation should go in
                // `notify_or_defer()` under the `bank.is_frozen()` case instead of here.
            }
            BankNotification::Frozen(bank) => {
                let frozen_slot = bank.slot();
                if let Some(parent) = bank.parent() {
                    let num_successful_transactions = bank
                        .transaction_count()
                        .saturating_sub(parent.transaction_count());
                    subscriptions.notify_slot_update(SlotUpdate::Frozen {
                        slot: frozen_slot,
                        timestamp: timestamp(),
                        stats: SlotTransactionStats {
                            num_transaction_entries: bank.transaction_entries_count(),
                            num_successful_transactions,
                            num_failed_transactions: bank.transaction_error_count(),
                            max_transactions_per_entry: bank.transactions_per_entry_max(),
                        },
                    });

                    Self::notify_slot_status(
                        slot_notification_subscribers,
                        SlotNotification::Frozen((bank.slot(), bank.parent_slot(), bank.bank_id())),
                    );
                }

                if pending_optimistically_confirmed_banks.remove(&(bank.slot(), bank.hash())) {
                    debug!(
                        "Calling notify_gossip_subscribers to send deferred notification \
                         {frozen_slot:?}"
                    );

                    Self::notify_or_defer_confirmed_banks(
                        subscriptions,
                        bank_forks,
                        bank.clone(),
                        *last_notified_confirmed_slot,
                        None,
                        last_notified_confirmed_slot,
                        pending_optimistically_confirmed_banks,
                        slot_notification_subscribers,
                        prioritization_fee_cache,
                    );
                    if frozen_slot > *highest_confirmed_slot {
                        *highest_confirmed_slot = frozen_slot;
                    }

                    let mut w_optimistically_confirmed_bank =
                        optimistically_confirmed_bank.write().unwrap();
                    if frozen_slot > w_optimistically_confirmed_bank.bank.slot() {
                        w_optimistically_confirmed_bank.bank = bank;
                    }
                    drop(w_optimistically_confirmed_bank);
                }
            }
            BankNotification::NewRootBank(bank) => {
                let root_slot = bank.slot();
                let mut w_optimistically_confirmed_bank =
                    optimistically_confirmed_bank.write().unwrap();
                if root_slot > w_optimistically_confirmed_bank.bank.slot() {
                    w_optimistically_confirmed_bank.bank = bank;
                }
                drop(w_optimistically_confirmed_bank);

                pending_optimistically_confirmed_banks.retain(|&(slot, _hash)| slot > root_slot);
            }
            BankNotification::NewRootedChain(mut roots, oldest_parent) => {
                Self::notify_new_root_slots(
                    &mut roots,
                    oldest_parent,
                    newest_root_slot,
                    slot_notification_subscribers,
                );
            }
        }
    }

    pub fn close(self) -> thread::Result<()> {
        self.join()
    }

    pub fn join(self) -> thread::Result<()> {
        self.thread_hdl.join()
    }
}

#[cfg(test)]
mod tests {
    use {
        super::*,
        crossbeam_channel::bounded,
        solana_ledger::genesis_utils::{GenesisConfigInfo, create_genesis_config},
        solana_runtime::{bank::SlotLeader, commitment::BlockCommitmentCache, dependency_tracker},
        std::sync::atomic::AtomicU64,
    };

    /// Receive the Root notifications from the channel, if no item received within 100 ms, break and return all
    /// of those received.
    fn get_root_notifications(receiver: &Receiver<SlotNotification>) -> Vec<SlotNotification> {
        let mut notifications = Vec::new();
        while let Ok(notification) = receiver.recv_timeout(Duration::from_millis(100)) {
            notifications.push(notification);
        }
        notifications
    }

    fn root_slot_notifications(root_bank: &Arc<Bank>) -> (Vec<(Slot, BankId)>, Slot) {
        let mut rooted_banks = root_bank.parents();
        let oldest_parent = rooted_banks
            .last()
            .map(|last| last.parent_slot())
            .unwrap_or_else(|| root_bank.parent_slot());
        rooted_banks.push(root_bank.clone());
        (
            rooted_banks
                .iter()
                .map(|bank| (bank.slot(), bank.bank_id()))
                .collect(),
            oldest_parent,
        )
    }

    #[test]
    fn test_process_notification() {
        let exit = Arc::new(AtomicBool::new(false));
        let GenesisConfigInfo { genesis_config, .. } = create_genesis_config(100);
        let bank = Bank::new_for_tests(&genesis_config);
        let bank_forks = BankForks::new_rw_arc(bank);
        let bank0 = bank_forks.read().unwrap().get(0).unwrap();
        let bank1 = Bank::new_from_parent(bank0, SlotLeader::default(), 1);
        bank_forks.write().unwrap().insert(bank1);
        let bank1 = bank_forks.read().unwrap().get(1).unwrap();
        let bank2 = Bank::new_from_parent(bank1, SlotLeader::default(), 2);
        bank_forks.write().unwrap().insert(bank2);
        let bank2 = bank_forks.read().unwrap().get(2).unwrap();
        let bank3 = Bank::new_from_parent(bank2, SlotLeader::default(), 3);
        bank_forks.write().unwrap().insert(bank3);
        let bank1_hash = bank_forks.read().unwrap().get(1).unwrap().hash();
        let bank2 = bank_forks.read().unwrap().get(2).unwrap();
        let bank2_hash = bank2.hash();
        let bank3_pending_hash = Hash::new_unique();

        let optimistically_confirmed_bank: Arc<RwLock<OptimisticallyConfirmedBank>> =
            OptimisticallyConfirmedBank::locked_from_bank_forks_root(&bank_forks);

        let block_commitment_cache = Arc::new(RwLock::new(BlockCommitmentCache::default()));
        let max_complete_transaction_status_slot = Arc::new(AtomicU64::default());
        let subscriptions = Arc::new(RpcSubscriptions::new_for_tests(
            exit,
            max_complete_transaction_status_slot,
            bank_forks.clone(),
            block_commitment_cache,
            optimistically_confirmed_bank.clone(),
        ));
        let mut pending_optimistically_confirmed_banks = PendingOptimisticallyConfirmedBanks::new();

        assert_eq!(optimistically_confirmed_bank.read().unwrap().bank.slot(), 0);

        let mut highest_confirmed_slot: Slot = 0;
        let mut newest_root_slot: Slot = 0;

        let mut last_notified_confirmed_slot: Slot = 0;
        OptimisticallyConfirmedBankTracker::process_notification(
            (
                BankNotification::OptimisticallyConfirmed(2, bank2_hash),
                None, /* no dependency work */
            ),
            &bank_forks,
            &optimistically_confirmed_bank,
            &subscriptions,
            &mut pending_optimistically_confirmed_banks,
            &mut last_notified_confirmed_slot,
            &mut highest_confirmed_slot,
            &mut newest_root_slot,
            &None,
            None,
            &None, // No dependency tracker
        );
        assert_eq!(optimistically_confirmed_bank.read().unwrap().bank.slot(), 2);
        assert_eq!(highest_confirmed_slot, 2);

        // Test max optimistically confirmed bank remains in the cache
        OptimisticallyConfirmedBankTracker::process_notification(
            (
                BankNotification::OptimisticallyConfirmed(1, bank1_hash),
                None, /* no dependency work */
            ),
            &bank_forks,
            &optimistically_confirmed_bank,
            &subscriptions,
            &mut pending_optimistically_confirmed_banks,
            &mut last_notified_confirmed_slot,
            &mut highest_confirmed_slot,
            &mut newest_root_slot,
            &None,
            None,
            &None, // No dependency tracker
        );
        assert_eq!(optimistically_confirmed_bank.read().unwrap().bank.slot(), 2);
        assert_eq!(highest_confirmed_slot, 2);

        // Test bank will only be cached when frozen
        OptimisticallyConfirmedBankTracker::process_notification(
            (
                BankNotification::OptimisticallyConfirmed(3, bank3_pending_hash),
                None, /* no dependency work */
            ),
            &bank_forks,
            &optimistically_confirmed_bank,
            &subscriptions,
            &mut pending_optimistically_confirmed_banks,
            &mut last_notified_confirmed_slot,
            &mut highest_confirmed_slot,
            &mut newest_root_slot,
            &None,
            None,
            &None, // No dependency tracker
        );
        assert_eq!(optimistically_confirmed_bank.read().unwrap().bank.slot(), 2);
        assert_eq!(pending_optimistically_confirmed_banks.len(), 1);
        assert!(pending_optimistically_confirmed_banks.contains(&(3, bank3_pending_hash)));
        assert_eq!(highest_confirmed_slot, 2);

        // Test bank will only be cached when frozen
        let bank3 = bank_forks.read().unwrap().get(3).unwrap();
        bank3.freeze();
        assert!(pending_optimistically_confirmed_banks.remove(&(3, bank3_pending_hash)));
        pending_optimistically_confirmed_banks.insert((3, bank3.hash()));

        OptimisticallyConfirmedBankTracker::process_notification(
            (
                BankNotification::Frozen(bank3),
                None, /* no dependency work */
            ),
            &bank_forks,
            &optimistically_confirmed_bank,
            &subscriptions,
            &mut pending_optimistically_confirmed_banks,
            &mut last_notified_confirmed_slot,
            &mut highest_confirmed_slot,
            &mut newest_root_slot,
            &None,
            None,
            &None, // No dependency tracker
        );
        assert_eq!(optimistically_confirmed_bank.read().unwrap().bank.slot(), 3);
        assert_eq!(highest_confirmed_slot, 3);
        assert_eq!(pending_optimistically_confirmed_banks.len(), 0);

        // Test higher root will be cached and clear pending_optimistically_confirmed_banks
        let bank3 = bank_forks.read().unwrap().get(3).unwrap();
        let bank4 = Bank::new_from_parent(bank3, SlotLeader::default(), 4);
        bank_forks.write().unwrap().insert(bank4);
        let bank4_hash = Hash::new_unique();
        OptimisticallyConfirmedBankTracker::process_notification(
            (
                BankNotification::OptimisticallyConfirmed(4, bank4_hash),
                None, /* no dependency work */
            ),
            &bank_forks,
            &optimistically_confirmed_bank,
            &subscriptions,
            &mut pending_optimistically_confirmed_banks,
            &mut last_notified_confirmed_slot,
            &mut highest_confirmed_slot,
            &mut newest_root_slot,
            &None,
            None,
            &None, // No dependency tracker
        );
        assert_eq!(optimistically_confirmed_bank.read().unwrap().bank.slot(), 3);
        assert_eq!(pending_optimistically_confirmed_banks.len(), 1);
        assert!(pending_optimistically_confirmed_banks.contains(&(4, bank4_hash)));
        assert_eq!(highest_confirmed_slot, 3);

        let bank4 = bank_forks.read().unwrap().get(4).unwrap();
        let bank5 = Bank::new_from_parent(bank4, SlotLeader::default(), 5);
        bank_forks.write().unwrap().insert(bank5);
        let bank5 = bank_forks.read().unwrap().get(5).unwrap();

        let mut bank_notification_senders = Vec::new();
        let (sender, receiver) = bounded(1024);
        bank_notification_senders.push(sender);

        let subscribers = Some(Arc::new(RwLock::new(bank_notification_senders)));
        let (parent_roots, oldest_parent) = root_slot_notifications(&bank5);

        OptimisticallyConfirmedBankTracker::process_notification(
            (
                BankNotification::NewRootBank(bank5),
                None, /* no dependency work */
            ),
            &bank_forks,
            &optimistically_confirmed_bank,
            &subscriptions,
            &mut pending_optimistically_confirmed_banks,
            &mut last_notified_confirmed_slot,
            &mut highest_confirmed_slot,
            &mut newest_root_slot,
            &subscribers,
            None,
            &None, // No dependency tracker
        );
        assert_eq!(optimistically_confirmed_bank.read().unwrap().bank.slot(), 5);
        assert_eq!(pending_optimistically_confirmed_banks.len(), 0);
        assert!(!pending_optimistically_confirmed_banks.contains(&(4, bank4_hash)));
        assert_eq!(highest_confirmed_slot, 3);
        // The newest_root_slot is updated via NewRootedChain only
        assert_eq!(newest_root_slot, 0);

        OptimisticallyConfirmedBankTracker::process_notification(
            (
                BankNotification::NewRootedChain(parent_roots, oldest_parent),
                None, /* no dependency work */
            ),
            &bank_forks,
            &optimistically_confirmed_bank,
            &subscriptions,
            &mut pending_optimistically_confirmed_banks,
            &mut last_notified_confirmed_slot,
            &mut highest_confirmed_slot,
            &mut newest_root_slot,
            &subscribers,
            None,
            &None, // No dependency tracker
        );

        assert_eq!(newest_root_slot, 5);

        // Obtain the root notifications, we expect 5, including that for bank5.
        let notifications = get_root_notifications(&receiver);
        assert_eq!(notifications.len(), 5);

        // Banks <= root do not get added to pending list, even if not frozen
        let bank5 = bank_forks.read().unwrap().get(5).unwrap();
        let bank6 = Bank::new_from_parent(bank5, SlotLeader::default(), 6);
        bank_forks.write().unwrap().insert(bank6);
        let bank5 = bank_forks.read().unwrap().get(5).unwrap();
        let bank7 = Bank::new_from_parent(bank5, SlotLeader::default(), 7);
        bank_forks.write().unwrap().insert(bank7);
        bank_forks.write().unwrap().set_root(7, None, None);
        let bank6_hash = Hash::new_unique();
        OptimisticallyConfirmedBankTracker::process_notification(
            (
                BankNotification::OptimisticallyConfirmed(6, bank6_hash),
                None, /* no dependency work */
            ),
            &bank_forks,
            &optimistically_confirmed_bank,
            &subscriptions,
            &mut pending_optimistically_confirmed_banks,
            &mut last_notified_confirmed_slot,
            &mut highest_confirmed_slot,
            &mut newest_root_slot,
            &None,
            None,
            &None, // No dependency tracker
        );
        assert_eq!(optimistically_confirmed_bank.read().unwrap().bank.slot(), 5);
        assert_eq!(pending_optimistically_confirmed_banks.len(), 0);
        assert!(!pending_optimistically_confirmed_banks.contains(&(6, bank6_hash)));
        assert_eq!(highest_confirmed_slot, 3);
        assert_eq!(newest_root_slot, 5);

        let bank7 = bank_forks.read().unwrap().get(7).unwrap();
        let (parent_roots, oldest_parent) = root_slot_notifications(&bank7);

        OptimisticallyConfirmedBankTracker::process_notification(
            (
                BankNotification::NewRootBank(bank7),
                None, /* no dependency work */
            ),
            &bank_forks,
            &optimistically_confirmed_bank,
            &subscriptions,
            &mut pending_optimistically_confirmed_banks,
            &mut last_notified_confirmed_slot,
            &mut highest_confirmed_slot,
            &mut newest_root_slot,
            &subscribers,
            None,
            &None, // No dependency tracker
        );
        assert_eq!(optimistically_confirmed_bank.read().unwrap().bank.slot(), 7);
        assert_eq!(pending_optimistically_confirmed_banks.len(), 0);
        assert!(!pending_optimistically_confirmed_banks.contains(&(6, bank6_hash)));
        assert_eq!(highest_confirmed_slot, 3);
        assert_eq!(newest_root_slot, 5);

        OptimisticallyConfirmedBankTracker::process_notification(
            (
                BankNotification::NewRootedChain(parent_roots, oldest_parent),
                None, /* no dependency work */
            ),
            &bank_forks,
            &optimistically_confirmed_bank,
            &subscriptions,
            &mut pending_optimistically_confirmed_banks,
            &mut last_notified_confirmed_slot,
            &mut highest_confirmed_slot,
            &mut newest_root_slot,
            &subscribers,
            None,
            &None, // No dependency tracker
        );

        assert_eq!(newest_root_slot, 7);

        // Obtain the root notifications, we expect 1, which is for bank7 only as its parent bank5 is already notified.
        let notifications = get_root_notifications(&receiver);
        assert_eq!(notifications.len(), 1);
    }

    #[test]
    fn test_event_synchronization() {
        let exit = Arc::new(AtomicBool::new(false));
        let dependency_tracker: Arc<DependencyTracker> =
            Arc::new(dependency_tracker::DependencyTracker::default());
        let work_id_1 = 345;
        let work_id_2 = 678;
        let tracker_clone = dependency_tracker.clone();
        let handle = thread::spawn(move || {
            let GenesisConfigInfo { genesis_config, .. } = create_genesis_config(100);
            let bank = Bank::new_for_tests(&genesis_config);
            let bank_forks = BankForks::new_rw_arc(bank);

            // Test bank will only be cached when frozen
            let bank0 = bank_forks.read().unwrap().get(0).unwrap();
            let bank1 = Bank::new_from_parent(bank0, SlotLeader::default(), 1);
            bank_forks.write().unwrap().insert(bank1);
            let bank1_pending_hash = Hash::new_unique();

            let mut pending_optimistically_confirmed_banks =
                PendingOptimisticallyConfirmedBanks::new();
            let max_complete_transaction_status_slot = Arc::new(AtomicU64::default());

            let block_commitment_cache = Arc::new(RwLock::new(BlockCommitmentCache::default()));

            let mut highest_confirmed_slot: Slot = 0;
            let mut newest_root_slot: Slot = 0;

            let mut last_notified_confirmed_slot: Slot = 0;

            let optimistically_confirmed_bank: Arc<RwLock<OptimisticallyConfirmedBank>> =
                OptimisticallyConfirmedBank::locked_from_bank_forks_root(&bank_forks);

            let subscriptions = Arc::new(RpcSubscriptions::new_for_tests(
                exit,
                max_complete_transaction_status_slot,
                bank_forks.clone(),
                block_commitment_cache,
                optimistically_confirmed_bank.clone(),
            ));

            // confirmed without fronzen received
            OptimisticallyConfirmedBankTracker::process_notification(
                (
                    BankNotification::OptimisticallyConfirmed(1, bank1_pending_hash),
                    Some(work_id_1), /* dependency work id */
                ),
                &bank_forks,
                &optimistically_confirmed_bank,
                &subscriptions,
                &mut pending_optimistically_confirmed_banks,
                &mut last_notified_confirmed_slot,
                &mut highest_confirmed_slot,
                &mut newest_root_slot,
                &None,
                None,
                &Some(tracker_clone.clone()),
            );

            assert_eq!(optimistically_confirmed_bank.read().unwrap().bank.slot(), 0);
            assert_eq!(highest_confirmed_slot, 0);
            assert_eq!(pending_optimistically_confirmed_banks.len(), 1);
            assert!(pending_optimistically_confirmed_banks.contains(&(1, bank1_pending_hash)));

            let bank1 = bank_forks.read().unwrap().get(1).unwrap();
            bank1.freeze();
            assert!(pending_optimistically_confirmed_banks.remove(&(1, bank1_pending_hash)));
            pending_optimistically_confirmed_banks.insert((1, bank1.hash()));

            OptimisticallyConfirmedBankTracker::process_notification(
                (
                    BankNotification::Frozen(bank1),
                    Some(work_id_2), /* dependency work id */
                ),
                &bank_forks,
                &optimistically_confirmed_bank,
                &subscriptions,
                &mut pending_optimistically_confirmed_banks,
                &mut last_notified_confirmed_slot,
                &mut highest_confirmed_slot,
                &mut newest_root_slot,
                &None,
                None,
                &Some(tracker_clone),
            );

            assert_eq!(optimistically_confirmed_bank.read().unwrap().bank.slot(), 1);
            assert_eq!(highest_confirmed_slot, 1);
            assert_eq!(pending_optimistically_confirmed_banks.len(), 0);
        });

        dependency_tracker.mark_this_and_all_previous_work_processed(work_id_1);
        dependency_tracker.mark_this_and_all_previous_work_processed(work_id_2);

        handle.join().unwrap();
    }
}