How to divide two Prometheus Counters

6
votes

I have two metrics, Counters to be precise, lets say they are called

  • NumberOfVisitors
  • NumberOfLogins

In grafana I would like to plot is the number-of-logins divided by the number of visitors (or the other way around) over time. So I tried

rate(NumberOfLogins) / rate(NumberOfVisitors)

but this results in an error

Error executing query: invalid parameter 'query': parse error at char 46: expected type range vector in call to function "rate", got instant vector

I'm not sure what all that means. Hopefully something like this is possible. Any help would be appreciated

1
prometheusmetricspromql

1 Answers

6
votes

The rate function expect a range vector, for example:

rate(NumberOfLogins[5m])

That means to calcualte the rate within the last 5 minutes at each time point. You can change the 5m to other time range.

Therefore this would fit you need:

rate(NumberOfLogins[5m]) / rate(NumberOfVisitors[5m])