Prometheus topk and sort_desc provides additional metrics

[HammaBamma]

I'm submitting a : Bug Report
Grafana Version: 3.1.1
DataSource: Prometheus (v. 1.3.1)
OS: Ubuntu 16.04 LTS
Query: sort_desc(topk(5, bsnAPIfNoOfUsers))
Expected Result: Top 5 Access Points by Stations Associated, Sorted from Top to Bottom
Result: Pie Chart visualizes anywhere from 5 - 13 Access Points in the list, Table Lists All APs

Query Returns Valid results in Prometheus.

Result in Grafana Pie Chart:

[torkelo]

can you open chrome dev tools network tab & show the request to prometheus and it's response?

[HammaBamma]

It does appear to be getting additional response data from Prometheus. I've reached out to contact them to figure out why. It's also not sorting the data correctly in their delivery either. When I set the time interval to 1 Second it returns with only 5 responses. Still not sorted though. Thanks again for this amazing product. Visualizing our meeting data in all sorts of new ways.

[ryanwalls]

@HammaBamma Did you ever hear back?

[antonagestam]

I think the problem here is that topk supplies the top elements for every timepoint in the series.

For example, at t0, ap4003 might have the highest value and would be picked up by topk(1, ...) at t1 it might be surpassed by ap4006 and then topk1 would now pick up both of them.

Not sure if I'm explaining it well, but to formulate it in a different way: topk gives you the access points that has been within the top 5 at any point within the time series. And since the top 5 changes over time, there can be more than 5 values.

[ptone]

For those running into this and finding this, for me this was resolved by checking the "Instant" checkbox in the metric query row

[evalizhangli]

For those running into this and finding this, for me this was resolved by checking the "Instant" checkbox in the metric query row

Hi. Prestone.
I use the topk(5, my_metrics) and get the sort list by value. but the parallel data is truncated.
For example. I have value sort 10,9,8,7,6,6,6,5......， the result only shows 10,9,8,7,6.
but 10.9.8.7.6.6.6 was expected.
so , depends on this situation. how to deal with it?
If you have any idea about this, look forward you reply~