refactor: move gather_default_metrics to metrics crate

Author: MegaRedHand

Cargo.lock

@@ -7,3 +7,4 @@ license.workspace = true
 
 [dependencies]
 prometheus.workspace = true
+thiserror.workspace = true

crates/common/metrics/Cargo.toml

@@ -1,6 +1,7 @@
 //! Metrics utilities and prometheus re-exports for ethlambda.
 
-use std::time::Instant;
+pub mod gather;
+pub mod timing;
 
 // Re-export prometheus types and macros we use
 pub use prometheus::{
@@ -9,23 +10,6 @@ pub use prometheus::{
     register_int_gauge, register_int_gauge_vec,
 };
 
-/// A guard that records elapsed time to a histogram when dropped.
-pub struct TimingGuard {
-    histogram: &'static Histogram,
-    start: Instant,
-}
-
-impl TimingGuard {
-    pub fn new(histogram: &'static Histogram) -> Self {
-        Self {
-            histogram,
-            start: Instant::now(),
-        }
-    }
-}
-
-impl Drop for TimingGuard {
-    fn drop(&mut self) {
-        self.histogram.observe(self.start.elapsed().as_secs_f64());
-    }
-}
+// Re-export commonly used items
+pub use gather::{GatherError, gather_default_metrics};
+pub use timing::TimingGuard;

crates/common/metrics/src/lib.rs

@@ -13,5 +13,4 @@ version.workspace = true
 axum = "0.8.1"
 tokio.workspace = true
 ethlambda-metrics.workspace = true
-thiserror.workspace = true
 tracing.workspace = true

crates/net/rpc/Cargo.toml

@@ -1,8 +1,7 @@
 use std::net::SocketAddr;
 
 use axum::{Router, http::HeaderValue, response::IntoResponse, routing::get};
-use ethlambda_metrics::*;
-use thiserror::Error;
+use ethlambda_metrics::gather_default_metrics;
 use tracing::warn;
 
 pub async fn start_prometheus_metrics_api(address: SocketAddr) -> Result<(), std::io::Error> {
@@ -32,27 +31,3 @@ pub(crate) async fn get_metrics() -> impl IntoResponse {
     response.headers_mut().insert("content-type", content_type);
     response
 }
-
-#[derive(Debug, Error)]
-pub enum Error {
-    #[error("Prometheus error: {0}")]
-    Prometheus(#[from] PrometheusError),
-    #[error("UTF-8 conversion error: {0}")]
-    FromUtf8(#[from] std::string::FromUtf8Error),
-}
-
-/// Returns all metrics currently registered in Prometheus' default registry.
-///
-/// Both profiling and RPC metrics register with this default registry, and the
-/// metrics API surfaces them by calling this helper.
-pub fn gather_default_metrics() -> Result<String, Error> {
-    let encoder = TextEncoder::new();
-    let metric_families = gather();
-
-    let mut buffer = Vec::new();
-    encoder.encode(&metric_families, &mut buffer)?;
-
-    let res = String::from_utf8(buffer)?;
-
-    Ok(res)
-}