1 files changed, 121 insertions, 0 deletions
diff --git a/src/metrics.rs b/src/metrics.rs
new file mode 100644
index 0000000..67ec30f
--- /dev/null
+++ b/src/metrics.rs
@@ -0,0 +1,121 @@
+//! Node metrics and observability.
+//!
+//! Atomic counters for messages, lookups, storage,
+//! and errors. Accessible via `Tessera::metrics()`.
+
+use std::sync::atomic::{AtomicU64, Ordering};
+
+/// Atomic metrics counters.
+pub struct Metrics {
+    pub messages_sent: AtomicU64,
+    pub messages_received: AtomicU64,
+    pub lookups_started: AtomicU64,
+    pub lookups_completed: AtomicU64,
+    pub rpc_timeouts: AtomicU64,
+    pub values_stored: AtomicU64,
+    pub packets_rejected: AtomicU64,
+    pub bytes_sent: AtomicU64,
+    pub bytes_received: AtomicU64,
+}
+
+impl Metrics {
+    pub fn new() -> Self {
+        Self {
+            messages_sent: AtomicU64::new(0),
+            messages_received: AtomicU64::new(0),
+            lookups_started: AtomicU64::new(0),
+            lookups_completed: AtomicU64::new(0),
+            rpc_timeouts: AtomicU64::new(0),
+            values_stored: AtomicU64::new(0),
+            packets_rejected: AtomicU64::new(0),
+            bytes_sent: AtomicU64::new(0),
+            bytes_received: AtomicU64::new(0),
+        }
+    }
+
+    /// Take a snapshot of all counters.
+    pub fn snapshot(&self) -> MetricsSnapshot {
+        MetricsSnapshot {
+            messages_sent: self.messages_sent.load(Ordering::Relaxed),
+            messages_received: self.messages_received.load(Ordering::Relaxed),
+            lookups_started: self.lookups_started.load(Ordering::Relaxed),
+            lookups_completed: self.lookups_completed.load(Ordering::Relaxed),
+            rpc_timeouts: self.rpc_timeouts.load(Ordering::Relaxed),
+            values_stored: self.values_stored.load(Ordering::Relaxed),
+            packets_rejected: self.packets_rejected.load(Ordering::Relaxed),
+            bytes_sent: self.bytes_sent.load(Ordering::Relaxed),
+            bytes_received: self.bytes_received.load(Ordering::Relaxed),
+        }
+    }
+}
+
+impl Default for Metrics {
+    fn default() -> Self {
+        Self::new()
+    }
+}
+
+/// Snapshot of metrics at a point in time.
+#[derive(Debug, Clone)]
+pub struct MetricsSnapshot {
+    pub messages_sent: u64,
+    pub messages_received: u64,
+    pub lookups_started: u64,
+    pub lookups_completed: u64,
+    pub rpc_timeouts: u64,
+    pub values_stored: u64,
+    pub packets_rejected: u64,
+    pub bytes_sent: u64,
+    pub bytes_received: u64,
+}
+
+impl std::fmt::Display for MetricsSnapshot {
+    fn fmt(&self, f: &mut std::fmt::Formatter<'_>) -> std::fmt::Result {
+        write!(
+            f,
+            "sent={} recv={} lookups={}/{} timeouts={} \
+             stored={} rejected={} bytes={}/{}",
+            self.messages_sent,
+            self.messages_received,
+            self.lookups_completed,
+            self.lookups_started,
+            self.rpc_timeouts,
+            self.values_stored,
+            self.packets_rejected,
+            self.bytes_sent,
+            self.bytes_received,
+        )
+    }
+}
+
+#[cfg(test)]
+mod tests {
+    use super::*;
+
+    #[test]
+    fn counters_start_zero() {
+        let m = Metrics::new();
+        let s = m.snapshot();
+        assert_eq!(s.messages_sent, 0);
+        assert_eq!(s.bytes_sent, 0);
+    }
+
+    #[test]
+    fn increment_and_snapshot() {
+        let m = Metrics::new();
+        m.messages_sent.fetch_add(5, Ordering::Relaxed);
+        m.bytes_sent.fetch_add(1000, Ordering::Relaxed);
+        let s = m.snapshot();
+        assert_eq!(s.messages_sent, 5);
+        assert_eq!(s.bytes_sent, 1000);
+    }
+
+    #[test]
+    fn display_format() {
+        let m = Metrics::new();
+        m.messages_sent.fetch_add(10, Ordering::Relaxed);
+        let s = m.snapshot();
+        let text = format!("{s}");
+        assert!(text.contains("sent=10"));
+    }
+}