Allow address instead of redis_address (#5412)

* addr

* wip

* fix typo

* add to start

* switch to ray address for train

* say address

* disambiguate help

* comments 2

python/ray/services.py

@@ -93,6 +93,38 @@ def include_java_from_redis(redis_client):
     return redis_client.get("INCLUDE_JAVA") == b"1"
 
 
+def find_redis_address_or_die():
+    try:
+        import psutil
+    except ImportError:
+        raise ImportError(
+            "Please install `psutil` to automatically detect the Ray cluster.")
+    pids = psutil.pids()
+    redis_addresses = set()
+    for pid in pids:
+        try:
+            proc = psutil.Process(pid)
+            for arglist in proc.cmdline():
+                for arg in arglist.split(" "):
+                    if arg.startswith("--redis-address="):
+                        addr = arg.split("=")[1]
+                        redis_addresses.add(addr)
+        except psutil.AccessDenied:
+            pass
+        except psutil.NoSuchProcess:
+            pass
+    if len(redis_addresses) > 1:
+        raise ConnectionError(
+            "Found multiple active Ray instances: {}. ".format(redis_addresses)
+            + "Please specify the one to connect to by setting `address`.")
+        sys.exit(1)
+    elif not redis_addresses:
+        raise ConnectionError(
+            "Could not find any running Ray instance. "
+            "Please specify the one to connect to by setting `address`.")
+    return redis_addresses.pop()
+
+
 def get_address_info_from_redis_helper(redis_address,
                                        node_ip_address,
                                        redis_password=None):