Disallow invalid label names on targets

[benley]

It looks like Prometheus will let you apply invalid labels to targets that come from file_sd targets at the very least; probably other types as well.

e.g.

[{
  "targets": ["1.2.3.4:9100"],
  "labels": {
    "some_valid_label": "asdfasdfasdf",
    "oops:this-label-is-invalid": "asdfasdfasdf"
  }
}]

The "oops:this-label-is-invalid" label will show up on the status page under base labels, but there doesn't seem to be any way to query for it. The client_golang library restricts labels to [A-Za-z0-9_], but I don't see the same happening inside prometheus.

[fabxc]

Thanks for reporting this.

Validation of label names goes via the client_golang library. The UnmarshalYAML method of the LabelName type checks the regex during unmarshaling. The respective UnmarshalJSON method that does the same was missing, thus you were able to provide wrong labelnames via JSON target groups.

As file SD is the only input of JSON target groups, this does not affect other areas.

So basically it's a bug in client_golang.
See #778, #132

[lock]

This thread has been automatically locked since there has not been any recent activity after it was closed. Please open a new issue for related bugs.