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prometheus

Exact time in the rate function with @ modifier

rate(http_requests_total[5m] @ 1609746000)

#This returns the 5-minute rate that http_requests_total had at 2021-01-04T07:40:00+00:00

Hi.Can anyone explain to me what does the above sentence mean? I am newbie to prometheus and i am a little confused about the exact time in the rate function.

Solution

  • rate is applied to the range vector selected by inner query.

    So let's compare the difference between: http_requests_total[5m] @ 1609746000 and http_requests_total[5m].

    First one creates a range vector with values of time series with name http_requests_total over five minute window that ends at 1609746000 regardless of the time parameter.

    Second one creates a range vector with values of time series with name http_requests_total over five minute window that ends at the time parameter of the query.

    This means, that graph of rate over first selector will always be a constant horizontal line, regardless of time range for your graph (as result is not dependent on that time at all), and for second one it will calculate rate over last 5 minutes for each point on graph. Demo