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Difficulty: MediumAWS CloudFormation Stack and Drift Management

A SysOps Administrator is managing an infrastructure stack deployed via AWS CloudFormation. During a stack update, a resource modification fails, prompting CloudFormation to roll back the stack. However, the rollback fails, and the stack enters the UPDATE_ROLLBACK_FAILED state because a DynamoDB table created by the stack was manually deleted outside of CloudFormation during the update process. Which of the following actions should the SysOps Administrator take to successfully resolve the update rollback failure and return the stack to a stable state? (Select TWO.)

  1. Continue the update rollback and specify the DynamoDB table as a resource to skip.Answer
  2. Manually recreate the DynamoDB table with the exact same name, and then continue the update rollback.Answer
  3. C
    Create a CloudFormation change set that removes the DynamoDB table from the template, and execute the change set.
  4. D
    Update the CloudFormation stack template to remove the DynamoDB table resource, and perform a stack update.
  5. E
    Modify the CloudFormation stack's service role to grant the iam:PassRole permission for DynamoDB, and restart the rollback.

Answer

To resolve the rollback failure, the administrator can either continue the update rollback and select the DynamoDB table to be skipped, or manually recreate the DynamoDB table with the exact same name and then continue the update rollback.
To resolve a stack that has failed to roll back and is in the UPDATE_ROLLBACK_FAILED state, you must either fix the underlying issue that caused the failure or skip the failed resources during the rollback. Recreating a manually deleted resource (like a DynamoDB table) with the same name allows CloudFormation to find the resource and complete the rollback process. Alternatively, choosing to skip the resource allows the rollback to finish, although the resource must then be manually reconciled to match the template.

Step-by-Step Solution

1
Identify the root cause of the rollback failure from the stack events.
The events show that the rollback failed because a DynamoDB table resource was manually deleted outside of CloudFormation.
Understanding the cause allows the administrator to decide whether to skip the resource or recreate it.
2
Choose to either skip the blocked resource or recreate it.
If skipping, CloudFormation continues rollback and marks it as UPDATE_COMPLETE. If recreating, recreating the table with the same name enables CloudFormation to perform rollback actions on it.
These are the only two valid pathways to resolve a rollback block.
3
Continue the update rollback from the CloudFormation console or AWS CLI.
The rollback completes successfully, returning the stack to a stable UPDATE_ROLLBACK_COMPLETE or ROLLBACK_COMPLETE state.
This clears the failed state and allows future updates to the stack.

Key Concept

Remediating CloudFormation rollback failures caused by missing resources
Estimated Time:2m 0s
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Topics

AWS CloudFormation Stack and Drift Management

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