Decomposing hot-path modules into focused submodules

Signed-off-by: Alexey <247128645+axkurcom@users.noreply.github.com>

src/proxy/relay/io/counters.rs

@@ -0,0 +1,51 @@
+use std::sync::atomic::{AtomicU64, Ordering};
+use std::time::Duration;
+
+use tokio::time::Instant;
+
+// ============= SharedCounters =============
+
+/// Atomic counters shared between the relay (via StatsIo) and the watchdog task.
+///
+/// Using `Relaxed` ordering is sufficient because:
+/// - Counters are monotonically increasing (no ABA problem)
+/// - Slight staleness in watchdog reads is harmless (±10s check interval anyway)
+/// - No ordering dependencies between different counters
+pub(in crate::proxy::relay) struct SharedCounters {
+    /// Bytes read from client (C→S direction)
+    pub(in crate::proxy::relay) c2s_bytes: AtomicU64,
+    /// Bytes written to client (S→C direction)
+    pub(in crate::proxy::relay) s2c_bytes: AtomicU64,
+    /// Number of poll_read completions (≈ C→S chunks)
+    pub(in crate::proxy::relay) c2s_ops: AtomicU64,
+    /// Number of poll_write completions (≈ S→C chunks)
+    pub(in crate::proxy::relay) s2c_ops: AtomicU64,
+    /// Milliseconds since relay epoch of last I/O activity
+    last_activity_ms: AtomicU64,
+}
+
+impl SharedCounters {
+    pub(in crate::proxy::relay) fn new() -> Self {
+        Self {
+            c2s_bytes: AtomicU64::new(0),
+            s2c_bytes: AtomicU64::new(0),
+            c2s_ops: AtomicU64::new(0),
+            s2c_ops: AtomicU64::new(0),
+            last_activity_ms: AtomicU64::new(0),
+        }
+    }
+
+    /// Record activity at this instant.
+    #[inline]
+    pub(in crate::proxy::relay) fn touch(&self, now: Instant, epoch: Instant) {
+        let ms = now.duration_since(epoch).as_millis() as u64;
+        self.last_activity_ms.store(ms, Ordering::Relaxed);
+    }
+
+    /// How long since last recorded activity.
+    pub(in crate::proxy::relay) fn idle_duration(&self, now: Instant, epoch: Instant) -> Duration {
+        let last_ms = self.last_activity_ms.load(Ordering::Relaxed);
+        let now_ms = now.duration_since(epoch).as_millis() as u64;
+        Duration::from_millis(now_ms.saturating_sub(last_ms))
+    }
+}