Incident Library

Component

Recursive DNS resolver service

재귀 DNS 리졸버 서비스 · recursive-dns-resolver

3 cases · 2021 to 2025

Root cause Software defect2Faulty deployment1
Contributing factor Harmful manual action2Gap in automated tests2Unverified assumption1Cache-masked failure1Limited debug access1Monitoring blind spot1Retry storm1Ineffective rollback1Unrepresentative staging1Unsafe failure behaviour1Dependence on a warm cache1
Symptom DNS resolution failures3High error rate1High latency1Intermittent timeouts1Memory pressure1
Organisation AdGuard DNS1Cloudflare1Slack1

Cases, by severity

  1. IL-0268 AdGuard DNS resolvers in Amsterdam, Frankfurt and London overloaded and answered with timeouts and SERVFAILAdGuard DNS · 2025

    Root cause Faulty deployment

  2. IL-0340 Cloudflare's 1.1.1.1 resolver returned SERVFAIL to some valid DNS queries for four hoursCloudflare · 2023

    Root cause Software defect

  3. IL-0250 slack.com stopped resolving on some DNSSEC-validating resolvers for about 24 hours after DNSSEC signing was turned onSlack · 2021

    Root cause Software defect

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