Added support for cgroup_parent

This change adds cgroup-parent support to compose project. It allows
each service to specify a 'cgroup_parent' option.

Signed-off-by: Mohit Soni <mosoni@paypal.com>

compose/config/config.py

@@ -21,6 +21,7 @@ from .validation import validate_top_level_object
 DOCKER_CONFIG_KEYS = [
     'cap_add',
     'cap_drop',
+    'cgroup_parent',
     'command',
     'cpu_shares',
     'cpuset',

compose/config/fields_schema.json

@@ -17,6 +17,7 @@
         "build": {"type": "string"},
         "cap_add": {"type": "array", "items": {"type": "string"}, "uniqueItems": true},
         "cap_drop": {"type": "array", "items": {"type": "string"}, "uniqueItems": true},
+        "cgroup_parent": {"type": "string"},
         "command": {
           "oneOf": [
             {"type": "string"},

compose/service.py

@@ -41,6 +41,7 @@ log = logging.getLogger(__name__)
 DOCKER_START_KEYS = [
     'cap_add',
     'cap_drop',
+    'cgroup_parent',
     'devices',
     'dns',
     'dns_search',
@@ -675,6 +676,7 @@ class Service(object):
         read_only = options.get('read_only', None)
 
         devices = options.get('devices', None)
+        cgroup_parent = options.get('cgroup_parent', None)
 
         return self.client.create_host_config(
             links=self._get_links(link_to_self=one_off),
@@ -696,7 +698,8 @@ class Service(object):
             read_only=read_only,
             pid_mode=pid,
             security_opt=security_opt,
-            ipc_mode=options.get('ipc')
+            ipc_mode=options.get('ipc'),
+            cgroup_parent=cgroup_parent
         )
 
     def build(self, no_cache=False, pull=False):