Added scale method to the Service model.

Signed-off-by: Felipe Ruhland <felipe.ruhland@gmail.com>

docker/models/services.py

@@ -1,6 +1,6 @@
 import copy
 from docker.errors import create_unexpected_kwargs_error
-from docker.types import TaskTemplate, ContainerSpec
+from docker.types import TaskTemplate, ContainerSpec, ServiceMode
 from .resource import Model, Collection
 
 
@@ -105,6 +105,22 @@ class Service(Model):
         )
         return self.client.api.service_logs(self.id, is_tty=is_tty, **kwargs)
 
+    def scale(self, replicas):
+        """
+        Scale service container.
+
+        Args:
+            replicas (int): The number of containers that should be running.
+
+        Returns:
+            ``True``if successful.
+        """
+
+        service_mode = ServiceMode('replicated', replicas)
+        return self.client.api.update_service(self.id, self.version,
+                                              service_mode,
+                                              fetch_current_spec=True)
+
 
 class ServiceCollection(Collection):
     """Services on the Docker server."""

tests/integration/models_services_test.py

@@ -203,6 +203,28 @@ class ServiceTest(unittest.TestCase):
         spec = service.attrs['Spec']['TaskTemplate']['ContainerSpec']
         assert spec.get('Command') == ['sleep', '300']
 
+    def test_scale_method_service(self):
+        client = docker.from_env(version=TEST_API_VERSION)
+        service = client.services.create(
+            # create arguments
+            name=helpers.random_name(),
+            # ContainerSpec arguments
+            image="alpine",
+            command="sleep 300"
+        )
+        tasks = []
+        while len(tasks) == 0:
+            tasks = service.tasks()
+        assert len(tasks) == 1
+        service.scale(2)
+        while len(tasks) == 1:
+            tasks = service.tasks()
+        assert len(tasks) >= 2
+        # check that the container spec is not overridden with None
+        service.reload()
+        spec = service.attrs['Spec']['TaskTemplate']['ContainerSpec']
+        assert spec.get('Command') == ['sleep', '300']
+
     @helpers.requires_api_version('1.25')
     def test_restart_service(self):
         client = docker.from_env(version=TEST_API_VERSION)