[runtime] Test atomic blob publication and recovery

[patrick-ogrady]

Summary

Adds exhaustive unit and backend-integrated coverage for the atomic blob engine in #4490, the remaining adapters in #4502, and the migration layer in #4495. The tests are isolated in runtime/src/atomic/tests.rs, with only narrow #[cfg(test)] pause and metric hooks added beside the owning backends.

This is layer 4 of 6 in the atomic blob stack. It changes no non-test runtime behavior.

Review focus

• Direct and grouped append, rewind, tag, integrity, sync, removal, scan, and migration lifecycles.
• Corrupt, torn, stale, aliased, oversized, and otherwise adversarial roots, identities, witnesses, and payloads.
• Recovery linearization, cleanup debt, cancellation after admission, detached work, and same-name namespace exclusion.
• Wrapper/backend symmetry across memory, Tokio, metered, audited, faulty, and deterministic storage.

Diff size

• Production code: +0 / -0 LOC
• Tests and test infrastructure: +8788 / -0 LOC
• Total: +8788 / -0 LOC

Counts are physical diff lines, including comments and blank lines. Test-only files, hooks, and lines inside #[cfg(test)] modules are counted as tests; everything else is counted as production code.

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Status	Name	Latest Commit	Updated (UTC)
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[github-actions]

Benchmark results

Regressions: 0.

✅ `qmdb::merkleize/v=any::unordered::fixed::mmr k=10000 ch=false s=true cc=true` (2/2 gates passed)

Field	Value
Package	commonware-storage
Benchmark target	qmdb_gungraun
Variant	qmdb::merkleize/v=any::unordered::fixed::mmr k=10000 ch=false s=true cc=true
Filter	*::bench_merkleize::any_unordered_fixed_mmr
Baseline suite	commonware-storage
Gates	EstimatedCycles should decrease; tolerance 10.00%; blob_reads should decrease; tolerance 10.00%
Cargo flags	--features test-traits

Metric	Baseline	Current	Delta	Gate
Ir	13,159,318	13,068,714	-0.69%	-
L1hits	16,819,414	16,688,464	-0.78%	-
LLhits	94,113	96,432	+2.46%	-
RamHits	11,467	10,789	-5.91%	-
TotalRW	16,924,994	16,795,685	-0.76%	-
EstimatedCycles	17,691,324	17,548,239	-0.81%	EstimatedCycles should decrease; tolerance 10.00%
blob_reads	158	158	+0.00%	blob_reads should decrease; tolerance 10.00%

✅ `qmdb::merkleize/v=current::ordered::fixed::mmb chunk=256 k=10000 ch=false s=true cc=true` (2/2 gates passed)

Field	Value
Package	commonware-storage
Benchmark target	qmdb_gungraun
Variant	qmdb::merkleize/v=current::ordered::fixed::mmb chunk=256 k=10000 ch=false s=true cc=true
Filter	*::bench_merkleize::current_ordered_fixed_mmb_chunk_256
Baseline suite	commonware-storage
Gates	EstimatedCycles should decrease; tolerance 10.00%; blob_reads should decrease; tolerance 10.00%
Cargo flags	--features test-traits

Metric	Baseline	Current	Delta	Gate
Ir	15,488,996	15,459,391	-0.19%	-
L1hits	20,313,311	20,335,673	+0.11%	-
LLhits	132,020	139,628	+5.76%	-
RamHits	17,946	17,377	-3.17%	-
TotalRW	20,463,277	20,492,678	+0.14%	-
EstimatedCycles	21,601,521	21,642,008	+0.19%	EstimatedCycles should decrease; tolerance 10.00%
blob_reads	235	235	+0.00%	blob_reads should decrease; tolerance 10.00%

Baseline commit(s): f04a442f1c3c

[cursor]

Cursor Bugbot has reviewed your changes using high effort and found 1 potential issue.

^{❌ Bugbot Autofix is OFF. To automatically fix reported issues with cloud agents, enable autofix in the Cursor dashboard.}

^{Reviewed by Cursor Bugbot for commit d826af2. Configure here.}

[cursor]

Weak migration cancel fencing check

Medium Severity

canceled_admitted_migration_fences_ordinary_retry_open treats a single yield_now plus !retry.is_finished() as proof that an ordinary open was fenced by the admitted migration. A just-spawned open almost never finishes in one yield whether or not it waits on namespace, so retry_was_blocked can pass without proving same-name exclusion. namespace_was_fenced only shows the migration holds the lock, not that open takes it.

 

^{Reviewed by Cursor Bugbot for commit d826af2. Configure here.}

[codecov]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 95.54%. Comparing base (e866a9d) to head (d826af2).

@@                    Coverage Diff                     @@
##           atomic-blobs-migration    #4491      +/-   ##
==========================================================
+ Coverage                   95.24%   95.54%   +0.30%     
==========================================================
  Files                         609      609              
  Lines                      280494   280523      +29     
  Branches                     6942     6944       +2     
==========================================================
+ Hits                       267149   268038     +889     
+ Misses                      10996    10228     -768     
+ Partials                     2349     2257      -92     

Files with missing lines	Coverage Δ
runtime/src/atomic.rs	97.35% <ø> (+26.32%)	⬆️
runtime/src/storage/metered.rs	100.00% <100.00%> (ø)
runtime/src/storage/tokio/blob.rs	89.88% <100.00%> (+4.41%)	⬆️
runtime/src/storage/tokio/mod.rs	96.32% <ø> (ø)

... and 12 files with indirect coverage changes

---

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