Ensure adaptive properties work as expected for SpecCluster

distributed/deploy/spec.py

@@ -380,8 +380,8 @@
                 workers.append(worker)
             if workers:
                 worker_futs = [asyncio.ensure_future(w) for w in workers]
-                await asyncio.wait(worker_futs)
                 self.workers.update(dict(zip(to_open, workers)))
+                await asyncio.wait(worker_futs)
                 for w in workers:
                     w._cluster = weakref.ref(self)
                 # Collect exceptions from failed workers. This must happen after all

distributed/deploy/tests/test_local.py

@@ -19,7 +19,7 @@
 from distributed.core import Status
 from distributed.metrics import time
 from distributed.system import MEMORY_LIMIT
-from distributed.utils import TimeoutError, open_port, sync
+from distributed.utils import Deadline, TimeoutError, open_port, sync
 from distributed.utils_test import (
     assert_can_connect_from_everywhere_4,
     assert_can_connect_from_everywhere_4_6,
@@ -1255,6 +1255,59 @@ def setup(self, worker=None):
         import my_nonexistent_library  # noqa
 
 
+class SlowPlugin:
+    def __init__(self, delay=0.1):
+        self.delay = delay
+
+    def setup(self, worker=None):
+        sleep(self.delay)
+
+
+@pytest.mark.slow()
+def test_localcluster_plan_requested_observed():
+    with LocalCluster(
+        n_workers=0,
+        threads_per_worker=1,
+        processes=True,
+        # FIXME: Ideally this would work with an IPC Event or a file to
+        # synchronize instead of sleeping
+        plugins={SlowPlugin(delay=2)},
+        dashboard_address=":0",
+    ) as cluster:
+        assert len(cluster.plan) == 0
+        assert len(cluster.requested) == 0
+        assert len(cluster.observed) == 0
+
+        cluster.scale(1)
+        assert len(cluster.plan) == 1
+        assert len(cluster.requested) == 0
+        assert len(cluster.observed) == 0
+
+        # This should pretty much trigger once we had the chance to run an event
+        # loop tick
+        dl = Deadline.after(1)
+        while not cluster.requested and dl.remaining:
+            sleep(0.01)
+
+        # The worker is requested. For the LocalCluster this means that the
+        # process is up but for generic SpecCluster implementation this merely
+        # means that an additional worker has been asked for but it is not yet
+        # up and running
+        assert not cluster.scheduler_info["workers"]
+        assert len(cluster.plan) == 1
+        assert len(cluster.requested) == 1
+        assert len(cluster.observed) == 0
+
+        with Client(cluster) as client:
+            client.wait_for_workers(1)
+
+        # The worker is fully functional and registered to the scheduler
+        assert cluster.scheduler_info["workers"]
+        assert len(cluster.requested) == 1
+        assert len(cluster.plan) == 1
+        assert len(cluster.observed) == 1
+
+
 @pytest.mark.slow
 def test_localcluster_start_exception(loop):
     with raises_with_cause(