How to get the average over time only during the day in Prometheus

问题

I'm currently trying to get the average percentage usage of RAM in the last month with the following query :

100 - ((avg_over_time(node_memory_MemAvailable_bytes{instance="...",job="..."}[4w]) * 100) / node_memory_MemTotal_bytes{instance="...",job="..."})

The query is working correctly, but now I would like to filter out the values that were collected during the night, in order to have a real usage percentage during the day : is it possible to get the average of the values collected only between 8AM and 8PM ?

Thanks in advance !

Mathias

回答1:

Since you can't have a range with holes (i.e. last 4 weeks but only 8 AM to 8 PM), you'd need to create a recorded rule that records available memory only during the day, then compute an avg_over_time over the time series produced by said rule.

The rule is relatively easy to set up

node_memory_MemAvailable_bytes
  and 
hour(timestamp(node_memory_MemAvailable_bytes)) >= 8
  and 
hour(timestamp(node_memory_MemAvailable_bytes)) < 20

but it will not have any history initially, so you'll have to wait for a few days before you get any meaningful data out of it. Also note that this expression will filter for samples between 8 AM UTC and 8 PM UTC. You may need to adjust it to your timezone.

来源：https://stackoverflow.com/questions/53059856/how-to-get-the-average-over-time-only-during-the-day-in-prometheus