aboutsummaryrefslogtreecommitdiff
path: root/src/table_sync.rs
blob: 5ef13d6db41030556c772160dddfdf39f2203fde (plain) (blame)
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
use rand::Rng;
use std::collections::{BTreeMap, BTreeSet, VecDeque};
use std::sync::Arc;
use std::time::{Duration, Instant};

use futures::future::BoxFuture;
use futures::{pin_mut, select};
use futures_util::future::*;
use futures_util::stream::*;
use serde::{Deserialize, Serialize};
use serde_bytes::ByteBuf;
use tokio::sync::watch;
use tokio::sync::Mutex;

use crate::data::*;
use crate::error::Error;
use crate::membership::Ring;
use crate::table::*;

const MAX_DEPTH: usize = 16;
const SCAN_INTERVAL: Duration = Duration::from_secs(3600);
const CHECKSUM_CACHE_TIMEOUT: Duration = Duration::from_secs(1800);

pub struct TableSyncer<F: TableSchema> {
	pub table: Arc<Table<F>>,
	pub todo: Mutex<SyncTodo>,
	pub cache: Vec<Mutex<BTreeMap<SyncRange, RangeChecksum>>>,
}

#[derive(Serialize, Deserialize)]
pub enum SyncRPC {
	Checksums(Vec<RangeChecksum>),
	DifferentSet(Vec<SyncRange>),
}

pub struct SyncTodo {
	pub todo: Vec<Partition>,
}

#[derive(Debug, Clone)]
pub struct Partition {
	pub begin: Hash,
	pub end: Hash,
	pub retain: bool,
}

#[derive(Hash, PartialEq, Eq, Debug, Clone, Serialize, Deserialize)]
pub struct SyncRange {
	pub begin: Vec<u8>,
	pub end: Vec<u8>,
	pub level: usize,
}

impl std::cmp::PartialOrd for SyncRange {
	fn partial_cmp(&self, other: &Self) -> Option<std::cmp::Ordering> {
		Some(self.cmp(other))
	}
}
impl std::cmp::Ord for SyncRange {
	fn cmp(&self, other: &Self) -> std::cmp::Ordering {
		self.begin.cmp(&other.begin)
	}
}

#[derive(Debug, Clone, Serialize, Deserialize)]
pub struct RangeChecksum {
	pub bounds: SyncRange,
	pub children: Vec<(SyncRange, Hash)>,
	pub found_limit: Option<Vec<u8>>,

	#[serde(skip, default = "std::time::Instant::now")]
	pub time: Instant,
}

impl<F: TableSchema + 'static> TableSyncer<F> {
	pub async fn launch(table: Arc<Table<F>>) -> Arc<Self> {
		let todo = SyncTodo { todo: Vec::new() };
		let syncer = Arc::new(TableSyncer {
			table: table.clone(),
			todo: Mutex::new(todo),
			cache: (0..MAX_DEPTH)
				.map(|_| Mutex::new(BTreeMap::new()))
				.collect::<Vec<_>>(),
		});

		let s1 = syncer.clone();
		table
			.system
			.background
			.spawn_worker(move |must_exit: watch::Receiver<bool>| s1.watcher_task(must_exit))
			.await;

		let s2 = syncer.clone();
		table
			.system
			.background
			.spawn_worker(move |must_exit: watch::Receiver<bool>| s2.syncer_task(must_exit))
			.await;

		syncer
	}

	async fn watcher_task(
		self: Arc<Self>,
		mut must_exit: watch::Receiver<bool>,
	) -> Result<(), Error> {
		tokio::time::delay_for(Duration::from_secs(10)).await;

		self.todo.lock().await.add_full_scan(&self.table);
		let mut next_full_scan = tokio::time::delay_for(SCAN_INTERVAL).fuse();
		let mut prev_ring: Arc<Ring> = self.table.system.ring.borrow().clone();
		let mut ring_recv: watch::Receiver<Arc<Ring>> = self.table.system.ring.clone();

		while !*must_exit.borrow() {
			let s_ring_recv = ring_recv.recv().fuse();
			let s_must_exit = must_exit.recv().fuse();
			pin_mut!(s_ring_recv, s_must_exit);

			select! {
				_ = next_full_scan => {
					next_full_scan = tokio::time::delay_for(SCAN_INTERVAL).fuse();
					eprintln!("({}) Adding full scan to syncer todo list", self.table.name);
					self.todo.lock().await.add_full_scan(&self.table);
				}
				new_ring_r = s_ring_recv => {
					if let Some(new_ring) = new_ring_r {
						eprintln!("({}) Adding ring difference to syncer todo list", self.table.name);
						self.todo.lock().await.add_ring_difference(&self.table, &prev_ring, &new_ring);
						prev_ring = new_ring;
					}
				}
				must_exit_v = s_must_exit => {
					if must_exit_v.unwrap_or(false) {
						break;
					}
				}
			}
		}
		Ok(())
	}

	async fn syncer_task(
		self: Arc<Self>,
		mut must_exit: watch::Receiver<bool>,
	) -> Result<(), Error> {
		while !*must_exit.borrow() {
			if let Some(partition) = self.todo.lock().await.pop_task() {
				let res = self
					.clone()
					.sync_partition(&partition, &mut must_exit)
					.await;
				if let Err(e) = res {
					eprintln!(
						"({}) Error while syncing {:?}: {}",
						self.table.name, partition, e
					);
				}
			} else {
				tokio::time::delay_for(Duration::from_secs(1)).await;
			}
		}
		Ok(())
	}

	async fn sync_partition(
		self: Arc<Self>,
		partition: &Partition,
		must_exit: &mut watch::Receiver<bool>,
	) -> Result<(), Error> {
		eprintln!("({}) Preparing to sync {:?}...", self.table.name, partition);
		let root_cks = self
			.root_checksum(&partition.begin, &partition.end, must_exit)
			.await?;

		let ring = self.table.system.ring.borrow().clone();
		let nodes = ring.walk_ring(&partition.begin, self.table.param.replication_factor);
		let mut sync_futures = nodes
			.iter()
			.map(|node| {
				self.clone()
					.do_sync_with(root_cks.clone(), node.clone(), must_exit.clone())
			})
			.collect::<FuturesUnordered<_>>();

		while let Some(r) = sync_futures.next().await {
			if let Err(e) = r {
				eprintln!("({}) Sync error: {}", self.table.name, e);
			}
		}
		if !partition.retain {
			self.table
				.delete_range(&partition.begin, &partition.end)
				.await?;
		}

		Ok(())
	}

	async fn root_checksum(
		self: &Arc<Self>,
		begin: &Hash,
		end: &Hash,
		must_exit: &mut watch::Receiver<bool>,
	) -> Result<RangeChecksum, Error> {
		for i in 1..MAX_DEPTH {
			let rc = self
				.range_checksum(
					&SyncRange {
						begin: begin.to_vec(),
						end: end.to_vec(),
						level: i,
					},
					must_exit,
				)
				.await?;
			if rc.found_limit.is_none() {
				return Ok(rc);
			}
		}
		Err(Error::Message(format!(
			"Unable to compute root checksum (this should never happen"
		)))
	}

	fn range_checksum<'a>(
		self: &'a Arc<Self>,
		range: &'a SyncRange,
		must_exit: &'a mut watch::Receiver<bool>,
	) -> BoxFuture<'a, Result<RangeChecksum, Error>> {
		async move {
			let mut cache = self.cache[range.level].lock().await;
			if let Some(v) = cache.get(&range) {
				if Instant::now() - v.time < CHECKSUM_CACHE_TIMEOUT {
					return Ok(v.clone());
				}
			}
			cache.remove(&range);
			drop(cache);

			let v = self.range_checksum_inner(&range, must_exit).await?;
			eprintln!(
				"({}) New checksum calculated for {}-{}/{}, {} children",
				self.table.name,
				hex::encode(&range.begin[..]),
				hex::encode(&range.end[..]),
				range.level,
				v.children.len()
			);

			let mut cache = self.cache[range.level].lock().await;
			cache.insert(range.clone(), v.clone());
			Ok(v)
		}
		.boxed()
	}

	async fn range_checksum_inner(
		self: &Arc<Self>,
		range: &SyncRange,
		must_exit: &mut watch::Receiver<bool>,
	) -> Result<RangeChecksum, Error> {
		if range.level == 1 {
			let mut children = vec![];
			for item in self
				.table
				.store
				.range(range.begin.clone()..range.end.clone())
			{
				let (key, value) = item?;
				let key_hash = hash(&key[..]);
				if key != range.begin && key_hash.as_slice()[0..range.level].iter().all(|x| *x == 0)
				{
					return Ok(RangeChecksum {
						bounds: range.clone(),
						children,
						found_limit: Some(key.to_vec()),
						time: Instant::now(),
					});
				}
				let item_range = SyncRange {
					begin: key.to_vec(),
					end: vec![],
					level: 0,
				};
				children.push((item_range, hash(&value[..])));
			}
			Ok(RangeChecksum {
				bounds: range.clone(),
				children,
				found_limit: None,
				time: Instant::now(),
			})
		} else {
			let mut children = vec![];
			let mut sub_range = SyncRange {
				begin: range.begin.clone(),
				end: range.end.clone(),
				level: range.level - 1,
			};
			let mut time = Instant::now();
			while !*must_exit.borrow() {
				let sub_ck = self.range_checksum(&sub_range, must_exit).await?;

				if sub_ck.children.len() > 0 {
					let sub_ck_hash = hash(&rmp_to_vec_all_named(&sub_ck)?[..]);
					children.push((sub_range.clone(), sub_ck_hash));
					if sub_ck.time < time {
						time = sub_ck.time;
					}
				}

				if sub_ck.found_limit.is_none() || sub_ck.children.len() == 0 {
					return Ok(RangeChecksum {
						bounds: range.clone(),
						children,
						found_limit: None,
						time,
					});
				}
				let found_limit = sub_ck.found_limit.unwrap();

				let actual_limit_hash = hash(&found_limit[..]);
				if actual_limit_hash.as_slice()[0..range.level]
					.iter()
					.all(|x| *x == 0)
				{
					return Ok(RangeChecksum {
						bounds: range.clone(),
						children,
						found_limit: Some(found_limit.clone()),
						time,
					});
				}

				sub_range.begin = found_limit;
			}
			Err(Error::Message(format!("Exiting.")))
		}
	}

	async fn do_sync_with(
		self: Arc<Self>,
		root_ck: RangeChecksum,
		who: UUID,
		mut must_exit: watch::Receiver<bool>,
	) -> Result<(), Error> {
		let mut todo = VecDeque::new();
		todo.push_back(root_ck);

		while !todo.is_empty() && !*must_exit.borrow() {
			let total_children = todo.iter().map(|x| x.children.len()).fold(0, |x, y| x + y);
			eprintln!(
				"({}) Sync with {:?}: {} ({}) remaining",
				self.table.name,
				who,
				todo.len(),
				total_children
			);

			let end = std::cmp::min(16, todo.len());
			let step = todo.drain(..end).collect::<Vec<_>>();

			let rpc_resp = self
				.table
				.rpc_call(&who, &TableRPC::<F>::SyncRPC(SyncRPC::Checksums(step)))
				.await?;
			if let TableRPC::<F>::SyncRPC(SyncRPC::DifferentSet(mut s)) = rpc_resp {
				let mut items = vec![];
				for differing in s.drain(..) {
					if differing.level == 0 {
						items.push(differing.begin);
					} else {
						let checksum = self.range_checksum(&differing, &mut must_exit).await?;
						todo.push_back(checksum);
					}
				}
				if items.len() > 0 {
					self.table
						.system
						.background
						.spawn(self.clone().send_items(who.clone(), items));
				}
			} else {
				return Err(Error::Message(format!(
					"Unexpected response to sync RPC checksums: {}",
					debug_serialize(&rpc_resp)
				)));
			}
		}
		Ok(())
	}

	async fn send_items(self: Arc<Self>, who: UUID, item_list: Vec<Vec<u8>>) -> Result<(), Error> {
		eprintln!(
			"({}) Sending {} items to {:?}",
			self.table.name,
			item_list.len(),
			who
		);

		let mut values = vec![];
		for item in item_list.iter() {
			if let Some(v) = self.table.store.get(&item[..])? {
				values.push(Arc::new(ByteBuf::from(v.as_ref())));
			}
		}
		let rpc_resp = self
			.table
			.rpc_call(&who, &TableRPC::<F>::Update(values))
			.await?;
		if let TableRPC::<F>::Ok = rpc_resp {
			Ok(())
		} else {
			Err(Error::Message(format!(
				"Unexpected response to RPC Update: {}",
				debug_serialize(&rpc_resp)
			)))
		}
	}

	pub async fn handle_rpc(
		self: &Arc<Self>,
		message: &SyncRPC,
		mut must_exit: watch::Receiver<bool>,
	) -> Result<SyncRPC, Error> {
		if let SyncRPC::Checksums(checksums) = message {
			let mut ret = vec![];
			for ckr in checksums.iter() {
				let our_ckr = self.range_checksum(&ckr.bounds, &mut must_exit).await?;
				for (range, hash) in ckr.children.iter() {
					match our_ckr
						.children
						.binary_search_by(|(our_range, _)| our_range.begin.cmp(&range.begin))
					{
						Err(_) => {
							ret.push(range.clone());
						}
						Ok(i) => {
							if our_ckr.children[i].1 != *hash {
								ret.push(range.clone());
							}
						}
					}
				}
			}
			let n_checksums = checksums
				.iter()
				.map(|x| x.children.len())
				.fold(0, |x, y| x + y);
			eprintln!(
				"({}) Checksum comparison RPC: {} different out of {}",
				self.table.name,
				ret.len(),
				n_checksums
			);
			return Ok(SyncRPC::DifferentSet(ret));
		}
		Err(Error::Message(format!("Unexpected sync RPC")))
	}

	pub async fn invalidate(self: Arc<Self>, item_key: Vec<u8>) -> Result<(), Error> {
		for i in 1..MAX_DEPTH {
			let needle = SyncRange {
				begin: item_key.to_vec(),
				end: vec![],
				level: i,
			};
			let mut cache = self.cache[i].lock().await;
			if let Some(cache_entry) = cache.range(..=needle).rev().next() {
				if cache_entry.0.begin <= item_key && cache_entry.0.end > item_key {
					let index = cache_entry.0.clone();
					drop(cache_entry);
					cache.remove(&index);
				}
			}
		}
		Ok(())
	}
}

impl SyncTodo {
	fn add_full_scan<F: TableSchema>(&mut self, table: &Table<F>) {
		let my_id = table.system.id.clone();

		self.todo.clear();

		let ring: Arc<Ring> = table.system.ring.borrow().clone();

		for i in 0..ring.ring.len() {
			let nodes = ring.walk_ring_from_pos(i, table.param.replication_factor);
			let begin = ring.ring[i].location.clone();

			if i == 0 {
				self.add_full_scan_aux(table, [0u8; 32].into(), begin.clone(), &nodes[..], &my_id);
			}

			if i == ring.ring.len() - 1 {
				self.add_full_scan_aux(table, begin, [0xffu8; 32].into(), &nodes[..], &my_id);
			} else {
				let end = ring.ring[i + 1].location.clone();
				self.add_full_scan_aux(table, begin, end, &nodes[..], &my_id);
			}
		}
	}

	fn add_full_scan_aux<F: TableSchema>(
		&mut self,
		table: &Table<F>,
		begin: Hash,
		end: Hash,
		nodes: &[UUID],
		my_id: &UUID,
	) {
		let retain = nodes.contains(my_id);
		if !retain {
			// Check if we have some data to send, otherwise skip
			if table
				.store
				.range(begin.clone()..end.clone())
				.next()
				.is_none()
			{
				return;
			}
		}

		self.todo.push(Partition { begin, end, retain });
	}

	fn add_ring_difference<F: TableSchema>(&mut self, table: &Table<F>, old: &Ring, new: &Ring) {
		let my_id = table.system.id.clone();

		let old_ring = ring_points(old);
		let new_ring = ring_points(new);
		let both_ring = old_ring.union(&new_ring).cloned().collect::<BTreeSet<_>>();

		let prev_todo_begin = self
			.todo
			.iter()
			.map(|x| x.begin.clone())
			.collect::<BTreeSet<_>>();
		let prev_todo_end = self
			.todo
			.iter()
			.map(|x| x.end.clone())
			.collect::<BTreeSet<_>>();
		let prev_todo = prev_todo_begin
			.union(&prev_todo_end)
			.cloned()
			.collect::<BTreeSet<_>>();

		let all_points = both_ring.union(&prev_todo).cloned().collect::<Vec<_>>();

		self.todo.sort_by(|x, y| x.begin.cmp(&y.begin));
		let mut new_todo = vec![];
		for i in 0..all_points.len() - 1 {
			let begin = all_points[i].clone();
			let end = all_points[i + 1].clone();
			let was_ours = old
				.walk_ring(&begin, table.param.replication_factor)
				.contains(&my_id);
			let is_ours = new
				.walk_ring(&begin, table.param.replication_factor)
				.contains(&my_id);
			let was_todo = match self.todo.binary_search_by(|x| x.begin.cmp(&begin)) {
				Ok(_) => true,
				Err(j) => {
					(j > 0 && self.todo[j - 1].begin < end && begin < self.todo[j - 1].end)
						|| (j < self.todo.len()
							&& self.todo[j].begin < end && begin < self.todo[j].end)
				}
			};
			if was_todo || (is_ours && !was_ours) || (was_ours && !is_ours) {
				new_todo.push(Partition {
					begin,
					end,
					retain: is_ours,
				});
			}
		}

		self.todo = new_todo;
	}

	fn pop_task(&mut self) -> Option<Partition> {
		if self.todo.is_empty() {
			return None;
		}

		let i = rand::thread_rng().gen_range::<usize, _, _>(0, self.todo.len());
		if i == self.todo.len() - 1 {
			self.todo.pop()
		} else {
			let replacement = self.todo.pop().unwrap();
			let ret = std::mem::replace(&mut self.todo[i], replacement);
			Some(ret)
		}
	}
}

fn ring_points(ring: &Ring) -> BTreeSet<Hash> {
	let mut ret = BTreeSet::new();
	ret.insert([0u8; 32].into());
	ret.insert([0xFFu8; 32].into());
	for i in 0..ring.ring.len() {
		ret.insert(ring.ring[i].location.clone());
	}
	ret
}