1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136
137
138
139
140
141
142
143
144
145
146
147
148
149
150
151
152
153
154
155
156
157
158
159
160
161
162
163
164
165
166
167
168
169
170
171
172
173
174
175
176
177
178
179
180
181
182
183
184
185
186
187
188
189
190
191
192
193
194
195
196
197
198
199
200
201
202
203
204
205
206
207
208
209
210
211
212
213
214
215
216
217
218
219
220
221
222
223
224
225
226
227
228
229
230
231
232
233
234
235
236
237
238
239
240
241
242
243
244
245
246
247
248
249
250
251
252
253
254
255
256
257
258
259
260
261
262
263
264
265
266
267
268
269
270
271
272
273
274
275
276
277
278
279
280
281
282
283
284
285
286
287
288
289
290
291
292
293
294
295
296
297
298
299
300
301
302
303
304
305
306
307
308
309
310
311
312
313
314
315
316
317
318
319
320
321
322
323
324
325
326
327
328
329
330
331
332
333
334
335
336
337
338
339
340
341
342
343
344
345
346
347
348
349
350
351
352
353
354
355
356
357
358
359
360
361
362
363
364
365
366
367
368
369
370
371
372
373
374
375
376
377
378
379
380
381
382
383
384
385
386
387
388
389
390
391
392
393
394
395
396
397
398
399
400
401
402
403
404
405
406
407
408
409
410
411
412
413
414
415
416
417
418
419
420
421
422
423
424
425
426
427
428
429
430
431
432
433
434
435
436
437
438
439
440
441
442
443
444
445
446
447
448
449
450
451
452
453
454
455
456
457
458
459
460
461
462
463
464
465
466
467
468
469
470
471
472
473
474
475
476
477
478
479
480
481
482
483
484
485
486
487
488
489
490
491
492
493
494
495
496
497
498
499
500
501
502
503
504
505
506
507
508
509
510
511
512
513
514
515
516
517
518
519
520
521
522
523
524
525
526
527
528
529
530
531
532
533
534
535
536
537
538
539
540
541
542
543
544
545
546
547
548
549
550
551
552
553
554
555
556
557
558
559
560
561
562
563
564
565
566
567
568
569
570
571
572
573
574
575
576
577
578
579
580
581
582
583
584
585
586
587
588
589
590
591
592
593
594
595
596
597
598
599
600
601
602
603
604
605
606
607
608
609
610
611
612
613
614
615
616
617
618
619
620
621
622
623
624
625
626
627
628
629
630
631
632
633
634
635
636
637
638
639
640
641
642
643
644
645
646
647
648
649
650
651
652
653
654
655
656
657
658
659
660
661
662
663
664
665
666
667
668
669
670
671
672
673
674
675
676
677
678
679
680
681
682
683
684
685
686
687
688
689
690
691
692
693
694
695
696
697
698
699
700
701
702
703
704
705
706
707
708
709
710
711
712
713
714
715
716
717
718
719
720
721
722
723
724
725
726
727
728
729
730
731
732
733
734
735
736
737
738
739
740
741
742
743
744
745
746
747
748
749
750
751
752
753
754
755
756
757
758
759
760
761
762
763
764
765
766
767
768
769
770
771
772
773
774
775
776
777
778
779
780
781
782
783
784
785
786
787
788
789
790
791
792
793
794
// 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/>.

//! Substrate transaction pool implementation.

#![recursion_limit = "256"]
#![warn(missing_docs)]
#![warn(unused_extern_crates)]

mod api;
mod enactment_state;
pub mod error;
mod graph;
mod metrics;
mod revalidation;
#[cfg(test)]
mod tests;

pub use crate::api::FullChainApi;
use async_trait::async_trait;
use enactment_state::{EnactmentAction, EnactmentState};
use futures::{
	channel::oneshot,
	future::{self, ready},
	prelude::*,
};
pub use graph::{
	base_pool::Limit as PoolLimit, ChainApi, Options, Pool, Transaction, ValidatedTransaction,
};
use parking_lot::Mutex;
use std::{
	collections::{HashMap, HashSet},
	pin::Pin,
	sync::Arc,
};

use graph::{ExtrinsicHash, IsValidator};
use sc_transaction_pool_api::{
	error::Error as TxPoolError, ChainEvent, ImportNotificationStream, MaintainedTransactionPool,
	PoolFuture, PoolStatus, ReadyTransactions, TransactionFor, TransactionPool, TransactionSource,
	TransactionStatusStreamFor, TxHash,
};
use sp_core::traits::SpawnEssentialNamed;
use sp_runtime::{
	generic::BlockId,
	traits::{AtLeast32Bit, Block as BlockT, Extrinsic, Header as HeaderT, NumberFor, Zero},
};
use std::time::Instant;

use crate::metrics::MetricsLink as PrometheusMetrics;
use prometheus_endpoint::Registry as PrometheusRegistry;

use sp_blockchain::{HashAndNumber, TreeRoute};

pub(crate) const LOG_TARGET: &str = "txpool";

type BoxedReadyIterator<Hash, Data> =
	Box<dyn ReadyTransactions<Item = Arc<graph::base_pool::Transaction<Hash, Data>>> + Send>;

type ReadyIteratorFor<PoolApi> =
	BoxedReadyIterator<graph::ExtrinsicHash<PoolApi>, graph::ExtrinsicFor<PoolApi>>;

type PolledIterator<PoolApi> = Pin<Box<dyn Future<Output = ReadyIteratorFor<PoolApi>> + Send>>;

/// A transaction pool for a full node.
pub type FullPool<Block, Client> = BasicPool<FullChainApi<Client, Block>, Block>;

/// Basic implementation of transaction pool that can be customized by providing PoolApi.
pub struct BasicPool<PoolApi, Block>
where
	Block: BlockT,
	PoolApi: graph::ChainApi<Block = Block>,
{
	pool: Arc<graph::Pool<PoolApi>>,
	api: Arc<PoolApi>,
	revalidation_strategy: Arc<Mutex<RevalidationStrategy<NumberFor<Block>>>>,
	revalidation_queue: Arc<revalidation::RevalidationQueue<PoolApi>>,
	ready_poll: Arc<Mutex<ReadyPoll<ReadyIteratorFor<PoolApi>, Block>>>,
	metrics: PrometheusMetrics,
	enactment_state: Arc<Mutex<EnactmentState<Block>>>,
}

struct ReadyPoll<T, Block: BlockT> {
	updated_at: NumberFor<Block>,
	pollers: Vec<(NumberFor<Block>, oneshot::Sender<T>)>,
}

impl<T, Block: BlockT> Default for ReadyPoll<T, Block> {
	fn default() -> Self {
		Self { updated_at: NumberFor::<Block>::zero(), pollers: Default::default() }
	}
}

impl<T, Block: BlockT> ReadyPoll<T, Block> {
	fn new(best_block_number: NumberFor<Block>) -> Self {
		Self { updated_at: best_block_number, pollers: Default::default() }
	}

	fn trigger(&mut self, number: NumberFor<Block>, iterator_factory: impl Fn() -> T) {
		self.updated_at = number;

		let mut idx = 0;
		while idx < self.pollers.len() {
			if self.pollers[idx].0 <= number {
				let poller_sender = self.pollers.swap_remove(idx);
				log::debug!(target: LOG_TARGET, "Sending ready signal at block {}", number);
				let _ = poller_sender.1.send(iterator_factory());
			} else {
				idx += 1;
			}
		}
	}

	fn add(&mut self, number: NumberFor<Block>) -> oneshot::Receiver<T> {
		let (sender, receiver) = oneshot::channel();
		self.pollers.push((number, sender));
		receiver
	}

	fn updated_at(&self) -> NumberFor<Block> {
		self.updated_at
	}
}

/// Type of revalidation.
pub enum RevalidationType {
	/// Light revalidation type.
	///
	/// During maintenance, transaction pool makes periodic revalidation
	/// of all transactions depending on number of blocks or time passed.
	/// Also this kind of revalidation does not resubmit transactions from
	/// retracted blocks, since it is too expensive.
	Light,

	/// Full revalidation type.
	///
	/// During maintenance, transaction pool revalidates some fixed amount of
	/// transactions from the pool of valid transactions.
	Full,
}

impl<PoolApi, Block> BasicPool<PoolApi, Block>
where
	Block: BlockT,
	PoolApi: graph::ChainApi<Block = Block> + 'static,
{
	/// Create new basic transaction pool with provided api, for tests.
	pub fn new_test(
		pool_api: Arc<PoolApi>,
		best_block_hash: Block::Hash,
		finalized_hash: Block::Hash,
	) -> (Self, Pin<Box<dyn Future<Output = ()> + Send>>) {
		let pool = Arc::new(graph::Pool::new(Default::default(), true.into(), pool_api.clone()));
		let (revalidation_queue, background_task) =
			revalidation::RevalidationQueue::new_background(pool_api.clone(), pool.clone());
		(
			Self {
				api: pool_api,
				pool,
				revalidation_queue: Arc::new(revalidation_queue),
				revalidation_strategy: Arc::new(Mutex::new(RevalidationStrategy::Always)),
				ready_poll: Default::default(),
				metrics: Default::default(),
				enactment_state: Arc::new(Mutex::new(EnactmentState::new(
					best_block_hash,
					finalized_hash,
				))),
			},
			background_task,
		)
	}

	/// Create new basic transaction pool with provided api and custom
	/// revalidation type.
	pub fn with_revalidation_type(
		options: graph::Options,
		is_validator: IsValidator,
		pool_api: Arc<PoolApi>,
		prometheus: Option<&PrometheusRegistry>,
		revalidation_type: RevalidationType,
		spawner: impl SpawnEssentialNamed,
		best_block_number: NumberFor<Block>,
		best_block_hash: Block::Hash,
		finalized_hash: Block::Hash,
	) -> Self {
		let pool = Arc::new(graph::Pool::new(options, is_validator, pool_api.clone()));
		let (revalidation_queue, background_task) = match revalidation_type {
			RevalidationType::Light =>
				(revalidation::RevalidationQueue::new(pool_api.clone(), pool.clone()), None),
			RevalidationType::Full => {
				let (queue, background) =
					revalidation::RevalidationQueue::new_background(pool_api.clone(), pool.clone());
				(queue, Some(background))
			},
		};

		if let Some(background_task) = background_task {
			spawner.spawn_essential("txpool-background", Some("transaction-pool"), background_task);
		}

		Self {
			api: pool_api,
			pool,
			revalidation_queue: Arc::new(revalidation_queue),
			revalidation_strategy: Arc::new(Mutex::new(match revalidation_type {
				RevalidationType::Light =>
					RevalidationStrategy::Light(RevalidationStatus::NotScheduled),
				RevalidationType::Full => RevalidationStrategy::Always,
			})),
			ready_poll: Arc::new(Mutex::new(ReadyPoll::new(best_block_number))),
			metrics: PrometheusMetrics::new(prometheus),
			enactment_state: Arc::new(Mutex::new(EnactmentState::new(
				best_block_hash,
				finalized_hash,
			))),
		}
	}

	/// Gets shared reference to the underlying pool.
	pub fn pool(&self) -> &Arc<graph::Pool<PoolApi>> {
		&self.pool
	}

	/// Get access to the underlying api
	pub fn api(&self) -> &PoolApi {
		&self.api
	}
}

impl<PoolApi, Block> TransactionPool for BasicPool<PoolApi, Block>
where
	Block: BlockT,
	PoolApi: 'static + graph::ChainApi<Block = Block>,
{
	type Block = PoolApi::Block;
	type Hash = graph::ExtrinsicHash<PoolApi>;
	type InPoolTransaction = graph::base_pool::Transaction<TxHash<Self>, TransactionFor<Self>>;
	type Error = PoolApi::Error;

	fn submit_at(
		&self,
		at: &BlockId<Self::Block>,
		source: TransactionSource,
		xts: Vec<TransactionFor<Self>>,
	) -> PoolFuture<Vec<Result<TxHash<Self>, Self::Error>>, Self::Error> {
		let pool = self.pool.clone();
		let at = *at;

		self.metrics
			.report(|metrics| metrics.submitted_transactions.inc_by(xts.len() as u64));

		async move { pool.submit_at(&at, source, xts).await }.boxed()
	}

	fn submit_one(
		&self,
		at: &BlockId<Self::Block>,
		source: TransactionSource,
		xt: TransactionFor<Self>,
	) -> PoolFuture<TxHash<Self>, Self::Error> {
		let pool = self.pool.clone();
		let at = *at;

		self.metrics.report(|metrics| metrics.submitted_transactions.inc());

		async move { pool.submit_one(&at, source, xt).await }.boxed()
	}

	fn submit_and_watch(
		&self,
		at: &BlockId<Self::Block>,
		source: TransactionSource,
		xt: TransactionFor<Self>,
	) -> PoolFuture<Pin<Box<TransactionStatusStreamFor<Self>>>, Self::Error> {
		let at = *at;
		let pool = self.pool.clone();

		self.metrics.report(|metrics| metrics.submitted_transactions.inc());

		async move {
			let watcher = pool.submit_and_watch(&at, source, xt).await?;

			Ok(watcher.into_stream().boxed())
		}
		.boxed()
	}

	fn remove_invalid(&self, hashes: &[TxHash<Self>]) -> Vec<Arc<Self::InPoolTransaction>> {
		let removed = self.pool.validated_pool().remove_invalid(hashes);
		self.metrics
			.report(|metrics| metrics.validations_invalid.inc_by(removed.len() as u64));
		removed
	}

	fn status(&self) -> PoolStatus {
		self.pool.validated_pool().status()
	}

	fn import_notification_stream(&self) -> ImportNotificationStream<TxHash<Self>> {
		self.pool.validated_pool().import_notification_stream()
	}

	fn hash_of(&self, xt: &TransactionFor<Self>) -> TxHash<Self> {
		self.pool.hash_of(xt)
	}

	fn on_broadcasted(&self, propagations: HashMap<TxHash<Self>, Vec<String>>) {
		self.pool.validated_pool().on_broadcasted(propagations)
	}

	fn ready_transaction(&self, hash: &TxHash<Self>) -> Option<Arc<Self::InPoolTransaction>> {
		self.pool.validated_pool().ready_by_hash(hash)
	}

	fn ready_at(&self, at: NumberFor<Self::Block>) -> PolledIterator<PoolApi> {
		let status = self.status();
		// If there are no transactions in the pool, it is fine to return early.
		//
		// There could be transaction being added because of some re-org happening at the relevant
		// block, but this is relative unlikely.
		if status.ready == 0 && status.future == 0 {
			return async { Box::new(std::iter::empty()) as Box<_> }.boxed()
		}

		if self.ready_poll.lock().updated_at() >= at {
			log::trace!(target: LOG_TARGET, "Transaction pool already processed block  #{}", at);
			let iterator: ReadyIteratorFor<PoolApi> = Box::new(self.pool.validated_pool().ready());
			return async move { iterator }.boxed()
		}

		self.ready_poll
			.lock()
			.add(at)
			.map(|received| {
				received.unwrap_or_else(|e| {
					log::warn!("Error receiving pending set: {:?}", e);
					Box::new(std::iter::empty())
				})
			})
			.boxed()
	}

	fn ready(&self) -> ReadyIteratorFor<PoolApi> {
		Box::new(self.pool.validated_pool().ready())
	}
}

impl<Block, Client> FullPool<Block, Client>
where
	Block: BlockT,
	Client: sp_api::ProvideRuntimeApi<Block>
		+ sc_client_api::BlockBackend<Block>
		+ sc_client_api::blockchain::HeaderBackend<Block>
		+ sp_runtime::traits::BlockIdTo<Block>
		+ sc_client_api::ExecutorProvider<Block>
		+ sc_client_api::UsageProvider<Block>
		+ sp_blockchain::HeaderMetadata<Block, Error = sp_blockchain::Error>
		+ Send
		+ Sync
		+ 'static,
	Client::Api: sp_transaction_pool::runtime_api::TaggedTransactionQueue<Block>,
{
	/// Create new basic transaction pool for a full node with the provided api.
	pub fn new_full(
		options: graph::Options,
		is_validator: IsValidator,
		prometheus: Option<&PrometheusRegistry>,
		spawner: impl SpawnEssentialNamed,
		client: Arc<Client>,
	) -> Arc<Self> {
		let pool_api = Arc::new(FullChainApi::new(client.clone(), prometheus, &spawner));
		let pool = Arc::new(Self::with_revalidation_type(
			options,
			is_validator,
			pool_api,
			prometheus,
			RevalidationType::Full,
			spawner,
			client.usage_info().chain.best_number,
			client.usage_info().chain.best_hash,
			client.usage_info().chain.finalized_hash,
		));

		pool
	}
}

impl<Block, Client> sc_transaction_pool_api::LocalTransactionPool
	for BasicPool<FullChainApi<Client, Block>, Block>
where
	Block: BlockT,
	Client: sp_api::ProvideRuntimeApi<Block>
		+ sc_client_api::BlockBackend<Block>
		+ sc_client_api::blockchain::HeaderBackend<Block>
		+ sp_runtime::traits::BlockIdTo<Block>
		+ sp_blockchain::HeaderMetadata<Block, Error = sp_blockchain::Error>,
	Client: Send + Sync + 'static,
	Client::Api: sp_transaction_pool::runtime_api::TaggedTransactionQueue<Block>,
{
	type Block = Block;
	type Hash = graph::ExtrinsicHash<FullChainApi<Client, Block>>;
	type Error = <FullChainApi<Client, Block> as graph::ChainApi>::Error;

	fn submit_local(
		&self,
		at: Block::Hash,
		xt: sc_transaction_pool_api::LocalTransactionFor<Self>,
	) -> Result<Self::Hash, Self::Error> {
		use sp_runtime::{
			traits::SaturatedConversion, transaction_validity::TransactionValidityError,
		};

		let validity = self
			.api
			.validate_transaction_blocking(
				&BlockId::hash(at),
				TransactionSource::Local,
				xt.clone(),
			)?
			.map_err(|e| {
				Self::Error::Pool(match e {
					TransactionValidityError::Invalid(i) => TxPoolError::InvalidTransaction(i),
					TransactionValidityError::Unknown(u) => TxPoolError::UnknownTransaction(u),
				})
			})?;

		let (hash, bytes) = self.pool.validated_pool().api().hash_and_length(&xt);
		let block_number = self
			.api
			.block_id_to_number(&BlockId::hash(at))?
			.ok_or_else(|| error::Error::BlockIdConversion(format!("{:?}", at)))?;

		let validated = ValidatedTransaction::valid_at(
			block_number.saturated_into::<u64>(),
			hash,
			TransactionSource::Local,
			xt,
			bytes,
			validity,
		);

		self.pool.validated_pool().submit(vec![validated]).remove(0)
	}
}

#[cfg_attr(test, derive(Debug))]
enum RevalidationStatus<N> {
	/// The revalidation has never been completed.
	NotScheduled,
	/// The revalidation is scheduled.
	Scheduled(Option<Instant>, Option<N>),
	/// The revalidation is in progress.
	InProgress,
}

enum RevalidationStrategy<N> {
	Always,
	Light(RevalidationStatus<N>),
}

struct RevalidationAction {
	revalidate: bool,
	resubmit: bool,
}

impl<N: Clone + Copy + AtLeast32Bit> RevalidationStrategy<N> {
	pub fn clear(&mut self) {
		if let Self::Light(status) = self {
			status.clear()
		}
	}

	pub fn next(
		&mut self,
		block: N,
		revalidate_time_period: Option<std::time::Duration>,
		revalidate_block_period: Option<N>,
	) -> RevalidationAction {
		match self {
			Self::Light(status) => RevalidationAction {
				revalidate: status.next_required(
					block,
					revalidate_time_period,
					revalidate_block_period,
				),
				resubmit: false,
			},
			Self::Always => RevalidationAction { revalidate: true, resubmit: true },
		}
	}
}

impl<N: Clone + Copy + AtLeast32Bit> RevalidationStatus<N> {
	/// Called when revalidation is completed.
	pub fn clear(&mut self) {
		*self = Self::NotScheduled;
	}

	/// Returns true if revalidation is required.
	pub fn next_required(
		&mut self,
		block: N,
		revalidate_time_period: Option<std::time::Duration>,
		revalidate_block_period: Option<N>,
	) -> bool {
		match *self {
			Self::NotScheduled => {
				*self = Self::Scheduled(
					revalidate_time_period.map(|period| Instant::now() + period),
					revalidate_block_period.map(|period| block + period),
				);
				false
			},
			Self::Scheduled(revalidate_at_time, revalidate_at_block) => {
				let is_required =
					revalidate_at_time.map(|at| Instant::now() >= at).unwrap_or(false) ||
						revalidate_at_block.map(|at| block >= at).unwrap_or(false);
				if is_required {
					*self = Self::InProgress;
				}
				is_required
			},
			Self::InProgress => false,
		}
	}
}

/// Prune the known txs for the given block.
async fn prune_known_txs_for_block<Block: BlockT, Api: graph::ChainApi<Block = Block>>(
	block_hash: Block::Hash,
	api: &Api,
	pool: &graph::Pool<Api>,
) -> Vec<ExtrinsicHash<Api>> {
	let extrinsics = api
		.block_body(block_hash)
		.await
		.unwrap_or_else(|e| {
			log::warn!("Prune known transactions: error request: {}", e);
			None
		})
		.unwrap_or_default();

	let hashes = extrinsics.iter().map(|tx| pool.hash_of(tx)).collect::<Vec<_>>();

	log::trace!(target: LOG_TARGET, "Pruning transactions: {:?}", hashes);

	let header = match api.block_header(block_hash) {
		Ok(Some(h)) => h,
		Ok(None) => {
			log::debug!(target: LOG_TARGET, "Could not find header for {:?}.", block_hash);
			return hashes
		},
		Err(e) => {
			log::debug!(target: LOG_TARGET, "Error retrieving header for {:?}: {}", block_hash, e);
			return hashes
		},
	};

	if let Err(e) = pool
		.prune(&BlockId::Hash(block_hash), &BlockId::hash(*header.parent_hash()), &extrinsics)
		.await
	{
		log::error!("Cannot prune known in the pool: {}", e);
	}

	hashes
}

impl<PoolApi, Block> BasicPool<PoolApi, Block>
where
	Block: BlockT,
	PoolApi: 'static + graph::ChainApi<Block = Block>,
{
	/// Handles enactment and retraction of blocks, prunes stale transactions
	/// (that have already been enacted) and resubmits transactions that were
	/// retracted.
	async fn handle_enactment(&self, tree_route: TreeRoute<Block>) {
		log::trace!(target: LOG_TARGET, "handle_enactment tree_route: {tree_route:?}");
		let pool = self.pool.clone();
		let api = self.api.clone();

		let (hash, block_number) = match tree_route.last() {
			Some(HashAndNumber { hash, number }) => (hash, number),
			None => {
				log::warn!(
					target: LOG_TARGET,
					"Skipping ChainEvent - no last block in tree route {:?}",
					tree_route,
				);
				return
			},
		};

		let next_action = self.revalidation_strategy.lock().next(
			*block_number,
			Some(std::time::Duration::from_secs(60)),
			Some(20u32.into()),
		);

		// We keep track of everything we prune so that later we won't add
		// transactions with those hashes from the retracted blocks.
		let mut pruned_log = HashSet::<ExtrinsicHash<PoolApi>>::new();

		// If there is a tree route, we use this to prune known tx based on the enacted
		// blocks. Before pruning enacted transactions, we inform the listeners about
		// retracted blocks and their transactions. This order is important, because
		// if we enact and retract the same transaction at the same time, we want to
		// send first the retract and than the prune event.
		for retracted in tree_route.retracted() {
			// notify txs awaiting finality that it has been retracted
			pool.validated_pool().on_block_retracted(retracted.hash);
		}

		future::join_all(
			tree_route
				.enacted()
				.iter()
				.map(|h| prune_known_txs_for_block(h.hash, &*api, &*pool)),
		)
		.await
		.into_iter()
		.for_each(|enacted_log| {
			pruned_log.extend(enacted_log);
		});

		self.metrics
			.report(|metrics| metrics.block_transactions_pruned.inc_by(pruned_log.len() as u64));

		if next_action.resubmit {
			let mut resubmit_transactions = Vec::new();

			for retracted in tree_route.retracted() {
				let hash = retracted.hash;

				let block_transactions = api
					.block_body(hash)
					.await
					.unwrap_or_else(|e| {
						log::warn!("Failed to fetch block body: {}", e);
						None
					})
					.unwrap_or_default()
					.into_iter()
					.filter(|tx| tx.is_signed().unwrap_or(true));

				let mut resubmitted_to_report = 0;

				resubmit_transactions.extend(block_transactions.into_iter().filter(|tx| {
					let tx_hash = pool.hash_of(tx);
					let contains = pruned_log.contains(&tx_hash);

					// need to count all transactions, not just filtered, here
					resubmitted_to_report += 1;

					if !contains {
						log::debug!(
							target: LOG_TARGET,
							"[{:?}]: Resubmitting from retracted block {:?}",
							tx_hash,
							hash,
						);
					}
					!contains
				}));

				self.metrics.report(|metrics| {
					metrics.block_transactions_resubmitted.inc_by(resubmitted_to_report)
				});
			}

			if let Err(e) = pool
				.resubmit_at(
					&BlockId::Hash(*hash),
					// These transactions are coming from retracted blocks, we should
					// simply consider them external.
					TransactionSource::External,
					resubmit_transactions,
				)
				.await
			{
				log::debug!(
					target: LOG_TARGET,
					"[{:?}] Error re-submitting transactions: {}",
					hash,
					e,
				)
			}
		}

		let extra_pool = pool.clone();
		// After #5200 lands, this arguably might be moved to the
		// handler of "all blocks notification".
		self.ready_poll
			.lock()
			.trigger(*block_number, move || Box::new(extra_pool.validated_pool().ready()));

		if next_action.revalidate {
			let hashes = pool.validated_pool().ready().map(|tx| tx.hash).collect();
			self.revalidation_queue.revalidate_later(*block_number, hashes).await;

			self.revalidation_strategy.lock().clear();
		}
	}
}

#[async_trait]
impl<PoolApi, Block> MaintainedTransactionPool for BasicPool<PoolApi, Block>
where
	Block: BlockT,
	PoolApi: 'static + graph::ChainApi<Block = Block>,
{
	async fn maintain(&self, event: ChainEvent<Self::Block>) {
		let prev_finalized_block = self.enactment_state.lock().recent_finalized_block();
		let compute_tree_route = |from, to| -> Result<TreeRoute<Block>, String> {
			match self.api.tree_route(from, to) {
				Ok(tree_route) => Ok(tree_route),
				Err(e) =>
					return Err(format!(
						"Error occurred while computing tree_route from {from:?} to {to:?}: {e}"
					)),
			}
		};
		let block_id_to_number =
			|hash| self.api.block_id_to_number(&BlockId::Hash(hash)).map_err(|e| format!("{}", e));

		let result =
			self.enactment_state
				.lock()
				.update(&event, &compute_tree_route, &block_id_to_number);

		match result {
			Err(msg) => {
				log::debug!(target: LOG_TARGET, "{msg}");
				self.enactment_state.lock().force_update(&event);
			},
			Ok(EnactmentAction::Skip) => return,
			Ok(EnactmentAction::HandleFinalization) => {},
			Ok(EnactmentAction::HandleEnactment(tree_route)) => {
				self.handle_enactment(tree_route).await;
			},
		};

		if let ChainEvent::Finalized { hash, tree_route } = event {
			log::trace!(
				target: LOG_TARGET,
				"on-finalized enacted: {tree_route:?}, previously finalized: \
				{prev_finalized_block:?}",
			);

			for hash in tree_route.iter().chain(std::iter::once(&hash)) {
				if let Err(e) = self.pool.validated_pool().on_block_finalized(*hash).await {
					log::warn!(
						target: LOG_TARGET,
						"Error occurred while attempting to notify watchers about finalization {}: {}",
						hash, e
					)
				}
			}
		}
	}
}

/// Inform the transaction pool about imported and finalized blocks.
pub async fn notification_future<Client, Pool, Block>(client: Arc<Client>, txpool: Arc<Pool>)
where
	Block: BlockT,
	Client: sc_client_api::BlockchainEvents<Block>,
	Pool: MaintainedTransactionPool<Block = Block>,
{
	let import_stream = client
		.import_notification_stream()
		.filter_map(|n| ready(n.try_into().ok()))
		.fuse();
	let finality_stream = client.finality_notification_stream().map(Into::into).fuse();

	futures::stream::select(import_stream, finality_stream)
		.for_each(|evt| txpool.maintain(evt))
		.await
}