how can I visualize a histogram with promdash or grafana

Question

I'm attracted to prometheus by the histogram (and summaries) time-series, but I've been unsuccessful to display a histogram in either promdash or grafana. What I expect is to be able to show:

• a histogram at a point in time, e.g. the buckets on the X axis and the count for the bucket on the Y axis and a column for each bucket
• a stacked graph of the buckets such that each bucket is shaded and the total of the stack equals the inf bucket

A sample metric would be the response time of an HTTP server.

Answer 1

Grafana v5+ provides direct support for representing Prometheus histograms as heatmap. http://docs.grafana.org/features/panels/heatmap/#histograms-and-buckets

Heatmaps are preferred over histogram because a histogram does not show you how the trend changes over time. So if you have a time-series histogram, then use the heatmap panel to picture it.

To get you started, here is an example (for Prometheus data):

Suppose you've a histogram as follows,

http_request_duration_seconds_bucket(le=0.2) 1,
http_request_duration_seconds_bucket(le=0.5) 2,
http_request_duration_seconds_bucket(le=1.0) 2,
http_request_duration_seconds_bucket(le=+inf) 5
http_request_duration_seconds_count 5
http_request_duration_seconds_sum 3.07

You can picture this histogram data as a heatmap by using the query:

Answer 2

The Answer from @brian-brazil above works almost, with some additional, not mentioned things, to be done.

You can do a standard non-stacked graph of the rate a histogram, and as Prometheus histograms are cumulative you'll get the result you're looking for.

1. The x-axis in Grafana needs to be in mode series
2. You need to aggregate the results by the le label, if you use additional distinct labels for the series

After that you'll get a beautiful histogram. The only thing that grinds my gears is that the x-axis sort order of grafana is natural string sorting. So the x axis starts with +Inf, then 0.1,0.2, .. 1,1.5,10,2,...

PS: In grafana 5.1 there will be working heatmap with prometheus datasource out-of-box. There was an issue for native support for heatmap visualization, which is also appropriate (if you want to see tendency/history) for visualizing histograms over time.

Answer 3

I don't believe that Grafana supports a barchart for a histogram.

You can do a standard non-stacked graph of the rate a histogram, and as Prometheus histograms are cumulative you'll get the result you're looking for.