Counter Rates & Increases
Learn how Prometheus handles counter resets with rate, irate, and increase functions.
Counter Resets
Counter metrics can reset to zero when a scraped process restarts (e.g., the server is restarted). Counter functions automatically handle counter resets by assuming that any decrease in a counter value was a reset. Internally, these functions compensate for the reset by adding the last sample value before the reset to all sample values after the reset.
Counter Functions
Rate
rate() - "rate of increase" - calculates a per-second increase of a counter as averaged over a specified window.
iRate
irate() - "instantaneous rate of increase" - calculates a per-second increase over the time window, only considering the last 2 points.
irate() is much more responsive than rate(). It is good for high-resolution metrics. It should not be used for alerting conditions.
Increase
increase() - "absolute increase" - calculates the absolute increase over a given time value, including extrapolation.
Logically, only the increase() function includes extrapolation because it measures an absolute increase. rate() and irate() functions calculate a slope (derivative), which will not change even if extrapolation is included.
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