Postmortem: Web Stack Outage on January, 2024
Issue Summary
Duration:
Start Time: January10, 2023, 14:30 EAT
End Time: January 11, 2024, 16:45 EAT
Impact:
The web server was completely down for 24 hour and 15 minutes.
All services hosted on the server were inaccessible.
Users experienced a 100% downtime during the outage.
Root Cause:
The root cause of the outage was identified as a misconfiguration in the load balancer settings, leading to a complete disruption in traffic routing.
Timeline
14:30 EAT: Issue detected through automated monitoring alerts, indicating a sudden drop in server responsiveness.
14:35 EAT: System engineers received automated alerts and started investigating the issue.
14:40 EAT: Initial assumption pointed to a possible DDoS attack due to the sudden spike in incoming requests.
14:50 EAT: The Network Operations team was notified of the potential attack, and traffic analysis began.
15:15 EAT: Further investigation revealed a misconfiguration in the load balancer, causing it to reject valid traffic.
15:30 EAT: The incident was escalated to the DevOps team for load balancer configuration correction.
16:00 EAT: Load balancer misconfiguration fixed, and services were gradually restored.
16:45 EAT: Full service recovery confirmed, and monitoring showed normal traffic patterns.
Root Cause and Resolution
Root Cause:
The misconfiguration in the load balancer was traced back to a recent update in the configuration files, where a syntax error went unnoticed during the deployment process. This error resulted in the load balancer rejecting all incoming traffic, leading to the outage.
Resolution:
The immediate fix involved rolling back the recent update and restarting the load balancer to apply the correct configuration. Additionally, a comprehensive review process for configuration changes was implemented to prevent similar incidents in the future.
Corrective and Preventative Measures
Improvements/Fixes:
Implement stricter pre-deployment checks for configuration files to catch syntax errors.
Enhance monitoring for load balancer performance and configuration changes.
Conduct a thorough review of the incident response process to identify areas for improvement.
Tasks:
Conduct a post-incident review with the DevOps and Network Operations teams to identify lessons learned.
Update the incident response playbook to include specific steps for load balancer misconfigurations.
Implement automated configuration testing in the deployment pipeline to catch syntax errors before production.
Schedule regular training sessions for the operations team on the latest load balancer configurations and best practices.
This postmortem highlights the importance of robust configuration management processes and continuous improvement in monitoring and incident response procedures. It serves as a valuable learning experience for the team to strengthen the system’s resilience and prevent future similar incidents.