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
// Copyright 2017-2019 Parity Technologies (UK) Ltd.
// This file is part of Substrate.

// Substrate 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.

// Substrate 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 Substrate.  If not, see <http://www.gnu.org/licenses/>.

//! State database maintenance. Handles canonicalization and pruning in the database. The input to
//! this module is a `ChangeSet` which is basically a list of key-value pairs (trie nodes) that
//! were added or deleted during block execution.
//!
//! # Canonicalization.
//! Canonicalization window tracks a tree of blocks identified by header hash. The in-memory
//! overlay allows to get any node that was inserted in any of the blocks within the window.
//! The tree is journaled to the backing database and rebuilt on startup.
//! Canonicalization function selects one root from the top of the tree and discards all other roots and
//! their subtrees.
//!
//! # Pruning.
//! See `RefWindow` for pruning algorithm details. `StateDb` prunes on each canonicalization until pruning
//! constraints are satisfied.

mod noncanonical;
mod pruning;
#[cfg(test)] mod test;

use std::fmt;
use parking_lot::RwLock;
use codec::Codec;
use std::collections::{HashMap, hash_map::Entry};
use noncanonical::NonCanonicalOverlay;
use pruning::RefWindow;
use log::trace;

/// Database value type.
pub type DBValue = Vec<u8>;

/// Basic set of requirements for the Block hash and node key types.
pub trait Hash: Send + Sync + Sized + Eq + PartialEq + Clone + Default + fmt::Debug + Codec + std::hash::Hash + 'static {}
impl<T: Send + Sync + Sized + Eq + PartialEq + Clone + Default + fmt::Debug + Codec + std::hash::Hash + 'static> Hash for T {}

/// Backend database trait. Read-only.
pub trait MetaDb {
	type Error: fmt::Debug;

	/// Get meta value, such as the journal.
	fn get_meta(&self, key: &[u8]) -> Result<Option<DBValue>, Self::Error>;
}

/// Backend database trait. Read-only.
pub trait NodeDb {
	type Key: ?Sized;
	type Error: fmt::Debug;

	/// Get state trie node.
	fn get(&self, key: &Self::Key) -> Result<Option<DBValue>, Self::Error>;
}

/// Error type.
pub enum Error<E: fmt::Debug> {
	/// Database backend error.
	Db(E),
	/// `Codec` decoding error.
	Decoding(codec::Error),
	/// Trying to canonicalize invalid block.
	InvalidBlock,
	/// Trying to insert block with invalid number.
	InvalidBlockNumber,
	/// Trying to insert block with unknown parent.
	InvalidParent,
}

/// Pinning error type.
pub enum PinError {
	/// Trying to pin invalid block.
	InvalidBlock,
}

impl<E: fmt::Debug> From<codec::Error> for Error<E> {
	fn from(x: codec::Error) -> Self {
		Error::Decoding(x)
	}
}

impl<E: fmt::Debug> fmt::Debug for Error<E> {
	fn fmt(&self, f: &mut fmt::Formatter) -> fmt::Result {
		match self {
			Error::Db(e) => e.fmt(f),
			Error::Decoding(e) => write!(f, "Error decoding slicable value: {}", e.what()),
			Error::InvalidBlock => write!(f, "Trying to canonicalize invalid block"),
			Error::InvalidBlockNumber => write!(f, "Trying to insert block with invalid number"),
			Error::InvalidParent => write!(f, "Trying to insert block with unknown parent"),
		}
	}
}

/// A set of state node changes.
#[derive(Default, Debug, Clone)]
pub struct ChangeSet<H: Hash> {
	/// Inserted nodes.
	pub inserted: Vec<(H, DBValue)>,
	/// Deleted nodes.
	pub deleted: Vec<H>,
}


/// A set of changes to the backing database.
#[derive(Default, Debug, Clone)]
pub struct CommitSet<H: Hash> {
	/// State node changes.
	pub data: ChangeSet<H>,
	/// Metadata changes.
	pub meta: ChangeSet<Vec<u8>>,
}

/// Pruning constraints. If none are specified pruning is
#[derive(Default, Debug, Clone, Eq, PartialEq)]
pub struct Constraints {
	/// Maximum blocks. Defaults to 0 when unspecified, effectively keeping only non-canonical states.
	pub max_blocks: Option<u32>,
	/// Maximum memory in the pruning overlay.
	pub max_mem: Option<usize>,
}

/// Pruning mode.
#[derive(Debug, Clone, Eq, PartialEq)]
pub enum PruningMode {
	/// Maintain a pruning window.
	Constrained(Constraints),
	/// No pruning. Canonicalization is a no-op.
	ArchiveAll,
	/// Canonicalization discards non-canonical nodes. All the canonical nodes are kept in the DB.
	ArchiveCanonical,
}

impl PruningMode {
	/// Create a mode that keeps given number of blocks.
	pub fn keep_blocks(n: u32) -> PruningMode {
		PruningMode::Constrained(Constraints {
			max_blocks: Some(n),
			max_mem: None,
		})
	}

	/// Is this an archive (either ArchiveAll or ArchiveCanonical) pruning mode?
	pub fn is_archive(&self) -> bool {
		match *self {
			PruningMode::ArchiveAll | PruningMode::ArchiveCanonical => true,
			PruningMode::Constrained(_) => false
		}
	}

}

impl Default for PruningMode {
	fn default() -> Self {
		PruningMode::keep_blocks(256)
	}
}

fn to_meta_key<S: Codec>(suffix: &[u8], data: &S) -> Vec<u8> {
	let mut buffer = data.encode();
	buffer.extend(suffix);
	buffer
}

struct StateDbSync<BlockHash: Hash, Key: Hash> {
	mode: PruningMode,
	non_canonical: NonCanonicalOverlay<BlockHash, Key>,
	pruning: Option<RefWindow<BlockHash, Key>>,
	pinned: HashMap<BlockHash, u32>,
}

impl<BlockHash: Hash, Key: Hash> StateDbSync<BlockHash, Key> {
	pub fn new<D: MetaDb>(mode: PruningMode, db: &D) -> Result<StateDbSync<BlockHash, Key>, Error<D::Error>> {
		trace!(target: "state-db", "StateDb settings: {:?}", mode);
		let non_canonical: NonCanonicalOverlay<BlockHash, Key> = NonCanonicalOverlay::new(db)?;
		let pruning: Option<RefWindow<BlockHash, Key>> = match mode {
			PruningMode::Constrained(Constraints {
				max_mem: Some(_),
				..
			}) => unimplemented!(),
			PruningMode::Constrained(_) => Some(RefWindow::new(db)?),
			PruningMode::ArchiveAll | PruningMode::ArchiveCanonical => None,
		};
		Ok(StateDbSync {
			mode,
			non_canonical,
			pruning,
			pinned: Default::default(),
		})
	}

	pub fn insert_block<E: fmt::Debug>(&mut self, hash: &BlockHash, number: u64, parent_hash: &BlockHash, mut changeset: ChangeSet<Key>) -> Result<CommitSet<Key>, Error<E>> {
		match self.mode {
			PruningMode::ArchiveAll => {
				changeset.deleted.clear();
				// write changes immediately
				Ok(CommitSet {
					data: changeset,
					meta: Default::default(),
				})
			},
			PruningMode::Constrained(_) | PruningMode::ArchiveCanonical => {
				self.non_canonical.insert(hash, number, parent_hash, changeset)
			}
		}
	}

	pub fn canonicalize_block<E: fmt::Debug>(&mut self, hash: &BlockHash) -> Result<CommitSet<Key>, Error<E>> {
		let mut commit = CommitSet::default();
		if self.mode == PruningMode::ArchiveAll {
			return Ok(commit)
		}
		match self.non_canonical.canonicalize(&hash, &mut commit) {
			Ok(()) => {
				if self.mode == PruningMode::ArchiveCanonical {
					commit.data.deleted.clear();
				}
			}
			Err(e) => return Err(e),
		};
		if let Some(ref mut pruning) = self.pruning {
			pruning.note_canonical(&hash, &mut commit);
		}
		self.prune(&mut commit);
		Ok(commit)
	}

	pub fn best_canonical(&self) -> Option<u64> {
		return self.non_canonical.last_canonicalized_block_number()
	}

	pub fn is_pruned(&self, hash: &BlockHash, number: u64) -> bool {
		match self.mode {
			PruningMode::ArchiveAll => false,
			PruningMode::ArchiveCanonical | PruningMode::Constrained(_) => {
				if self.best_canonical().map(|c| number > c).unwrap_or(true) {
					!self.non_canonical.have_block(hash)
				} else {
					self.pruning.as_ref().map_or(false, |pruning| number < pruning.pending() || !pruning.have_block(hash))
				}
			}
		}
	}

	fn prune(&mut self, commit: &mut CommitSet<Key>) {
		if let (&mut Some(ref mut pruning), &PruningMode::Constrained(ref constraints)) = (&mut self.pruning, &self.mode) {
			loop {
				if pruning.window_size() <= constraints.max_blocks.unwrap_or(0) as u64 {
					break;
				}

				if constraints.max_mem.map_or(false, |m| pruning.mem_used() > m) {
					break;
				}

				let pinned = &self.pinned;
				if pruning.next_hash().map_or(false, |h| pinned.contains_key(&h)) {
					break;
				}
				pruning.prune_one(commit);
			}
		}
	}

	/// Revert all non-canonical blocks with the best block number.
	/// Returns a database commit or `None` if not possible.
	/// For archive an empty commit set is returned.
	pub fn revert_one(&mut self) -> Option<CommitSet<Key>> {
		match self.mode {
			PruningMode::ArchiveAll => {
				Some(CommitSet::default())
			},
			PruningMode::ArchiveCanonical | PruningMode::Constrained(_) => {
				self.non_canonical.revert_one()
			},
		}
	}

	pub fn pin(&mut self, hash: &BlockHash) -> Result<(), PinError> {
		match self.mode {
			PruningMode::ArchiveAll => Ok(()),
			PruningMode::ArchiveCanonical | PruningMode::Constrained(_) => {
				if self.non_canonical.have_block(hash) ||
					self.pruning.as_ref().map_or(false, |pruning| pruning.have_block(hash))
				{
					let refs = self.pinned.entry(hash.clone()).or_default();
					if *refs == 0 {
						trace!(target: "state-db", "Pinned block: {:?}", hash);
						self.non_canonical.pin(hash);
					}
					*refs += 1;
					Ok(())
				} else {
					Err(PinError::InvalidBlock)
				}
			}
		}
	}

	pub fn unpin(&mut self, hash: &BlockHash) {
		match self.pinned.entry(hash.clone()) {
			Entry::Occupied(mut entry) => {
				*entry.get_mut() -= 1;
				if *entry.get() == 0 {
					trace!(target: "state-db", "Unpinned block: {:?}", hash);
					entry.remove();
					self.non_canonical.unpin(hash);
				} else {
					trace!(target: "state-db", "Releasing reference for {:?}", hash);
				}
			},
			Entry::Vacant(_) => {},
		}
	}

	pub fn get<D: NodeDb>(&self, key: &Key, db: &D) -> Result<Option<DBValue>, Error<D::Error>>
		where Key: AsRef<D::Key>
	{
		if let Some(value) = self.non_canonical.get(key) {
			return Ok(Some(value));
		}
		db.get(key.as_ref()).map_err(|e| Error::Db(e))
	}

	pub fn apply_pending(&mut self) {
		self.non_canonical.apply_pending();
		if let Some(pruning) = &mut self.pruning {
			pruning.apply_pending();
		}
		trace!(target: "forks", "First available: {:?} ({}), Last canon: {:?} ({}), Best forks: {:?}",
			self.pruning.as_ref().and_then(|p| p.next_hash()),
			self.pruning.as_ref().map(|p| p.pending()).unwrap_or(0),
			self.non_canonical.last_canonicalized_hash(),
			self.non_canonical.last_canonicalized_block_number().unwrap_or(0),
			self.non_canonical.top_level(),
		);
	}

	pub fn revert_pending(&mut self) {
		if let Some(pruning) = &mut self.pruning {
			pruning.revert_pending();
		}
		self.non_canonical.revert_pending();
	}
}

/// State DB maintenance. See module description.
/// Can be shared across threads.
pub struct StateDb<BlockHash: Hash, Key: Hash> {
	db: RwLock<StateDbSync<BlockHash, Key>>,
}

impl<BlockHash: Hash, Key: Hash> StateDb<BlockHash, Key> {
	/// Creates a new instance. Does not expect any metadata in the database.
	pub fn new<D: MetaDb>(mode: PruningMode, db: &D) -> Result<StateDb<BlockHash, Key>, Error<D::Error>> {
		Ok(StateDb {
			db: RwLock::new(StateDbSync::new(mode, db)?)
		})
	}

	/// Add a new non-canonical block.
	pub fn insert_block<E: fmt::Debug>(&self, hash: &BlockHash, number: u64, parent_hash: &BlockHash, changeset: ChangeSet<Key>) -> Result<CommitSet<Key>, Error<E>> {
		self.db.write().insert_block(hash, number, parent_hash, changeset)
	}

	/// Finalize a previously inserted block.
	pub fn canonicalize_block<E: fmt::Debug>(&self, hash: &BlockHash) -> Result<CommitSet<Key>, Error<E>> {
		self.db.write().canonicalize_block(hash)
	}

	/// Prevents pruning of specified block and its descendants.
	pub fn pin(&self, hash: &BlockHash) -> Result<(), PinError> {
		self.db.write().pin(hash)
	}

	/// Allows pruning of specified block.
	pub fn unpin(&self, hash: &BlockHash) {
		self.db.write().unpin(hash)
	}

	/// Get a value from non-canonical/pruning overlay or the backing DB.
	pub fn get<D: NodeDb>(&self, key: &Key, db: &D) -> Result<Option<DBValue>, Error<D::Error>>
		where Key: AsRef<D::Key>
	{
		self.db.read().get(key, db)
	}

	/// Revert all non-canonical blocks with the best block number.
	/// Returns a database commit or `None` if not possible.
	/// For archive an empty commit set is returned.
	pub fn revert_one(&self) -> Option<CommitSet<Key>> {
		self.db.write().revert_one()
	}

	/// Returns last finalized block number.
	pub fn best_canonical(&self) -> Option<u64> {
		return self.db.read().best_canonical()
	}

	/// Check if block is pruned away.
	pub fn is_pruned(&self, hash: &BlockHash, number: u64) -> bool {
		return self.db.read().is_pruned(hash, number)
	}

	/// Apply all pending changes
	pub fn apply_pending(&self) {
		self.db.write().apply_pending();
	}

	/// Revert all pending changes
	pub fn revert_pending(&self) {
		self.db.write().revert_pending();
	}
}

#[cfg(test)]
mod tests {
	use std::io;
	use primitives::H256;
	use crate::{StateDb, PruningMode, Constraints};
	use crate::test::{make_db, make_changeset, TestDb};

	fn make_test_db(settings: PruningMode) -> (TestDb, StateDb<H256, H256>) {
		let mut db = make_db(&[91, 921, 922, 93, 94]);
		let state_db = StateDb::new(settings, &db).unwrap();

		db.commit(
			&state_db
				.insert_block::<io::Error>(
					&H256::from_low_u64_be(1),
					1,
					&H256::from_low_u64_be(0),
					make_changeset(&[1], &[91]),
				)
				.unwrap(),
		);
		db.commit(
			&state_db
				.insert_block::<io::Error>(
					&H256::from_low_u64_be(21),
					2,
					&H256::from_low_u64_be(1),
					make_changeset(&[21], &[921, 1]),
				)
				.unwrap(),
		);
		db.commit(
			&state_db
				.insert_block::<io::Error>(
					&H256::from_low_u64_be(22),
					2,
					&H256::from_low_u64_be(1),
					make_changeset(&[22], &[922]),
				)
				.unwrap(),
		);
		db.commit(
			&state_db
				.insert_block::<io::Error>(
					&H256::from_low_u64_be(3),
					3,
					&H256::from_low_u64_be(21),
					make_changeset(&[3], &[93]),
				)
				.unwrap(),
		);
		state_db.apply_pending();
		db.commit(&state_db.canonicalize_block::<io::Error>(&H256::from_low_u64_be(1)).unwrap());
		state_db.apply_pending();
		db.commit(
			&state_db
				.insert_block::<io::Error>(
					&H256::from_low_u64_be(4),
					4,
					&H256::from_low_u64_be(3),
					make_changeset(&[4], &[94]),
				)
				.unwrap(),
		);
		state_db.apply_pending();
		db.commit(&state_db.canonicalize_block::<io::Error>(&H256::from_low_u64_be(21)).unwrap());
		state_db.apply_pending();
		db.commit(&state_db.canonicalize_block::<io::Error>(&H256::from_low_u64_be(3)).unwrap());
		state_db.apply_pending();

		(db, state_db)
	}

	#[test]
	fn full_archive_keeps_everything() {
		let (db, sdb) = make_test_db(PruningMode::ArchiveAll);
		assert!(db.data_eq(&make_db(&[1, 21, 22, 3, 4, 91, 921, 922, 93, 94])));
		assert!(!sdb.is_pruned(&H256::from_low_u64_be(0), 0));
	}

	#[test]
	fn canonical_archive_keeps_canonical() {
		let (db, _) = make_test_db(PruningMode::ArchiveCanonical);
		assert!(db.data_eq(&make_db(&[1, 21, 3, 91, 921, 922, 93, 94])));
	}

	#[test]
	fn prune_window_0() {
		let (db, _) = make_test_db(PruningMode::Constrained(Constraints {
			max_blocks: Some(0),
			max_mem: None,
		}));
		assert!(db.data_eq(&make_db(&[21, 3, 922, 94])));
	}

	#[test]
	fn prune_window_1() {
		let (db, sdb) = make_test_db(PruningMode::Constrained(Constraints {
			max_blocks: Some(1),
			max_mem: None,
		}));
		assert!(sdb.is_pruned(&H256::from_low_u64_be(0), 0));
		assert!(sdb.is_pruned(&H256::from_low_u64_be(1), 1));
		assert!(sdb.is_pruned(&H256::from_low_u64_be(21), 2));
		assert!(sdb.is_pruned(&H256::from_low_u64_be(22), 2));
		assert!(db.data_eq(&make_db(&[21, 3, 922, 93, 94])));
	}

	#[test]
	fn prune_window_2() {
		let (db, sdb) = make_test_db(PruningMode::Constrained(Constraints {
			max_blocks: Some(2),
			max_mem: None,
		}));
		assert!(sdb.is_pruned(&H256::from_low_u64_be(0), 0));
		assert!(sdb.is_pruned(&H256::from_low_u64_be(1), 1));
		assert!(!sdb.is_pruned(&H256::from_low_u64_be(21), 2));
		assert!(sdb.is_pruned(&H256::from_low_u64_be(22), 2));
		assert!(db.data_eq(&make_db(&[1, 21, 3, 921, 922, 93, 94])));
	}
}