AWS Fault Injection Simulator (FIS) helps you test the resilience of your applications by safely inducing faults. In this guide, we’ll define and launch an FIS experiment using three core components: Actions , Targets , and Stop Conditions . You’ll also learn how to apply guardrails to contain the blast radius.
Table of Contents
Core Components Prerequisites Step 1: Define the Action Step 2: Specify the Target Step 3: Add a Stop Condition Step 4: Launch the Experiment Cleanup Links and References
Core Components Component Description Example Action The fault you inject into the system. Terminating an EC2 instance Target The resource(s) on which the action runs. EC2 instances identified by tag Service=api Stop Condition A criterion—such as a CloudWatch alarm—that halts and rolls back the experiment when met. CPU utilization > 80% for 5 minutes
Stop conditions are optional but strongly recommended . They prevent runaway experiments and ensure safety.
Prerequisites
AWS CLI v2 installed and configured
IAM role with permissions:
fis:CreateExperimentTemplatefis:StartExperimentec2:TerminateInstancescloudwatch:DescribeAlarms
EC2 instances tagged with FaultInject=true
Step 1: Define the Action We’ll terminate EC2 instances tagged for the experiment. Use the following snippet in your experiment template:
"actions" : { "terminateInstances" : { "actionId" : "aws:ec2:terminate-instances" , "description" : "Terminate targeted EC2 instances" , "parameters" : { "instances" : [ "${TargetInstanceIDs}" ] } } }
Step 2: Specify the Target Identify EC2 instances by tag. You can also use resource IDs or ARNs.
"targets" : { "TargetInstanceIDs" : { "resourceType" : "aws:ec2:instance" , "resourceTags" : { "FaultInject" : "true" } } }
Step 3: Add a Stop Condition Define a CloudWatch alarm that stops the experiment when CPU usage exceeds 80% for 5 minutes:
"stopConditions" : [ { "source" : "aws:cloudwatch:alarm" , "value" : "arn:aws:cloudwatch:us-east-1:123456789012:alarm:HighCPUAlarm" } ]
Ensure your CloudWatch alarm ARN is correct. A misconfigured stop condition may not trigger, leaving experiments running longer than intended.
Step 4: Launch the Experiment Combine the components into a single template and create it with the AWS CLI:
aws fis create-experiment-template \ --tags Name=TerminateEC2Test \ --description "Terminate EC2 instances with guardrails" \ --role-arn arn:aws:iam::123456789012:role/AWSFISRole \ --actions file://actions.json \ --targets file://targets.json \ --stop-conditions file://stop-conditions.json
Once the template is created, start the experiment:
aws fis start-experiment \ --experiment-template-id et-0123456789abcdef0
Cleanup After testing, delete your experiment template to avoid orphaned resources:
aws fis delete-experiment-template \ --experiment-template-id et-0123456789abcdef0
Links and References 
