GitHub outage caused by infrastructure capacity failures

GitHub experienced a major service outage on August 17 that lasted 7 hours and 47 minutes, disrupting core services including github.com, authentication, GitHub Actions, APIs, pull requests, and GitHub Copilot. The disruption affected developers and organizations globally.

An investigation revealed the outage was caused by capacity failures during a period of peak traffic. Specifically, a critical infrastructure component in GitHub’s Central US data center failed to scale. The technical root cause involved an Istio sidecar pod reaching concurrency limits and failing to auto-scale due to a misconfigured policy. This triggered a cascade of failures, including load balancers reaching saturation and HAProxy nodes exhausting flow limits, which degraded authentication paths.

GitHub noted that monthly commits have grown from 1.4 billion to 2.9 billion since April, contributing to the increased pressure on systems. The company stated that neither the August 6 nor the August 17 incidents were caused by code or configuration changes, but rather by failures to scale critical components before demand exceeded capacity. GitHub is currently focusing on adding capacity and improving efficiency to prevent future occurrences.