RoutingClient: match Client's (host, port, tls=...) signature

[ramakrishnap-nv]

Summary

Fixes #1839. cuopt.grpc.routing.RoutingClient diverged from the LP/MIP cuopt.grpc.linear_programming.Client: it took a single "host:port" string and had no way to configure TLS, even though it reuses the exact same grpc_python_client_t C++ shim Client uses -- which already had TLS support (via a grpc_python_client_connect_options_t overload) more than 5 weeks before RoutingClient was added. See #1839 for the full chronology and evidence this was an oversight from a POC-scoped first cut (#1597), not a deliberate design choice -- it never came up in that PR's review, unlike every other follow-up from it.

Changes

• RoutingClient.__cinit__ now takes (host: str, port: int, *, tls=None), mirroring Client.__init__ exactly: tls=None reads CUOPT_TLS_* from the environment (same default as before), tls=False forces plain TCP, tls=TlsConfig(...) sets explicit TLS/mTLS. Reuses the existing _connect_options_from_tls() helper and the TLS-options constructor overload Client already used -- no new C++ needed, both .pxd overloads were already declared.
• Updated the two existing call sites: the cuopt.grpc.routing package docstring example, and test_routing_grpc_client.py's _client() helper (parses CUOPT_GRPC_SERVER=host:port into the two args now).
• Added test_routing_grpc_client_tls.py: an offline TypeError-on-bad-tls-value test, plus a TestRoutingClientTls class mirroring TestGrpcClientTls from the LP test suite (TLS submit, plain-client-against-TLS-server rejection, mTLS submit, mTLS-missing-client-cert rejection) using the existing tls_server_info/mtls_server_info fixtures -- these don't need CUOPT_GRPC_SERVER, they start their own server subprocess.

This is a breaking signature change, not additive -- RoutingClient was added in #1597 and isn't in a stable release yet (the docs describing it, #1838, are still in review), so there's no compatibility surface to preserve.

Out of scope

• 2 GiB chunked upload/download -- already tracked separately in VRP gRPC: chunked upload/download for large problems and solutions #1629, a materially larger feature (server + client, mirroring the LP/MIP chunked path).
• Log/incumbent streaming parity -- VRP gRPC: log streaming and incumbent parity with LP/MILP #1630.

Test plan

• .pyx → .cxx Cython transpile and C++ compile clean (ninja cuopt/grpc/client/CMakeFiles/grpc_client_grpc_client.dir/grpc_client.cxx.o).
• Full extension module links clean (ninja grpc_client_grpc_client).
• Pre-commit hooks pass (ruff, pydocstyle, copyright, etc.).
• Live pytest run against a cuopt_grpc_server -- the installed dev environment's cuopt package predates the grpc/routing merge (Routing over gRPC: VRP server + compiled C++/Cython client #1597), so a full reinstall would be needed locally; CI's environment builds from this branch and should exercise the new tests.

[ramakrishnap-nv]

#1838 (docs) has been updated to document this PR's new RoutingClient(host, port, *, tls=None) signature -- please merge this one first, or merge them together.

[coderabbitai]

📝 Walkthrough

Walkthrough

RoutingClient now requires separate host and port arguments and accepts optional TLS configuration. Connection setup supports environment-derived TLS, plaintext connections, and explicit TLS or mTLS. Examples and routing tests use the new signature and validate TLS behavior.

Changes

RoutingClient connection configuration

Layer / File(s)	Summary
Client connection options python/cuopt/cuopt/grpc/client/grpc_client.pyx	RoutingClient now accepts host, port, and optional tls arguments. It validates TLS settings and passes derived gRPC options to the client connection.
Call-site migration and TLS validation python/cuopt/cuopt/grpc/routing/__init__.py, python/cuopt/cuopt/tests/routing/test_routing_grpc_client.py, python/cuopt/cuopt/tests/routing/test_routing_grpc_client_tls.py	The example and existing integration tests use separate host and port values. New tests cover TLS and mTLS solves, invalid TLS arguments, plaintext rejection, and missing client certificates.

Estimated code review effort: 3 (Moderate) | ~20 minutes

Merge Risk: 🔵 Low · up to 5b0a2

RoutingClient now requires separate host and port arguments and supports TLS/mTLS configuration. TLS behavior is covered, but callers using the former single-string constructor must migrate, so the PR is mergeable with explicit owner awareness of this bounded breaking API risk.

Suggested reviewers: tmckayus

🚥 Pre-merge checks | ✅ 4 | ❌ 1

❌ Failed checks (1 warning)

Check name	Status	Explanation	Resolution
Docstring Coverage	⚠️ Warning	Docstring coverage is 0.00% which is insufficient. The required threshold is 80.00%. Docstring coverage is scoped to functions touched by this diff. Analyzed 10 functions across 3 files. (1 skipped: 1…	Write docstrings for the functions missing them to satisfy the coverage threshold.

✅ Passed checks (4 passed)

Check name	Status	Explanation
Title check	✅ Passed	The title clearly identifies the main change: aligning RoutingClient with Client's host, port, and tls signature.
Description check	✅ Passed	The description directly explains the constructor change, TLS support, updated call sites, tests, and compatibility impact.
Linked Issues check	✅ Passed	The changes satisfy issue #1839 by matching Client's constructor signature and adding environment-based, plaintext, TLS, and mTLS configuration with relevant tests.
Out of Scope Changes check	✅ Passed	The changes remain within issue #1839. Documentation updates, call-site updates, and TLS tests directly support the requested API and behavior.

Full details: Docstring Coverage

Explanation

Docstring coverage is 0.00% which is insufficient. The required threshold is 80.00%. Docstring coverage is scoped to functions touched by this diff. Analyzed 10 functions across 3 files. (1 skipped: 1 unsupported.)

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[coderabbitai]

Actionable comments posted: 1

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Inline comments:
In `@python/cuopt/cuopt/grpc/client/grpc_client.pyx`:
- Line 973: The RoutingClient __cinit__ signature must remain
backward-compatible during deprecation: accept the legacy single target form and
the previous default target as well as the new host/port form, emit a
DeprecationWarning that names a specific removal version for legacy usage, and
add regression coverage for the warning and both constructor forms.

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ℹ️ Review info

⚙️ Run configuration

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Run ID: 74dc71f3-3bee-4ad4-a7b5-2f7c51c8a6e7

📥 Commits

Reviewing files that changed from the base of the PR and between 8fc0115 and 5b0a223.

📒 Files selected for processing (4)

• python/cuopt/cuopt/grpc/client/grpc_client.pyx
• python/cuopt/cuopt/grpc/routing/__init__.py
• python/cuopt/cuopt/tests/routing/test_routing_grpc_client.py
• python/cuopt/cuopt/tests/routing/test_routing_grpc_client_tls.py

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[github-actions]

CI Test Summary

✅ All 22 test job(s) passed. (1 skipped)

[ramakrishnap-nv]

/merge