QA
Senior LevelCloud Computing (AWS/GCP/Azure)

How do you execute Chaos Engineering experiments using AWS Fault Injection Simulator (FIS)?

❓ Interview Prompt: Explain Chaos Engineering principles, AWS Fault Injection Simulator (FIS), steady-state hypothesis, and controlled fault injection.

Chaos Engineering is the discipline of experimenting on a system to build confidence in its capability to withstand turbulent conditions in production.

AWS Fault Injection Simulator (FIS) Architecture:

1
Steady-State Hypothesis: Define measurable metrics proving normal system operation (e.g. HTTP 200 rate > 99.9%, Latency < 100ms).
2
Target Selection: Specify targets (EC2 instances, EKS pods, RDS databases, ASGs).
3
Action Injection: Inject real controlled faults:
•
Terminate random EC2 instances in an ASG.
•
Inject 500ms network latency on VPC ENIs.
•
Trigger RDS Primary failover.
4
Stop Conditions: CloudWatch alarms automatically abort the experiment if steady-state metrics breach safety thresholds!

Code Implementation Example

hcl
# AWS FIS Experiment Template injecting CPU stress fault
resource "aws_fis_experiment_template" "cpu_stress" {
  description = "Inject CPU stress on staging workers"
  role_arn    = aws_iam_role.fis_role.arn

  action {
    name      = "cpu-stress-action"
    action_id = "aws:ec2:send-spot-instance-interruptions"
    target { key = "Instances"; value = "app-instances" }
  }

  target {
    name          = "app-instances"
    resource_type = "aws:ec2:instance"
    selection_mode = "PERCENT(50)"
  }

  stop_condition {
    source = "aws:cloudwatch:alarm"
    value  = aws_cloudwatch_metric_alarm.error_rate_alarm.arn
  }
}
💡Terraform AWS FIS experiment template injecting Spot interruptions with CloudWatch stop condition.
🎯 Interview Key Takeaway

AWS FIS injects controlled faults (instance crashes, network latency) to validate system self-healing resilience against CloudWatch stop conditions.

#Chaos Engineering#AWS FIS#Resilience#Testing#Senior
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