[autoscaler] Add a 'request_cores' function for manual autoscaling (#4754)

python/ray/tests/test_autoscaler.py

@@ -275,6 +275,33 @@ class AutoscalingTest(unittest.TestCase):
         autoscaler.update()
         self.waitForNodes(2)
 
+    def testManualAutoscaling(self):
+        config = SMALL_CLUSTER.copy()
+        config["min_workers"] = 0
+        config["max_workers"] = 50
+        cores_per_node = 2
+        config["worker_nodes"] = {"Resources": {"CPU": cores_per_node}}
+        config_path = self.write_config(config)
+        self.provider = MockProvider()
+        autoscaler = StandardAutoscaler(
+            config_path,
+            LoadMetrics(),
+            max_launch_batch=5,
+            max_concurrent_launches=5,
+            max_failures=0,
+            update_interval_s=0)
+        assert len(self.provider.non_terminated_nodes({})) == 0
+        autoscaler.update()
+        self.waitForNodes(0)
+        autoscaler.request_resources({"CPU": cores_per_node * 10})
+        for _ in range(3):  # Maximum launch batch is 5
+            autoscaler.update()
+        self.waitForNodes(10)
+        autoscaler.request_resources({"CPU": cores_per_node * 30})
+        for _ in range(4):  # Maximum launch batch is 5
+            autoscaler.update()
+        self.waitForNodes(30)
+
     def testTerminateOutdatedNodesGracefully(self):
         config = SMALL_CLUSTER.copy()
         config["min_workers"] = 5