// This file is part of Substrate.
// Copyright (C) Parity Technologies (UK) Ltd.
// SPDX-License-Identifier: GPL-3.0-or-later WITH Classpath-exception-2.0
// This program is free software: you can redistribute it and/or modify
// it under the terms of the GNU General Public License as published by
// the Free Software Foundation, either version 3 of the License, or
// (at your option) any later version.
// This program is distributed in the hope that it will be useful,
// but WITHOUT ANY WARRANTY; without even the implied warranty of
// MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
// GNU General Public License for more details.
// You should have received a copy of the GNU General Public License
// along with this program. If not, see <https://www.gnu.org/licenses/>.
use std::{collections::HashMap, fmt::Debug, hash};
use linked_hash_map::LinkedHashMap;
use tracing::trace;
use super::{watcher, BlockHash, ChainApi, ExtrinsicHash};
static LOG_TARGET: &str = "txpool::watcher";
/// The `EventHandler` trait provides a mechanism for clients to respond to various
/// transaction-related events. It offers a set of callback methods that are invoked by the
/// transaction pool's event dispatcher to notify about changes in the status of transactions.
///
/// This trait can be implemented by any component that needs to respond to transaction lifecycle
/// events, enabling custom logic and handling of these events.
pub trait EventHandler<C: ChainApi> {
/// Called when a transaction is broadcasted.
fn broadcasted(&self, _hash: ExtrinsicHash<C>, _peers: Vec<String>) {}
/// Called when a transaction is ready for execution.
fn ready(&self, _tx: ExtrinsicHash<C>) {}
/// Called when a transaction is deemed to be executable in the future.
fn future(&self, _tx: ExtrinsicHash<C>) {}
/// Called when transaction pool limits result in a transaction being affected.
fn limits_enforced(&self, _tx: ExtrinsicHash<C>) {}
/// Called when a transaction is replaced by another.
fn usurped(&self, _tx: ExtrinsicHash<C>, _by: ExtrinsicHash<C>) {}
/// Called when a transaction is dropped from the pool.
fn dropped(&self, _tx: ExtrinsicHash<C>) {}
/// Called when a transaction is found to be invalid.
fn invalid(&self, _tx: ExtrinsicHash<C>) {}
/// Called when a transaction was pruned from the pool due to its presence in imported block.
fn pruned(&self, _tx: ExtrinsicHash<C>, _block_hash: BlockHash<C>, _tx_index: usize) {}
/// Called when a transaction is retracted from inclusion in a block.
fn retracted(&self, _tx: ExtrinsicHash<C>, _block_hash: BlockHash<C>) {}
/// Called when a transaction has not been finalized within a timeout period.
fn finality_timeout(&self, _tx: ExtrinsicHash<C>, _hash: BlockHash<C>) {}
/// Called when a transaction is finalized in a block.
fn finalized(&self, _tx: ExtrinsicHash<C>, _block_hash: BlockHash<C>, _tx_index: usize) {}
}
impl<C: ChainApi> EventHandler<C> for () {}
/// The `EventDispatcher` struct is responsible for dispatching transaction-related events from the
/// validated pool to interested observers and an optional event handler. It acts as the primary
/// liaison between the transaction pool and clients that are monitoring transaction statuses.
pub struct EventDispatcher<H: hash::Hash + Eq, C: ChainApi, L: EventHandler<C>> {
/// Map containing per-transaction sinks for emitting transaction status events.
watchers: HashMap<H, watcher::Sender<H, BlockHash<C>>>,
finality_watchers: LinkedHashMap<ExtrinsicHash<C>, Vec<H>>,
/// Optional event handler (listener) that will be notified about all transactions status
/// changes from the pool.
event_handler: Option<L>,
}
/// Maximum number of blocks awaiting finality at any time.
const MAX_FINALITY_WATCHERS: usize = 512;
impl<H: hash::Hash + Eq + Debug, C: ChainApi, L: EventHandler<C>> Default
for EventDispatcher<H, C, L>
{
fn default() -> Self {
Self {
watchers: Default::default(),
finality_watchers: Default::default(),
event_handler: None,
}
}
}
impl<C: ChainApi, L: EventHandler<C>> EventDispatcher<ExtrinsicHash<C>, C, L> {
/// Creates a new instance with provided event handler.
pub fn new_with_event_handler(event_handler: Option<L>) -> Self {
Self { event_handler, ..Default::default() }
}
fn fire<F>(&mut self, hash: &ExtrinsicHash<C>, fun: F)
where
F: FnOnce(&mut watcher::Sender<ExtrinsicHash<C>, ExtrinsicHash<C>>),
{
let clean = if let Some(h) = self.watchers.get_mut(hash) {
fun(h);
h.is_done()
} else {
false
};
if clean {
self.watchers.remove(hash);
}
}
/// Creates a new watcher for given verified extrinsic.
///
/// The watcher can be used to subscribe to life-cycle events of that extrinsic.
pub fn create_watcher(
&mut self,
hash: ExtrinsicHash<C>,
) -> watcher::Watcher<ExtrinsicHash<C>, ExtrinsicHash<C>> {
let sender = self.watchers.entry(hash).or_insert_with(watcher::Sender::default);
sender.new_watcher(hash)
}
/// Notify the listeners about the extrinsic broadcast.
pub fn broadcasted(&mut self, tx_hash: &ExtrinsicHash<C>, peers: Vec<String>) {
trace!(
target: LOG_TARGET,
?tx_hash,
"Broadcasted."
);
self.fire(tx_hash, |watcher| watcher.broadcast(peers.clone()));
self.event_handler.as_ref().map(|l| l.broadcasted(*tx_hash, peers));
}
/// New transaction was added to the ready pool or promoted from the future pool.
pub fn ready(&mut self, tx: &ExtrinsicHash<C>, old: Option<&ExtrinsicHash<C>>) {
trace!(
target: LOG_TARGET,
tx_hash = ?*tx,
replaced_with = ?old,
"Ready."
);
self.fire(tx, |watcher| watcher.ready());
if let Some(old) = old {
self.fire(old, |watcher| watcher.usurped(*tx));
}
self.event_handler.as_ref().map(|l| l.ready(*tx));
}
/// New transaction was added to the future pool.
pub fn future(&mut self, tx_hash: &ExtrinsicHash<C>) {
trace!(
target: LOG_TARGET,
?tx_hash,
"Future."
);
self.fire(tx_hash, |watcher| watcher.future());
self.event_handler.as_ref().map(|l| l.future(*tx_hash));
}
/// Transaction was dropped from the pool because of enforcing the limit.
pub fn limits_enforced(&mut self, tx_hash: &ExtrinsicHash<C>) {
trace!(
target: LOG_TARGET,
?tx_hash,
"Dropped (limits enforced)."
);
self.fire(tx_hash, |watcher| watcher.limit_enforced());
self.event_handler.as_ref().map(|l| l.limits_enforced(*tx_hash));
}
/// Transaction was replaced with other extrinsic.
pub fn usurped(&mut self, tx: &ExtrinsicHash<C>, by: &ExtrinsicHash<C>) {
trace!(
target: LOG_TARGET,
tx_hash = ?tx,
?by,
"Dropped (replaced)."
);
self.fire(tx, |watcher| watcher.usurped(*by));
self.event_handler.as_ref().map(|l| l.usurped(*tx, *by));
}
/// Transaction was dropped from the pool because of the failure during the resubmission of
/// revalidate transactions or failure during pruning tags.
pub fn dropped(&mut self, tx_hash: &ExtrinsicHash<C>) {
trace!(
target: LOG_TARGET,
?tx_hash,
"Dropped."
);
self.fire(tx_hash, |watcher| watcher.dropped());
self.event_handler.as_ref().map(|l| l.dropped(*tx_hash));
}
/// Transaction was removed as invalid.
pub fn invalid(&mut self, tx_hash: &ExtrinsicHash<C>) {
trace!(
target: LOG_TARGET,
?tx_hash,
"Extrinsic invalid."
);
self.fire(tx_hash, |watcher| watcher.invalid());
self.event_handler.as_ref().map(|l| l.invalid(*tx_hash));
}
/// Transaction was pruned from the pool.
pub fn pruned(&mut self, block_hash: BlockHash<C>, tx_hash: &ExtrinsicHash<C>) {
trace!(
target: LOG_TARGET,
?tx_hash,
?block_hash,
"Pruned at."
);
// Get the transactions included in the given block hash.
let txs = self.finality_watchers.entry(block_hash).or_insert(vec![]);
txs.push(*tx_hash);
// Current transaction is the last one included.
let tx_index = txs.len() - 1;
self.fire(tx_hash, |watcher| watcher.in_block(block_hash, tx_index));
self.event_handler.as_ref().map(|l| l.pruned(*tx_hash, block_hash, tx_index));
while self.finality_watchers.len() > MAX_FINALITY_WATCHERS {
if let Some((hash, txs)) = self.finality_watchers.pop_front() {
for tx in txs {
self.fire(&tx, |watcher| watcher.finality_timeout(hash));
self.event_handler.as_ref().map(|l| l.finality_timeout(tx, block_hash));
}
}
}
}
/// The block this transaction was included in has been retracted.
pub fn retracted(&mut self, block_hash: BlockHash<C>) {
if let Some(hashes) = self.finality_watchers.remove(&block_hash) {
for hash in hashes {
self.fire(&hash, |watcher| watcher.retracted(block_hash));
self.event_handler.as_ref().map(|l| l.retracted(hash, block_hash));
}
}
}
/// Notify all watchers that transactions have been finalized
pub fn finalized(&mut self, block_hash: BlockHash<C>) {
if let Some(hashes) = self.finality_watchers.remove(&block_hash) {
for (tx_index, tx_hash) in hashes.into_iter().enumerate() {
trace!(
target: LOG_TARGET,
?tx_hash,
?block_hash,
"Sent finalization event."
);
self.fire(&tx_hash, |watcher| watcher.finalized(block_hash, tx_index));
self.event_handler.as_ref().map(|l| l.finalized(tx_hash, block_hash, tx_index));
}
}
}
/// Provides hashes of all watched transactions.
pub fn watched_transactions(&self) -> impl Iterator<Item = &ExtrinsicHash<C>> {
self.watchers.keys()
}
}