Replace hostnames with numerical IP addresses in redis address. (#1177)

* Replace hostnames with numerical IP addresses in redis address.

* Also do conversion for node_ip_address. Add test.

* Simplifications.

python/ray/scripts/scripts.py

@@ -81,6 +81,12 @@ def start(node_ip_address, redis_address, redis_port, num_redis_shards,
     # temporary fix. We should actually redirect stdout and stderr to Redis in
     # some way.
 
+    # Convert hostnames to numerical IP address.
+    if node_ip_address is not None:
+        node_ip_address = services.address_to_ip(node_ip_address)
+    if redis_address is not None:
+        redis_address = services.address_to_ip(redis_address)
+
     if head:
         # Start Ray on the head node.
         if redis_address is not None:

python/ray/services.py

@@ -165,6 +165,25 @@ def all_processes_alive(exclude=[]):
     return True
 
 
+def address_to_ip(address):
+    """Convert a hostname to a numerical IP addresses in an address.
+
+    This should be a no-op if address already contains an actual numerical IP
+    address.
+
+    Args:
+        address: This can be either a string containing a hostname (or an IP
+            address) and a port or it can be just an IP address.
+
+    Returns:
+        The same address but with the hostname replaced by a numerical IP
+            address.
+    """
+    address_parts = address.split(":")
+    ip_address = socket.gethostbyname(address_parts[0])
+    return ":".join([ip_address] + address_parts[1:])
+
+
 def get_node_ip_address(address="8.8.8.8:53"):
     """Determine the IP address of the local node.
 

python/ray/worker.py

@@ -1359,6 +1359,12 @@ def init(redis_address=None, node_ip_address=None, object_id_seed=None,
         Exception: An exception is raised if an inappropriate combination of
             arguments is passed in.
     """
+    # Convert hostnames to numerical IP address.
+    if node_ip_address is not None:
+        node_ip_address = services.address_to_ip(node_ip_address)
+    if redis_address is not None:
+        redis_address = services.address_to_ip(redis_address)
+
     info = {"node_ip_address": node_ip_address,
             "redis_address": redis_address}
     return _init(address_info=info, start_ray_local=(redis_address is None),

test/multi_node_test.py

@@ -208,6 +208,24 @@ class StartRayScriptTest(unittest.TestCase):
                                      "--redis-address", "127.0.0.1:6379"])
         subprocess.Popen(["ray", "stop"]).wait()
 
+    def testUsingHostnames(self):
+        # Start the Ray processes on this machine.
+        subprocess.check_output(
+            ["ray", "start", "--head",
+                             "--node-ip-address=localhost",
+                             "--redis-port=6379"]).decode("ascii")
+
+        ray.init(node_ip_address="localhost", redis_address="localhost:6379")
+
+        @ray.remote
+        def f():
+            return 1
+
+        self.assertEqual(ray.get(f.remote()), 1)
+
+        # Kill the Ray cluster.
+        subprocess.Popen(["ray", "stop"]).wait()
+
 
 if __name__ == "__main__":
     unittest.main(verbosity=2)