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
// Copyright Materialize, Inc. and contributors. All rights reserved.
//
// Use of this software is governed by the Business Source License
// included in the LICENSE file.
//
// As of the Change Date specified in that file, in accordance with
// the Business Source License, use of this software will be governed
// by the Apache License, Version 2.0.
use std::borrow::Borrow;
use std::collections::BTreeSet;
use std::fmt::Debug;
use std::marker::PhantomData;
use std::mem;
use std::sync::Arc;
use std::time::Instant;
use differential_dataflow::difference::Semigroup;
use differential_dataflow::lattice::Lattice;
use futures_util::stream::FuturesUnordered;
use futures_util::StreamExt;
use prometheus::Counter;
use timely::progress::Timestamp;
use tokio::sync::mpsc::UnboundedSender;
use tokio::sync::{mpsc, oneshot, Semaphore};
use tracing::{debug, debug_span, error, warn, Instrument, Span};
use crate::async_runtime::IsolatedRuntime;
use crate::batch::PartDeletes;
use crate::cfg::GC_BLOB_DELETE_CONCURRENCY_LIMIT;
use mz_ore::cast::CastFrom;
use mz_ore::collections::HashSet;
use mz_persist::location::{Blob, SeqNo};
use mz_persist_types::{Codec, Codec64};
use crate::internal::machine::{retry_external, Machine};
use crate::internal::maintenance::RoutineMaintenance;
use crate::internal::metrics::{GcStepTimings, RetryMetrics};
use crate::internal::paths::{BlobKey, PartialBlobKey, PartialRollupKey};
use crate::internal::state::HollowBlobRef;
use crate::internal::state_versions::{InspectDiff, StateVersionsIter};
use crate::ShardId;
#[derive(Debug, Clone, PartialEq)]
pub struct GcReq {
pub shard_id: ShardId,
pub new_seqno_since: SeqNo,
}
#[derive(Debug)]
pub struct GarbageCollector<K, V, T, D> {
sender: UnboundedSender<(GcReq, oneshot::Sender<RoutineMaintenance>)>,
_phantom: PhantomData<fn() -> (K, V, T, D)>,
}
impl<K, V, T, D> Clone for GarbageCollector<K, V, T, D> {
fn clone(&self) -> Self {
GarbageCollector {
sender: self.sender.clone(),
_phantom: PhantomData,
}
}
}
/// Cleanup for no longer necessary blobs and consensus versions.
///
/// - Every read handle, snapshot, and listener is given a capability on seqno
/// with a very long lease (allowing for infrequent heartbeats). This is a
/// guarantee that no blobs referenced by the state at that version will be
/// deleted (even if they've been compacted in some newer version of the
/// state). This is called a seqno_since in the code as it has obvious
/// parallels to how sinces work at the shard/collection level. (Is reusing
/// "since" here a good idea? We could also call it a "seqno capability" or
/// something else instead.)
/// - Every state transition via apply_unbatched_cmd has the opportunity to
/// determine that the overall seqno_since for the shard has changed. In the
/// common case in production, this will be in response to a snapshot
/// finishing or a listener emitting some batch.
/// - It would be nice if this only ever happened in response to read-y things
/// (there'd be a nice parallel to how compaction background work is only
/// spawned by write activity), but if there are no readers, we still very
/// much want to continue to garbage collect. Notably, if there are no
/// readers, we naturally only need to hold a capability on the current
/// version of state. This means that if there are only writers, a write
/// commands will result in the seqno_since advancing immediately from the
/// previous version of the state to the new one.
/// - Like Compacter, GarbageCollector uses a heuristic to ignore some requests
/// to save work. In this case, the tradeoff is between consensus traffic
/// (plus a bit of cpu) and keeping blobs around longer than strictly
/// necessary. This is correct because a process could always die while
/// executing one of these requests (or be slow and still working on it when
/// the next request is generated), so we anyway need to handle them being
/// dropped.
/// - GarbageCollector works by `Consensus::scan`-ing for every live version of
/// state (ignoring what the request things the prev_state_seqno was for the
/// reasons mentioned immediately above). It then walks through them in a
/// loop, accumulating a BTreeSet of every referenced blob key. When it finds
/// the version corresponding to the new_seqno_since, it removes every blob in
/// that version of the state from the BTreeSet and exits the loop. This
/// results in the BTreeSet containing every blob eligible for deletion. It
/// deletes those blobs and then truncates the state to the new_seqno_since to
/// indicate that this work doesn't need to be done again.
/// - Note that these requests are being processed concurrently, so it's always
/// possible that some future request has already deleted the blobs and
/// truncated consensus. It's also possible that this is the future request.
/// As a result, the only guarantee that we get is that the current version of
/// head is >= new_seqno_since.
/// - (Aside: The above also means that if Blob is not linearizable, there is a
/// possible race where a blob gets deleted before it written and thus is
/// leaked. We anyway always have the possibility of a write process being
/// killed between when it writes a blob and links it into state, so this is
/// fine; it'll be caught and fixed by the same mechanism.)
impl<K, V, T, D> GarbageCollector<K, V, T, D>
where
K: Debug + Codec,
V: Debug + Codec,
T: Timestamp + Lattice + Codec64 + Sync,
D: Semigroup + Codec64,
{
pub fn new(machine: Machine<K, V, T, D>, isolated_runtime: Arc<IsolatedRuntime>) -> Self {
let (gc_req_sender, mut gc_req_recv) =
mpsc::unbounded_channel::<(GcReq, oneshot::Sender<RoutineMaintenance>)>();
// spin off a single task responsible for executing GC requests.
// work is enqueued into the task through a channel
let _worker_handle = mz_ore::task::spawn(|| "PersistGcWorker", async move {
while let Some((req, completer)) = gc_req_recv.recv().await {
let mut consolidated_req = req;
let mut gc_completed_senders = vec![completer];
// check if any further gc requests have built up. we'll merge their requests
// together and run a single GC pass to satisfy all of them
while let Ok((req, completer)) = gc_req_recv.try_recv() {
assert_eq!(req.shard_id, consolidated_req.shard_id);
gc_completed_senders.push(completer);
consolidated_req.new_seqno_since =
std::cmp::max(req.new_seqno_since, consolidated_req.new_seqno_since);
}
let merged_requests = gc_completed_senders.len() - 1;
if merged_requests > 0 {
machine
.applier
.metrics
.gc
.merged
.inc_by(u64::cast_from(merged_requests));
debug!(
"Merged {} gc requests together for shard {}",
merged_requests, consolidated_req.shard_id
);
}
let gc_span = debug_span!(parent: None, "gc_and_truncate", shard_id=%consolidated_req.shard_id);
gc_span.follows_from(&Span::current());
let start = Instant::now();
machine.applier.metrics.gc.started.inc();
let (mut maintenance, _stats) = {
let name = format!("gc_and_truncate ({})", &consolidated_req.shard_id);
let machine = machine.clone();
isolated_runtime
.spawn_named(|| name, async move {
Self::gc_and_truncate(&machine, consolidated_req)
.instrument(gc_span)
.await
})
.await
.expect("gc_and_truncate failed")
};
machine.applier.metrics.gc.finished.inc();
machine.applier.shard_metrics.gc_finished.inc();
machine
.applier
.metrics
.gc
.seconds
.inc_by(start.elapsed().as_secs_f64());
// inform all callers who enqueued GC reqs that their work is complete
for sender in gc_completed_senders {
// we can safely ignore errors here, it's possible the caller
// wasn't interested in waiting and dropped their receiver.
// maintenance will be somewhat-arbitrarily assigned to the first oneshot.
let _ = sender.send(mem::take(&mut maintenance));
}
}
});
GarbageCollector {
sender: gc_req_sender,
_phantom: PhantomData,
}
}
/// Enqueues a [GcReq] to be consumed by the GC background task when available.
///
/// Returns a future that indicates when GC has cleaned up to at least [GcReq::new_seqno_since]
pub fn gc_and_truncate_background(
&self,
req: GcReq,
) -> Option<oneshot::Receiver<RoutineMaintenance>> {
let (gc_completed_sender, gc_completed_receiver) = oneshot::channel();
let new_gc_sender = self.sender.clone();
let send = new_gc_sender.send((req, gc_completed_sender));
if let Err(e) = send {
// In the steady state we expect this to always succeed, but during
// shutdown it is possible the destination task has already spun down
warn!(
"gc_and_truncate_background failed to send gc request: {}",
e
);
return None;
}
Some(gc_completed_receiver)
}
pub(crate) async fn gc_and_truncate(
machine: &Machine<K, V, T, D>,
req: GcReq,
) -> (RoutineMaintenance, GcResults) {
let mut step_start = Instant::now();
let mut report_step_timing = |counter: &Counter| {
let now = Instant::now();
counter.inc_by(now.duration_since(step_start).as_secs_f64());
step_start = now;
};
assert_eq!(req.shard_id, machine.shard_id());
// Double check our GC req: seqno_since will never regress
// so we can verify it's not somehow greater than the last-
// known seqno_since
if req.new_seqno_since > machine.applier.seqno_since() {
machine
.applier
.fetch_and_update_state(Some(req.new_seqno_since))
.await;
let current_seqno_since = machine.applier.seqno_since();
assert!(
req.new_seqno_since <= current_seqno_since,
"invalid gc req: {:?} vs machine seqno_since {}",
req,
current_seqno_since
);
}
// First, check the latest known state to this process to see
// if there's relevant GC work for this seqno_since
let gc_rollups =
GcRollups::new(machine.applier.rollups_lte_seqno(req.new_seqno_since), &req);
let rollups_to_remove_from_state = gc_rollups.rollups_to_remove_from_state();
report_step_timing(&machine.applier.metrics.gc.steps.find_removable_rollups);
let mut gc_results = GcResults::default();
if rollups_to_remove_from_state.is_empty() {
// If there are no rollups to remove from state (either the work has already
// been done, or the there aren't enough rollups <= seqno_since to have any
// to delete), we can safely exit.
machine.applier.metrics.gc.noop.inc();
return (RoutineMaintenance::default(), gc_results);
}
debug!(
"Finding all rollups <= ({}). Will truncate: {:?}. Will remove rollups from state: {:?}",
req.new_seqno_since,
gc_rollups.truncate_seqnos().collect::<Vec<_>>(),
rollups_to_remove_from_state,
);
let mut states = machine
.applier
.state_versions
.fetch_all_live_states(req.shard_id)
.await
.expect("state is initialized")
.check_ts_codec()
.expect("ts codec has not changed");
let initial_seqno = states.state().seqno;
report_step_timing(&machine.applier.metrics.gc.steps.fetch_seconds);
machine
.applier
.shard_metrics
.gc_live_diffs
.set(u64::cast_from(states.len()));
debug!(
"gc seqno_since: ({}) got {} versions from scan",
req.new_seqno_since,
states.len()
);
Self::incrementally_delete_and_truncate(
&mut states,
&gc_rollups,
machine,
&mut report_step_timing,
&mut gc_results,
)
.await;
// Now that the blobs are deleted / Consensus is truncated, remove
// the rollups from state. Doing this at the end ensures that our
// invariant is maintained that the current state contains a rollup
// to the earliest state in Consensus, and ensures that if GC crashes
// part-way through, we still have a reference to these rollups to
// resume their deletion.
//
// This does mean that if GC crashes part-way through we would
// repeat work when it resumes. However the redundant work should
// be minimal as Consensus is incrementally truncated, allowing
// the next run of GC to skip any work needed for rollups less
// than the last truncation.
//
// In short, while this step is not incremental, it does not need
// to be for GC to efficiently resume. And in fact, making it
// incremental could be quite expensive (e.g. more CaS operations).
let (removed_rollups, maintenance) =
machine.remove_rollups(rollups_to_remove_from_state).await;
report_step_timing(&machine.applier.metrics.gc.steps.remove_rollups_from_state);
debug!("CaS removed rollups from state: {:?}", removed_rollups);
gc_results.rollups_removed_from_state = removed_rollups;
// Everything here and below is not strictly needed for GC to complete,
// but it's a good opportunity, while we have all live states in hand,
// to run some metrics and assertions.
// Apply all remaining live states to rollup some metrics, like how many
// parts are being held (in Blob) that are not part of the latest state.
let mut seqno_held_parts = 0;
while let Some(_) = states.next(|diff| match diff {
InspectDiff::FromInitial(_) => {}
InspectDiff::Diff(diff) => {
diff.blob_deletes().for_each(|blob| match blob {
HollowBlobRef::Batch(batch) => {
seqno_held_parts += batch.part_count();
}
HollowBlobRef::Rollup(_) => {}
});
}
}) {}
machine
.applier
.shard_metrics
.gc_seqno_held_parts
.set(u64::cast_from(seqno_held_parts));
// verify that the "current" state (as of `fetch_all_live_states`) contains
// a rollup to the earliest state we fetched. this invariant isn't affected
// by the GC work we just performed, but it is a property of GC correctness
// overall / is a convenient place to run the assertion.
let valid_pre_gc_state = states
.state()
.collections
.rollups
.contains_key(&initial_seqno);
debug_assert!(
valid_pre_gc_state,
"rollups = {:?}, state seqno = {}",
states.state().collections.rollups,
initial_seqno
);
if !valid_pre_gc_state {
// this should never be true in the steady-state, but may be true the
// first time GC runs after fixing any correctness bugs related to our
// state version invariants. we'll make it an error so we can track
// any violations in Sentry, but opt not to panic because the root
// cause of the violation cannot be from this GC run (in fact, this
// GC run, assuming it's correct, should have fixed the violation!)
error!("earliest state fetched during GC did not have corresponding rollup: rollups = {:?}, state seqno = {}",
states.state().collections.rollups,
initial_seqno
);
}
report_step_timing(
&machine
.applier
.metrics
.gc
.steps
.post_gc_calculations_seconds,
);
(maintenance, gc_results)
}
/// Physically deletes all blobs from Blob and live diffs from Consensus that
/// are safe to delete, given the `seqno_since`, ensuring that the earliest
/// live diff in Consensus has a rollup of seqno `<= seqno_since`.
///
/// Internally, performs deletions for each rollup encountered, ensuring that
/// incremental progress is made even if the process is interrupted before
/// completing all gc work.
async fn incrementally_delete_and_truncate<F>(
states: &mut StateVersionsIter<T>,
gc_rollups: &GcRollups,
machine: &Machine<K, V, T, D>,
timer: &mut F,
gc_results: &mut GcResults,
) where
F: FnMut(&Counter),
{
assert_eq!(states.state().shard_id, machine.shard_id());
let shard_id = states.state().shard_id;
let mut batch_parts_to_delete = PartDeletes::default();
let mut rollups_to_delete: BTreeSet<PartialRollupKey> = BTreeSet::new();
for truncate_lt in gc_rollups.truncate_seqnos() {
assert!(batch_parts_to_delete.is_empty());
assert!(rollups_to_delete.is_empty());
// our state is already past the truncation point. there's no work to do --
// some process already truncated this far
if states.state().seqno >= truncate_lt {
continue;
}
// By our invariant, `states` should always begin on a rollup.
assert!(
gc_rollups.contains_seqno(&states.state().seqno),
"rollups = {:?}, state seqno = {}",
gc_rollups,
states.state().seqno
);
Self::find_removable_blobs(
states,
truncate_lt,
&machine.applier.metrics.gc.steps,
timer,
&mut batch_parts_to_delete,
&mut rollups_to_delete,
);
// After finding removable blobs, our state should be exactly `truncate_lt`,
// to ensure we've seen all blob deletions in the diffs needed to reach
// this seqno.
//
// That we can always reach `truncate_lt` given the live diffs we fetched
// earlier is a little subtle:
// * Our GC request was generated after `seqno_since` was written.
// * If our initial seqno on this loop was < `truncate_lt`, then our read
// to `fetch_all_live_states` must have seen live diffs through at least
// `seqno_since`, because the diffs were not yet truncated.
// * `seqno_since` >= `truncate_lt`, therefore we must have enough live
// diffs to reach `truncate_lt`.
assert_eq!(states.state().seqno, truncate_lt);
// `truncate_lt` _is_ the seqno of a rollup, but let's very explicitly
// assert that we're about to truncate everything less than a rollup
// to maintain our invariant.
assert!(
gc_rollups.contains_seqno(&states.state().seqno),
"rollups = {:?}, state seqno = {}",
gc_rollups,
states.state().seqno
);
// Extra paranoia: verify that none of the blobs we're about to delete
// are in our current state (we should only be truncating blobs from
// before this state!)
states.state().blobs().for_each(|blob| match blob {
HollowBlobRef::Batch(batch) => {
for live_part in &batch.parts {
assert!(!batch_parts_to_delete.contains(live_part));
}
}
HollowBlobRef::Rollup(live_rollup) => {
assert_eq!(rollups_to_delete.get(&live_rollup.key), None);
// And double check that the rollups we're about to delete are
// earlier than our truncation point:
match BlobKey::parse_ids(&live_rollup.key.complete(&shard_id)) {
Ok((_shard, PartialBlobKey::Rollup(rollup_seqno, _rollup))) => {
assert!(rollup_seqno < truncate_lt);
}
_ => {
panic!("invalid rollup during deletion: {:?}", live_rollup);
}
}
}
});
gc_results.truncated_consensus_to.push(truncate_lt);
gc_results.batch_parts_deleted_from_blob += batch_parts_to_delete.len();
gc_results.rollups_deleted_from_blob += rollups_to_delete.len();
Self::delete_and_truncate(
truncate_lt,
&mut batch_parts_to_delete,
&mut rollups_to_delete,
machine,
timer,
)
.await;
}
}
/// Iterates through `states`, accumulating all deleted blobs (both batch parts
/// and rollups) until reaching the seqno `truncate_lt`.
///
/// * The initial seqno of `states` MUST be less than `truncate_lt`.
/// * The seqno of `states` after this fn will be exactly `truncate_lt`.
fn find_removable_blobs<F>(
states: &mut StateVersionsIter<T>,
truncate_lt: SeqNo,
metrics: &GcStepTimings,
timer: &mut F,
batch_parts_to_delete: &mut PartDeletes<T>,
rollups_to_delete: &mut BTreeSet<PartialRollupKey>,
) where
F: FnMut(&Counter),
{
assert!(states.state().seqno < truncate_lt);
while let Some(state) = states.next(|diff| match diff {
InspectDiff::FromInitial(_) => {}
InspectDiff::Diff(diff) => {
diff.blob_deletes().for_each(|blob| match blob {
HollowBlobRef::Batch(batch) => {
for part in &batch.parts {
// we use BTreeSets for fast lookups elsewhere, but we should never
// see repeat blob insertions within a single GC run, otherwise we
// have a logic error or our diffs are incorrect (!)
assert!(batch_parts_to_delete.add(part));
}
}
HollowBlobRef::Rollup(rollup) => {
assert!(rollups_to_delete.insert(rollup.key.to_owned()));
}
});
}
}) {
if state.seqno == truncate_lt {
break;
}
}
timer(&metrics.find_deletable_blobs_seconds);
}
/// Deletes `batch_parts` and `rollups` from Blob.
/// Truncates Consensus to `truncate_lt`.
async fn delete_and_truncate<F>(
truncate_lt: SeqNo,
batch_parts: &mut PartDeletes<T>,
rollups: &mut BTreeSet<PartialRollupKey>,
machine: &Machine<K, V, T, D>,
timer: &mut F,
) where
F: FnMut(&Counter),
{
let shard_id = machine.shard_id();
let concurrency_limit = GC_BLOB_DELETE_CONCURRENCY_LIMIT.get(&machine.applier.cfg);
let delete_semaphore = Semaphore::new(concurrency_limit);
let batch_parts = std::mem::take(batch_parts);
batch_parts
.delete(
machine.applier.state_versions.blob.borrow(),
shard_id,
concurrency_limit,
&*machine.applier.metrics,
&machine.applier.metrics.retries.external.batch_delete,
)
.instrument(debug_span!("batch::delete"))
.await;
timer(&machine.applier.metrics.gc.steps.delete_batch_part_seconds);
Self::delete_all(
machine.applier.state_versions.blob.borrow(),
rollups.iter().map(|k| k.complete(&shard_id)),
&machine.applier.metrics.retries.external.rollup_delete,
debug_span!("rollup::delete"),
&delete_semaphore,
)
.await;
rollups.clear();
timer(&machine.applier.metrics.gc.steps.delete_rollup_seconds);
machine
.applier
.state_versions
.truncate_diffs(&shard_id, truncate_lt)
.await;
timer(&machine.applier.metrics.gc.steps.truncate_diff_seconds);
}
// There's also a bulk delete API in s3 if the performance of this
// becomes an issue. Maybe make Blob::delete take a list of keys?
//
// https://docs.aws.amazon.com/AmazonS3/latest/API/API_DeleteObjects.html
async fn delete_all(
blob: &dyn Blob,
keys: impl Iterator<Item = BlobKey>,
metrics: &RetryMetrics,
span: Span,
semaphore: &Semaphore,
) {
let futures = FuturesUnordered::new();
for key in keys {
futures.push(
retry_external(metrics, move || {
let key = key.clone();
async move {
let _permit = semaphore
.acquire()
.await
.expect("acquiring permit from open semaphore");
blob.delete(&key).await.map(|_| ())
}
})
.instrument(span.clone()),
)
}
futures.collect().await
}
}
#[derive(Debug, Default)]
pub(crate) struct GcResults {
pub(crate) batch_parts_deleted_from_blob: usize,
pub(crate) rollups_deleted_from_blob: usize,
pub(crate) truncated_consensus_to: Vec<SeqNo>,
pub(crate) rollups_removed_from_state: Vec<SeqNo>,
}
#[derive(Debug)]
struct GcRollups {
rollups_lte_seqno_since: Vec<(SeqNo, PartialRollupKey)>,
rollup_seqnos: HashSet<SeqNo>,
}
impl GcRollups {
fn new(rollups_lte_seqno_since: Vec<(SeqNo, PartialRollupKey)>, gc_req: &GcReq) -> Self {
assert!(rollups_lte_seqno_since
.iter()
.all(|(seqno, _rollup)| *seqno <= gc_req.new_seqno_since));
let rollup_seqnos = rollups_lte_seqno_since.iter().map(|(x, _)| *x).collect();
Self {
rollups_lte_seqno_since,
rollup_seqnos,
}
}
fn contains_seqno(&self, seqno: &SeqNo) -> bool {
self.rollup_seqnos.contains(seqno)
}
/// Returns the seqnos we can safely truncate state to when performing
/// incremental GC (all rollups with seqnos <= seqno_since).
fn truncate_seqnos(&self) -> impl Iterator<Item = SeqNo> + '_ {
self.rollups_lte_seqno_since
.iter()
.map(|(seqno, _rollup)| *seqno)
}
/// Returns the rollups we can safely remove from state (all rollups
/// `<` than the latest rollup `<=` seqno_since).
///
/// See the full explanation in [crate::internal::state_versions::StateVersions]
/// for how this is derived.
fn rollups_to_remove_from_state(&self) -> &[(SeqNo, PartialRollupKey)] {
match self.rollups_lte_seqno_since.split_last() {
None => &[],
Some((_rollup_to_keep, rollups_to_remove_from_state)) => rollups_to_remove_from_state,
}
}
}