prometheus exporter sanitizes valid metric names

[goller]

I have a metric compaction_level2_duration_ns that is sanitized into compaction_level__duration_ns. I believe this metric is a valid prometheus name..

Here is a test that shows that it fails:

    #[test]
    fn check_sanitize() {
        let name = "compaction_level2_duration_ns".to_owned();
        let actual = sanitize_metric_name(&name);
        assert_eq!(name, actual);
    }

The sanitize code is here:

metrics/metrics-exporter-prometheus/src/formatting.rs

Lines 111 to 115 in 5f720a0

	pub fn sanitize_metric_name(name: &str) -> String {
	// The first character must be [a-zA-Z_:], and all subsequent characters must be [a-zA-Z0-9_:].
	name.replacen(invalid_metric_name_start_character, "_", 1)
	.replace(invalid_metric_name_character, "_")
	}

I think it is because it replaces the first n occurrences matching the predicate, regardless of their position.

[tobz]

Yep, you're definitely right.

@gnuvince has graciously submitted a PR to fix this over in #290.