Circular Dependency when using AWSEBAutoScalingGroup with CreationPolicy

问题

I'm trying to set up my Elastic Beanstalk environment to have an auto scaling group with a creation and update policy that waits for a signal from any new instances. Unfortunately I'm having issues getting this to work, and I believe it's because of a circular dependency. I have one config file in .ebextensions with the auto scaling configuration:

Resources:
  AWSEBAutoScalingGroup:
    Type: AWS::AutoScaling::AutoScalingGroup
    Properties:
      HealthCheckType: ELB
      HealthCheckGracePeriod: 300
    UpdatePolicy:
      ResourceSignal:
        Timeout: PT30M
    CreationPolicy:
      ResourceSignal:
        Timeout: PT30M

I have another configuration file which is supposed to run the cfn-signal script which will allow the auto scaling group to finish creating or updating:

commands:
  "01cfn-bootstrap-update":
    command: yum update -y aws-cfn-bootstrap
  "02cfn-signal":
    env:
      stackName:
        Ref: AWS::StackName
      region:
        Ref: AWS::Region
    command: /opt/aws/bin/cfn-signal -e $? --stack ${stackName} --resource AWSEBAutoScalingGroup --region ${region}

When I create the environment, the auto scaling group is created and waits for the signal. However, the signal is never sent by the instance. I ssh'd into the instance and, looking at the logs, I saw that the cfn-signal command (or any commands in .ebextensions) was not being executed.

I believe that this is because Elastic Beanstalk processes the .ebextensions one at a time, so it is not ever processing the cfn-signal config file until after the auto scaling config file is completed. Because this resource waits for that same signal, it never completes and the signal command never runs. I have also tried removing the auto scaling config file completely, and the cfn-signal command was able to run in that case (although it failed because the auto scaling group was not waiting for the signal). I have also tried renaming the files so that the cfn-signal file is before the auto scaling config file alphabetically, but that didn't make any difference. Is my understanding correct, that there is a circular dependency here? Is there any work around for it?

来源：https://stackoverflow.com/questions/56225111/circular-dependency-when-using-awsebautoscalinggroup-with-creationpolicy