feat: single shard tracking State cleanup #12734

staffik · 2025-01-14T13:37:39Z

Cleanup parent shard State if neither child was tracked for GC window epochs.
That also implements shards garbage collection in general, see #11883.

TODO: add more tests

Summary

We cleanup the unused shards State with the delay of GC window epochs. One reason is that GC modifies the State, and removing the State earlier would result at least in negative refcounts, if not more serious problems.
For that, we need to know if a shard was not tracked since GC window epochs. One caveat is that validator operator could potentially changed the validator key in this period, so we should not rely on the current validator key (or even tracking config) to tell what shards were tracked in past.
We use TrieChanges column, to determine what shards were tracked at the given epoch. We rely on TrieChanges being saved to the last block of an epoch, for all shards that were tracked at given epoch. TODO: add a test that focuses on that
The cleanup for shards is only triggered when we gc-ed the last block of an epoch, always a final block and in canonical chain.
For each shard that we cleaned up, we remove State mapping for it, as the shard being deleted means we do not have the State for any descendant shard too.
Of course we should not remove the State of shards that are currently tracked. And we do not remove State of shards that we care about in the next epoch.

Testing

GC num epochs to keep set to 3.

Notation

P - parent shard
C - child shard
U - unrelated shard
Schedule: (epoch before resharding) | (epoch after resharding) | ... next epochs

Tested scenarios

P | C | U ... test_resharding_v3_state_cleanup
P | U ... test_resharding_v3_do_not_track_children_after_resharding
P | C | U | U | U | U | U | C ... test_resharding_v3_stop_track_child_for_5_epochs (in the end we do not map to parent)
P | C1 | U | U | C2 | U | U | C1 ... test_resharding_v3_stop_track_child_for_5_epochs_with_sibling_in_between (in the end we map to parent)
P | U | C ... test_resharding_v3_shard_shuffling_untrack_then_track
U | U | C ... test_resharding_v3_sync_child

codecov · 2025-01-14T16:22:18Z

Codecov Report

Attention: Patch coverage is 92.64706% with 15 lines in your changes missing coverage. Please review.

Project coverage is 70.81%. Comparing base (483a0e8) to head (6b191d9).
Report is 2 commits behind head on master.

Files with missing lines	Patch %	Lines
chain/chain/src/garbage_collection.rs	89.70%	0 Missing and 14 partials ⚠️
core/store/src/adapter/flat_store.rs	0.00%	0 Missing and 1 partial ⚠️

Additional details and impacted files

@@             Coverage Diff             @@
##           master   #12734       +/-   ##
===========================================
+ Coverage    1.65%   70.81%   +69.15%     
===========================================
  Files         670      848      +178     
  Lines      120798   174365    +53567     
  Branches   120798   174365    +53567     
===========================================
+ Hits         2001   123476   +121475     
+ Misses     118694    45734    -72960     
- Partials      103     5155     +5052

Flag	Coverage Δ
backward-compatibility	`0.16% <0.00%> (?)`
db-migration	`0.16% <0.00%> (-0.01%)`	⬇️
genesis-check	`1.35% <0.00%> (-0.01%)`	⬇️
linux	`69.26% <78.43%> (+67.60%)`	⬆️
linux-nightly	`70.37% <92.64%> (?)`
pytests	`1.65% <0.00%> (-0.01%)`	⬇️
sanity-checks	`1.46% <0.00%> (-0.01%)`	⬇️
unittests	`70.64% <92.64%> (?)`
upgradability	`0.20% <0.00%> (-0.01%)`	⬇️

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chain/client/src/gc_actor.rs

chain/epoch-manager/src/shard_tracker.rs

core/store/src/adapter/flat_store.rs

wacban

I didn't finish the review but so far looks good. I'll let others approve or come back to it tomorrow.

wacban · 2025-01-15T16:17:27Z

chain/chain/src/garbage_collection.rs

+                let tracked_shards_in_gced_epoch_to_check_for_cleanup = if !shard_tracker
+                    .tracks_all_shards()
+                    && epoch_manager.is_last_block_in_finished_epoch(block_hash)?
+                {
+                    Some(get_tracked_shards_in_past_epoch(
+                        &chain_store_update,
+                        &epoch_manager,
+                        block_hash,
+                    )?)
+                } else {
+                    None
+                };


nit: Maybe move to a helper method?

wacban · 2025-01-15T16:20:03Z

chain/chain/src/garbage_collection.rs

+                if let Some(potential_shards_for_cleanup) =
+                    tracked_shards_in_gced_epoch_to_check_for_cleanup


nit: Keep consistent naming e.g. call both potential_shards_for_cleanup.

wacban · 2025-01-15T16:24:00Z

chain/chain/src/garbage_collection.rs

+fn get_tracked_shards_in_past_epoch(
+    chain_store_update: &ChainStoreUpdate,
+    epoch_manager: &Arc<dyn EpochManagerAdapter>,
+    past_epoch_block_hash: &CryptoHash,
+) -> Result<Vec<ShardUId>, Error> {


I don't think this method relies on the fact that the block is in past epoch or that it is the last block of that epoch. I would suggest removing past_epoch from the method method and argument names.

wacban · 2025-01-15T16:25:17Z

chain/chain/src/garbage_collection.rs

+/// State cleanup for single shard tracking. Removes State of shards that are no longer in use.
+///
+/// It has to be run after we clear block data for the `last_block_hash_in_gced_epoch`.
+/// `tracked_shards_in_gced_epoch` are shards that were tracked in the gc-ed epoch,
+/// and these are shards that we potentially no longer use and that can be cleaned up.
+/// We do not clean up a shard if it has been tracked in any epoch later,
+/// or we care about it in the current or the next epoch (relative to Head).
+///
+/// With ReshardingV3, we use State mapping (see DBCol::StateShardUIdMapping),
+/// where each `ShardUId` is potentially mapped to its ancestor to get the database key prefix.
+/// We only remove a shard State if all its descendants are ready to be cleaned up,
+/// in which case, we also remove the mapping from `StateShardUIdMapping`.


wacban

LGTM, great stuff!

Trisfald

🚀

Trisfald · 2025-01-16T12:54:59Z

chain/chain/src/garbage_collection.rs

                    return Err(Error::GCError(
                        "block on canonical chain shouldn't have refcount 0".into(),
                    ));
                }
+                debug_assert_eq!(blocks_current_height.len(), 1);
+
+                // Do not clean up immediatelly, as we still need the State to run gc for this block.


Suggested change

// Do not clean up immediatelly, as we still need the State to run gc for this block.

// Do not clean up immediately, as we still need the State to run gc for this block.

Trisfald · 2025-01-16T13:01:45Z

chain/chain/src/sharding.rs

@@ -13,6 +15,18 @@ pub fn shuffle_receipt_proofs<ReceiptProofType>(
    receipt_proofs.shuffle(&mut rng);
 }

+pub fn cares_about_shard_this_or_next_epoch(


nit: As I read this function, it might as well be a member of shard tracker.
Feel free to ignore

Trisfald · 2025-01-16T13:03:42Z

integration-tests/src/test_loop/tests/resharding_v3.rs

-/// Maximum number of epochs under which the test should finish.
-const TESTLOOP_NUM_EPOCHS_TO_WAIT: u64 = 8;
+/// Default number of epochs for resharding testloop to run.
+// TODO(resharding) Fix nearcore and set it to 10.


Do you have any insight on why it fails with 10? If you do it might be good to capture that in a comment or issue.

If you don't have any relevant clue, feel free to ignore this comment

staffik and others added 4 commits January 14, 2025 14:36

Single shard tracking State cleanup

73c6ce4

clippy

66befc4

Merge branch 'master' into stafik/resharding/state-cleanup-impl

b58dfb7

comments

29bfb4f

staffik requested review from wacban, Trisfald, shreyan-gupta and marcelo-gonzalez January 14, 2025 16:07

Trisfald reviewed Jan 15, 2025

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Trisfald reviewed Jan 15, 2025

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staffik added 2 commits January 15, 2025 12:53

tests

6b191d9

fmt

abb0454

staffik marked this pull request as ready for review January 15, 2025 13:23

staffik requested a review from a team as a code owner January 15, 2025 13:23

wacban reviewed Jan 15, 2025

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wacban approved these changes Jan 16, 2025

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Trisfald approved these changes Jan 16, 2025

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feat: single shard tracking State cleanup #12734

feat: single shard tracking State cleanup #12734

staffik commented Jan 14, 2025 •

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Trisfald Jan 16, 2025

		if let Some(potential_shards_for_cleanup) =
		tracked_shards_in_gced_epoch_to_check_for_cleanup

	// Do not clean up immediatelly, as we still need the State to run gc for this block.
	// Do not clean up immediately, as we still need the State to run gc for this block.

feat: single shard tracking State cleanup #12734

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feat: single shard tracking State cleanup #12734

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staffik commented Jan 14, 2025 • edited Loading

Summary

Testing

Notation

Tested scenarios

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