feat(monitoring): wire real CPU/memory/disk metrics via sysinfo

Replace hardcoded 0.0 system metrics with live values from sysinfo
crate (already in dependencies). Uses Arc<RwLock<System>> for thread-
safe refreshing. Network I/O left at 0.0 (requires sustained sampling).

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

services/trading_service/src/services/monitoring.rs

@@ -12,7 +12,9 @@ use crate::proto::monitoring::{
     SystemStatusEvent, ThroughputMetric,
 };
 use crate::state::{HealthStatus, TradingServiceState};
+use std::sync::Arc;
 use std::time::Instant;
+use tokio::sync::RwLock;
 use tonic::{Request, Response, Status};
 
 /// Monitoring service implementation
@@ -21,18 +23,92 @@ pub struct MonitoringServiceImpl {
     state: TradingServiceState,
     /// Tracks when this service instance was started for real uptime reporting
     started_at: Instant,
+    /// System info handle for CPU/memory metrics (refreshed on each status query)
+    sys: Arc<RwLock<sysinfo::System>>,
+    /// Disk info handle (refreshed on each status query)
+    disks: Arc<RwLock<sysinfo::Disks>>,
 }
 
 impl MonitoringServiceImpl {
     /// Create new monitoring service
     pub fn new(state: TradingServiceState) -> Self {
+        // Construct with initial refresh so the first CPU reading has a baseline.
+        let mut sys = sysinfo::System::new();
+        sys.refresh_cpu_all();
+        sys.refresh_memory();
+
         Self {
             state,
             started_at: Instant::now(),
+            sys: Arc::new(RwLock::new(sys)),
+            disks: Arc::new(RwLock::new(sysinfo::Disks::new_with_refreshed_list())),
         }
     }
 }
 
+/// Collected system-level metrics (CPU, memory, disk).
+struct LiveSystemMetrics {
+    cpu_usage_percent: f64,
+    memory_usage_percent: f64,
+    disk_usage_percent: f64,
+    /// Network I/O requires sustained measurement; always 0.0 for now.
+    network_io_mbps: f64,
+}
+
+/// Collect real system metrics from sysinfo handles.
+///
+/// CPU usage is computed as the global average across all cores since the last
+/// refresh. Memory and disk are point-in-time snapshots.  The function is
+/// non-blocking apart from acquiring the `RwLock`.
+async fn collect_system_metrics(
+    sys: &Arc<RwLock<sysinfo::System>>,
+    disks: &Arc<RwLock<sysinfo::Disks>>,
+) -> LiveSystemMetrics {
+    // --- CPU + Memory --------------------------------------------------
+    let (cpu_usage, mem_pct) = {
+        let mut s = sys.write().await;
+        // Refresh CPU counters (delta since last refresh).
+        s.refresh_cpu_all();
+        s.refresh_memory();
+
+        let cpu = s.global_cpu_usage() as f64; // 0-100 across all cores
+
+        let total = s.total_memory();
+        let used = s.used_memory();
+        let mem = if total > 0 {
+            (used as f64 / total as f64) * 100.0
+        } else {
+            0.0
+        };
+        (cpu, mem)
+    };
+
+    // --- Disk ----------------------------------------------------------
+    let disk_pct = {
+        let mut d = disks.write().await;
+        d.refresh(true);
+
+        let (total_space, available_space) =
+            d.iter().fold((0u64, 0u64), |(ts, avail), disk| {
+                (ts + disk.total_space(), avail + disk.available_space())
+            });
+        if total_space > 0 {
+            let used_space = total_space.saturating_sub(available_space);
+            (used_space as f64 / total_space as f64) * 100.0
+        } else {
+            0.0
+        }
+    };
+
+    LiveSystemMetrics {
+        cpu_usage_percent: cpu_usage,
+        memory_usage_percent: mem_pct,
+        disk_usage_percent: disk_pct,
+        // Network I/O measurement requires sustained sampling; leave as 0.0.
+        network_io_mbps: 0.0,
+    }
+}
+
 #[tonic::async_trait]
 impl MonitoringService for MonitoringServiceImpl {
     async fn get_health_check(
@@ -152,6 +228,9 @@ impl MonitoringService for MonitoringServiceImpl {
             }
         }
 
+        // Collect real system metrics (CPU, memory, disk) from sysinfo.
+        let live = collect_system_metrics(&self.sys, &self.disks).await;
+
         let system_status = SystemStatus {
             overall_health: overall_health as i32,
             healthy_services: 3,
@@ -159,10 +238,10 @@ impl MonitoringService for MonitoringServiceImpl {
             critical_issues,
             system_uptime_seconds: uptime_seconds,
             system_metrics: Some(SystemMetrics {
-                cpu_usage_percent: 0.0,    // TODO: wire to sysinfo crate
-                memory_usage_percent: 0.0, // TODO: wire to sysinfo crate
-                disk_usage_percent: 0.0,   // TODO: wire to sysinfo crate
-                network_io_mbps: 0.0,      // TODO: wire to sysinfo crate
+                cpu_usage_percent: live.cpu_usage_percent,
+                memory_usage_percent: live.memory_usage_percent,
+                disk_usage_percent: live.disk_usage_percent,
+                network_io_mbps: live.network_io_mbps,
                 active_connections: 25,
                 total_requests: 1000,
                 avg_response_time_ms: 2.5,