Bug report

Current behavior (here is your code):

func (f *Filter) shouldTagsPass(tags map[string]string) bool {
if f.TagPass != nil {
for _, pat := range f.TagPass {
if pat.filter == nil {
continue
}
if tagval, ok := tags[pat.Name]; ok {
if pat.filter.Match(tagval) {
return true
}
}
}
return false
}

if f.TagDrop != nil {
	for _, pat := range f.TagDrop {
		if pat.filter == nil {
			continue
		}
		if tagval, ok := tags[pat.Name]; ok {
			if pat.filter.Match(tagval) {
				return false
			}
		}
	}
	return true
}

return true

}

Desired behavior:

tagdrop: The inverse of tagpass. If a match is found the point is discarded. This is tested on points after they have passed the tagpass test.

e.g. I have:
abc, tag1=1, tag2=2 values tms
abc, tag1=1, tag2=3 values tms
abc, tag1=8, tag2=2 values tms

I want all metrics with tag1=1 and tag2!=3.

Based on your document, I could set tagpass tag1=1 and set tagdrop tag2=3. However, based on your code, it is not possible.

Use case: [Why is this important (helps with prioritizing requests)]

further filter tags after tagpass