Remove alias resolving to fix queuing (#8933)

Author: phofl

distributed/scheduler.py

@@ -54,14 +54,9 @@
 
 import dask
 import dask.utils
-from dask._task_spec import (
-    DependenciesMapping,
-    GraphNode,
-    convert_legacy_graph,
-    resolve_aliases,
-)
+from dask._task_spec import DependenciesMapping, GraphNode, convert_legacy_graph
 from dask.base import TokenizationError, normalize_token, tokenize
-from dask.core import istask, reverse_dict, validate_key
+from dask.core import istask, validate_key
 from dask.typing import Key, no_default
 from dask.utils import (
     _deprecated,
@@ -9411,19 +9406,10 @@ def _materialize_graph(
                 )
 
     dsk2 = convert_legacy_graph(dsk)
-    dependents = reverse_dict(DependenciesMapping(dsk2))
-    # This is removing weird references like "x-foo": "foo" which often make up
-    # a substantial part of the graph
-    # This also performs culling!
-    dsk3 = resolve_aliases(dsk2, keys, dependents)
-
-    logger.debug(
-        "Removing aliases. Started with %i and got %i left", len(dsk2), len(dsk3)
-    )
     # FIXME: There should be no need to fully materialize and copy this but some
     # sections in the scheduler are mutating it.
-    dependencies = {k: set(v) for k, v in DependenciesMapping(dsk3).items()}
-    return dsk3, dependencies, annotations_by_type
+    dependencies = {k: set(v) for k, v in DependenciesMapping(dsk2).items()}
+    return dsk2, dependencies, annotations_by_type
 
 
 def _cull(dsk: dict[Key, GraphNode], keys: set[Key]) -> dict[Key, GraphNode]:

distributed/tests/test_scheduler.py

@@ -5304,3 +5304,17 @@ async def before_close(self):
 async def test_rootish_taskgroup_configuration(c, s, *workers):
     assert s.rootish_tg_threshold == 10
     assert s.rootish_tg_dependencies_threshold == 15
+
+
+@gen_cluster(client=True, nthreads=[("", 1)])
+async def test_alias_resolving_break_queuing(c, s, a):
+    pytest.importorskip("numpy")
+    import dask.array as da
+
+    arr = da.random.random((90, 100), chunks=(10, 50))
+    result = arr.rechunk(((10, 7, 7, 6) * 3, (50, 50)))
+    result = result.sum(split_every=1000)
+    x = result.persist()
+    while not s.tasks:
+        await asyncio.sleep(0.01)
+    assert sum([s.is_rootish(v) for v in s.tasks.values()]) == 18