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# AWS::ECS::Service DeploymentController
<a name="aws-properties-ecs-service-deploymentcontroller"></a>

The deployment controller to use for the service. 

## Syntax
<a name="aws-properties-ecs-service-deploymentcontroller-syntax"></a>

To declare this entity in your CloudFormation template, use the following syntax:

### JSON
<a name="aws-properties-ecs-service-deploymentcontroller-syntax.json"></a>

```
{
  "[Type](#cfn-ecs-service-deploymentcontroller-type)" : String
}
```

### YAML
<a name="aws-properties-ecs-service-deploymentcontroller-syntax.yaml"></a>

```
  [Type](#cfn-ecs-service-deploymentcontroller-type): String
```

## Properties
<a name="aws-properties-ecs-service-deploymentcontroller-properties"></a>

`Type`  <a name="cfn-ecs-service-deploymentcontroller-type"></a>
The deployment controller type to use.  
The deployment controller is the mechanism that determines how tasks are deployed for your service. The valid options are:  
+ ECS

  When you create a service which uses the `ECS` deployment controller, you can choose between the following deployment strategies:
  + `ROLLING`: When you create a service which uses the *rolling update* (`ROLLING`) deployment strategy, the Amazon ECS service scheduler replaces the currently running tasks with new tasks. The number of tasks that Amazon ECS adds or removes from the service during a rolling update is controlled by the service deployment configuration. 

    Rolling update deployments are best suited for the following scenarios:
    + Gradual service updates: You need to update your service incrementally without taking the entire service offline at once.
    + Limited resource requirements: You want to avoid the additional resource costs of running two complete environments simultaneously (as required by blue/green deployments).
    + Acceptable deployment time: Your application can tolerate a longer deployment process, as rolling updates replace tasks one by one.
    + No need for instant roll back: Your service can tolerate a rollback process that takes minutes rather than seconds.
    + Simple deployment process: You prefer a straightforward deployment approach without the complexity of managing multiple environments, target groups, and listeners.
    + No load balancer requirement: Your service doesn't use or require a load balancer, Application Load Balancer, Network Load Balancer, or Service Connect (which are required for blue/green deployments).
    + Stateful applications: Your application maintains state that makes it difficult to run two parallel environments.
    + Cost sensitivity: You want to minimize deployment costs by not running duplicate environments during deployment.

    Rolling updates are the default deployment strategy for services and provide a balance between deployment safety and resource efficiency for many common application scenarios.
  + `BLUE_GREEN`: A *blue/green* deployment strategy (`BLUE_GREEN`) is a release methodology that reduces downtime and risk by running two identical production environments called blue and green. With Amazon ECS blue/green deployments, you can validate new service revisions before directing production traffic to them. This approach provides a safer way to deploy changes with the ability to quickly roll back if needed.

    Amazon ECS blue/green deployments are best suited for the following scenarios:
    + Service validation: When you need to validate new service revisions before directing production traffic to them
    + Zero downtime: When your service requires zero-downtime deployments
    + Instant roll back: When you need the ability to quickly roll back if issues are detected
    + Load balancer requirement: When your service uses Application Load Balancer, Network Load Balancer, or Service Connect
+ External

  Use a third-party deployment controller.
+ Blue/green deployment (powered by CodeDeploy)

  CodeDeploy installs an updated version of the application as a new replacement task set and reroutes production traffic from the original application task set to the replacement task set. The original task set is terminated after a successful deployment. Use this deployment controller to verify a new deployment of a service before sending production traffic to it.
When updating the deployment controller for a service, consider the following depending on the type of migration you're performing.  
+ If you have a template that contains the `EXTERNAL` deployment controller information as well as `TaskSet` and `PrimaryTaskSet` resources, and you remove the task set resources from the template when updating from `EXTERNAL` to `ECS`, the `DescribeTaskSet` and `DeleteTaskSet` API calls will return a 400 error after the deployment controller is updated to `ECS`. This results in a delete failure on the task set resources, even though the stack transitions to `UPDATE_COMPLETE` status. For more information, see [Resource removed from stack but not deleted](https://docs.aws.amazon.com/AWSCloudFormation/latest/UserGuide/troubleshooting.html#troubleshooting-errors-resource-removed-not-deleted) in the AWS CloudFormation User Guide. To fix this issue, delete the task sets directly using the Amazon ECS`DeleteTaskSet` API. For more information about how to delete a task set, see [DeleteTaskSet](https://docs.aws.amazon.com/AmazonECS/latest/APIReference/API_DeleteTaskSet.html) in the Amazon Elastic Container Service API Reference.
+ If you're migrating from `CODE_DEPLOY` to `ECS` with a new task definition and CloudFormation performs a rollback operation, the Amazon ECS`UpdateService` request fails with the following error:

  Resource handler returned message: "Invalid request provided: Unable to update task definition on services with a CODE\$1DEPLOY deployment controller. 
+ After a successful migration from `ECS` to `EXTERNAL` deployment controller, you need to manually remove the `ACTIVE` task set, because Amazon ECS no longer manages the deployment. For information about how to delete a task set, see [DeleteTaskSet](https://docs.aws.amazon.com/AmazonECS/latest/APIReference/API_DeleteTaskSet.html) in the Amazon Elastic Container Service API Reference.
*Required*: No  
*Type*: String  
*Allowed values*: `CODE_DEPLOY | ECS | EXTERNAL`  
*Update requires*: [No interruption](https://docs.aws.amazon.com/AWSCloudFormation/latest/UserGuide/using-cfn-updating-stacks-update-behaviors.html#update-no-interrupt)