Initial commit: Sentry-Emote system monitor

- Aggregator: Flask-based event broker with priority queue
- Frontend: OLED-optimized UI with animations
- Detectors: disk, cpu, memory, service, network
- Unified entry point (sentry.py) with process management
- Heartbeat TTL system for auto-clearing stale events

Co-Authored-By: Claude Opus 4.5 <noreply@anthropic.com>

detectors/cpu.py

@@ -0,0 +1,83 @@
+"""
+CPU Usage Detector
+Monitors CPU usage and reports to the aggregator when thresholds are exceeded.
+
+Environment variables:
+    AGGREGATOR_URL      - URL of the aggregator (default: http://localhost:5000)
+    CHECK_INTERVAL      - Seconds between checks (default: 30)
+    THRESHOLD_CRITICAL  - Percent usage for critical alert (default: 95)
+    THRESHOLD_WARNING   - Percent usage for warning alert (default: 85)
+"""
+
+import os
+import time
+import psutil
+import requests
+
+# Configuration from environment
+AGGREGATOR_URL = os.environ.get("AGGREGATOR_URL", "http://localhost:5000")
+CHECK_INTERVAL = int(os.environ.get("CHECK_INTERVAL", 30))
+THRESHOLD_CRITICAL = int(os.environ.get("THRESHOLD_CRITICAL", 95))
+THRESHOLD_WARNING = int(os.environ.get("THRESHOLD_WARNING", 85))
+
+EVENT_ID = "cpu_usage"
+
+
+def send_event(priority, message):
+    """Send an event to the aggregator with heartbeat TTL."""
+    ttl = CHECK_INTERVAL * 2
+    try:
+        response = requests.post(
+            f"{AGGREGATOR_URL}/event",
+            json={"id": EVENT_ID, "priority": priority, "message": message, "ttl": ttl},
+            timeout=5
+        )
+        print(f"[EVENT] {message} (priority {priority}, ttl {ttl}s) -> {response.status_code}")
+    except requests.RequestException as e:
+        print(f"[ERROR] Failed to send event: {e}")
+
+
+def clear_event():
+    """Clear the event from the aggregator."""
+    try:
+        response = requests.post(
+            f"{AGGREGATOR_URL}/clear",
+            json={"id": EVENT_ID},
+            timeout=5
+        )
+        if response.status_code == 200:
+            print(f"[CLEAR] {EVENT_ID}")
+    except requests.RequestException as e:
+        print(f"[ERROR] Failed to clear event: {e}")
+
+
+def main():
+    print(f"CPU Usage Detector started")
+    print(f"  Aggregator: {AGGREGATOR_URL}")
+    print(f"  Interval: {CHECK_INTERVAL}s")
+    print(f"  Thresholds: Warning={THRESHOLD_WARNING}%, Critical={THRESHOLD_CRITICAL}%")
+    print()
+
+    alert_active = False
+
+    while True:
+        # Get CPU usage over a 1-second sample
+        cpu_percent = psutil.cpu_percent(interval=1)
+
+        if cpu_percent >= THRESHOLD_CRITICAL:
+            send_event(1, f"CPU at {cpu_percent:.0f}%")
+            alert_active = True
+        elif cpu_percent >= THRESHOLD_WARNING:
+            send_event(2, f"CPU at {cpu_percent:.0f}%")
+            alert_active = True
+        else:
+            print(f"[OK] CPU: {cpu_percent:.0f}%")
+            if alert_active:
+                clear_event()
+                alert_active = False
+
+        time.sleep(CHECK_INTERVAL - 1)  # Account for 1s sample time
+
+
+if __name__ == "__main__":
+    main()