Method metrics

core/station/impl/src/controllers/http.rs:39–61

(&self, request: HttpRequest)

    }

    async fn metrics(&self, request: HttpRequest) -> HttpResponse {
        if request.method.to_lowercase() != "get" {
            return HttpResponse {
                status_code: 405,
                headers: vec![HeaderField("Allow".into(), "GET".into())],
                body: "405 Method Not Allowed".as_bytes().to_owned(),
            };
        }

        // Add dynamic metrics, dropped after the request since query calls don't save state changes.
        with_metrics_registry(SERVICE_NAME, |registry| {
            registry
                .gauge_mut(
                    "canister_cycles_balance",
                    "cycles balance available to the canister",
                )
                .set(canister_balance() as f64);
        });

        with_metrics_registry(SERVICE_NAME, |registry| {
            registry.export_metrics_as_http_response()
        })
    }
}