AWS DVA-C02 Drill: ECS Fargate Migration - Minimizing Downtime with Capacity Providers

Jeff’s Note

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Unlike generic exam dumps, ADH analyzes this scenario through the lens of a Real-World Lead Developer.

For DVA-C02 candidates, the confusion often lies in correctly leveraging ECS capacity providers during migration to Fargate with zero or minimal downtime. In production, this is about knowing exactly how to configure capacity provider order and base values to control task placement on different compute platforms without service disruption. Let’s drill down.

The Certification Drill (Simulated Question)

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Scenario

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TechNova Solutions currently runs a business-critical microservices application on Amazon ECS backed by Amazon EC2 instances. The development team plans to migrate this application to run fully on Fargate to reduce infrastructure management overhead. To enable a seamless migration, they want to configure ECS capacity providers so tasks gradually transition from EC2 Launch Type to Fargate Launch Type with minimal downtime and no service disruption.

The Requirement:

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Determine the ECS capacity provider API operation and configuration strategy that meets these conditions with the LEAST downtime during migration.

The Options

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• A) Use the PutClusterCapacityProviders API operation to associate the ECS cluster with the FARGATE and FARGATE_SPOT capacity providers. Set FARGATE as Provider 1 with a base value, and FARGATE_SPOT as Provider 2 for failover.
• B) Use the CreateCapacityProvider API operation to associate the ECS cluster with the FARGATE and FARGATE_SPOT capacity providers. Set FARGATE as Provider 1 with a base value, and FARGATE_SPOT as Provider 2 for failover.
• C) Use the PutClusterCapacityProviders API operation to associate the ECS cluster with the FARGATE and FARGATE_SPOT capacity providers. Set FARGATE_SPOT as Provider 1 with a base value, and FARGATE as Provider 2 for failover.
• D) Use the CreateCapacityProvider API operation to associate the ECS cluster with the FARGATE and FARGATE_SPOT capacity providers. Set FARGATE_SPOT as Provider 1 with a base value, and FARGATE as Provider 2 for failover.

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Correct Answer

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A

Quick Insight: The DVA-C02 Imperative

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• When migrating ECS tasks to Fargate with minimal downtime, using the PutClusterCapacityProviders API to update an existing ECS cluster’s capacity providers is essential. This allows a smooth transition by setting FARGATE as the primary capacity provider with a base value to ensure a minimum number of tasks run on Fargate immediately.
• The base value influences how many tasks launch initially on that provider during deployment; using FARGATE as Provider 1 with base value ensures new tasks start on Fargate.
• Failover to FARGATE_SPOT for cost savings without sacrificing availability is a savvy option, but primary placement must be FARGATE for stability during migration.
• CreateCapacityProvider is for creating new capacity providers, not for associating pre-existing ones with clusters.

Content Locked: The Expert Analysis

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You’ve identified the answer. But do you know the implementation details that separate a Junior from a Senior?

The Expert’s Analysis

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Correct Answer

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Option A

The Winning Logic

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This solution utilizes the PutClusterCapacityProviders API operation, which is the correct method to update the capacity providers for an existing ECS cluster. It associates both the FARGATE and FARGATE_SPOT capacity providers and sets FARGATE as Provider 1 with a base value, ensuring that a minimum number of tasks run on Fargate immediately upon deployment. This approach helps maintain service availability and minimizes downtime during the migration. Placing FARGATE_SPOT as the secondary provider for failover saves costs without risking availability.

By contrast:

• Using CreateCapacityProvider (Options B and D) is incorrect because this API call creates new capacity providers but does not assign capacity providers to clusters. The capacity providers FARGATE and FARGATE_SPOT are AWS-managed and pre-existing, so you associate them with clusters via PutClusterCapacityProviders.

• Reversing provider priority by setting FARGATE_SPOT as Provider 1 with a base (Options C and D) increases risk since spot interruptions can cause downtime, which is unacceptable during migrations.

The Technical Blueprint

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# Example CLI command equivalent to Option A
aws ecs put-cluster-capacity-providers \
  --cluster technova-ecs-cluster \
  --capacity-providers FARGATE FARGATE_SPOT \
  --default-capacity-provider-strategy capacityProvider=FARGATE,base=1,weight=1 capacityProvider=FARGATE_SPOT,weight=1

This command associates the pre-existing AWS managed capacity providers FARGATE and FARGATE_SPOT with the ECS cluster. It sets FARGATE as the primary capacity provider with a base of 1 task to ensure at least one task runs on Fargate, enabling task placement without downtime.

The Comparative Analysis

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Real-World Application (Practitioner Insight)

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Exam Rule

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“For the exam, always use PutClusterCapacityProviders to associate ECS capacity providers when updating an existing cluster.”

Real World

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“In production, a staged migration from EC2 launch type to Fargate often uses capacity providers with base values to gradually shift running tasks without killing services. Fargate Spot is a cost optimization but not ideal as primary placement during critical migrations due to possible interruptions.”

(CTA) Stop Guessing, Start Mastering

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Disclaimer

This is a study note based on simulated scenarios for the AWS DVA-C02 exam.