Postmortem Report: Database Connection Outage

Issue Summary

Duration:

• Start: August 17, 2024, 14:00 UTC

• End: August 17, 2024, 16:30 UTC

Impact:
The outage affected the main database server, leading to the unavailability of the application for 2 hours and 30 minutes. During this time, 80% of users were unable to access the service, experiencing timeouts and error messages when attempting to log in or perform transactions.

Root Cause:
The root cause was a misconfiguration in the database connection pool, which exhausted available connections, causing the server to be unable to handle new requests.

Timeline

• 14:00 UTC:
  The issue was detected by an automated monitoring alert indicating a sharp increase in database query response times.

• 14:05 UTC:
  An engineer noticed a high number of failed requests in the application logs, confirming the issue.

• 14:10 UTC:
  Initial investigation focused on possible network issues or hardware failures. Network connectivity checks were performed, and server health was verified, but no abnormalities were found.

• 14:30 UTC:
  The team reviewed recent configuration changes and identified a possible link to a recent update in the database connection pool settings. However, this was initially dismissed as unlikely to be the cause.

• 15:00 UTC:
  After exhausting other possibilities, the team revisited the connection pool configuration. It was discovered that the maximum number of connections allowed was set too low, which led to all connections being consumed during peak traffic.

• 15:15 UTC:
  The issue was escalated to the database administration team for immediate action.

• 15:30 UTC:
  The database connection pool settings were adjusted to increase the maximum number of connections. This change resolved the issue.

• 16:00 UTC:
  The application was fully operational again, and users could access the service without any issues.

• 16:30 UTC:
  Monitoring was enhanced to ensure the issue did not recur, and the incident was formally closed.

Root Cause and Resolution

Root Cause:
The root cause of the outage was a misconfigured database connection pool. The maximum number of connections allowed was too low to handle the high volume of traffic during peak hours. As a result, all available connections were consumed, leading to a bottleneck where new requests could not be processed, causing the application to become unresponsive.

Resolution:
The database connection pool configuration was corrected by increasing the maximum number of connections. This adjustment allowed the application to handle the increased traffic, restoring normal operation. Additionally, the connection timeout settings were fine-tuned to ensure that unused connections were released promptly.

Corrective and Preventative Measures

Improvements Needed:

• Implement more comprehensive monitoring of database connection metrics, including connection usage and availability.

• Review and optimize connection pool settings to ensure they are aligned with the application’s traffic patterns.

• Conduct regular stress testing to identify potential configuration issues under peak load conditions.

Task List:

1. Patch Database Connection Pool:
   Apply the configuration changes across all environments to prevent similar issues in the future.

2. Add Monitoring for Connection Metrics:
   Set up alerts for when connection usage exceeds 80% of the maximum limit.

3. Conduct Load Testing:
   Perform load testing every quarter to identify and mitigate potential bottlenecks.

4. Review Configuration Management Process:
   Ensure all configuration changes are documented and reviewed by multiple team members before deployment.