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Difficulty: MediumDeployment Strategies

A developer is configuring a rolling update deployment for an Amazon ECS service. The service has a desired task count of 12. To ensure high availability and prevent performance degradation under peak load, the service must maintain 100% of its desired capacity at all times during the deployment. Furthermore, due to CPU and memory constraints on the underlying container instances, the deployment can run at most 3 additional tasks concurrently. Which parameters for minimum healthy percent and maximum percent should the developer configure for the ECS service?

  1. Minimum healthy percent of 100% and maximum percent of 125%Answer
  2. B
    Minimum healthy percent of 75% and maximum percent of 125%
  3. C
    Minimum healthy percent of 100% and maximum percent of 100%
  4. D
    Minimum healthy percent of 75% and maximum percent of 100%

Answer

Minimum healthy percent of 100% and maximum percent of 125%
The correct configuration is to set the minimum healthy percent to 100% and the maximum percent to 125%. The minimum healthy percent of 100% ensures that the ECS service always has at least 12 healthy tasks running (100% of the desired count of 12). The maximum percent of 125% allows the service to temporarily scale up to 15 tasks (125% of 12) during the deployment, representing the 3 additional tasks permitted by the resource constraints.

Step-by-Step Solution

1
Calculate the minimum number of running tasks required based on the capacity constraint.
The minimum number of running tasks must be 12 (100% of the desired count of 12 tasks). Therefore, the minimum healthy percent is 100%.
The requirement states that the service must maintain 100% of its desired capacity at all times during the deployment.
2
Calculate the maximum number of running tasks allowed based on container instance resources.
The maximum number of running tasks allowed is 15 tasks (12 desired + 3 additional tasks).
The requirement states that the deployment can run at most 3 additional tasks concurrently.
3
Convert the maximum task count into a percentage of the desired count.
Maximum percent = (15 / 12) * 100 = 125%.
ECS service definitions express the maximum task limit during deployment as a percentage of the desired task count.

Key Concept

Amazon ECS rolling update deployment configuration parameters (minimumHealthyPercent and maximumPercent)
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Topics

Deployment Strategies

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