Jun 29 - Implement auto reminder 45 min before user's shift end if not finish checking websites

app.py

@@ -17,6 +17,46 @@ logging.basicConfig(
 logger = logging.getLogger("app")
 
 
+def _run_reminder_job():
+    """Background job: send shift-incomplete reminders if within the reminder window."""
+    from routes.admin_shifts import do_send_incomplete_reminders
+    try:
+        result = do_send_incomplete_reminders(triggered_by_user_id=None)
+        if result["sent"] > 0:
+            logger.info(f"[scheduler] Shift reminders sent: {result}")
+    except Exception as e:
+        logger.error(f"[scheduler] Shift reminder job error: {e}")
+
+
+def _start_scheduler():
+    """
+    Start a background scheduler that fires shift-incomplete reminder emails
+    every 5 minutes. Guards against double-start in Flask's debug reloader.
+    Uses daemon threads so the process exits cleanly even if the scheduler is running.
+    """
+    if os.environ.get("WERKZEUG_RUN_MAIN") == "false":
+        # Flask reloader: skip in the parent monitor process; the child sets WERKZEUG_RUN_MAIN=true
+        return
+    try:
+        from apscheduler.schedulers.background import BackgroundScheduler
+        import atexit
+
+        scheduler = BackgroundScheduler(daemon=True)
+        scheduler.add_job(
+            func=_run_reminder_job,
+            trigger="interval",
+            minutes=5,
+            id="shift_incomplete_reminders",
+            max_instances=1,
+            misfire_grace_time=120,
+        )
+        scheduler.start()
+        atexit.register(lambda: scheduler.shutdown(wait=False))
+        logger.info("[scheduler] Background scheduler started — shift reminders every 5 min.")
+    except Exception as e:
+        logger.error(f"[scheduler] Failed to start background scheduler: {e}")
+
+
 def create_app():
     app = Flask(__name__)
 
@@ -73,10 +113,12 @@ def create_app():
 
     if not os.environ.get("CRON_SECRET"):
         logger.warning(
-            "CRON_SECRET not set in .env — the /internal/cron/* endpoints are "
-            "disabled. Set CRON_SECRET to enable automated shift reminders."
+            "CRON_SECRET not set in .env — the /internal/cron/* endpoints are disabled."
         )
 
+    # ── Background scheduler: automatic shift-incomplete reminders ────────────
+    _start_scheduler()
+
     # ── CSRF protection (Flask-WTF) ────────────────────────────────────────────
     from flask_wtf.csrf import CSRFProtect
     CSRFProtect(app)

models.py

@@ -1771,8 +1771,11 @@ def get_incomplete_shift_users_near_end(window_minutes: int = 40) -> list:
             conn.close()
 
 
-def record_shift_reminder(user_id: int, shift_id: int) -> None:
-    """Mark that a reminder was sent to this user for this shift today (idempotent)."""
+def record_shift_reminder(user_id: int, shift_id: int) -> int:
+    """
+    Atomically claim a reminder slot for this user+shift today via INSERT IGNORE.
+    Returns 1 if the slot was claimed (caller should send), 0 if already claimed.
+    """
     conn = None
     try:
         conn = get_connection()
@@ -1783,7 +1786,9 @@ def record_shift_reminder(user_id: int, shift_id: int) -> None:
             (user_id, shift_id),
         )
         conn.commit()
+        rows = cur.rowcount
         cur.close()
+        return rows
     finally:
         if conn:
             conn.close()

requirements.txt

@@ -11,3 +11,4 @@ bcrypt==4.1.3
 pypdf==4.3.1
 python-docx==1.1.2
 openpyxl==3.1.5
+APScheduler>=3.10,<4

routes/admin_shifts.py

@@ -118,7 +118,7 @@ def edit(shift_id):
     return redirect(url_for("admin_shifts.shifts_list"))
 
 
-REMINDER_WINDOW_MIN = 40
+REMINDER_WINDOW_MIN = 45
 
 
 def _fmt_time(t) -> str:
@@ -144,6 +144,11 @@ def do_send_incomplete_reminders(triggered_by_user_id=None) -> dict:
             skipped += 1
             continue
 
+        # Atomically claim this reminder slot before sending.
+        # If another worker already claimed it (rowcount == 0), skip to avoid duplicates.
+        if not record_shift_reminder(row["user_id"], row["shift_id"]):
+            continue
+
         end_str    = _fmt_time(row["end_time"])
         site_lines = "\n".join(
             f"  • {s['name']} — {s['url']}" for s in row["unchecked_sites"]
@@ -163,7 +168,6 @@ def do_send_incomplete_reminders(triggered_by_user_id=None) -> dict:
                 f"Action required — complete your shift checks by {end_str}",
                 body,
             )
-            record_shift_reminder(row["user_id"], row["shift_id"])
             log_action(
                 triggered_by_user_id, "SHIFT_INCOMPLETE_REMINDER", "shifts", row["shift_id"],
                 f"Reminder sent to {row['username']} ({row['email']}): "
@@ -180,7 +184,7 @@ def do_send_incomplete_reminders(triggered_by_user_id=None) -> dict:
 @admin_shifts_bp.route("/send-incomplete-reminders", methods=["POST"])
 @admin_required
 def send_incomplete_reminders():
-    """Manual trigger: email staff with incomplete checks in shifts ending within 40 min."""
+    """Manual trigger: email staff with incomplete checks in shifts ending within 45 min."""
     result = do_send_incomplete_reminders(triggered_by_user_id=session["user"]["id"])
 
     if result["total"] == 0: