Heat 支持查询 Autoscaling Group 下的虚拟机
OpenStack mailing list 有这么一封邮件：
[Openstack] heat autoscaling group/instance relationships
I’m trying to figure out how to determine all instances that were created as part of a given autoscaling group. I want to take a given autoscaling group and list all of its instances. So far I can’t figure out how to do this. The instances themselves have a tag called “AutoScalingGroupName” (mystack-MyServerGroup-f3r72ifsj2jq for example) but the value of that doesn’t seem to map to anything. A resource-show on the autoscaling group doesn’t seem to show any identifier that maps to the autoscaling group name.
Any ideas on how I can do this? Thanks!
上述的大意是如何获取 autoscaling group 里的虚拟机列表。
Autoscaling Group 介绍
以 Heat 推荐的 autoscaling group 的 template 为例，采用该模板创建 stack 后，查询该 stack 包含的 resource 如下，可知 asg 即为 autoscaling group。
$ heat resource-list asg_stack
+------------------+----------------------------+-----------------+---------------+
| resource_name | resource_type | resource_status | updated_time |
+------------------+----------------------------+-----------------+---------------+
| monitor | OS::Neutron::HealthMonitor | CREATE_COMPLETE | 2014-04-26... |
| pool | OS::Neutron::Pool | CREATE_COMPLETE | 2014-04-26... |
| lb | OS::Neutron::LoadBalancer | CREATE_COMPLETE | 2014-04-26... |
| lb_floating_ip | OS::Neutron::FloatingIP | CREATE_COMPLETE | 2014-04-26... |
| asg | OS::Heat::AutoScalingGroup | CREATE_COMPLETE | 2014-04-26... |
| scaledown_policy | OS::Heat::ScalingPolicy | CREATE_COMPLETE | 2014-04-26... |
| scaleup_policy | OS::Heat::ScalingPolicy | CREATE_COMPLETE | 2014-04-26... |
| cpu_alarm_low | OS::Ceilometer::Alarm | CREATE_COMPLETE | 2014-04-26... |
| cpu_alarm_high | OS::Ceilometer::Alarm | CREATE_COMPLETE | 2014-04-26... |
+------------------+----------------------------+-----------------+---------------+
继续查询 asg 详情，未发现任何和虚拟机相关的信息，而事实上，autoscaling group 作为一群虚拟机的集合，用户非常希望获取它所包含的虚拟机信息。如果 Heat 未提供该 API，那么用户只能通过 Nova API 查询相关的虚拟机，对用户来说，无疑增加了操作的复杂度。
$ heat resource-show asg_stack asg
+------------------------+---------------------------------------------------------------------+
| Property | Value |
+------------------------+---------------------------------------------------------------------+
| description | |
| links | http://ip:8004/v1/tenant_id/stacks/asg_stack/stack_id/resources/asg |
| | http://ip:8004/v1/tenant_id/stacks/asg_stack/stack_id |
| logical_resource_id | asg |
| physical_resource_id | 525954ea-a309-44a7-9e40-d793b7c754a |
| required_by | scaleup_policy |
| | scaledown_policy |
| resource_name | asg |
| resource_status | CREATE_COMPLETE |
| resource_status_reason | state changed |
| resource_type | OS::Heat::AutoScalingGroup |
| updated_time | 2014-04-26T09:33:04Z |
+------------------------+---------------------------------------------------------------------+
事实上，经 Nova 查询到的虚拟机如下：
$ nova list
+----------+---------------+--------+------------+-------------+-----+
| ID | Name | Status | Task State | Power State | ... |
+----------+---------------+--------+------------+-------------+-----+
| 22c...0a | as-47g2...de8 | ACTIVE | - | Running | ... |
| 3f0...c8 | as-47g2...ds3 | ACTIVE | - | Running | ... |
+----------+---------------+--------+------------+-------------+-----+
Nested Stack
讲解 nested stack 之前，先问一个问题：请问一共创建了多少个 stack？
一个！它的名字就叫 asg_stack ！……
貌似言之有理，再查询数据库看看，却出现四个名字均以 asg_stack 开头的 stack，并且 owner_id 和 id 有如下关系：
- heat stack-list 查询到的 stack, 其 owner_id 为 NULL
- nested stack 的 owner_id 和父 stack 的 id 一致
mysql> select id,name,owner_id where deleted_at is Null;
+-----------+------------------------------------+-----------+
| id | name | owner_id |
+-----------+------------------------------------+-----------+
| 5259...4a | asg_stack-asg-ll5qfhea47g2 | 8dd9...c3 |
| 8dd9...c3 | asg_stack | NULL |
| 9986...04 | asg_stack-asg-ll5qfhea47g2-ue...iu | 5259...4a |
| cad9...7a | asg_stack-asg-ll5qfhea47g2-4s...cr | 5259...4a |
+-----------+------------------------------------+-----------+
4 个 stack 的关系如下图所示：
继续查询 asg_stack-asg-ll5qfhea47g2-4s…cr 这个 stack 包含的资源：
$ heat resource-list 99860cfb-1110-4eb6-89be-0dfff14b3a04
+---------------+-------------------------+-----------------+---------------+
| resource_name | resource_type | resource_status | updated_time |
+---------------+-------------------------+-----------------+---------------+
| server | OS::Nova::Server | CREATE_COMPLETE | 2014-04-26... |
| member | OS::Neutron::PoolMember | CREATE_COMPLETE | 2014-04-26... |
+---------------+-------------------------+-----------------+---------------+
从上不难发现另外一条规律，nested stack 的 id 和父 stack 的某个 resource_id 完全一致。事实上，Heat 的以下资源支持 nested stack：
- OS::Heat::InstanceGroup
- OS::Heat::ResourceGroup
- OS::Heat::AutoScalingGroup
- AWS::AutoScaling::AutoScalingGroup
解决方案
理解了 nested stack，很容易实现查询 autoscaling group 资源时返回其旗下的虚拟机列表。如下：
$ heat resource-show asg_stack asg
+------------------------+---------------------------------------------------------------------+
| Property | Value |
+------------------------+---------------------------------------------------------------------+
| description | |
| instances | [{'name': 'asg_stack-asg-ll5qfhea47g2...5w', 'uuid': '43de...e3'}, |
| | {'name': 'asg_stack-asg-ll5qfhea47g2...4d', 'uuid': '43a4...7d'}] |
| links | http://ip:8004/v1/tenant_id/stacks/asg_stack/stack_id/resources/asg |
| | http://ip:8004/v1/tenant_id/stacks/asg_stack/stack_id |
| logical_resource_id | asg |
| physical_resource_id | 525954ea-a309-44a7-9e40-d793b7c754a |
| required_by | scaleup_policy |
| | scaledown_policy |
| resource_name | asg |
| resource_status | CREATE_COMPLETE |
| resource_status_reason | state changed |
| resource_type | OS::Heat::AutoScalingGroup |
| updated_time | 2014-04-26T09:33:04Z |
+------------------------+---------------------------------------------------------------------+
由于实现简单，详情见该 commit，核心代码为如下：
def _get_scaling_group_instances(self, resource):
instance_list = []
if hasattr(resource, 'nested') and callable(resource.nested):
nested_stack = resource.nested()
else:
nested_stack = None
if nested_stack:
for r in nested_stack.values():
instance_list.extend(self._get_scaling_group_instances(r))
else:
if resource.type() in INSTANCE_RESOURCES:
instance_name = resource.physical_resource_name()
instance_uuid = resource.resource_id
instance_info = {'instance_name': instance_name,
'instance_uuid': instance_uuid}
return [instance_info]
return instance_list
@request_context
def describe_stack_resource(self, cnxt, stack_identity, resource_name):
s = self._get_stack(cnxt, stack_identity)
stack = parser.Stack.load(cnxt, stack=s)
if cfg.CONF.heat_stack_user_role in cnxt.roles:
if not self._authorize_stack_user(cnxt, stack, resource_name):
logger.warning(_("Access denied to resource %s")
% resource_name)
raise exception.Forbidden()
if resource_name not in stack:
raise exception.ResourceNotFound(resource_name=resource_name,
stack_name=stack.name)
resource = stack[resource_name]
if resource.id is None:
raise exception.ResourceNotAvailable(resource_name=resource_name)
if resource.type() in SCALING_GROUP_RESOURCES:
instance_list = self._get_scaling_group_instances(resource)
resource.instance_list = instance_list
return api.format_stack_resource(resource)