Valid customer configuration change triggers a latent software bug across a CDN (Fastly, 2021)
A software deployment on May 12, 2021 introduced a bug that a specific valid customer configuration could trigger; on June 8 a customer pushed such a change.
What happened
- The bug caused about 85% of Fastly's network to return errors; the issue was detected within a minute and 95% of the network was back to normal within 49 minutes.Summary of June 8 outage
The failure pattern
Watch the pattern: Global change without a staged rollout
Safeguards that address it
CollectSEA's engineering analysis of what would have prevented or contained this failure.
- Canary software changes and watch for latent bugsRoll out to a small share of the network first and verify behaviour under real customer configurations.
- Enable fast detection and rollbackDetect errors within a minute and keep a one-step way to disable the triggering configuration.
Related standards
CollectSEA's mapping through this incident's failure pattern; not an official determination by the standards bodies.
- ASI08 Cascading Failures
- LLM06 Unbounded Consumption
- CM-3 Configuration Change Control
- CM-4 Impact Analyses
- SC-5 Denial-of-Service Protection
- RV.3.4 Update the development process
- MAP 5.1 Estimate impacts from past uses and public incident reports
- CWE-770 Allocation of Resources Without Limits or Throttling
Building something similar?
Describe your design and see every precedent that applies, with safeguards you can hand to your coding agent.
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