SOA-C02 Deployment, Provisioning, and Automation Practice Question
Network Topology
A SysOps administrator is investigating a failed CloudFormation stack creation. The describe-stack-events output shows that the stack creation failed with the reason 'Resource creation cancelled'. What is the most likely cause of this failure?
Answer choices
Why each option matters
Answer the question above first, then reveal the full breakdown to understand why each option is right or wrong.
Correct answer & explanation
✓
A WaitCondition resource did not receive the required signal within the specified timeout period.
The WaitCondition timed out before receiving the required signal, causing CloudFormation to cancel the stack creation. Option A is incorrect because a parameter validation error would appear as a different reason. Option B is incorrect because there is no indication of missing IAM permissions. Option D is incorrect because the stack creation was cancelled due to the wait condition timeout, not a nested stack failure.
Answer analysis
Option-by-option breakdown
For each option: why learners choose it and why it is or isn't the right answer here.
- ✗
The stack template contains an invalid parameter value.
Why it's wrong here
An invalid parameter value in the stack template is detected during the 'ValidateTemplate' or parameter resolution phase before CloudFormation begins provisioning any resources. If a parameter fails validation, the stack creation fails immediately with an error such as 'Parameters: [Environment] must have a value of [prod, dev]' and the stack status becomes 'ROLLBACK_COMPLETE' without any resources being created. The 'Resource creation cancelled' status only appears after resource creation has started and a WaitCondition or CreationPolicy times out. Since the template validation error occurs before any resource is instantiated, CloudFormation would never report a resource-level cancellation event for that reason.
- ✗
The IAM role used by CloudFormation does not have sufficient permissions to create the resources.
Why it's wrong here
Insufficient IAM permissions for the CloudFormation service role would produce an 'AccessDenied' or 'UnauthorizedOperation' error as the resource creation attempt is rejected by the underlying AWS service. In that scenario, the resource would be marked as 'CREATE_FAILED' and the stack would enter 'ROLLBACK_IN_PROGRESS' with an error message explaining the denied API action. The signal-based 'Resource creation cancelled' status, on the other hand, occurs after the resource was already created successfully (e.g., an EC2 instance launched) but the WaitCondition did not receive the success signal within the timeout window. Thus, IAM issues never result in a 'cancelled' status; they result in immediate permission errors during the resource provisioning phase.
- ✓
A WaitCondition resource did not receive the required signal within the specified timeout period.
Why this is correct
In the CloudFormation event history, a 'Resource creation cancelled' status for a stack resource is the result of a WaitCondition or WaitConditionHandle timing out. For a WaitCondition resource, CloudFormation pauses the stack creation until it receives a success signal (typically sent by cfn-signal) from the launched resources. If that signal is not delivered within the specified Timeout period, the resource is marked as cancelled and the entire stack creation is stopped and rolled back. This failure mode is distinct from error-driven rollbacks because the resource itself never finished creating — it was simply waiting on an external signal that never arrived.
- ✗
A nested stack within the parent stack failed to create.
Why it's wrong here
A failure in a nested stack would appear as a 'CREATE_FAILED' event on the nested stack resource within the parent stack, followed by 'ROLLBACK_IN_PROGRESS' for the parent — not as 'Resource creation cancelled'. Each nested stack is a separate CloudFormation stack with its own stack ID, and its events are logged under that stack. When a nested stack fails, CloudFormation reports the nested stack's status as 'CREATE_FAILED' and the error message references the nested stack resource type, such as 'AWS::CloudFormation::Stack'. The message 'Resource creation cancelled' is specifically reserved for resources that were waiting on a WaitCondition or a CreationPolicy, so a nested stack failure would never cause that exact status string to appear.
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Written by Johnson Ajibi, MSc IT Security
Senior Network & Security Engineer · founder of Courseiva
This SOA-C02 practice question is part of Courseiva's free Amazon Web Services certification practice question bank. Courseiva provides original exam-style practice questions with explanations, topic-based practice, mock exams, readiness tracking, and study analytics to help learners prepare for the SOA-C02 exam.