(fix): use dask cluster as a session param

Author: ilan-gold

tests/conftest.py

@@ -13,14 +13,14 @@
     from dask.base import normalize_seq
 else:
     from dask.tokenize import normalize_seq
-from filelock import FileLock
+
+import dask.distributed as dd
 from scipy import sparse
 
 import anndata as ad
 from anndata.tests.helpers import subset_func  # noqa: F401
 
 if TYPE_CHECKING:
-    from collections.abc import Generator
     from types import EllipsisType
 
 
@@ -77,37 +77,17 @@ def equivalent_ellipsis_index(
     return ellipsis_index_with_equivalent[1]
 
 
-@pytest.fixture(scope="session")
-def local_cluster_addr(
-    tmp_path_factory: pytest.TempPathFactory, worker_id: str
-) -> Generator[str, None, None]:
-    # Adapted from https://pytest-xdist.readthedocs.io/en/latest/how-to.html#making-session-scoped-fixtures-execute-only-once
-    import dask.distributed as dd
-
-    def make_cluster() -> dd.LocalCluster:
-        return dd.LocalCluster(n_workers=1, threads_per_worker=1)
-
-    if worker_id == "master":
-        with make_cluster() as cluster:
-            yield cluster.scheduler_address
-            return
-
-    # get the temp directory shared by all workers
-    root_tmp_dir = tmp_path_factory.getbasetemp().parent
-
-    fn = root_tmp_dir / "dask_scheduler_address.txt"
-    lock = FileLock(str(fn) + ".lock")
-    lock.acquire()  # can’t use context manager, because we need to release the lock before yielding
-    address = fn.read_text() if fn.is_file() else None
-    if address:
-        lock.release()
-        yield address
-        return
-
-    with make_cluster() as cluster:
-        fn.write_text(cluster.scheduler_address)
-        lock.release()
-        yield cluster.scheduler_address
+@pytest.fixture(
+    scope="session",
+    params=[
+        pytest.param(
+            dd.LocalCluster(n_workers=1, threads_per_worker=1),
+            # marks=pytest.mark.xdist_group("dask"), # if we ever want to do this setup only once
+        )
+    ],
+)
+def local_cluster_addr(request):
+    return request.param
 
 
 #####################