Lock-free Observations for Prometheus Histograms
summary
Shows how Prometheus histograms get near lock-free updates by using the atomic package to write into a hot buffer while reads snapshot a cold buffer, switching them by atomically flipping a packed 64-bit word that holds a counter and a 1-bit index (63-bit packing). Unit tests run a million iterations and expose a flaky failure caused by 64-bit alignment and slice layout on 32-bit platforms, fixed by heap-allocating the counters, after which the approach reliably works.
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chapters (5)
- 0:00Start
- 16:00Write method part 1
- 17:26attempt 1: Wait for cool-down
- 22:19Lock-free observe revised
- 23:13Write method revised
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