323 lines
11 KiB
Rust
323 lines
11 KiB
Rust
//! Zebra mempool.
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use std::{
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collections::HashSet,
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future::Future,
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iter,
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pin::Pin,
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task::{Context, Poll},
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};
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use futures::{future::FutureExt, stream::Stream};
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use tower::{buffer::Buffer, timeout::Timeout, util::BoxService, Service};
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use zebra_chain::{
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chain_tip::ChainTip,
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parameters::Network,
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transaction::{UnminedTx, UnminedTxId},
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};
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use zebra_consensus::{error::TransactionError, transaction};
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use zebra_network as zn;
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use zebra_state as zs;
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use zebra_state::{ChainTipChange, TipAction};
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pub use crate::BoxError;
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mod crawler;
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pub mod downloads;
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mod error;
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mod storage;
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#[cfg(test)]
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mod tests;
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pub use self::crawler::Crawler;
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pub use self::error::MempoolError;
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#[cfg(test)]
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pub use self::storage::tests::unmined_transactions_in_blocks;
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use self::downloads::{
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Downloads as TxDownloads, Gossip, TRANSACTION_DOWNLOAD_TIMEOUT, TRANSACTION_VERIFY_TIMEOUT,
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};
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use super::sync::SyncStatus;
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type Outbound = Buffer<BoxService<zn::Request, zn::Response, zn::BoxError>, zn::Request>;
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type State = Buffer<BoxService<zs::Request, zs::Response, zs::BoxError>, zs::Request>;
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type TxVerifier = Buffer<
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BoxService<transaction::Request, transaction::Response, TransactionError>,
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transaction::Request,
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>;
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type InboundTxDownloads = TxDownloads<Timeout<Outbound>, Timeout<TxVerifier>, State>;
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#[derive(Debug, Eq, PartialEq)]
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#[allow(dead_code)]
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pub enum Request {
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TransactionIds,
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TransactionsById(HashSet<UnminedTxId>),
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RejectedTransactionIds(HashSet<UnminedTxId>),
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Queue(Vec<Gossip>),
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}
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#[derive(Debug)]
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pub enum Response {
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Transactions(Vec<UnminedTx>),
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TransactionIds(Vec<UnminedTxId>),
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RejectedTransactionIds(Vec<UnminedTxId>),
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Queued(Vec<Result<(), MempoolError>>),
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}
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/// The state of the mempool.
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///
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/// Indicates wether it is enabled or disabled and, if enabled, contains
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/// the necessary data to run it.
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enum ActiveState {
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/// The Mempool is disabled.
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Disabled,
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/// The Mempool is enabled.
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Enabled {
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/// The Mempool storage itself.
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///
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/// ##: Correctness: only components internal to the [`Mempool`] struct are allowed to
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/// inject transactions into `storage`, as transactions must be verified beforehand.
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storage: storage::Storage,
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/// The transaction download and verify stream.
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tx_downloads: Pin<Box<InboundTxDownloads>>,
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},
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}
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/// Mempool async management and query service.
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///
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/// The mempool is the set of all verified transactions that this node is aware
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/// of that have yet to be confirmed by the Zcash network. A transaction is
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/// confirmed when it has been included in a block ('mined').
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pub struct Mempool {
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/// The state of the mempool.
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active_state: ActiveState,
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/// Allows checking if we are near the tip to enable/disable the mempool.
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sync_status: SyncStatus,
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/// Allow efficient access to the best tip of the blockchain.
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latest_chain_tip: zs::LatestChainTip,
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/// Allows the detection of chain tip resets.
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chain_tip_change: ChainTipChange,
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/// Handle to the outbound service.
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/// Used to construct the transaction downloader.
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outbound: Outbound,
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/// Handle to the state service.
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/// Used to construct the transaction downloader.
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state: State,
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/// Handle to the transaction verifier service.
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/// Used to construct the transaction downloader.
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tx_verifier: TxVerifier,
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}
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impl Mempool {
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pub(crate) fn new(
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_network: Network,
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outbound: Outbound,
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state: State,
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tx_verifier: TxVerifier,
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sync_status: SyncStatus,
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latest_chain_tip: zs::LatestChainTip,
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chain_tip_change: ChainTipChange,
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) -> Self {
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Mempool {
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active_state: ActiveState::Disabled,
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sync_status,
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latest_chain_tip,
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chain_tip_change,
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outbound,
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state,
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tx_verifier,
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}
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}
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/// Update the mempool state (enabled / disabled) depending on how close to
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/// the tip is the synchronization, including side effects to state changes.
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fn update_state(&mut self) {
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let is_close_to_tip = self.sync_status.is_close_to_tip();
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if self.is_enabled() == is_close_to_tip {
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// the active state is up to date
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return;
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}
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// Update enabled / disabled state
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if is_close_to_tip {
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let tx_downloads = Box::pin(TxDownloads::new(
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Timeout::new(self.outbound.clone(), TRANSACTION_DOWNLOAD_TIMEOUT),
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Timeout::new(self.tx_verifier.clone(), TRANSACTION_VERIFY_TIMEOUT),
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self.state.clone(),
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));
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self.active_state = ActiveState::Enabled {
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storage: Default::default(),
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tx_downloads,
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};
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} else {
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self.active_state = ActiveState::Disabled
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}
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}
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/// Return whether the mempool is enabled or not.
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pub fn is_enabled(&self) -> bool {
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match self.active_state {
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ActiveState::Disabled => false,
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ActiveState::Enabled { .. } => true,
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}
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}
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/// Check if transaction should be downloaded and/or verified.
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///
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/// If it is already in the mempool (or in its rejected list)
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/// then it shouldn't be downloaded/verified.
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fn should_download_or_verify(
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storage: &mut storage::Storage,
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txid: UnminedTxId,
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) -> Result<(), MempoolError> {
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// Check if the transaction is already in the mempool.
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if storage.contains(&txid) {
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return Err(MempoolError::InMempool);
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}
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if storage.contains_rejected(&txid) {
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return Err(MempoolError::Rejected);
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}
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Ok(())
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}
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}
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impl Service<Request> for Mempool {
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type Response = Response;
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type Error = BoxError;
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type Future =
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Pin<Box<dyn Future<Output = Result<Self::Response, Self::Error>> + Send + 'static>>;
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fn poll_ready(&mut self, cx: &mut Context<'_>) -> Poll<Result<(), Self::Error>> {
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self.update_state();
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match &mut self.active_state {
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ActiveState::Enabled {
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storage,
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tx_downloads,
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} => {
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if let Some(tip_action) = self.chain_tip_change.last_tip_change() {
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match tip_action {
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// Clear the mempool and cancel downloads if there has been a chain tip reset.
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TipAction::Reset { .. } => {
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storage.clear();
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tx_downloads.cancel_all();
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}
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// Cancel downloads/verifications of transactions with the same
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// IDs as recently mined transactions.
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TipAction::Grow { block } => {
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let txid_set = block.transaction_hashes.iter().collect();
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tx_downloads.cancel(txid_set);
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}
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}
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}
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// Clean up completed download tasks and add to mempool if successful.
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while let Poll::Ready(Some(r)) = tx_downloads.as_mut().poll_next(cx) {
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if let Ok(tx) = r {
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// Storage handles conflicting transactions or a full mempool internally,
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// so just ignore the storage result here
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let _ = storage.insert(tx);
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}
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}
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// Remove expired transactions from the mempool.
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if let Some(tip_height) = self.latest_chain_tip.best_tip_height() {
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remove_expired_transactions(storage, tip_height);
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}
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}
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ActiveState::Disabled => {
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// When the mempool is disabled we still return that the service is ready.
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// Otherwise, callers could block waiting for the mempool to be enabled,
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// which may not be the desired behavior.
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}
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}
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Poll::Ready(Ok(()))
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}
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/// Call the mempool service.
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///
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/// Errors indicate that the peer has done something wrong or unexpected,
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/// and will cause callers to disconnect from the remote peer.
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#[instrument(name = "mempool", skip(self, req))]
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fn call(&mut self, req: Request) -> Self::Future {
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match &mut self.active_state {
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ActiveState::Enabled {
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storage,
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tx_downloads,
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} => match req {
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Request::TransactionIds => {
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let res = storage.tx_ids();
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async move { Ok(Response::TransactionIds(res)) }.boxed()
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}
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Request::TransactionsById(ids) => {
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let rsp = Ok(storage.transactions(ids)).map(Response::Transactions);
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async move { rsp }.boxed()
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}
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Request::RejectedTransactionIds(ids) => {
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let rsp = Ok(storage.rejected_transactions(ids))
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.map(Response::RejectedTransactionIds);
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async move { rsp }.boxed()
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}
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Request::Queue(gossiped_txs) => {
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let rsp: Vec<Result<(), MempoolError>> = gossiped_txs
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.into_iter()
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.map(|gossiped_tx| {
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Self::should_download_or_verify(storage, gossiped_tx.id())?;
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tx_downloads.download_if_needed_and_verify(gossiped_tx)?;
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Ok(())
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})
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.collect();
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async move { Ok(Response::Queued(rsp)) }.boxed()
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}
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},
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ActiveState::Disabled => {
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// We can't return an error since that will cause a disconnection
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// by the peer connection handler. Therefore, return successful
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// empty responses.
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let resp = match req {
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Request::TransactionIds => Response::TransactionIds(Default::default()),
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Request::TransactionsById(_) => Response::Transactions(Default::default()),
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Request::RejectedTransactionIds(_) => {
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Response::RejectedTransactionIds(Default::default())
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}
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// Special case; we can signal the error inside the response.
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Request::Queue(gossiped_txs) => Response::Queued(
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iter::repeat(Err(MempoolError::Disabled))
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.take(gossiped_txs.len())
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.collect(),
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),
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};
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async move { Ok(resp) }.boxed()
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}
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}
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}
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}
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/// Remove transactions from the mempool if they have not been mined after a specified height.
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///
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/// https://zips.z.cash/zip-0203#specification
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fn remove_expired_transactions(
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storage: &mut storage::Storage,
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tip_height: zebra_chain::block::Height,
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) {
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let ids = storage.tx_ids().iter().copied().collect();
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let transactions = storage.transactions(ids);
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for t in transactions {
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if let Some(expiry_height) = t.transaction.expiry_height() {
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if tip_height >= expiry_height {
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storage.remove(&t.id);
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}
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}
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}
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}
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