Event and schedule-based auto scaling with Heat¶
Brief summary¶
Rackspace Auto Scale supports both schedule-based and event-based auto scaling. Schedule-based auto scaling can be used to scale your application up or down at a specific time of the day, whereas event-based auto scaling can be used to automatically scale your application up or down according to load. In this tutorial, we will use Rackspace Orchestration to automate the configuration of both event-based and schedule-based auto scaling.
Pre-reading¶
If you are just getting started with Rackspace Auto Scale, Cloud Monitoring, or Cloud Orchestration, the following introductory material should give you enough background to proceed with this tutorial.
Auto Scale¶
Easily Scale Your Cloud With Rackspace Auto Scale gives a brief overview of the different types of scaling policies for Auto Scale.
Cloud Monitoring¶
Cloud Orchestration¶
Schedule-based auto scaling¶
Schedule-based auto scaling can be useful if there is a particular time when your application experiences a higher load. By scheduling a scaling event, you will be able to proactively scale your application.
In this example, we will create a scaling group that scales up by one node each Monday at 1:00 AM and down by one node each Saturday at 1:00 AM.
Start by adding the top-level template sections:
heat_template_version: 2014-10-16
description: |
Rackspace Cloud Monitoring and Event-based scaling using Rackspace Cloud Autoscale
resources:
outputs:
Resources section¶
Add an OS::Nova::KeyPair resource that will generate an SSH keypair which you can use to login to your web servers if you need to:
access_key:
type: OS::Nova::KeyPair
properties:
name: { get_param: "OS::stack_name" }
save_private_key: true
Add a Rackspace::Cloud::LoadBalancer resource that will balance the load between web servers.
scaling_lb:
type: Rackspace::Cloud::LoadBalancer
properties:
name: { get_param: "OS::stack_name" }
protocol: HTTP
port: 80
algorithm: ROUND_ROBIN
nodes: []
virtualIps:
- type: PUBLIC
ipVersion: IPV4
Add a Rackspace::AutoScale::Group resource:
scaled_servers:
type: Rackspace::AutoScale::Group
properties:
groupConfiguration:
name: { get_param: "OS::stack_name" }
maxEntities: 5
minEntities: 1
cooldown: 120
launchConfiguration:
type: launch_server
args:
loadBalancers:
- loadBalancerId: { get_resource: scaling_lb }
port: 80
server:
name: { get_param: "OS::stack_name" }
flavorRef: performance1-1
imageRef: 6f29d6a6-9972-4ae0-aa80-040fa2d6a9cf # Ubuntu 14.04 LTS (Trusty Tahr) (PVHVM)
key_name: { get_resource: access_key }
networks:
- uuid: 11111111-1111-1111-1111-111111111111
This resource will be responsible for creating/destroying Cloud Servers based on the auto scaling policy. The maxEntities and minEntities properties above ensure that the group will create at least 1 server but not more than 5 servers.
Add a Rackspace::AutoScale::ScalingPolicy for scaling up:
scale_up_policy:
type: Rackspace::AutoScale::ScalingPolicy
properties:
group: { get_resource: scaled_servers }
name:
str_replace:
template: stack scale up policy
params:
stack: { get_param: "OS::stack_name" }
args:
cron: "0 1 * * 1"
change: 1
cooldown: 600
type: schedule
This resource will create a scaling policy that scales the auto scaling group up by one server every Monday at 1:00 AM.
Finally, add a Rackspace::AutoScale::ScalingPolicy for scaling down:
scale_down_policy:
type: Rackspace::AutoScale::ScalingPolicy
properties:
group: { get_resource: scaled_servers }
name:
str_replace:
template: stack scale down policy
params:
stack: { get_param: "OS::stack_name" }
args:
cron: "0 1 * * 6"
change: -1
cooldown: 600
type: schedule
Similarly, this resource will scale the auto scaling group down by one server every Saturday at 1:00 AM.
Outputs section¶
Add the private SSH key to the outputs section. You will be able to log into your scaling group servers using this SSH key.
"Access Private Key":
value: { get_attr: [ access_key, private_key ] }
description: Private key for accessing the scaled server instances if needed
To see the stack outputs, issue a heat stack-show <stack name> on
the created stack.
Full template¶
heat_template_version: 2014-10-16
description: |
Rackspace Cloud Monitoring and schedule-based scaling using Rackspace Cloud Autoscale
resources:
access_key:
type: OS::Nova::KeyPair
properties:
name: { get_param: "OS::stack_name" }
save_private_key: true
scaling_lb:
type: Rackspace::Cloud::LoadBalancer
properties:
name: { get_param: "OS::stack_name" }
protocol: HTTP
port: 80
algorithm: ROUND_ROBIN
nodes: []
virtualIps:
- type: PUBLIC
ipVersion: IPV4
scaled_servers:
type: Rackspace::AutoScale::Group
properties:
groupConfiguration:
name: { get_param: "OS::stack_name" }
maxEntities: 10
minEntities: 2
cooldown: 120
launchConfiguration:
type: launch_server
args:
loadBalancers:
- loadBalancerId: { get_resource: scaling_lb }
port: 80
server:
name: { get_param: "OS::stack_name" }
flavorRef: performance1-1
imageRef: 6f29d6a6-9972-4ae0-aa80-040fa2d6a9cf # Ubuntu 14.04 LTS (Trusty Tahr) (PVHVM)
key_name: { get_resource: access_key }
networks:
- uuid: 11111111-1111-1111-1111-111111111111
scale_up_policy:
type: Rackspace::AutoScale::ScalingPolicy
properties:
group: { get_resource: scaled_servers }
name:
str_replace:
template: stack scale up policy
params:
stack: { get_param: "OS::stack_name" }
args:
cron: "0 1 * * 1"
change: 1
cooldown: 600
type: schedule
scale_down_policy:
type: Rackspace::AutoScale::ScalingPolicy
properties:
group: { get_resource: scaled_servers }
name:
str_replace:
template: stack scale down policy
params:
stack: { get_param: "OS::stack_name" }
args:
cron: "0 1 * * 6"
change: -1
cooldown: 600
type: schedule
outputs:
"Access Private Key":
value: { get_attr: [ access_key, private_key ] }
description: Private key for accessing the scaled server instances if needed
Event-based auto scaling¶
To configure your web application running on the Rackspace Cloud to automatically scale up or down according to load, Rackspace Auto Scale can be used in conjunction with Rackspace Cloud Monitoring. The Cloud Monitoring agent monitors various resources on the servers inside the scaling group and makes calls to the Auto Scale API when it is time to scale up or down.
In the following example template, we will set up a web application with a load balancer and a scaling group that contains between 2 and 10 web servers. For the sake of simplicity, we will not use template parameters in this example.
Start by adding the top-level template sections:
heat_template_version: 2014-10-16
description: |
Rackspace Cloud Monitoring and Event-based scaling using Rackspace Cloud Autoscale
resources:
outputs:
Resources section¶
Add an OS::Nova::KeyPair resource and a Rackspace::Cloud::LoadBalancer as in the previous example:
access_key:
type: OS::Nova::KeyPair
properties:
name: { get_param: "OS::stack_name" }
save_private_key: true
Add a Rackspace::Cloud::LoadBalancer resource that will balance the load between web servers.
scaling_lb:
type: Rackspace::Cloud::LoadBalancer
properties:
name: { get_param: "OS::stack_name" }
protocol: HTTP
port: 80
algorithm: ROUND_ROBIN
nodes: []
virtualIps:
- type: PUBLIC
ipVersion: IPV4
Autoscale resources¶
Add the Rackspace::AutoScale::Group resource, which will contain at least 2 servers and not more than 10 servers:
scaled_servers:
type: Rackspace::AutoScale::Group
properties:
groupConfiguration:
name: { get_param: "OS::stack_name" }
maxEntities: 10
minEntities: 2
cooldown: 120
launchConfiguration:
type: launch_server
args:
loadBalancers:
- loadBalancerId: { get_resource: scaling_lb }
port: 80
server:
name: { get_param: "OS::stack_name" }
flavorRef: performance1-1
imageRef: 6f29d6a6-9972-4ae0-aa80-040fa2d6a9cf # Ubuntu 14.04 LTS (Trusty Tahr) (PVHVM)
key_name: { get_resource: access_key }
config_drive: true
networks:
- uuid: 11111111-1111-1111-1111-111111111111
user_data:
str_replace:
template: |
#cloud-config
apt_upgrade: true
apt_sources:
- source: deb http://stable.packages.cloudmonitoring.rackspace.com/ubuntu-14.04-x86_64 cloudmonitoring main
key: | # This is the apt repo signing key
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write_files:
- path: /etc/rackspace-monitoring-agent.conf.d/load.yaml
content: |
type: agent.load_average
label: Load Average
period: 60
timeout: 10
alarms:
load_alarm:
label: load average alarm
notification_plan_id: {notification_plan}
criteria: |
:set consecutiveCount=3
if (metric['5m'] > 0.85){
return new AlarmStatus(CRITICAL);
}
if (metric['15m'] < 0.3){
return new AlarmStatus(WARNING);
}
return new AlarmStatus(OK);
- path: /etc/rackspace-monitoring-agent.cfg
content: |
monitoring_token {agent_token}
packages:
- rackspace-monitoring-agent
- apache2
params:
"{notification_plan}": { get_resource: scaling_plan }
"{agent_token}": { get_resource: agent_token }
In the resource above, the Cloud Monitoring agent is installed and
configured via the user_data section (using the cloud-config
format).
The alarm is configured to trigger a warning state when the system load
is below 0.3 for 15 minutes and a critical state when the system load is
above 0.85 for 5 minutes. We use the warning state here to trigger
scale-down events in lieu of an alternative alarm status.
The scaling_plan and agent_token resources referenced in the
user_data section will be defined below.
Next, define a Rackspace::AutoScale::ScalingPolicy resource for scaling up:
scale_up_policy:
type: Rackspace::AutoScale::ScalingPolicy
properties:
group: { get_resource: scaled_servers }
name:
str_replace:
template: stack scale up policy
params:
stack: { get_param: "OS::stack_name" }
change: 1
cooldown: 600
type: webhook
Add a Rackspace::AutoScale::WebHook resource:
scale_up_webhook:
type: Rackspace::AutoScale::WebHook
properties:
name:
str_replace:
template: stack scale up hook
params:
stack: { get_param: "OS::stack_name" }
policy: { get_resource: scale_up_policy }
The webhook resource generates a URL that will be used to trigger the scale-up policy above.
Similarly to the previous two resources for scaling-up, we will add another Rackspace::AutoScale::ScalingPolicy and Rackspace::AutoScale::WebHook resource for scaling down:
scale_down_policy:
type: Rackspace::AutoScale::ScalingPolicy
properties:
group: { get_resource: scaled_servers }
name:
str_replace:
template: stack scale down policy
params:
stack: { get_param: "OS::stack_name" }
change: -1
cooldown: 600
type: webhook
scale_down_webhook:
type: Rackspace::AutoScale::WebHook
properties:
name:
str_replace:
template: stack scale down hook
params:
stack: { get_param: "OS::stack_name" }
policy: { get_resource: scale_down_policy }
Cloud Monitoring resources¶
Add a Rackspace::CloudMonitoring::AgentToken resource that will create a token used by the monitoring agent to authenticate with the monitoring service:
agent_token:
type: Rackspace::CloudMonitoring::AgentToken
properties:
label:
str_replace:
template: stack monitoring agent token
params:
stack: { get_param: "OS::stack_name" }
Add a Rackspace::CloudMonitoring::Notification resource that will call the scale-up webhook created above:
scaleup_notification:
type: Rackspace::CloudMonitoring::Notification
properties:
label:
str_replace:
template: stack scale up notification
params:
stack: { get_param: "OS::stack_name" }
type: webhook
details:
url: { get_attr: [ scale_up_webhook, executeUrl ] }
Below, the notification resource will be associated with an alarm state using a notification plan.
Add another Rackspace::CloudMonitoring::Notification resource that will call the scale-down webhook:
scaledown_notification:
type: Rackspace::CloudMonitoring::Notification
properties:
label:
str_replace:
template: stack scale down notification
params:
stack: { get_param: "OS::stack_name" }
type: webhook
details:
url: { get_attr: [ scale_down_webhook, executeUrl ] }
Finally, create a Rackspace::CloudMonitoring::NotificationPlan and Rackspace::CloudMonitoring::PlanNotifications resource.
scaling_plan:
type: Rackspace::CloudMonitoring::NotificationPlan
properties:
label:
str_replace:
template: stack scaling notification plan
params:
stack: { get_param: "OS::stack_name" }
plan_notifications:
type: Rackspace::CloudMonitoring::PlanNotifications
properties:
plan: { get_resource: scaling_plan }
warning_state: # scale down on warning since this is configured for low load
- { get_resource: scaledown_notification }
critical_state:
- { get_resource: scaleup_notification }
The scaling_plan resource was referenced in the Cloud Monitoring
agent configuration inside of the user_data section of the
Rackspace::AutoScale::Group resource above. It tells the monitoring
agent how to respond to certain alarm states.
The Rackspace::CloudMonitoring::PlanNotifications resource is a way to update an existing NotificationPlan resource. This allows us to associate the alarm state with the Notification resource while avoiding circular dependencies.
This notification plan will trigger a scale up event when any of the
load_alarm alarms configured in the scaling group (via cloud-init)
issue a CRITICAL alarm state. This plan also triggers a scale down
event when any of the load_alarm alarms configured in the scaling
group issue a WARNING alarm state.
Outputs section¶
Add the private SSH key and, optionally, the webhook URLs to the outputs section. You can use the webhooks to manually scale your scaling group up or down.
"Access Private Key":
value: { get_attr: [ access_key, private_key ] }
description: Private key for accessing the scaled server instances if needed
"Scale UP servers webhook":
value: { get_attr: [ scale_up_webhook, executeUrl ] }
description: Scale UP API servers webhook
"Scale DOWN servers webhook":
value: { get_attr: [ scale_down_webhook, executeUrl ] }
Full template¶
heat_template_version: 2014-10-16
description: |
Rackspace Cloud Monitoring and Event-based scaling using Rackspace Cloud Autoscale
resources:
access_key:
type: OS::Nova::KeyPair
properties:
name: { get_param: "OS::stack_name" }
save_private_key: true
scaling_lb:
type: Rackspace::Cloud::LoadBalancer
properties:
name: { get_param: "OS::stack_name" }
protocol: HTTP
port: 80
algorithm: ROUND_ROBIN
nodes: []
virtualIps:
- type: PUBLIC
ipVersion: IPV4
scaled_servers:
type: Rackspace::AutoScale::Group
properties:
groupConfiguration:
name: { get_param: "OS::stack_name" }
maxEntities: 10
minEntities: 2
cooldown: 120
launchConfiguration:
type: launch_server
args:
loadBalancers:
- loadBalancerId: { get_resource: scaling_lb }
port: 80
server:
name: { get_param: "OS::stack_name" }
flavorRef: performance1-1
imageRef: 6f29d6a6-9972-4ae0-aa80-040fa2d6a9cf # Ubuntu 14.04 LTS (Trusty Tahr) (PVHVM)
key_name: { get_resource: access_key }
config_drive: true
networks:
- uuid: 11111111-1111-1111-1111-111111111111
user_data:
str_replace:
template: |
#cloud-config
apt_upgrade: true
apt_sources:
- source: deb http://stable.packages.cloudmonitoring.rackspace.com/ubuntu-14.04-x86_64 cloudmonitoring main
key: | # This is the apt repo signing key
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write_files:
- path: /etc/rackspace-monitoring-agent.conf.d/load.yaml
content: |
type: agent.load_average
label: Load Average
period: 60
timeout: 10
alarms:
load_alarm:
label: load average alarm
notification_plan_id: {notification_plan}
criteria: |
:set consecutiveCount=3
if (metric['5m'] > 0.85){
return new AlarmStatus(CRITICAL);
}
if (metric['15m'] < 0.3){
return new AlarmStatus(WARNING);
}
return new AlarmStatus(OK);
- path: /etc/rackspace-monitoring-agent.cfg
content: |
monitoring_token {agent_token}
packages:
- rackspace-monitoring-agent
- apache2
params:
"{notification_plan}": { get_resource: scaling_plan }
"{agent_token}": { get_resource: agent_token }
scale_up_policy:
type: Rackspace::AutoScale::ScalingPolicy
properties:
group: { get_resource: scaled_servers }
name:
str_replace:
template: stack scale up policy
params:
stack: { get_param: "OS::stack_name" }
change: 1
cooldown: 600
type: webhook
scale_up_webhook:
type: Rackspace::AutoScale::WebHook
properties:
name:
str_replace:
template: stack scale up hook
params:
stack: { get_param: "OS::stack_name" }
policy: { get_resource: scale_up_policy }
scale_down_policy:
type: Rackspace::AutoScale::ScalingPolicy
properties:
group: { get_resource: scaled_servers }
name:
str_replace:
template: stack scale down policy
params:
stack: { get_param: "OS::stack_name" }
change: -1
cooldown: 600
type: webhook
scale_down_webhook:
type: Rackspace::AutoScale::WebHook
properties:
name:
str_replace:
template: stack scale down hook
params:
stack: { get_param: "OS::stack_name" }
policy: { get_resource: scale_down_policy }
agent_token:
type: Rackspace::CloudMonitoring::AgentToken
properties:
label:
str_replace:
template: stack monitoring agent token
params:
stack: { get_param: "OS::stack_name" }
scaleup_notification:
type: Rackspace::CloudMonitoring::Notification
properties:
label:
str_replace:
template: stack scale up notification
params:
stack: { get_param: "OS::stack_name" }
type: webhook
details:
url: { get_attr: [ scale_up_webhook, executeUrl ] }
scaledown_notification:
type: Rackspace::CloudMonitoring::Notification
properties:
label:
str_replace:
template: stack scale down notification
params:
stack: { get_param: "OS::stack_name" }
type: webhook
details:
url: { get_attr: [ scale_down_webhook, executeUrl ] }
scaling_plan:
type: Rackspace::CloudMonitoring::NotificationPlan
properties:
label:
str_replace:
template: stack scaling notification plan
params:
stack: { get_param: "OS::stack_name" }
plan_notifications:
type: Rackspace::CloudMonitoring::PlanNotifications
properties:
plan: { get_resource: scaling_plan }
warning_state: # scale down on warning since this is configured for low load
- { get_resource: scaledown_notification }
critical_state:
- { get_resource: scaleup_notification }
outputs:
"Access Private Key":
value: { get_attr: [ access_key, private_key ] }
description: Private key for accessing the scaled server instances if needed
"Scale UP servers webhook":
value: { get_attr: [ scale_up_webhook, executeUrl ] }
description: Scale UP API servers webhook
"Scale DOWN servers webhook":
value: { get_attr: [ scale_down_webhook, executeUrl ] }
Auto-scaling using webhooks¶
If you decide to use a monitoring system other than Rackspace Cloud Monitoring, you can remove the monitoring agent configuration from the Rackspace::Autoscale::Group resource and remove the Rackspace::CloudMonitoring resources. Be sure to include the webhooks in the output values, as they will be needed when configuring monitoring.
Here is an example template for auto scaling with webhooks alone:
heat_template_version: 2014-10-16
description: |
Rackspace Cloud Monitoring and Event-based scaling using Rackspace Cloud Autoscale
resources:
access_key:
type: OS::Nova::KeyPair
properties:
name: { get_param: "OS::stack_name" }
save_private_key: true
scaling_lb:
type: Rackspace::Cloud::LoadBalancer
properties:
name: { get_param: "OS::stack_name" }
protocol: HTTP
port: 80
algorithm: ROUND_ROBIN
nodes: []
virtualIps:
- type: PUBLIC
ipVersion: IPV4
scaled_servers:
type: Rackspace::AutoScale::Group
properties:
groupConfiguration:
name: { get_param: "OS::stack_name" }
maxEntities: 10
minEntities: 2
cooldown: 120
launchConfiguration:
type: launch_server
args:
loadBalancers:
- loadBalancerId: { get_resource: scaling_lb }
port: 80
server:
name: { get_param: "OS::stack_name" }
flavorRef: performance1-1
imageRef: 6f29d6a6-9972-4ae0-aa80-040fa2d6a9cf # Ubuntu 14.04 LTS (Trusty Tahr) (PVHVM)
key_name: { get_resource: access_key }
config_drive: true
networks:
- uuid: 11111111-1111-1111-1111-111111111111
scale_up_policy:
type: Rackspace::AutoScale::ScalingPolicy
properties:
group: { get_resource: scaled_servers }
name:
str_replace:
template: stack scale up policy
params:
stack: { get_param: "OS::stack_name" }
change: 1
cooldown: 600
type: webhook
scale_up_webhook:
type: Rackspace::AutoScale::WebHook
properties:
name:
str_replace:
template: stack scale up hook
params:
stack: { get_param: "OS::stack_name" }
policy: { get_resource: scale_up_policy }
scale_down_policy:
type: Rackspace::AutoScale::ScalingPolicy
properties:
group: { get_resource: scaled_servers }
name:
str_replace:
template: stack scale down policy
params:
stack: { get_param: "OS::stack_name" }
change: -1
cooldown: 600
type: webhook
scale_down_webhook:
type: Rackspace::AutoScale::WebHook
properties:
name:
str_replace:
template: stack scale down hook
params:
stack: { get_param: "OS::stack_name" }
policy: { get_resource: scale_down_policy }
outputs:
"Access Private Key":
value: { get_attr: [ access_key, private_key ] }
description: Private key for accessing the scaled server instances if needed
"Scale UP servers webhook":
value: { get_attr: [ scale_up_webhook, executeUrl ] }
description: Scale UP API servers webhook
"Scale DOWN servers webhook":
value: { get_attr: [ scale_down_webhook, executeUrl ] }