Postmortem Report: Load Balancer Outage

Issue Summary:

On June 18th, 2024, from 10:00 AM to 11:00 AM SAT, our web application experienced a significant outage due to a load balancer error. Users encountered HTTP 500 Internal Server Errors, impacting approximately 40% of our user base. The root cause was a communication issue between the load balancer and backend servers.

Timeline: (SAT)

• 10:00 AM: An engineer noticed increased error rates in the logs.
• 10:02 AM: The engineer notified the team via Discord.
• 10:05 AM: Initial investigation began, focusing on server logs and load balancer health checks.
• 10:15 AM: Identified intermittent communication failures between the load balancer and backend servers.
• 10:20 AM: The initial hypothesis formed was that the issue was related to network connectivity or misconfigured load balancer settings.
• 10:30 AM: Engineers investigated potential connectivity issues but found none.
• 10:40 AM: Load balancer configuration reviewed and identified a recent update causing the issue.
• 10:45 AM: Reverted load balancer settings to the previous stable configuration.
• 10:50 AM: Verified that the web application was operational and error-free.
• 11:00 AM: Full service restored and monitoring confirmed stability.

Root Cause and Resolution:

The outage was caused by a misconfiguration in the load balancer settings during a recent update, leading to communication failures with backend servers. The issue was resolved by reverting the load balancer configuration to its previous stable state.

Corrective and Preventive Measures:

Improvement Areas:

1. Implement pre-deployment configuration validation.
2. Enhance monitoring to detect configuration issues promptly.
3. Increase redundancy to mitigate single points of failure.

Specific Tasks:

1. Deploy Configuration Validation Tools: Integrate tools to validate load balancer configurations before deployment.
2. Training Sessions: Conduct training for engineers on load balancer management best practices.
3. Enhanced Monitoring: Implement more detailed health checks and alerts to quickly identify and resolve similar issues.