Add default ecs attributes and format in response obj (#1346)

* Initialize EC2ContainerServiceBackend and ContainerInstance objects with region_name

* Initialize ContainerInstance with default attributes
  * These attributes are automatically applied by ECS when a container is registered
  * Docs: http://docs.aws.amazon.com/AmazonECS/latest/developerguide/task-placement-constraints.html#attributes

* Format container_instance.attributes for response_object

* Python3

* Only use available ECS regions for ecs_backends

* Sort dictionaries on key='name' using lambda

* Sort all dicts in tests using lambda

moto/ecs/models.py

@@ -2,6 +2,7 @@ from __future__ import unicode_literals
 import uuid
 from datetime import datetime
 from random import random, randint
+import boto3
 
 import pytz
 from moto.core.exceptions import JsonRESTError
@@ -261,7 +262,7 @@ class Service(BaseObject):
 
 class ContainerInstance(BaseObject):
 
-    def __init__(self, ec2_instance_id):
+    def __init__(self, ec2_instance_id, region_name):
         self.ec2_instance_id = ec2_instance_id
         self.agent_connected = True
         self.status = 'ACTIVE'
@@ -321,14 +322,29 @@ class ContainerInstance(BaseObject):
             'agentHash': '4023248',
             'dockerVersion': 'DockerVersion: 1.5.0'
         }
-
-        self.attributes = {}
+        ec2_backend = ec2_backends[region_name]
+        ec2_instance = ec2_backend.get_instance(ec2_instance_id)
+        self.attributes = {
+            'ecs.ami-id': ec2_instance.image_id,
+            'ecs.availability-zone': ec2_instance.placement,
+            'ecs.instance-type': ec2_instance.instance_type,
+            'ecs.os-type': ec2_instance.platform if ec2_instance.platform == 'windows' else 'linux'  # options are windows and linux, linux is default
+        }
 
     @property
     def response_object(self):
         response_object = self.gen_response_object()
+        response_object['attributes'] = [self._format_attribute(name, value) for name, value in response_object['attributes'].items()]
         return response_object
 
+    def _format_attribute(self, name, value):
+        formatted_attr = {
+            'name': name,
+        }
+        if value is not None:
+            formatted_attr['value'] = value
+        return formatted_attr
+
 
 class ContainerInstanceFailure(BaseObject):
 
@@ -347,12 +363,19 @@ class ContainerInstanceFailure(BaseObject):
 
 class EC2ContainerServiceBackend(BaseBackend):
 
-    def __init__(self):
+    def __init__(self, region_name):
+        super(EC2ContainerServiceBackend, self).__init__()
         self.clusters = {}
         self.task_definitions = {}
         self.tasks = {}
         self.services = {}
         self.container_instances = {}
+        self.region_name = region_name
+
+    def reset(self):
+        region_name = self.region_name
+        self.__dict__ = {}
+        self.__init__(region_name)
 
     def describe_task_definition(self, task_definition_str):
         task_definition_name = task_definition_str.split('/')[-1]
@@ -669,7 +692,7 @@ class EC2ContainerServiceBackend(BaseBackend):
         cluster_name = cluster_str.split('/')[-1]
         if cluster_name not in self.clusters:
             raise Exception("{0} is not a cluster".format(cluster_name))
-        container_instance = ContainerInstance(ec2_instance_id)
+        container_instance = ContainerInstance(ec2_instance_id, self.region_name)
         if not self.container_instances.get(cluster_name):
             self.container_instances[cluster_name] = {}
         container_instance_id = container_instance.container_instance_arn.split(
@@ -866,6 +889,5 @@ class EC2ContainerServiceBackend(BaseBackend):
             yield task_fam
 
 
-ecs_backends = {}
-for region, ec2_backend in ec2_backends.items():
-    ecs_backends[region] = EC2ContainerServiceBackend()
+available_regions = boto3.session.Session().get_available_regions("ecs")
+ecs_backends = {region: EC2ContainerServiceBackend(region) for region in available_regions}