solti-prometheus 0.0.2

Solti SDK Prometheus metrics.
Documentation 
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//! Private helpers for building and registering Prometheus metrics.
//!
//! All solti collectors share the `solti_<subsystem>_<name>` naming scheme and the same "build → register clone" boilerplate.
//! [`Sub`] binds a [`Registry`] and a subsystem name together so constructors collapse to one line per metric.

use prometheus::{
    Counter, CounterVec, Gauge, GaugeVec, Histogram, HistogramOpts, HistogramVec, Opts, Registry,
};

/// Scoped registrar bound to a `solti` subsystem (e.g. `runner`, `sv`, `api`).
pub(crate) struct Sub<'a> {
    registry: &'a Registry,
    subsystem: &'static str,
}

impl<'a> Sub<'a> {
    pub(crate) fn new(registry: &'a Registry, subsystem: &'static str) -> Self {
        Self {
            registry,
            subsystem,
        }
    }

    fn opts(&self, name: &str, help: &str) -> Opts {
        Opts::new(name, help)
            .namespace("solti")
            .subsystem(self.subsystem)
    }

    fn hist_opts(&self, name: &str, help: &str, buckets: Vec<f64>) -> HistogramOpts {
        HistogramOpts::new(name, help)
            .namespace("solti")
            .subsystem(self.subsystem)
            .buckets(buckets)
    }

    pub(crate) fn counter(&self, name: &str, help: &str) -> Result<Counter, prometheus::Error> {
        let c = Counter::with_opts(self.opts(name, help))?;
        self.registry.register(Box::new(c.clone()))?;
        Ok(c)
    }

    pub(crate) fn counter_vec(
        &self,
        name: &str,
        help: &str,
        labels: &[&str],
    ) -> Result<CounterVec, prometheus::Error> {
        let c = CounterVec::new(self.opts(name, help), labels)?;
        self.registry.register(Box::new(c.clone()))?;
        Ok(c)
    }

    pub(crate) fn gauge(&self, name: &str, help: &str) -> Result<Gauge, prometheus::Error> {
        let g = Gauge::with_opts(self.opts(name, help))?;
        self.registry.register(Box::new(g.clone()))?;
        Ok(g)
    }

    pub(crate) fn gauge_vec(
        &self,
        name: &str,
        help: &str,
        labels: &[&str],
    ) -> Result<GaugeVec, prometheus::Error> {
        let g = GaugeVec::new(self.opts(name, help), labels)?;
        self.registry.register(Box::new(g.clone()))?;
        Ok(g)
    }

    pub(crate) fn histogram(
        &self,
        name: &str,
        help: &str,
        buckets: Vec<f64>,
    ) -> Result<Histogram, prometheus::Error> {
        let h = Histogram::with_opts(self.hist_opts(name, help, buckets))?;
        self.registry.register(Box::new(h.clone()))?;
        Ok(h)
    }

    /// Build a [`GaugeVec`] **without** registering it into a registry.
    ///
    /// Used by composite collectors that expose a `GaugeVec` via [`prometheus::core::Collector::collect`];
    /// the collector itself is registered by the caller, so the inner metric must not be registered twice.
    #[inline]
    pub(crate) fn gauge_vec_unregistered(
        subsystem: &'static str,
        name: &str,
        help: &str,
        labels: &[&str],
    ) -> Result<GaugeVec, prometheus::Error> {
        let opts = Opts::new(name, help)
            .namespace("solti")
            .subsystem(subsystem);
        GaugeVec::new(opts, labels)
    }

    pub(crate) fn histogram_vec(
        &self,
        name: &str,
        help: &str,
        buckets: Vec<f64>,
        labels: &[&str],
    ) -> Result<HistogramVec, prometheus::Error> {
        let h = HistogramVec::new(self.hist_opts(name, help, buckets), labels)?;
        self.registry.register(Box::new(h.clone()))?;
        Ok(h)
    }
}

/// Convert milliseconds to seconds for histogram observation.
#[inline]
pub(crate) fn ms_to_secs(ms: u64) -> f64 {
    ms as f64 / 1000.0
}