GitHub Availability Report: April 2021

In April, we experienced two incidents resulting in significant impact and degraded state of availability for API requests and the GitHub Packages service, specifically the GitHub Packages Container registry service.

April 1 21:30 UTC (lasting one hour and 34 minutes)

This incident was caused by failures in our DNS resolution, resulting in a degraded state of availability for the GitHub Packages Container registry service. During this incident, some of our internal services that support the Container registry experienced intermittent failures when trying to connect to dependent services. The inability to resolve requests to these services resulted in users being unable to push new container images to the Container registry as well as pull existing images. The Container registry is currently in a public beta, and only beta users were impacted during this incident. The broader GitHub Packages service remained unaffected.

As a next step, we are looking at increasing the cache times of our DNS resolutions to decrease the impact of intermittent DNS resolution failures in the future.

April 22 17:16 UTC (lasting 53 minutes)

Our service monitors detected an elevated error rate when using API requests, which resulted in a degraded state of availability for repository creation. Upon further investigation of this incident, we identified the issue was caused by a bug from a recent data migration. In a data migration to isolate our secret scanning tables into their own cluster, a bug was discovered that broke the ability of the application to successfully write to the secret scanning database. The incident revealed a hitherto unknown dependency that repository creation had upon secret scanning, which makes a call for every repository created. Due to this dependency, repository creation was blocked until we were able to roll back the data migration.

As next steps, we are actively working with our vendor to update the data migration tool and have amended our migration process to include revised steps for remediation, in case similar incidents occur. Furthermore, our application code has been updated to remove the dependency on secret scanning for the creation of repositories.

In summary

From scaling the GitHub API to improving large monorepo performance, we will continue to keep you updated on the progress and investments we’re making to ensure the reliability of our services. To learn more about what we’re working on, check out the GitHub engineering blog.

Written by

Keith Ballinger

@keithballinger