(aws-ecs): (Add deregistration delay parameter to FargateService construct)

[lorenzozamponi]

Describe the feature

Currently, when deploying a service using ECS Fargate without a load balancer, there is a fixed deregistration delay of 5 minutes for replaced tasks (old tasks enter a draining state and remain there for 5 minutes), which is non-configurable unless a load balancer with target groups is used. I am proposing the addition of a deregistrationDelay parameter to the FargateService construct in AWS CDK, allowing developers to customize this delay when a load balancer is not used.

Use Case

When deploying a service to ECS Fargate that does not require a load balancer, the deployment process is unnecessarily slowed down by the default 5-minute deregistration delay. For example, when tasks are replaced during a deployment, the old tasks enter a draining state and remain there for 5 minutes, even though the service doesn't need this full delay. This results in a longer deployment time than necessary, impacting deployment pipelines and delaying new service availability. Allowing users to specify a custom deregistration delay would optimize this process.

Proposed Solution

Introduce a deregistrationDelay option to the FargateService construct to specify the amount of time, in seconds, to wait before changing the state of a deregistering target from draining to unused. The range is 0-3600 seconds. The default value is 300 seconds.

Other Information

deregistration_delay.timeout_seconds used in aws_elasticloadbalancingv2

Acknowledgements

• I may be able to implement this feature request
• This feature might incur a breaking change

CDK version used

v2.150.0

Environment details (OS name and version, etc.)

Mac OS Sequoia

[ashishdhingra]

@lorenzozamponi Good afternoon. Thanks for opening the issue. Referring some of the articles like How to Speed Up Amazon ECS Container Deployments, deregistration_delay.timeout_seconds is used for configuring load balancer connection draining. Please advise:

• How exposing deregistration_delay property at FargateService level would would be used for scenario where ECS Fargate is used without a load balancer?
  • • If possible, could you also demonstrate your use case with sample CDK code?
• Where are you observing the 5 minute delay?

Thanks,
Ashish

[lorenzozamponi]

Hi Ashish,

Thank you for your reply. As explained in the article Optimize load balancer connection draining parameters for Amazon ECS, the ECS agent ensures that the load balancer target is in an unused state before proceeding from draining to removing the old task. This means that an amount of time can be set to reduce the draining time of a task. This wait time (in the case of using a load balancer) can be reduced by using the deregistration_delay.timeout_seconds parameter. For example, by setting it to 5 seconds, the time between the draining state and task removal would be much faster, significantly reducing the deployment time.

• How would exposing the deregistration_delay property at the FargateService level be used for scenarios where ECS Fargate is used without a load balancer?
  It would help reduce deployment time by shortening the draining period of a task, which by default seems to be set at 300 seconds. The general idea is to add a property that allows setting the task's drain time.

• Where are you observing the 5-minute delay?
  The 300-second delay can be observed during the deployment of a service: once the new task is up, the old task remains in the draining state for 300 seconds before being removed.

Thank you very much,
Lorenzo