Use "loadgroup" scheduling in the test suite runner (3cf1d6d) - derivepassphrase.git

Use "loadgroup" scheduling in the test suite runner

Marco Ricci commited on 2026-01-17 19:00:49
Zeige 3 geänderte Dateien mit 47 Einfügungen und 2 Löschungen.

Parallelize the test suite via the "loadgroup" scheduler, instead of the
"worksteal" scheduler.  There is currently only one `xtest_group` marker
value, so effectively, the scheduler schedules the *marked* tests all to
the same worker, and the others in whatever manner.  We can thus rely on
the marked tests executing serially, and do not need locks to protect
them (or their fixture calls) from concurrent access.

This eliminates "locking implementations" as both a source of errors and
as another group of code that needs debugging, testing, and coverage.
(Which was, unfortunately, our experience with the `filelock` package we
used to protect non-isolated SSH agents on The Annoying OS during
fixture setup and teardown.)

As a bonus, because the "loadgroup" scheduler lazily assigns work items
as other items are completed, the performance is similar to the
"worksteal" scheduler it is replacing.

pyproject.toml 40963da..4d1dd9b
tests/conftest.py f452dda..124b595
tests/machinery/pytest.py a22dc5e..c383c69

pyproject.toml

Zeige Datei @ 3cf1d6d

@@ -412,7 +412,7 @@ sqlite_cache = true
 enable_error_code = ['ignore-without-code']
 
 [tool.pytest.ini_options]
-addopts = '--doctest-modules --dist=worksteal --import-mode=importlib'
+addopts = '--doctest-modules --dist=loadgroup --import-mode=importlib'
 pythonpath = ['src']
 testpaths = ['src', 'tests']
 xfail_strict = true

tests/conftest.py

Zeige Datei @ 3cf1d6d

@@ -26,6 +26,7 @@ from derivepassphrase import _types, ssh_agent
 from derivepassphrase.ssh_agent import socketprovider
 from tests import data, machinery
 from tests.data import callables
+from tests.machinery import pytest as pytest_machinery
 
 if TYPE_CHECKING:
     from collections.abc import Iterator, Sequence
@@ -509,6 +510,12 @@ for key, handler in spawn_handlers.items():
             "environment variable.",
         ),
     ]
+    # Mark non-isolated agents as, well, using non-isolated agents.
+    # Assume by default that an agent is potentially non-isolated unless
+    # we can be absolutely sure it is isolated, by design.  (The "stub"
+    # agents fall into the latter category.)
+    if handler.agent_type != data.KnownSSHAgent.StubbedSSHAgent:
+        marks.append(pytest_machinery.non_isolated_agent_use)
     # Some agents require UNIX domain socket support.
     if key in {"unix-pageant", "openssh"}:
         marks.append(
@@ -719,8 +726,21 @@ def spawn_named_agent(  # noqa: C901
     )
 
 
-@pytest.fixture
+# Hack: We cannot associate markers with fixtures (the pytest devs say
+# there are many unresolved questions when it comes to fixture and
+# marker overriding in such a case), so we fake this by trivially
+# parametrizing the fixture.  (The parametrizations *can* contain the
+# necessary marks.)
+@pytest.fixture(
+    params=[
+        pytest.param(
+            "non_isolated_agent_use",
+            marks=pytest_machinery.non_isolated_agent_use,
+        )
+    ]
+)
 def running_ssh_agent(  # pragma: no cover [external]
+    request: pytest.FixtureRequest,
 ) -> Iterator[data.RunningSSHAgentInfo]:
     """Ensure a running SSH agent, if possible, as a pytest fixture.
 
@@ -742,6 +762,7 @@ def running_ssh_agent(  # pragma: no cover [external]
             If no agent is running or can be spawned, skip this test.
 
     """
+    del request
 
     def prepare_environment(
         agent_type: data.KnownSSHAgent,

tests/machinery/pytest.py

Zeige Datei @ 3cf1d6d

@@ -151,6 +151,30 @@ All current heavy duty tests are integration tests.
 """
 
 
+non_isolated_agent_use = pytest.mark.xdist_group("non_isolated_agent_use")
+"""
+A cached `pytest` mark, for use with xdist's "loadgroup" scheduling,
+that marks a test as part of the group of tests that use a potentially
+non-isolated agent, and thus need to be run serially, in the same worker
+(because of the setup and teardown).
+
+This is a pessimistic approach: all agent use is marked with this mark
+*unless* we know for sure that this constellation is guaranteed safe.
+To date, this is only the case for the fake agents from this very test
+suite.
+
+The use of this mark is, if not outright a hack, at least an abuse of
+xdist features.  The "correct" way to handle this situation is to employ
+a lock, but we have had bad experiences with trying to do this in
+a portable way without adding oodles of extra code (that also needs to be
+tested), or effectively forcing *everything* into serial execution.  It
+also only works because we have precisely one group, and because we have
+no work stealing (at least, not with the only scheduler that honors
+`xdist_group`).  In particular, it bars us from adding more groups or
+grouping along different criteria.
+"""
+
+
 # Parameter sets
 # ==============
 


...	...	@@ -412,7 +412,7 @@ sqlite_cache = true
412	412	enable_error_code = ['ignore-without-code']
413	413
414	414	[tool.pytest.ini_options]
415		-addopts = '--doctest-modules --dist=worksteal --import-mode=importlib'
	415	+addopts = '--doctest-modules --dist=loadgroup --import-mode=importlib'
416	416	pythonpath = ['src']
417	417	testpaths = ['src', 'tests']
418	418	xfail_strict = true

...	...	@@ -26,6 +26,7 @@ from derivepassphrase import _types, ssh_agent
26	26	from derivepassphrase.ssh_agent import socketprovider
27	27	from tests import data, machinery
28	28	from tests.data import callables
	29	+from tests.machinery import pytest as pytest_machinery
29	30
30	31	if TYPE_CHECKING:
31	32	from collections.abc import Iterator, Sequence
...	...	@@ -509,6 +510,12 @@ for key, handler in spawn_handlers.items():
509	510	"environment variable.",
510	511	),
511	512	]
	513	+ # Mark non-isolated agents as, well, using non-isolated agents.
	514	+ # Assume by default that an agent is potentially non-isolated unless
	515	+ # we can be absolutely sure it is isolated, by design. (The "stub"
	516	+ # agents fall into the latter category.)
	517	+ if handler.agent_type != data.KnownSSHAgent.StubbedSSHAgent:
	518	+ marks.append(pytest_machinery.non_isolated_agent_use)
512	519	# Some agents require UNIX domain socket support.
513	520	if key in {"unix-pageant", "openssh"}:
514	521	marks.append(
...	...	@@ -719,8 +726,21 @@ def spawn_named_agent( # noqa: C901
719	726	)
720	727
721	728
722		-@pytest.fixture
	729	+# Hack: We cannot associate markers with fixtures (the pytest devs say
	730	+# there are many unresolved questions when it comes to fixture and
	731	+# marker overriding in such a case), so we fake this by trivially
	732	+# parametrizing the fixture. (The parametrizations can contain the
	733	+# necessary marks.)
	734	+@pytest.fixture(
	735	+ params=[
	736	+ pytest.param(
	737	+ "non_isolated_agent_use",
	738	+ marks=pytest_machinery.non_isolated_agent_use,
	739	+ )
	740	+ ]
	741	+)
723	742	def running_ssh_agent( # pragma: no cover [external]
	743	+ request: pytest.FixtureRequest,
724	744	) -> Iterator[data.RunningSSHAgentInfo]:
725	745	"""Ensure a running SSH agent, if possible, as a pytest fixture.
726	746
...	...	@@ -742,6 +762,7 @@ def running_ssh_agent( # pragma: no cover [external]
742	762	If no agent is running or can be spawned, skip this test.
743	763
744	764	"""
	765	+ del request
745	766
746	767	def prepare_environment(
747	768	agent_type: data.KnownSSHAgent,

...	...	@@ -151,6 +151,30 @@ All current heavy duty tests are integration tests.
151	151	"""
152	152
153	153
	154	+non_isolated_agent_use = pytest.mark.xdist_group("non_isolated_agent_use")
	155	+"""
	156	+A cached `pytest` mark, for use with xdist's "loadgroup" scheduling,
	157	+that marks a test as part of the group of tests that use a potentially
	158	+non-isolated agent, and thus need to be run serially, in the same worker
	159	+(because of the setup and teardown).
	160	+
	161	+This is a pessimistic approach: all agent use is marked with this mark
	162	+unless we know for sure that this constellation is guaranteed safe.
	163	+To date, this is only the case for the fake agents from this very test
	164	+suite.
	165	+
	166	+The use of this mark is, if not outright a hack, at least an abuse of
	167	+xdist features. The "correct" way to handle this situation is to employ
	168	+a lock, but we have had bad experiences with trying to do this in
	169	+a portable way without adding oodles of extra code (that also needs to be
	170	+tested), or effectively forcing everything into serial execution. It
	171	+also only works because we have precisely one group, and because we have
	172	+no work stealing (at least, not with the only scheduler that honors
	173	+`xdist_group`). In particular, it bars us from adding more groups or
	174	+grouping along different criteria.
	175	+"""
	176	+
	177	+
154	178	# Parameter sets
155	179	# ==============
156	180
157	181