How can I visualize a histogram with Promdash or Grafana?
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
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: sum(increase(http_request_duration_seconds_bucket[10m])) by (le), making sure to set the format as "heatmap," the legend format as {{ le }}, and setting the visualization in the panel settings to "heatmap."
