Fix can_be_scaled() to use docker-py's split_port()

... to determine if there are any external port bindings, to in-turn
determine if the service is scalable.

Signed-off-by: Viranch Mehta <viranch.mehta@gmail.com>

Author: viranch

compose/service.py

@@ -8,7 +8,7 @@
 
 import six
 from docker.errors import APIError
-from docker.utils import create_host_config, LogConfig
+from docker.utils import create_host_config, LogConfig, ports
 
 from . import __version__
 from .config import DOCKER_CONFIG_KEYS, merge_environment
@@ -678,10 +678,21 @@ def labels(self, one_off=False):
         ]
 
     def can_be_scaled(self):
-        for port in self.options.get('ports', []):
-            if ':' in str(port):
+        # TODO: this function should ideally move to docker.utils.ports
+        # get rid of it once its accepted into docker-py
+        def has_external_port(external_binding):
+            if external_binding is None:
                 return False
-        return True
+            if isinstance(external_binding, tuple) and \
+                    (len(external_binding) < 2 or external_binding[1] is None):
+                return False
+            return True
+
+        return not any(
+            has_external_port(external_binding)
+            for binding in self.options.get('ports', [])
+            for external_binding in (ports.split_port(binding)[1] or [])
+        )
 
     def pull(self, insecure_registry=False):
         if 'image' not in self.options: