A usage circuit breaker for Cloudflare Workers
Yingjie Zhao describes a self-facing circuit breaker that pauses cron jobs on his Workers-based news aggregator as monthly usage nears plan allowances.
- Products
- WorkersKVQueues
- Source
- Author experienceYingjie Zhao’s blog
- Author
- Yingjie Zhao
Key points
- Every five minutes, the cron scheduler queries the GraphQL Analytics API and the Observability Telemetry API for month-to-date usage across eight resources and caches it in KV. Between checks, it reads the cached state from KV.
- Thresholds differ by resource: every resource warns at 80%, but only resources with costly overages that pausing cron can reduce (KV operations, Queues, Observability) trip at 90% and recover below 85%. Workers requests and CPU only warn. The gap between trip and recover prevents oscillation.
- If the usage API fails, the breaker keeps its last known state. Warnings are deduplicated per resource per month and trip alerts once per month, sent by email and Feishu. The author reports that it caught an 82% KV-read spike early in a month, before reaching the trip threshold.
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cf-usage-guard
An open-source library that reads account usage from the Cloudflare GraphQL API and circuit-breaks individual Worker bindings before overages.