perf(tests): cut subprocess worker startup ~55% via lazy imports

rustyconover · claude · rustyconover · commit 540ec855bd33 · 2026-04-28T16:51:08.000-04:00
Test workers used to spend ~310ms per spawn on import overhead, dominated
by two avoidable costs:

1. Workers imported `tests.test_rpc` to get `RpcFixtureService` /
   `RpcFixtureServiceImpl`, dragging in pytest, conftest, and httpx —
   none of which the worker uses at runtime. Extract the fixture service
   (Protocol, Impl, state classes, _CancelProbe, DescribeResult,
   StreamHeader, Color) into a new `tests/_fixture_service.py`. The
   seven `serve_fixture_*.py` workers import from there directly;
   `tests.test_rpc` re-exports the names so existing test imports keep
   working.

2. `vgi_rpc/__init__.py` eagerly imported `vgi_rpc.http` (Falcon, httpx),
   `vgi_rpc.sentry` (sentry_sdk), `vgi_rpc.otel`, `vgi_rpc.s3`, and
   `vgi_rpc.gcs` even though most callers — and every pipe/subprocess
   worker — never use them. Convert to module-level `__getattr__` lazy
   loading keyed by `_LAZY_ATTRS`. `__all__` is built once at import
   time by probing the *leaf* third-party deps via
   `importlib.util.find_spec` (probing `vgi_rpc.http._oauth_jwt` would
   import `vgi_rpc.http` and defeat the lazy point).

Results on this machine:
- Worker cold start: 312ms → 140ms (-55%)
- `import vgi_rpc`: ~250ms → ~115ms (-54%)
- Full pytest suite: 132s → 94s (-29%)

Public surface unchanged: `from vgi_rpc import http_connect`,
`vgi_rpc.SentryConfig`, `from vgi_rpc import *` all behave identically.

Co-Authored-By: Claude Opus 4.7 (1M context) &lt;noreply@anthropic.com&gt;
diff --git a/tests/_fixture_service.py b/tests/_fixture_service.py
diff --git a/tests/serve_fixture_describe.py b/tests/serve_fixture_describe.py
@@ -7,7 +7,7 @@
 stdin/stdout for introspection via the CLI.
 """
 
-from tests.test_rpc import RpcFixtureService, RpcFixtureServiceImpl
+from tests._fixture_service import RpcFixtureService, RpcFixtureServiceImpl
 from vgi_rpc.rpc import RpcServer, serve_stdio
 
 
diff --git a/tests/serve_fixture_describe_http.py b/tests/serve_fixture_describe_http.py
@@ -13,7 +13,7 @@
 
 import waitress
 
-from tests.test_rpc import RpcFixtureService, RpcFixtureServiceImpl
+from tests._fixture_service import RpcFixtureService, RpcFixtureServiceImpl
 from vgi_rpc.http import make_wsgi_app
 from vgi_rpc.rpc import RpcServer
 
diff --git a/tests/serve_fixture_describe_unix.py b/tests/serve_fixture_describe_unix.py
@@ -9,7 +9,7 @@
 
 import sys
 
-from tests.test_rpc import RpcFixtureService, RpcFixtureServiceImpl
+from tests._fixture_service import RpcFixtureService, RpcFixtureServiceImpl
 from vgi_rpc.rpc import RpcServer, serve_unix
 
 
diff --git a/tests/serve_fixture_http.py b/tests/serve_fixture_http.py
@@ -15,7 +15,7 @@
 
 import waitress
 
-from tests.test_rpc import RpcFixtureService, RpcFixtureServiceImpl
+from tests._fixture_service import RpcFixtureService, RpcFixtureServiceImpl
 from vgi_rpc.http import make_wsgi_app
 from vgi_rpc.rpc import RpcServer
 
diff --git a/tests/serve_fixture_pipe.py b/tests/serve_fixture_pipe.py
@@ -10,7 +10,7 @@
 RPC requests over stdin/stdout.
 """
 
-from tests.test_rpc import RpcFixtureService, RpcFixtureServiceImpl
+from tests._fixture_service import RpcFixtureService, RpcFixtureServiceImpl
 from vgi_rpc.rpc import run_server
 
 
diff --git a/tests/serve_fixture_unix.py b/tests/serve_fixture_unix.py
@@ -11,7 +11,7 @@
 
 import sys
 
-from tests.test_rpc import RpcFixtureService, RpcFixtureServiceImpl
+from tests._fixture_service import RpcFixtureService, RpcFixtureServiceImpl
 from vgi_rpc.rpc import RpcServer, serve_unix
 
 
diff --git a/tests/serve_fixture_unix_threaded.py b/tests/serve_fixture_unix_threaded.py
@@ -11,7 +11,7 @@
 
 import sys
 
-from tests.test_rpc import RpcFixtureService, RpcFixtureServiceImpl
+from tests._fixture_service import RpcFixtureService, RpcFixtureServiceImpl
 from vgi_rpc.rpc import RpcServer, serve_unix
 
 
diff --git a/tests/test_rpc.py b/tests/test_rpc.py
diff --git a/vgi_rpc/__init__.py b/vgi_rpc/__init__.py
