Rollbacks and Rollback Triggers

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Rollbacks and Rollback Triggers in AWS CloudFormation enable you to automatically revert your stack to the previous state if a stack operation fails, ensuring stability and minimizing risk during updates. Rollbacks can be configured to occur based on any predefined conditions, such as resource creation failures, update failures, or customer-defined alarms. With Rollback Triggers, you can specify AWS CloudWatch Alarms that, when triggered, automatically initiate a rollback of the stack operation. This allows you to closely monitor your stack resources and automatically revert changes in case of threshold breaches or unexpected issues. These features help you maintain a reliable, consistent state of your infrastructure, minimizing downtime and errors during the evolution of your architectures.

Guide to AWS Rollbacks and Rollback Triggers

Rollbacks and Rollback Triggers are crucial components within AWS CloudFormation.

What are Rollbacks and Rollback Triggers?
They are mechanisms employed by AWS to ensure that any failure happening during set changes in a stack does not affect cloud resources. Rollback helps revert the entire stack operation to the previously deployed state when a failure happens. Rollback Triggers provide an added layer of control by allowing you to specify CloudWatch alarm that CloudFormation monitors during the create and update stack operations.

Why are they important?
They are essential for maintaining system stability and resilience. Automated rollback on error ensures that resources are not left in an inconsistent state when stack creation or update fails.

How do they work?
When you set a stack to roll back on failure, CloudFormation monitors the specified alarms during the stack create or update process, and if any of the alarms go off, CloudFormation rolls back the entire stack operation to the previous deployed state.

Exam Tips: Answering Questions on Rollbacks and Rollback Triggers
1. Understand the basic function of AWS CloudFormation Rollback and Rollback triggers.
2. Remember that automated rollback on error attempts to recover the stack to the previously deployed state.
3. Be clear that Rollback Triggers add an extra layer of control and use CloudWatch alarms to trigger rollbacks.
4. Make sure you know how to set up Rollback Triggers.

Remember, the overall success in an exam depends primarily on a thorough understanding of the concepts and effective application of the same.

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Question 1

How can you configure a CloudFormation stack to automatically roll back on specific alarms during an update?

Manually monitor the alarms and initiate rollback if necessary. Add the AWS CloudFormation RollbackTrigger property to your stack template. Configure the stack policy to include specific alarms. Specify the alarms in the Rollback Triggers section of the AWS Management Console.

Correct Answer: Specify the alarms in the Rollback Triggers section of the AWS Management Console.

You can configure a CloudFormation stack to automatically roll back on specific alarms during an update by specifying the alarms in the Rollback Triggers section of the AWS Management Console. The other options do not provide an automatic method of rolling back on specified alarms.

Question 2

A CloudFormation stack update was nearly complete when it failed. Which action should you take to roll back to the stable state?

Manually fix the resources and continue the update. Delete the stack and recreate it. Rollback the stack update. Wait for AWS to automatically roll back.

Correct Answer: Rollback the stack update.

When a stack update fails, the best course of action is to roll back the stack update to return to the last stable state. Deleting and recreating the stack is time-consuming and risks losing data, whereas manually fixing resource issues should be done after rollback. AWS will not automatically roll back, and contacting support is unnecessary.

Question 3

Your CloudFormation stack update has failed, and you are troubleshooting the issue. What is the best way to identify the exact error that caused the failure?

Manually inspect the updated resources. Check the CloudFormation Events in the AWS Management Console. Review the AWS CloudTrail logs. Use the AWS SDK to query the stack events.

Correct Answer: Check the CloudFormation Events in the AWS Management Console.

To identify the exact error that caused the CloudFormation stack update failure, check the CloudFormation Events in the AWS Management Console. CloudFormation Events provide detailed information about each action taken during the stack update, including the cause of the failure. The other options may provide relevant information but are not the most direct or efficient method.

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