OpenStack Heat AutoScaling详解及实例代码

OpenStack Heat AutoScaling

一、背景

Openstack的Heat是在H版之后加入的组件，旨在创建一套业务流程，更轻松的管理一个集群。集群内的虚拟机可以作为一个整体，统一的为客户提供服务。Heat中把功能定义成资源，在Heat中会用到Nova，Neutron，Ceilometer等组件，这些都可以看成是资源，通过模板文件来描述，模板文件可以是yaml格式，也可以是json格式，一般是yaml格式。
AutoScaling的概念最早出现在AWS，AutoScaling是一项Web服务，目的是根据用户定义的策略，时间表的运行状态检查启动或终止虚拟机，达到自动伸缩。

Openstack里的Auto Scale是由Heat和Ceilometer模块一起配合完成的。Ceilometer负责收集处理性能数据，一旦达到Heat模版里定义的阀值，就发告警信息给heat-engine，由heat-engine调动Heat模版里定义的其它的OpenStack资源实现auto scale。

二、Heat AutoScaling Resources

实现AutoScaling功能涉及到的资源如下：

1.AWS::AutoScaling::AutoScalingGroup

伸缩组是具有相同应用场景的实例的集合，定义了组内实例数的最大值和最小值，冷却时间等等。
注：冷却时间是指一个伸缩活动后的一段锁定时间，在这个时间内不能进行其他的伸缩活动。

语法如下：

{
 "Type" : "AWS::AutoScaling::AutoScalingGroup",
 "Properties" : {
  "AvailabilityZones" : [ String, ... ],
  "Cooldown" : String,
  "DesiredCapacity" : String,
  "HealthCheckGracePeriod" : Integer,
  "HealthCheckType" : String,
  "InstanceId" : String,
  "LaunchConfigurationName" : String,
  "LoadBalancerNames" : [ String, ... ],
  "MaxSize" : String,
  "MetricsCollection" : [ MetricsCollection, ... ]
  "MinSize" : String,
  "NotificationConfigurations" : [ NotificationConfigurations, ... ],
  "PlacementGroup" : String,
  "Tags" : [ Auto Scaling Tag, ..., ],
  "TargetGroupARNs" : [ String, ... ],
  "TerminationPolicies" : [ String, ..., ],
  "VPCZoneIdentifier" : [ String, ... ]
 }
}

2.AWS::AutoScaling::LaunchConfiguration

伸缩配置定义了用于弹性伸缩的实例的配置。由AutoScalingGroup用于配置组内的实例。

语法如下：

{
  "Type" : "AWS::AutoScaling::LaunchConfiguration",
  "Properties" : {
   "AssociatePublicIpAddress" : Boolean,
   "BlockDeviceMappings" : [ BlockDeviceMapping, ... ],
   "ClassicLinkVPCId" : String,
   "ClassicLinkVPCSecurityGroups" : [ String, ... ],
   "EbsOptimized" : Boolean,
   "IamInstanceProfile" : String,
   "ImageId" : String,
   "InstanceId" : String,
   "InstanceMonitoring" : Boolean,
   "InstanceType" : String,
   "KernelId" : String,
   "KeyName" : String,
   "PlacementTenancy" : String,
   "RamDiskId" : String,
   "SecurityGroups" : [ SecurityGroup, ... ],
   "SpotPrice" : String,
   "UserData" : String
  }
}

3.AWS::AutoScaling::ScalingPolicy

为auto scale group添加伸缩的策略，定义了具体的扩展或者收缩的操作，以及伸缩的数量。

语法如下：

{
  "Type" : "AWS::AutoScaling::ScalingPolicy",
  "Properties" : {
   "AdjustmentType" : String,
   "AutoScalingGroupName" : String,
   "Cooldown" : String,
   "EstimatedInstanceWarmup" : Integer,
   "MetricAggregationType" : String,
   "MinAdjustmentMagnitude" : Integer,
   "PolicyType" : String,
   "ScalingAdjustment" : Integer,
   "StepAdjustments" : [ StepAdjustments, ... ]
  }
}

此外，Heat中AutoScaling还需配合OS::Ceilometer::Alarm使用，由Alarm监控实例的运行状况，一旦超过阈值，则会产生告警。

三、 Heat AutoScaling Template

下面是一个简单的例子:

heat_template_version: 2013-05-23
description: Heat template for autoscaling
parameters:#定义一些变量
 flavor:
  type: string
  default: m1.small
 image:
  type: string
  default: 1a2b3c4f-1a2b-3c4f-5d6e-4130ff5203de
 availability_zone:
  type: string
  default: nova
 alarm_scaleout_threshold:#阈值
  type: number
  default: 80
 alarm_scalein_threshold:#阈值
  type: number
  default: 20
resources:
 neutron_network:
  type: OS::Neutron::Net
  properties:
   name: {get_param: "OS::stack_name"}

 neutron_subnet:
  type: OS::Neutron::Subnet
  properties:
   name: {get_param: "OS::stack_name"}
   network_id: { get_resource: neutron_network }
   cidr: '192.168.111.0/24'
   gateway_ip: '192.168.111.1'
   allocation_pools:
    - start: '192.168.111.2'
     end: '192.168.111.254'
 neutron_router:
  type: OS::Neutron::Router
  properties:
   name: {get_param: "OS::stack_name"}
 add_router_interface:
  type: OS::Neutron::RouterInterface
  properties:
   router_id: { get_resource: neutron_router }
   subnet_id: { get_resource: neutron_subnet }
 nova_server_security_group:
  type: OS::Neutron::SecurityGroup
  properties:
   description: 'security group for VM'
   name: {get_param: "OS::stack_name"}
   rules: [
    {direction: 'ingress',
     remote_ip_prefix: '0.0.0.0/0',
     port_range_min: 0,
     port_range_max: 30000,
     ethertype: IPv4,
     protocol: 'tcp'},
    {direction: 'egress',
     remote_ip_prefix: '0.0.0.0/0',
     port_range_min: 0,
     port_range_max: 65535,
     ethertype: 'IPv4',
     protocol: 'tcp'},
    {direction: 'egress',
     remote_ip_prefix: '0.0.0.0/0',
     port_range_min: 0,
     port_range_max: 65535,
     ethertype: 'IPv4',
     protocol: 'udp'},
    {direction: 'ingress',
     remote_ip_prefix: '0.0.0.0/0',
     port_range_min: null,
     port_range_max: null,
     ethertype: 'IPv4',
     protocol: 'icmp'},
    {direction: egress,
     remote_ip_prefix: '0.0.0.0/0',
     port_range_min: null,
     port_range_max: null,
     ethertype: 'IPv4',
     protocol: 'icmp'}
   ]
 launch_config:#Scale group中的实例的配置
  type: AWS::AutoScaling::LaunchConfiguration
  properties:
   ImageId: { get_param: image }#实例使用的image
   InstanceType: { get_param: flavor }#实例使用的flavor
   SecurityGroups: [ get_resource: nova_server_security_group ]
   UserData: |#实例启动时运行的脚本
     #!/bin/bash
     passwd root << EOD
     123456
     123456
     EOD
 server_group:#伸缩组
  type: AWS::AutoScaling::AutoScalingGroup
  properties:
   AvailabilityZones: []
   Cooldown: '60'#冷却时间
   LaunchConfigurationName: { get_resource: launch_config }#组中实例的配置
   MinSize: '1'#最小实例数
   MaxSize: '4'#最大实例数
   VPCZoneIdentifier: [ get_resource: neutron_subnet ]
 scaleout_policy:#向上扩展的策略
  type: AWS::AutoScaling::ScalingPolicy
  properties:
   AdjustmentType: ChangeInCapacity
#heat 支持三种调整方式：change_in_capacity (new = current + adjustment), #exact_capacity (new = adjustment), percent_change_in_capacity (在current 的基#础上上按照 adjustment 的 百分比调整)
   AutoScalingGroupName: { get_resource: server_group }
   ScalingAdjustment: '1'#每次的调整量，即增加一个实例
 scalein_policy:#向下收缩的策略
  type: AWS::AutoScaling::ScalingPolicy
  properties:
   AdjustmentType: ChangeInCapacity
   AutoScalingGroupName: { get_resource: server_group }
   ScalingAdjustment: '-1'#每次的调整量，即减少一个实例
 neutron_port:
  type: OS::Neutron::Port
  properties:
   network_id: { get_resource: neutron_network }
   fixed_ips:
    - subnet_id: { get_resource: neutron_subnet }
   security_groups: [ { get_resource: nova_server_security_group } ]
 alarm_scaleout: #定义一个 ceilometer alarm
  type: OS::Ceilometer::Alarm
  properties:
   description: Scale-up if the average CPU > 80% for 10 minute
   meter_name: cpu_util #监控虚拟机的 cpu_util
   statistic: avg #statistic 的计算方法为 avg 即平均值法
   period: 600 #统计周期
   evaluation_periods: 1 #连续几个周期才算有效
   repeat_actions: true
   threshold: { get_param: alarm_scaleout_threshold }# cpu_util 的阈值
   alarm_actions: #该告警在alarm 状态时的 action。
    - {get_attr: [scaleout_policy, AlarmUrl]}
   matching_metadata: {'metadata.user_metadata.groupname': {get_resource: 'server_group'}}
   comparison_operator: gt #检测值和阈值的比较方式为 gt 即大于
 alarm_scalein:
  type: OS::Ceilometer::Alarm
  properties:
   description: Scale-down if the average CPU < 20% for 10 minutes
   meter_name: cpu_util
   statistic: avg
   period: 600
   evaluation_periods: 1
   repeat_actions: true
   threshold: { get_param: alarm_scalein_threshold }
   alarm_actions:
    - {get_attr: [scalein_policy, AlarmUrl]}
   matching_metadata: {'metadata.user_metadata.groupname': {get_resource: 'server_group'}}
   comparison_operator: lt#检测值和阈值的比较方式为 lt 即小于
outputs:
 scale_in_url:
  value: { get_attr: [ scalein_policy, AlarmUrl ] }
 scale_out_url:
  value: { get_attr: [ scaleout_policy, AlarmUrl ] }

这个stack的功能是监控实例的CPU使用率,当CPU使用率大于80%时,将会启动一个新的实例,当CPU使用率小于20%,将会减少一个实例。

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