Determine node IP address programatically. (ray-project#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 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

scripts/start_ray.py

@@ -8,7 +8,7 @@
 import ray.services as services
 
 parser = argparse.ArgumentParser(description="Parse addresses for the worker to connect to.")
-parser.add_argument("--node-ip-address", required=True, type=str, help="the ip address of the worker's node")
+parser.add_argument("--node-ip-address", required=False, type=str, help="the IP address of the worker's node")
 parser.add_argument("--redis-address", required=False, type=str, help="the address to use for Redis")
 parser.add_argument("--num-workers", default=10, required=False, type=int, help="the number of workers to start on this node")
 parser.add_argument("--head", action="store_true", help="provide this argument for the head node")
@@ -41,7 +41,13 @@ def check_no_existing_redis_clients(node_ip_address, redis_address):
     # Start Ray on the head node.
     if args.redis_address is not None:
       raise Exception("If --head is passed in, a Redis server will be started, so a Redis address should not be provided.")
-    address_info = services.start_ray_local(node_ip_address=args.node_ip_address,
+    # Get the node IP address if one is not provided.
+    if args.node_ip_address is None:
+      node_ip_address = services.get_node_ip_address()
+    else:
+      node_ip_address = args.node_ip_address
+    print("Using IP address {} for this node.".format(node_ip_address))
+    address_info = services.start_ray_local(node_ip_address=node_ip_address,
                                             num_workers=args.num_workers,
                                             cleanup=False,
                                             redirect_output=True)
@@ -53,11 +59,17 @@ def check_no_existing_redis_clients(node_ip_address, redis_address):
     # Wait for the Redis server to be started. And throw an exception if we
     # can't connect to it.
     services.wait_for_redis_to_start(redis_host, int(redis_port))
+    # Get the node IP address if one is not provided.
+    if args.node_ip_address is None:
+      node_ip_address = services.get_node_ip_address(args.redis_address)
+    else:
+      node_ip_addess = args.node_ip_address
+    print("Using IP address {} for this node.".format(node_ip_address))
     # Check that there aren't already Redis clients with the same IP address
     # connected with this Redis instance. This raises an exception if the Redis
     # server already has clients on this node.
-    check_no_existing_redis_clients(args.node_ip_address, args.redis_address)
-    address_info = services.start_ray_node(node_ip_address=args.node_ip_address,
+    check_no_existing_redis_clients(node_ip_address, args.redis_address)
+    address_info = services.start_ray_node(node_ip_address=node_ip_address,
                                            redis_address=args.redis_address,
                                            num_workers=args.num_workers,
                                            cleanup=False,