It is possible to export the name of the autoscaling group which elastic beanstalk provisions as part of each elastic beanstalk environment. This exported value can then be used from other cloud formation stacks in order to add custom scaling triggers, etc. We can export values by adding an outputs section into a .ebextensions file.

If you have large numbers of stacks it is very helpful if one can use a consistent naming scheme for the exported values. There is a way to pass a namespace into elastic beanstalk by using a custom option.

Here is the CloudFormation yaml to be included in an elastic beanstalk extension file:

Parameters:
  BeanstalkASGName:
    Type: String
    Description: "The name to export the autoscaling group name under"
    Default:
      Fn::GetOptionSetting:
        OptionName: MyBeanstalkStackInfoName
        DefaultValue: unknown
Outputs:
  OutputAutoScalingGroupName:
    Description: Beanstalk AutoScalingGroup Name
    Value:
      Ref: "AWSEBAutoScalingGroup"
    Export:
      Name:
        Fn::Join:
          - "-"
          - - { "Ref" : "BeanstalkASGName" }
            - "AutoScalingGroup"

Note that Fn::GetOptionSetting does not seem to be allowed directly in the Outputs section. So we have to use it instead to set the value of a parameter in a Parameters section, and then use the value indirectly via the parameter.

Here is a snippet to use in your master CloudFormation file:

Namespace: aws:elasticbeanstalk:customoption
OptionName: MyBeanstalkStackInfoName
Value: anyvalue