refactor(amber): collapse the single-subclass ReplayLogger base into ReplayLoggerImpl

[aglinxinyuan]

What changes were proposed in this PR?

Collapses the ReplayLogger abstract base into its only subclass, ReplayLoggerImpl. Once #7452 removes EmptyReplayLogger, the base has a single subclass and is never named as a type anywhere:

ReplayLogger	Subclasses	Declared-type sites
on main	2	1 — EmptyReplayLoggerSpec.scala:125, itself deleted by #7452
after #7452	1	0

ReplayLogManager.scala:109  private val replayLogger = new ReplayLoggerImpl()  -> infers the concrete class
ReplayLoggerImpl.scala:31   class ReplayLoggerImpl extends ReplayLogger        -> the only subclass
ReplayLogger.scala:28       abstract class ReplayLogger                        -> nothing else refers to it

So the base declares three abstract methods that exactly one class implements and that no call site dispatches through. Dropping it removes extends ReplayLogger, one override keyword that no longer overrides anything, and ReplayLogger.scala itself. The three method bodies are untouched: −42 / +2 lines, no behaviour change.

ReplayLoggerImpl keeps its name. ReplayLogManagerImpl sits beside a genuine ReplayLogManager trait in the same package, so the ...Impl suffix stays consistent there.

Stacked on #7452, which needs to merge first — without it the base still has two subclasses. Until then the diff here carries both commits; the collapse is the second one, ReplayLogger.scala + 2 lines.

Any related issues, documentation, discussions?

Closes #7673

How was this PR tested?

Existing tests only — this is a structural change with no behaviour change, and LogreplayPrimitivesSpec already covers ReplayLoggerImpl by constructing it directly (new ReplayLoggerImpl()), so it pins all three methods across the refactor without modification.

Locally, from the repo root with Java 17:

• sbt "WorkflowExecutionService/Test/compile" — success.
• sbt "WorkflowExecutionService/testOnly *LogreplayPrimitivesSpec *EmptyReplayLogManagerImplSpec *ReplayLogGeneratorSpec" — all green.
• sbt scalafmtCheckAll "scalafixAll --check" — clean.

Verification, re-runnable by a reviewer:

git grep -n ReplayLogger -- '*.scala' | grep -v ReplayLoggerImpl   # empty

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⚠️ Benchmark changes need a look

🟢 2 better · 🔴 1 worse · ⚪ 12 noise (<±5%) · 0 without baseline

Compared against main 3b19f76 benchmarked on this same runner, so the delta is largely free of cross-runner hardware noise. The "7d avg" column still reflects the gh-pages dashboard. Treat <±5% as noise unless repeated.

Dashboard · Run

	config	throughput	MB/s	latency	max Δ latest / 7d
🔴	bs=10 sw=10 sl=64	353	0.216	27,479/39,045/39,045 us	🔴 +20.8% / 🔴 +138.9%
⚪	bs=100 sw=10 sl=64	781	0.477	126,177/143,343/143,343 us	⚪ within ±5% / 🔴 +34.6%
⚪	bs=1000 sw=10 sl=64	906	0.553	1,102,489/1,186,504/1,186,504 us	⚪ within ±5% / 🔴 +16.1%

Baseline details

Latest main 3b19f76 from same runner

config	metric	PR	latest main	7d avg	Δ latest	Δ 7d
bs=10 sw=10 sl=64	throughput	353 tuples/sec	369 tuples/sec	779.28 tuples/sec	-4.3%	-54.7%
bs=10 sw=10 sl=64	MB/s	0.216 MB/s	0.225 MB/s	0.476 MB/s	-4.0%	-54.6%
bs=10 sw=10 sl=64	p50	27,479 us	22,754 us	12,712 us	+20.8%	+116.2%
bs=10 sw=10 sl=64	p95	39,045 us	45,993 us	16,345 us	-15.1%	+138.9%
bs=10 sw=10 sl=64	p99	39,045 us	45,993 us	19,050 us	-15.1%	+105.0%
bs=100 sw=10 sl=64	throughput	781 tuples/sec	821 tuples/sec	1,017 tuples/sec	-4.9%	-23.2%
bs=100 sw=10 sl=64	MB/s	0.477 MB/s	0.501 MB/s	0.621 MB/s	-4.8%	-23.2%
bs=100 sw=10 sl=64	p50	126,177 us	120,241 us	100,048 us	+4.9%	+26.1%
bs=100 sw=10 sl=64	p95	143,343 us	150,326 us	106,477 us	-4.6%	+34.6%
bs=100 sw=10 sl=64	p99	143,343 us	150,326 us	114,739 us	-4.6%	+24.9%
bs=1000 sw=10 sl=64	throughput	906 tuples/sec	913 tuples/sec	1,048 tuples/sec	-0.8%	-13.5%
bs=1000 sw=10 sl=64	MB/s	0.553 MB/s	0.557 MB/s	0.639 MB/s	-0.7%	-13.5%
bs=1000 sw=10 sl=64	p50	1,102,489 us	1,090,997 us	976,350 us	+1.1%	+12.9%
bs=1000 sw=10 sl=64	p95	1,186,504 us	1,170,039 us	1,022,084 us	+1.4%	+16.1%
bs=1000 sw=10 sl=64	p99	1,186,504 us	1,170,039 us	1,053,520 us	+1.4%	+12.6%

Raw CSV

config_idx,batch_size,schema_width,string_len,num_batches,total_ms,total_tuples,total_bytes,tuples_per_sec,mb_per_sec,lat_p50_us,lat_p95_us,lat_p99_us
0,10,10,64,20,566.39,200,128000,353,0.216,27479.28,39044.65,39044.65
1,100,10,64,20,2561.32,2000,1280000,781,0.477,126177.04,143343.37,143343.37
2,1000,10,64,20,22066.15,20000,12800000,906,0.553,1102489.20,1186503.64,1186503.64

[codecov-commenter]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 87.47%. Comparing base (e03d971) to head (a76889e).
⚠️ Report is 105 commits behind head on main.
✅ All tests successful. No failed tests found.

Additional details and impacted files

@@             Coverage Diff              @@
##               main    #7674      +/-   ##
============================================
+ Coverage     85.32%   87.47%   +2.15%     
- Complexity     4151     4381     +230     
============================================
  Files          1169     1174       +5     
  Lines         46740    46980     +240     
  Branches       5202     5250      +48     
============================================
+ Hits          39882    41097    +1215     
+ Misses         5148     4090    -1058     
- Partials       1710     1793      +83     

Flag	Coverage Δ		*Carryforward flag
access-control-service	70.00% <ø> (ø)		Carriedforward from ac3a565
agent-service	85.50% <ø> (ø)		Carriedforward from ac3a565
amber	86.78% <100.00%> (+5.89%)	⬆️
computing-unit-managing-service	50.72% <ø> (ø)		Carriedforward from ac3a565
config-service	65.97% <ø> (ø)		Carriedforward from ac3a565
file-service	69.05% <ø> (ø)		Carriedforward from ac3a565
frontend	87.85% <ø> (ø)		Carriedforward from ac3a565
notebook-migration-service	78.89% <ø> (ø)		Carriedforward from ac3a565
pyamber	97.51% <ø> (ø)		Carriedforward from ac3a565
workflow-compiling-service	26.31% <ø> (ø)		Carriedforward from ac3a565

*This pull request uses carry forward flags. Click here to find out more.

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