Postmortem Report: Service Outage
Olawuni Emmanuel K
Software Engineer | Rising Tech Voice | Digital Solutions Expert | Multiply Business Traffic with Digital Tools
This article was written as part of ALX 0x19-Postmoterm Task
Issue Summary
Duration of Outage:
- Start Time: June 5, 2024, 10:00 AM (UTC)
- End Time: June 5, 2024, 12:30 PM (UTC)
Impact:
- Service Down: Main web application was inaccessible.
- User Experience: Users encountered 503 Service Unavailable errors.
- Affected Users: 85% of total user base experienced the outage.
Root Cause:
- A misconfiguration in the load balancer led to an unexpected increase in traffic to a single server, causing it to crash.
Timeline
- 10:00 AM: Issue detected via monitoring alert indicating a spike in 503 errors.
- 10:05 AM: Engineering team alerted through automated paging system.
- 10:10 AM: Initial investigation started; assumption was a potential database issue due to similar past incidents.
- 10:25 AM: Database team confirmed no issues; attention shifted to the application servers.
- 10:40 AM: Misleading path: checked recent application code deployments but found no errors.
- 11:00 AM: Network team investigated and identified a misconfiguration in the load balancer.
- 11:15 AM: Incident escalated to the DevOps team.
- 11:30 AM: DevOps team began reconfiguring the load balancer.
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- 12:00 PM: Load balancer configuration corrected and services started to recover.
- 12:30 PM: Full service restoration confirmed; monitoring continued to ensure stability.
Root Cause and Resolution
Root Cause:
The issue was traced to a recent update in the load balancer configuration. A parameter that controls traffic distribution was incorrectly set, directing the majority of incoming traffic to a single application server. This server became overwhelmed, leading to its failure and the resulting 503 errors for users.
Resolution:
The load balancer configuration was reviewed and corrected to ensure even traffic distribution across all application servers. The DevOps team implemented a rolling restart of the application servers to restore full functionality. Continuous monitoring was employed to confirm that the service was stable post-resolution.
Corrective and Preventative Measures
Improvements and Fixes:
1. Configuration Management: Review and tighten the configuration change process for critical infrastructure components such as load balancers.
2. Enhanced Monitoring: Implement more granular monitoring for load balancer configurations and traffic distribution.
3. Training: Conduct regular training sessions for the engineering and DevOps teams on best practices for configuration management and issue detection.
Specific Tasks:
1. Review Load Balancer Configuration: Conduct a comprehensive review of all load balancer settings and ensure they adhere to best practices.
2. Add Monitoring Alerts: Set up alerts for unusual traffic patterns and load balancer configurations.
3. Implement Configuration Audits: Establish regular automated audits of configuration changes for critical components.
4. Update Incident Response Plan: Revise the incident response plan to include steps for quicker identification and resolution of load balancer-related issues.
5. Documentation: Improve documentation for load balancer configurations and common troubleshooting steps.
6. Training Session: Schedule and conduct a training session focused on configuration management and monitoring.
By implementing these measures, we aim to reduce the likelihood of similar incidents and improve our response time for any future issues.