问题
Given the following prometheus time series called requests :
the vector query requests[3 seconds] is :
and the rate of the vector query requests[3 seconds], rate(requests[3 sec]) (computed by the shown formula) is :
My question is : what is sum(rate(requests[3 sec])) evaluated at seconds 5, 4 and 3 respectively is it 16.5, 6.5 and 1. Any idea?
回答1:
You are misunderstanding the purpose of sum. It is not performing a sum over time but over the dimensions for your metric.
In your example, assuming there are multiple requests metrics (with a dimension page by exemple), rate(requests[3 sec]) will give you (at some point in time):
{page="A"} 12.4
{page="B"} 1.5
{page="C"} 0 .... (and so on for each metrics requests with different label set)
The sum function will sum the values of the different rates; and sum(ate(requests[3 sec])) will give you only one value:
{} 42.13 <-- the sum of all rate(requests[3s]) values
BONUS: In the case you metric have multiple dimensions (represented by multiple labels in your metric) you can tell sum() to operate on a subset of them: sum(ate(requests[3 sec])) ON(foo)
来源：https://stackoverflow.com/questions/65003764/sum-of-rate-function-in-prometheus