PromQL expression to find common labels in two intervals

Question

Lets say i have the following metrics collected from now-60m to now-30m -

fruits{name="apple"} 1
fruits{name="orange"} 1
fruits{name="pear"} 1

and the following metrics collected from now-30m to now

fruits{name="banana"} 1
fruits{name="pear"} 1
fruits{name="watermelon"} 1

How would i go about writing an alert rule to check if any fruit is present in both collections and it's name? In this case it will be

pear

Answer 1

Try the following query:

count(last_over_time(fruits[30m] offset 30m)) by (name)
and
count(last_over_time(fruits[30m])) by (name)

It should return name labels, which existed on both time ranges - (now-60m .. now-30m] and (now-30m .. now].

It uses the following functions:

• last_over_time for selecting all the time series, which were existed during the last 30 minutes
• offset modifier
• count aggregate function
• and operator