Fix multiple drivers for named actors and add test (#5956)

python/ray/tests/test_multi_node.py

@@ -172,6 +172,55 @@ print("success")
         assert "success" in out
 
 
+def test_drivers_named_actors(call_ray_start):
+    # This test will create some drivers that submit some tasks to the same
+    # named actor.
+    address = call_ray_start
+
+    ray.init(address=address)
+
+    # Define a driver that creates a named actor then sleeps for a while.
+    driver_script1 = """
+import ray
+import time
+ray.init(address="{}")
+@ray.remote
+class Counter(object):
+    def __init__(self):
+        self.count = 0
+    def increment(self):
+        self.count += 1
+        return self.count
+counter = Counter.remote()
+ray.experimental.register_actor("Counter", counter)
+time.sleep(100)
+""".format(address)
+
+    # Define a driver that submits to the named actor and exits.
+    driver_script2 = """
+import ray
+import time
+ray.init(address="{}")
+while True:
+    try:
+        counter = ray.experimental.get_actor("Counter")
+        break
+    except ValueError:
+        time.sleep(1)
+assert ray.get(counter.increment.remote()) == {}
+print("success")
+""".format(address, "{}")
+
+    process_handle = run_string_as_driver_nonblocking(driver_script1)
+
+    for i in range(3):
+        driver_script = driver_script2.format(i + 1)
+        out = run_string_as_driver(driver_script)
+        assert "success" in out
+
+    process_handle.kill()
+
+
 def test_receive_late_worker_logs():
     # Make sure that log messages from tasks appear in the stdout even if the
     # script exits quickly.