What did you do?

In the PromQL React UI, gave a PromQL expression where the Y values are over a small range, then view as a graph.

To replicate: e.g. foo < 0.10 > 0.096 or foo < 0.11 > 0.096

What did you expect to see?

Each Y-axis label should be distinct, with sufficient significant digits to distinguish them. e.g.

• 0.096
• 0.097
• 0.098
• 0.099
• 0.100
• 0.101

What did you see instead? Under which circumstances?

In the following graph, the data points range from 0.0965 to 0.0999:

I believe the Y axis label positions actually correspond to 0.0960, 0.0965, 0.0970 ... 0.1000, 0.1005, but all are showing as 0.10.

With values from 0.0965 to 0.11:

In this case I believe the Y axis positions correspond to 0.096, 0.098, 0.100, 0.102, ... 0.110, 0.112; but half of them show as 0.10 and half as 0.11

(Real-world use case which triggered this: alerts set at disks having less than 10% free space, then viewing the graph of the alerting expression when the values are only just dipping below and above 10%)

Workaround

Manually add * 100 (or other scale as required) to the expression you are graphing.

Reference

Possibly relates to old issue #3084

Environment

• System information:

  Linux 4.15.0-153-generic x86_64
  

• Prometheus version:

  prometheus, version 2.28.1 (branch: HEAD, revision: b0944590a1c9a6b35dc5a696869f75f422b107a1)
    build user:       root@2915dd495090
    build date:       20210701-15:20:10
    go version:       go1.16.5
    platform:         linux/amd64
  

• Alertmanager version:

  n/a

• Prometheus configuration file:

  n/a

• Alertmanager configuration file:

  n/a

• Logs:

  n/a