test(pyamber): add test coverage for AsyncRPCHandlerInitializer

[eugenegujing]

What changes were proposed in this PR?

Adds test_async_rpc_handler_initializer.py (50 tests) for core/architecture/rpc/async_rpc_handler_initializer.py — the class whose body is pass and whose mixin list is the entire wiring between the generated WorkerService and the Python worker's control handlers. Nothing covered it before: test_async_rpc_server.py deliberately substitutes a stub initializer, so a proto RPC added without a Python handler was only discovered at runtime.

Expectations are derived from the generated code rather than hand-listed, so a newly generated RPC joins the parametrization on its own and fails until a handler exists. The spec pins:

• every declared RPC resolves to an async coroutine on a ControlHandler mixin, taking exactly the request type and returning exactly the reply type the generated mapping declares;
• the deliberately-unimplemented set is exactly prepare_checkpoint, finalize_checkpoint, retrieve_state and flush_network_buffer, as a set equality in both directions — implementing one without updating the set fails too. (One correction to the issue text: flush_network_buffer is a Scala-side network concern, not checkpoint-related, so the set is four RPCs rather than "the checkpoint-related ones".)
• no RPC is defined by more than one mixin — an MRO-shadowed duplicate is dead code invisible to every other check;
• every ControlHandler subclass on disk is wired into the initializer's bases — the one check not derived from the MRO, so a handler that was written but never wired is reported by name;
• every request type is registered in ControlRequest's oneof, and the reply types missing from ControlReturn's oneof are exactly evaluate_python_expression. That last one is a real, currently-broken shape: the worker service declares EvaluatedValue as its reply but the oneof only registers the coordinator-side wrapper, so set_one_of packs an empty ControlReturn and the answer is silently dropped. The fix is a .proto change and out of scope here; pinning the current shape forces whoever fixes it to clean up the exception set in the same change.
• the real AsyncRPCServer registers one collision-free lowercased lookup key per RPC, each bound to the real initializer, NoOperation round-trips end to end through the unmodified production wiring, and each unimplemented RPC replies with an UNIMPLEMENTED ControlError instead of taking the worker down.

Not redundant with test_async_rpc_server.py: that spec pins the server's dispatch and packing mechanics against a stub (including set_one_of swallowing a wrong-typed reply, exercised with a synthetic type); this one pins the real wiring and names which actual RPC hits that mechanism. The Scala twin of this file gained its spec in #7729; this is the Python side.

Any related issues, documentation, discussions?

Closes #7747.

How was this PR tested?

50 new tests, all green locally:

cd amber
pytest src/test/python/core/architecture/rpc/test_async_rpc_handler_initializer.py -q   # 50 passed
pytest src/test/python/core/architecture/ -q                                            # 341 passed
pytest -m "not integration" -q                                                          # 1106 passed
ruff check src/main/python src/test/python && ruff format --check src/main/python src/test/python

The only full-suite failures are the pre-existing core/storage/iceberg/test_iceberg_document.py items that need a local catalog stack; they fail identically without this PR.

The tests were also mutation-checked: removing a mixin from the bases, renaming a handler method away from the proto name, turning a handler async def into a plain def, adding a new RPC to the generated base without a handler, implementing one of the acknowledged-unimplemented RPCs, duplicating an RPC on a second mixin, hiding an unwired handler in a subpackage, and deleting a oneof registration each turn the expected tests red.

Was this PR authored or co-authored using generative AI tooling?

Generated-by: Claude Code (Claude Opus 5)

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Automated Reviewer Suggestions

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[codecov-commenter]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 91.03%. Comparing base (e80add4) to head (ec22984).
⚠️ Report is 1 commits behind head on main.

Additional details and impacted files

@@            Coverage Diff            @@
##               main    #7749   +/-   ##
=========================================
  Coverage     91.03%   91.03%           
  Complexity     4459     4459           
=========================================
  Files          1174     1174           
  Lines         47139    47139           
  Branches       5284     5284           
=========================================
  Hits          42915    42915           
  Misses         2549     2549           
  Partials       1675     1675           

Flag	Coverage Δ		*Carryforward flag
access-control-service	81.00% <ø> (ø)		Carriedforward from e80add4
agent-service	98.62% <ø> (ø)		Carriedforward from e80add4
amber	87.49% <ø> (ø)		Carriedforward from e80add4
computing-unit-managing-service	73.67% <ø> (ø)		Carriedforward from e80add4
config-service	86.73% <ø> (ø)		Carriedforward from e80add4
file-service	68.90% <ø> (ø)		Carriedforward from e80add4
frontend	92.58% <ø> (ø)		Carriedforward from e80add4
notebook-migration-service	83.74% <ø> (ø)		Carriedforward from e80add4
pyamber	97.57% <ø> (ø)
workflow-compiling-service	77.19% <ø> (ø)		Carriedforward from e80add4

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

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⚠️ Benchmark changes need a look

🟢 2 better · 🔴 5 worse · ⚪ 8 noise (<±5%) · 0 without baseline

Compared against main 60300e3 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	384	0.235	26,700/33,700/33,700 us	🔴 +5.3% / 🔴 +110.8%
🔴	bs=100 sw=10 sl=64	909	0.555	109,487/137,105/137,105 us	🔴 +9.3% / 🔴 +27.8%
🔴	bs=1000 sw=10 sl=64	1,080	0.659	924,291/1,026,642/1,026,642 us	🔴 +5.9% / 🟢 -5.5%

Baseline details

Latest main 60300e3 from same runner

config	metric	PR	latest main	7d avg	Δ latest	Δ 7d
bs=10 sw=10 sl=64	throughput	384 tuples/sec	404 tuples/sec	779.07 tuples/sec	-5.0%	-50.7%
bs=10 sw=10 sl=64	MB/s	0.235 MB/s	0.247 MB/s	0.476 MB/s	-4.9%	-50.6%
bs=10 sw=10 sl=64	p50	26,700 us	25,359 us	12,818 us	+5.3%	+108.3%
bs=10 sw=10 sl=64	p95	33,700 us	35,580 us	15,986 us	-5.3%	+110.8%
bs=10 sw=10 sl=64	p99	33,700 us	35,580 us	19,339 us	-5.3%	+74.3%
bs=100 sw=10 sl=64	throughput	909 tuples/sec	932 tuples/sec	1,011 tuples/sec	-2.5%	-10.1%
bs=100 sw=10 sl=64	MB/s	0.555 MB/s	0.569 MB/s	0.617 MB/s	-2.5%	-10.1%
bs=100 sw=10 sl=64	p50	109,487 us	108,549 us	100,965 us	+0.9%	+8.4%
bs=100 sw=10 sl=64	p95	137,105 us	125,457 us	107,295 us	+9.3%	+27.8%
bs=100 sw=10 sl=64	p99	137,105 us	125,457 us	115,531 us	+9.3%	+18.7%
bs=1000 sw=10 sl=64	throughput	1,080 tuples/sec	1,079 tuples/sec	1,049 tuples/sec	+0.1%	+3.0%
bs=1000 sw=10 sl=64	MB/s	0.659 MB/s	0.659 MB/s	0.64 MB/s	0.0%	+2.9%
bs=1000 sw=10 sl=64	p50	924,291 us	929,816 us	978,248 us	-0.6%	-5.5%
bs=1000 sw=10 sl=64	p95	1,026,642 us	969,801 us	1,021,881 us	+5.9%	+0.5%
bs=1000 sw=10 sl=64	p99	1,026,642 us	969,801 us	1,050,075 us	+5.9%	-2.2%

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
0,10,10,64,20,520.38,200,128000,384,0.235,26699.83,33700.09,33700.09
1,100,10,64,20,2201.21,2000,1280000,909,0.555,109486.78,137105.29,137105.29
2,1000,10,64,20,18520.61,20000,12800000,1080,0.659,924290.93,1026642.25,1026642.25