metrics: Implement FmtMetrics for Option

linkerd/app/core/src/metrics/mod.rs

@@ -180,15 +180,15 @@ impl Metrics {
         };
 
         let report = endpoint_report
-            .and_then(route_report)
-            .and_then(retry_report)
-            .and_then(actual_report)
-            .and_then(control_report)
-            .and_then(transport_report)
-            .and_then(opencensus_report)
-            .and_then(stack)
-            .and_then(process)
-            .and_then(build_info);
+            .and_report(route_report)
+            .and_report(retry_report)
+            .and_report(actual_report)
+            .and_report(control_report)
+            .and_report(transport_report)
+            .and_report(opencensus_report)
+            .and_report(stack)
+            .and_report(process)
+            .and_report(build_info);
 
         (metrics, report)
     }

linkerd/app/src/identity.rs

@@ -74,10 +74,10 @@ impl Identity {
         }
     }
 
-    pub fn metrics(&self) -> metrics::Report {
+    pub fn metrics(&self) -> Option<metrics::Report> {
         match self {
-            Identity::Disabled => metrics::Report::disabled(),
-            Identity::Enabled { ref local, .. } => local.metrics(),
+            Identity::Disabled => None,
+            Identity::Enabled { ref local, .. } => Some(local.metrics()),
         }
     }
 

linkerd/app/src/lib.rs

@@ -117,7 +117,7 @@ impl Config {
         let identity = info_span!("identity")
             .in_scope(|| identity.build(dns.resolver.clone(), metrics.control.clone()))?;
 
-        let report = identity.metrics().and_then(report);
+        let report = identity.metrics().and_report(report);
 
         let (drain_tx, drain_rx) = drain::channel();
 
@@ -163,8 +163,8 @@ impl Config {
             let policy = inbound_policies.clone();
             let report = inbound
                 .metrics()
-                .and_then(outbound.metrics())
-                .and_then(report);
+                .and_report(outbound.metrics())
+                .and_report(report);
             info_span!("admin").in_scope(move || {
                 admin.build(
                     bind_admin,

linkerd/metrics/src/prom.rs

@@ -12,7 +12,7 @@ pub trait FmtMetrics {
         DisplayMetrics(self)
     }
 
-    fn and_then<N>(self, next: N) -> AndThen<Self, N>
+    fn and_report<N>(self, next: N) -> AndThen<Self, N>
     where
         N: FmtMetrics,
         Self: Sized,
@@ -191,12 +191,24 @@ impl<A: FmtLabels, B: FmtLabels> FmtLabels for (Option<A>, B) {
 // ===== impl FmtMetrics =====
 
 impl<'a, A: FmtMetrics + 'a> FmtMetrics for &'a A {
+    #[inline]
     fn fmt_metrics(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
         (*self).fmt_metrics(f)
     }
 }
 
+impl<M: FmtMetrics> FmtMetrics for Option<M> {
+    #[inline]
+    fn fmt_metrics(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
+        if let Some(m) = self.as_ref() {
+            m.fmt_metrics(f)?;
+        }
+        Ok(())
+    }
+}
+
 impl<A: FmtMetrics, B: FmtMetrics> FmtMetrics for AndThen<A, B> {
+    #[inline]
     fn fmt_metrics(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
         self.0.fmt_metrics(f)?;
         self.1.fmt_metrics(f)?;

linkerd/proxy/identity/src/metrics.rs

@@ -5,7 +5,8 @@ use tokio::sync::watch;
 
 #[derive(Debug, Clone)]
 pub struct Report {
-    inner: Option<Inner>,
+    crt_key_watch: watch::Receiver<Option<CrtKey>>,
+    refreshes: Arc<Counter>,
 }
 
 metrics! {
@@ -24,32 +25,15 @@ impl Report {
         refreshes: Arc<Counter>,
     ) -> Self {
         Self {
-            inner: Some(Inner {
-                crt_key_watch,
-                refreshes,
-            }),
+            crt_key_watch,
+            refreshes,
         }
     }
-
-    pub fn disabled() -> Self {
-        Self { inner: None }
-    }
-}
-
-#[derive(Debug, Clone)]
-struct Inner {
-    crt_key_watch: watch::Receiver<Option<CrtKey>>,
-    refreshes: Arc<Counter>,
 }
 
 impl FmtMetrics for Report {
     fn fmt_metrics(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
-        let this = match self.inner.as_ref() {
-            Some(inner) => inner,
-            None => return Ok(()),
-        };
-
-        if let Some(ref crt_key) = *(this.crt_key_watch.borrow()) {
+        if let Some(ref crt_key) = *(self.crt_key_watch.borrow()) {
             let dur = crt_key
             .expiry()
             .duration_since(UNIX_EPOCH)
@@ -63,7 +47,7 @@ impl FmtMetrics for Report {
         }
 
         identity_cert_refresh_count.fmt_help(f)?;
-        identity_cert_refresh_count.fmt_metric(f, &this.refreshes)?;
+        identity_cert_refresh_count.fmt_metric(f, &self.refreshes)?;
 
         Ok(())
     }