auto_scaling.yaml

heat_template_version: 2021-04-16


description: Example auto scale group policy and alarm

parameters:
  key_name:
    type: string
    description: Keypair for SSH access
    constraints:
      - custom_constraint: nova.keypair
        description: Must be an existing keypair

  flavor:
    type: string
    description: Flavor
    default: t3.xsmall
    constraints:
      - custom_constraint: nova.flavor
        description: Must be an existing flavor

  image:
    type: string
    description: Image ID or name
    default: NeCTAR Ubuntu 22.04 LTS (Jammy) amd64

  availability_zone:
    type: string
    description: Availability Zone


resources:
  security_group:
    # https://docs.openstack.org/heat/latest/template_guide/openstack.html#OS::Neutron::SecurityGroup
    type: OS::Neutron::SecurityGroup
    properties:
      rules:
        - remote_ip_prefix: 0.0.0.0/0
          protocol: icmp
        - remote_ip_prefix: 0.0.0.0/0
          protocol: tcp
          port_range_min: 22
          port_range_max: 22
        - remote_ip_prefix: 0.0.0.0/0
          protocol: tcp
          port_range_min: 80
          port_range_max: 80

  scaling_group:
    # https://docs.openstack.org/heat/pike/template_guide/openstack.html#OS::Heat::AutoScalingGroup
    type: OS::Heat::AutoScalingGroup
    properties:
      cooldown: 300
      desired_capacity: 1
      max_size: 3
      min_size: 1
      resource:
        type: OS::Nova::Server
        properties:
          key_name: { get_param: key_name }
          image: { get_param: image }
          flavor: { get_param: flavor }
          availability_zone: { get_param: availability_zone }
          security_groups:
          - { get_resource: security_group }
          networks:
            - allocate_network: auto
          metadata:
            metering.server_group: { get_param: "OS::stack_id" }

  scaleup_policy:
    # https://docs.openstack.org/heat/pike/template_guide/openstack.html#OS::Heat::ScalingPolicy
    type: OS::Heat::ScalingPolicy
    properties:
      adjustment_type: change_in_capacity
      auto_scaling_group_id: { get_resource: scaling_group }
      cooldown: 300
      scaling_adjustment: 1

  scaledown_policy:
    # https://docs.openstack.org/heat/pike/template_guide/openstack.html#OS::Heat::ScalingPolicy
    type: OS::Heat::ScalingPolicy
    properties:
      adjustment_type: change_in_capacity
      auto_scaling_group_id: { get_resource: scaling_group }
      cooldown: 300
      scaling_adjustment: -1

  cpu_alarm_high:
    # https://docs.openstack.org/heat/pike/template_guide/openstack.html#OS::Aodh::GnocchiAggregationByResourcesAlarm
    type: OS::Aodh::GnocchiAggregationByResourcesAlarm
    properties:
      description: Scale up if CPU > 75%
      metric: cpu_util
      aggregation_method: mean
      granularity: 600
      evaluation_periods: 1
      threshold: 75
      resource_type: instance
      comparison_operator: gt
      alarm_actions:
        - str_replace:
            template: trust+url
            params:
              url: { get_attr: [scaleup_policy, signal_url] }
      query:
        list_join:
          - ''
          - - { '=': { server_group: { get_param: "OS::stack_id" } } }

  cpu_alarm_low:
    # https://docs.openstack.org/heat/pike/template_guide/openstack.html#OS::Aodh::GnocchiAggregationByResourcesAlarm
    type: OS::Aodh::GnocchiAggregationByResourcesAlarm
    properties:
      description: Scale down if CPU < 15%
      metric: cpu_util
      aggregation_method: mean
      granularity: 600
      evaluation_periods: 1
      threshold: 15
      resource_type: instance
      comparison_operator: lt
      alarm_actions:
        - str_replace:
            template: trust+url
            params:
              url: {get_attr: [scaledown_policy, signal_url]}
      query:
        list_join:
          - ''
          - - { '=': { server_group: { get_param: "OS::stack_id" } } }


outputs:
  scaleup_policy_signal_url:
    value: { get_attr: [scaleup_policy, signal_url] }

  scaledown_policy_signal_url:
    value: { get_attr: [scaledown_policy, signal_url] }