2026-08-20: Gitaly concurrency saturation

Gitaly concurrency saturation (Severity 2)

Problem: The web service’s load balancer and request-processing SLOs showed elevated error rates in the main stage.

Impact: The web service's main-stage load balancer and request-processing SLOs violated target error rates. This also increased load on affected Gitaly systems and blocked deployments and feature flag changes.

Causes: We traced the issue to Gitaly saturation and resource exhaustion, driven by heavy unauthenticated Git clone traffic against forks of gitlab.git under personal namespaces. A gitlab-monitor/1.0 agent generating traffic across many users was also identified as a contributor.

Response strategy: We added a Cloudflare rule to block suspicious unauthenticated git-upload-pack traffic, and service signals had stabilised by 11:04pm UTC. We are also drafting a safer longer-term rate limit to replace the block and have opened a follow-up item to address recurring Gitaly saturation.