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HEAT

heatarch.png

Some examples of resource:

  resource:
    type: OS::Nova::Server
    properties:
      flavor: { get_param: flavor }
      image: { get_param: image }
      metadata: {"scale_group": {get_param: "OS::stack_id"}}
      networks:
      - network: private
      security_groups:
      - testvm

Some of the resouce groups relevant today for us are:

  • OS::Heat::AutoScalingGroup
  • OS::Heat::ScalingPolicy
  • OS::Monasca::Notification
  • OS::Monasca::AlarmDefinition

OS::Heat::AutoScalingGroup

Properties:

  • name: Convenient name.
  • max_size: Maximum size of the group.
  • min_size: Minimum size of the group.
  • desired_capacity: Initial Capacity of the group.
  • cooldown: minimum time before any autoscaling related operation.
  • resources: set of resource that should be scaled up or down.

Example:

group:
  type: OS::Heat::AutoScalingGroup
  properties:
    ... specify propoerties from above ..
    resource:
      type: OS::Nova::Server
      properties:
        flavor: { get_param: flavor }
        image: { get_param: image }
        # pass scale_group as metadata,
        # monasca will store this as vm metadata and
        # later can be used to group vms together from
        # same stack
        metadata: {"scale_group": {get_param: "OS::stack_id"}}
        networks:
        - network: private
        security_groups:
        - testvm

OS::Heat::ScalingPolicy

Properties:

  • change: a number that has an effect based on change_type.
  • auto_scaling_group_id: the AutoscalingGroup id for this policy.
  • scaling_adjustment: change in number (eg: 1,-1,5,-6).
  • change_type: (meaning of "change")
    • "change_in_capacity"
    • "percentage_change_in_capacity",
    • "exact_capacity"
  • cooldown: minimum amount of time (in seconds) between allowable executions of this policy.
  • name: Convenient name

Attributes: (outputs)

  • alarm_url: the url which triggers the policy

Example:

policy_for_autoscaling_group:
  type: OS::Heat::ScalingPolicy
  properties:
    adjustment_type: change_in_capacity
    auto_scaling_group_id: { get_resource: group }
    cooldown: 60
    scaling_adjustment: -1

OS::Monasca::Notification

Properties:

  • address: Address of the notification. - email address - url - service key based on notification type.
  • type: Type of the notification. - email - webhook - pagerduty

Example:

notification_object:
  type: OS::Monasca::Notification
  properties:
    type: webhook  # we want the notification to trigger the policy via a url
    address: {get_attr: [some_policy, alarm_url]} # this get the alarm_url to trigger the policy

OS::Monasca::AlarmDefinition

Properties:

  • expression: Expression of the alarm to evaluate.

    eg: avg(cpu.utilization_perc{group_by=something}) > 50 times 3

Optional Properties

  • alarm_actions
  • ok_actions
  • undetermined_actions
  • actions_enabled
  • match_by
  • severity
  • description
  • name

Example:

fire_alarm:
type: OS::Monasca::AlarmDefinition
properties:
  ....
  expression:
    str_replace:
      template: avg(cpu.utilization_perc{scale_group=group_by}) > 50 times 3
      params:
        group_by: {get_param: "OS::stack_id"} # use stack_id to group instances
  severity: high
  alarm_actions:
    - {get_resource: notification_object_from_the_stack }

Big Picture

AlarmDefinition >>> has
	Notification   >>> triggers
		ScalingPolicy     >>> scales up/down
			AutoScalingGroup  >>> Resources scaling by heat

References