OpenStack Heat AutoScaling

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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: 2013-05-23description: Heat template for autoscalingparameters:#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: 20resources:  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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