The filter is too restrictive compared to what is allowed.

Steps to reproduce:

metric,tag=foo bar,foo bar=baz field=123 1234567890000000

Expected behavior:

metric.field;tag=foo bar;foo bar=baz 123 1234567890

Actual behavior:

metric.field;tag=foo_bar;foo_bar=baz 123 1234567890

Additional info:

https://graphite.readthedocs.io/en/latest/tags.html

Tag names must have a length >= 1 and may contain any ascii characters except ;!^=. Tag values must also have a length >= 1, they may contain any ascii characters except ; and the first character must not be ~.