feat: use histogram in place of Gauge for signer (#349)

Author: greged93

crates/signer/src/lib.rs

@@ -88,7 +88,7 @@ impl Signer {
                             let future = Box::pin(async move {
                                 let now = Instant::now();
                                 let res = sign_block(block, signer).await;
-                                metric.signing_duration.set(now.elapsed().as_secs_f64());
+                                metric.signing_duration.record(now.elapsed().as_secs_f64());
                                 res
                             });
                             self.in_progress.push_back(future);

crates/signer/src/metrics.rs

@@ -1,10 +1,10 @@
-use metrics::Gauge;
+use metrics::Histogram;
 use metrics_derive::Metrics;
 
 /// The metrics for the [`super::Signer`].
 #[derive(Metrics, Clone)]
 #[metrics(scope = "signer")]
 pub struct SignerMetrics {
     /// The signing duration.
-    pub signing_duration: Gauge,
+    pub signing_duration: Histogram,
 }