Auto Scaling


Engine Yard announces support for AWS Auto Scaling.

Auto scaling

Auto Scaling makes sure you have the correct number of EC2 instances to handle your application's load. It can create and terminate instances based on schedule or on-demand by monitoring instances' metrics like CPU utilization.

The components of Auto Scaling are Groups, Launch Configurations, and Scaling Plans. You don't need to manage any of these as Engine Yard does it for you. We provide a simple interface to set the minimum and the maximum number of app instances in your environment. Auto Scaling will then do the following:

  • Boot instances if the current number of instances is lower than the minimum.

  • Replace instances if any of the instances fail their status checks.

  • In a future update, boot instances to handle your application's load and terminate if they're not needed.

Adding Auto Scaling Group

1. Enable Early Access Feature

Auto Scaling is available as an Early Access feature. Open a Support ticket to enable the feature.

2. Check the Requirements

Before you can use Auto Scaling, the environment must:

  • Have a VPC network attached. Create the network if necessary. Some regions also use a default VPC depending on your account. 

  • Have no EC2 Classic instances created before you attached a VPC network. Replace them if necessary.

  • Have running instances.

3. Create Auto Scaling Group

On the environment page, click Auto Scaling. On the Auto Scaling page, specify the Minimum and Maximum Size.


Note on Desired Capacity

Aside from the Minimum and Maximum Size, an Auto Scaling Group also has a desired capacity. This number is set by Engine Yard.

If the current number of app instances is lower than the minimum number of instances, Auto Scaling boots the required instances and the desired capacity is set to the Minimum Size.

If the current number of app instances is higher than the minimum number of instances, Auto Scaling doesn't boot any instances and the desired capacity is set to the current number of app instances

In a future update, the desired capacity will change depending on your Scaling Plan. For example, you can configure a target tracking scaling policy to keep the average aggregate CPU utilization of your Auto Scaling Group at 70%. Auto Scaling will create or terminate instances to meet this requirement. It will still follow the Minimum and Maximum Size.

Questions and Feedback

We are excited to bring this feature to our customers. It has always been easy to add instances at Engine Yard. Auto Scaling makes it even easier by doing it automatically for you. We will add more Auto Scaling features soon.

We like to hear from you. Let us know if you have any questions or feedback on the Auto Scaling feature.

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Christopher Rigor

Christopher Rigor is a Senior Technical Evangelist at Engine Yard. He’s a long time Rails user, system administrator, and recently became a contributor of RailsInstaller. Previously, he was the DevOps Support Manager for Asia-Pacific at Engine Yard.
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