Determine node IP address programatically. (#151)

* Determine node ip address programatically.

* Factor out methods for getting node IP addresses.

* Address comments.

lib/python/ray/services.py

@@ -7,6 +7,7 @@ import os
 import random
 import redis
 import signal
+import socket
 import string
 import subprocess
 import sys
@@ -72,6 +73,21 @@ def cleanup():
 def all_processes_alive():
   return all([p.poll() is None for p in all_processes])
 
+def get_node_ip_address(address="8.8.8.8:53"):
+  """Determine the IP address of the local node.
+
+  Args:
+    address (str): The IP address and port of any known live service on the
+      network you care about.
+
+  Returns:
+    The IP address of the current node.
+  """
+  host, port = address.split(":")
+  s = socket.socket(socket.AF_INET, socket.SOCK_DGRAM)
+  s.connect((host, int(port)))
+  return s.getsockname()[0]
+
 def wait_for_redis_to_start(redis_host, redis_port, num_retries=5):
   """Wait for a Redis server to be available.
 

lib/python/ray/worker.py

@@ -674,7 +674,7 @@ def get_address_info_from_redis(redis_address, node_ip_address, num_retries=5):
       time.sleep(1)
     counter += 1
 
-def init(node_ip_address="127.0.0.1", redis_address=None, start_ray_local=False, object_id_seed=None, num_workers=None, num_local_schedulers=None, driver_mode=SCRIPT_MODE):
+def init(node_ip_address=None, redis_address=None, start_ray_local=False, object_id_seed=None, num_workers=None, num_local_schedulers=None, driver_mode=SCRIPT_MODE):
   """Either connect to an existing Ray cluster or start one and connect to it.
 
   This method handles two cases. Either a Ray cluster already exists and we
@@ -735,12 +735,13 @@ def init(node_ip_address="127.0.0.1", redis_address=None, start_ray_local=False,
   else:
     if redis_address is None:
       raise Exception("If start_ray_local=False, then redis_address must be provided.")
-    if node_ip_address is None:
-      raise Exception("If start_ray_local=False, then node_ip_address must be provided.")
     if num_workers is not None:
       raise Exception("If start_ray_local=False, then num_workers must not be provided.")
     if num_local_schedulers is not None:
       raise Exception("If start_ray_local=False, then num_local_schedulers must not be provided.")
+    # Get the node IP address if one is not provided.
+    if node_ip_address is None:
+      node_ip_address = services.get_node_ip_address(redis_address)
     # Get the address info of the processes to connect to from Redis.
     info = get_address_info_from_redis(redis_address, node_ip_address)
   # Connect this driver to Redis, the object store, and the local scheduler. The