Reduce dashboard CPU: cache DB, suppress logs, add systemd service

- Suppress Flask request logs (werkzeug ERROR only)
- Cache SQLite connection with WAL + 8MB cache
- Increase poll_ms 500->1000, history refresh 30s->60s
- Show 'waiting for pipeline...' when /dev/shm empty
- Add chicken-dashboard.service for systemd auto-start

dashboard.py

@@ -9,20 +9,43 @@ from __future__ import annotations
 
 import argparse
 import json
+import logging
 import sqlite3
+import threading
 from pathlib import Path
 
 from flask import Flask, Response, jsonify, render_template, send_file
 
+# Suppress Flask request logs
+log = logging.getLogger("werkzeug")
+log.setLevel(logging.ERROR)
+
 DEFAULT_SHM_DIR = "/dev/shm"
 DEFAULT_PORT = 8080
 
 app = Flask(__name__)
 app.config["shm_dir"] = DEFAULT_SHM_DIR
-app.config["poll_ms"] = 500
+app.config["poll_ms"] = 1000
 app.config["run_date"] = ""
 app.config["db_path"] = ""
 
+_db_conn = None
+_db_lock = threading.Lock()
+
+
+def _get_db():
+    global _db_conn
+    db = app.config["db_path"]
+    if not db or not Path(db).exists():
+        return None
+    with _db_lock:
+        if _db_conn is None:
+            _db_conn = sqlite3.connect(db, check_same_thread=False)
+            _db_conn.row_factory = sqlite3.Row
+            _db_conn.execute("PRAGMA journal_mode=WAL")
+            _db_conn.execute("PRAGMA cache_size=-8000")
+        return _db_conn
+
 
 def _discover_cameras():
     shm = Path(app.config["shm_dir"])
@@ -88,7 +111,6 @@ def db_summary():
                ROUND(SUM(elapsed_seconds)/3600.0, 1) AS total_hours
         FROM batch_runs
     """).fetchone()
-    conn.close()
     return jsonify(dict(row))
 
 
@@ -107,7 +129,6 @@ def db_history():
         ORDER BY date DESC, location
         LIMIT 50
     """).fetchall()
-    conn.close()
     return jsonify([dict(r) for r in rows])
 
 
@@ -125,7 +146,6 @@ def db_date(date):
     total = conn.execute(
         "SELECT SUM(total_entered) AS total, ROUND(SUM(elapsed_seconds)/60.0,1) AS minutes "
         "FROM batch_runs WHERE date=?", (date,)).fetchone()
-    conn.close()
     return jsonify({"date": date, "total": dict(total), "cameras": [dict(r) for r in cameras]})
 
 
@@ -139,7 +159,6 @@ def db_camera(camera_id):
                ROUND(elapsed_seconds,1) AS elapsed_seconds, stopped_reason
         FROM batch_runs WHERE camera_id=? ORDER BY date DESC LIMIT 50
     """, (camera_id,)).fetchall()
-    conn.close()
     return jsonify([dict(r) for r in rows])
 
 
@@ -159,7 +178,6 @@ def db_location(location):
                ROUND(SUM(elapsed_seconds)/3600.0,1) AS hours
         FROM batch_runs WHERE location=?
     """, (location,)).fetchone()
-    conn.close()
     return jsonify({"location": location, "summary": dict(summary), "history": [dict(r) for r in history]})