Counter HELP and TYPE lack _total suffix

[link2xt]

When encoding counters, prometheus-client adds _total suffix to sample name:

client_rust/src/encoding/text.rs

Line 187 in b462e61

self.write_suffix("total")?;

This suffix is however not added in HELP and TYPE lines. This is visible in tests, for example:

client_rust/src/encoding/text.rs

Lines 20 to 23 in b462e61

	//! let expected = "# HELP my_counter This is my counter.\n".to_owned() +
	//! "# TYPE my_counter counter\n" +
	//! "my_counter_total 1\n" +
	//! "# EOF\n";

HELP and TYPE lines should have the same suffix, it is shown in example at https://prometheus.io/docs/instrumenting/exposition_formats/#text-format-example:

# HELP http_requests_total The total number of HTTP requests.
# TYPE http_requests_total counter
http_requests_total{method="post",code="200"} 1027 1395066363000
http_requests_total{method="post",code="400"}    3 1395066363000

Because of this bug Grafana does not display help for counters. At the same time for gauge type metrics help is displayed.

[mxinden]

This is inline with the OpenMetrics specification:

https://github.com/OpenObservability/OpenMetrics/blob/main/specification/OpenMetrics.md#counter-1

When exporting, are you setting the correct content type?

client_rust/examples/hyper.rs

Lines 69 to 70 in b462e61

	hyper::header::CONTENT_TYPE,
	"application/openmetrics-text; version=1.0.0; charset=utf-8",

[mxinden]

I don't feel strongly about following the specification. That said, I want to be either (a) consistent with the specification or (b) consistent with the other client implementations and ideally (a) and (b).

[link2xt]

I set content type here:
https://github.com/deltachat/notifiers/blob/6ef14e3b891c878f0bfd990f8436aeb3ba9f60eb/src/metrics.rs#L87-L90

Go library seems to include _total into HELP and TYPE:
https://github.com/prometheus/client_golang/blob/d038ab96c0c7b9cd217a39072febd610bcdf1fd8/prometheus/promhttp/http_test.go#L141-L144

OpenMetrics is indeed different from Prometheus documentation and what Go library does :/

I found that incompatibilities are documented here:
https://github.com/prometheus/client_java/blob/058b39959dff82ef5fcb126834d5c392cc64df37/docs/content/otel/names.md
And here:
https://opentelemetry.io/docs/specs/otel/compatibility/prometheus_and_openmetrics/

So currently Rust client library follows OpenMetrics specification and this is different from what Prometheus expects.

[link2xt]

OpenMetrics support is also on roadmap: https://prometheus.io/docs/introduction/roadmap/#adopt-openmetrics

I will try updating Prometheus to the latest version and file a Prometheus bug then.

[link2xt]

I have filed Prometheus bug: prometheus/prometheus#13944