A Counter Reset Changes the Story in the Graph

A counter accumulates events over time, but some counters start over when a process restarts. Subtracting the next value from the previous one can then produce an impossible negative event. The events did not run backward; the measurement history was reset.

That is why it matters to understand how a monitoring tool calculates rates from counters. Which reset patterns does it handle? What sample interval does it use? A short or long rate window can change the meaning of the graph.

Suppose a traffic graph changes suddenly after a restart. Do not assume user behavior changed. Check collection timing, process lifetime, and metric type as well.

Before telling a story with data, it helps to understand how the data remembers. A counter is a kind of memory, but that memory has a lifetime. Knowing that boundary prevents strange conclusions from otherwise clean graphs.

Source: official reference.