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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