Use gauges instead of counters for GC Pause Total and Num GCs#174
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miguelmolina95 wants to merge 2 commits intomasterfrom
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Use gauges instead of counters for GC Pause Total and Num GCs#174miguelmolina95 wants to merge 2 commits intomasterfrom
miguelmolina95 wants to merge 2 commits intomasterfrom
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meow #dev-go @connor15mcc |
jcapote-lyft
approved these changes
May 14, 2025
| lastGC: scope.NewGauge("lastGC"), | ||
| pauseTotalNs: scope.NewCounter("pauseTotalNs"), | ||
| numGC: scope.NewCounter("numGC"), | ||
| pauseTotalNs: scope.NewGauge("pauseTotalNs"), |
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https://cs.opensource.google/go/go/+/refs/tags/go1.24.3:src/runtime/mstats.go;l=258-263
// PauseTotalNs is the cumulative nanoseconds in GC
// stop-the-world pauses since the program started
so pauseTotalNs is not a gauge, it is actually a counter
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yeah I think we were looking at one of the broken charts wrong and the reason it was broken I gave more context in the thread https://lyft.slack.com/archives/C0KLXB3KN/p1747250876491629 and updated the doc
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closing this with context on thread https://lyft.slack.com/archives/C0KLXB3KN/p1747250876491629 as we will fix the charts first |
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First of a series of fixes to make the obs of Go runtime stats better: WIP doc https://docs.google.com/document/d/1qGNgOgRV1FEuMlXIy0vzEvKdqRXYlYLGONaI0czs5d8/edit?tab=t.0
First issue we found is a couple of counters that are being misused and leading to an unbounded increment and then being divided by itself leading to a 1 value all the time.
Example with Etaproxy
If you look at the 2 counters we are changing right now and check the units you can see how they are growing unbounded and why gauge might be better:
pauseTotalNs: https://alerts.lyft.net/chart_v2/c6u11FIXgf?qs=%7B%22t%22%3A%7B%22startTimeMs%22%3A1747242870566%2C%22endTimeMs%22%3A1747249917735%7D%2C%22s%22%3A%5B%5D%7D
numGC: https://alerts.lyft.net/chart_v2/mTZNYUVfav?qs=%7B%22t%22%3A%7B%22startTimeMs%22%3A1747242881886%2C%22endTimeMs%22%3A1747249889433%7D%2C%22s%22%3A%5B%5D%7D