[Core] Custom socket name (#9766)

* fix issues

* hot fixes

* test

* test

* socket name change only

python/ray/node.py

@@ -472,7 +472,8 @@ class Node:
 
         This method helps to prepare a socket file.
         1. Make the directory if the directory does not exist.
-        2. If the socket file exists, raise exception.
+        2. If the socket file exists, do nothing (this just means we aren't the
+           first worker on the node).
 
         Args:
             socket_path (string): the socket file to prepare.
@@ -488,9 +489,6 @@ class Node:
                 result = self._make_inc_temp(
                     prefix=default_prefix, directory_name=self._sockets_dir)
             else:
-                if os.path.exists(socket_path):
-                    raise RuntimeError(
-                        "Socket file {} exists!".format(socket_path))
                 try_to_create_directory(os.path.dirname(socket_path))
 
             # Check socket path length to make sure it's short enough

python/ray/tests/test_advanced_3.py

@@ -421,7 +421,14 @@ def test_socket_dir_not_existing(shutdown_only):
                                               "tests", random_name)
         temp_raylet_socket_name = os.path.join(temp_raylet_socket_dir,
                                                "raylet_socket")
-        ray.init(num_cpus=1, raylet_socket_name=temp_raylet_socket_name)
+        ray.init(num_cpus=2, raylet_socket_name=temp_raylet_socket_name)
+
+        @ray.remote
+        def foo(x):
+            time.sleep(1)
+            return 2 * x
+
+        ray.get([foo.remote(i) for i in range(2)])
 
 
 def test_raylet_is_robust_to_random_messages(ray_start_regular):