Fix #2776

server/model/maintenance_timeslot.js

@@ -41,6 +41,8 @@ class MaintenanceTimeslot extends BeanModel {
      * @returns {Promise<MaintenanceTimeslot>}
      */
     static async generateTimeslot(maintenance, minDate = null, removeExist = false) {
+        log.info("maintenance", "Generate Timeslot for maintenance id: " + maintenance.id);
+
         if (removeExist) {
             await R.exec("DELETE FROM maintenance_timeslot WHERE maintenance_id = ? ", [
                 maintenance.id

server/uptime-kuma-server.js

@@ -272,6 +272,10 @@ class UptimeKumaServer {
     /** Load the timeslots for maintenance */
     async generateMaintenanceTimeslots() {
 
+        // Prevent #2776
+        // Remove duplicate maintenance_timeslot with same start_date, end_date and maintenance_id
+        await R.exec("DELETE FROM maintenance_timeslot WHERE id NOT IN (SELECT MIN(id) FROM maintenance_timeslot GROUP BY start_date, end_date, maintenance_id)");
+
         let list = await R.find("maintenance_timeslot", " generated_next = 0 AND start_date <= DATETIME('now') ");
 
         for (let maintenanceTimeslot of list) {