# Considerations when managing ECS blue/green deployments using CloudFormation
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The process of using CloudFormation to perform your ECS blue/green deployments through CodeDeploy is different from a standard ECS deployment using just CodeDeploy. For a detailed understanding of these differences, see [Differences between Amazon ECS blue/green deployments through CodeDeploy and CloudFormation](https://docs.aws.amazon.com/codedeploy/latest/userguide/deployments-create-ecs-cfn.html#differences-ecs-bg-cfn) in the *AWS CodeDeploy User Guide*. 

When managing your blue/green deployment using CloudFormation, there are certain limitations and considerations to keep in mind:
+ Only updates to certain resources will initiate a green deployment. For more information, see [Resource updates that initiate green deployments](about-blue-green-deployments.md#blue-green-resources).
+ You can't include updates to resources that initiate green deployments and updates to other resources in the same stack update. For more information, see [Resource updates that initiate green deployments](about-blue-green-deployments.md#blue-green-resources).
+ You can only specify a single ECS service as the deployment target.
+ Parameters whose values are obfuscated by CloudFormation can't be updated by CodeDeploy during a green deployment, and will lead to an error and stack update failure. These include:
  + Parameters defined with the `NoEcho` attribute.
  + Parameters that use dynamic references to retrieve their values from external services. For more information about dynamic references, see [Get values stored in other services using dynamic references](dynamic-references.md).
+ To cancel a green deployment that's still in progress, cancel the stack update in CloudFormation, not CodeDeploy or ECS. For more information, see [Cancel a stack update](using-cfn-stack-update-cancel.md). After an update has finished, you can't cancel it. However, you can update a stack again with any previous settings.
+ The following CloudFormation features are not currently supported for templates that define ECS blue/green deployments:
  + Declaring [outputs](outputs-section-structure.md) or using [Fn::ImportValue](https://docs.aws.amazon.com/AWSCloudFormation/latest/TemplateReference/intrinsic-function-reference-importvalue.html) to import values from other stacks.
  + Importing resources. For more information about importing resources, see [Import AWS resources into a CloudFormation stack](import-resources.md).
  + Using the `AWS::CodeDeploy::BlueGreen` hook in a template that includes nested stack resources. For more information about nested stacks, see [Split a template into reusable pieces using nested stacks](using-cfn-nested-stacks.md).
  + Using the `AWS::CodeDeploy::BlueGreen` hook in a nested stack.