Cron UI Visual Guide

Cron Dialog UI Changes - Visual Guide

New UI Structure

The cron expression builder form now has the following order:

┌─────────────────────────────────────────────────┐
│  Schedule                                       │
│                                                 │
│  ● Every N seconds          [NEW - FIRST]      │
│    └─ Seconds: [5____]                          │
│                                                 │
│  ○ Every N minutes                              │
│    └─ Minutes: [5____]                          │
│                                                 │
│  ○ Every N hours                                │
│    └─ Hours: [1____]  Minute: [0____]          │
│                                                 │
│  ○ Daily at time                                │
│    └─ Hour: [0____]  Minute: [0____]           │
│       Second: [0____]  [NEW]                    │
│                                                 │
│  ○ Weekly on days                               │
│    └─ [☐Sun ☐Mon ☐Tue ☐Wed ☐Thu ☐Fri ☐Sat]    │
│       Hour: [0____]  Minute: [0____]           │
│       Second: [0____]  [NEW]                    │
│                                                 │
│  ○ Monthly on day                               │
│    └─ Day: [1____]  Hour: [0____]              │
│       Minute: [0____]  Second: [0____]  [NEW]  │
│                                                 │
│  ○ Custom cron expression                      │
│    └─ [_______________________________]         │
│                                                 │
│  Generated cron: */5 * * * * *                  │
└─────────────────────────────────────────────────┘

Key Changes

1. New “Every N seconds” Option

• Position: First option (above minutes)
• Default: 5 seconds
• Expression: */5 * * * * *
• Default mode: This is now the default selection

2. Seconds Fields Added

All time-based modes now include a seconds field:

• Daily: Hour, Minute, Second
• Weekly: Hour, Minute, Second
• Monthly: Day, Hour, Minute, Second

3. Expression Format

The generated expressions now use 6 fields (with seconds):

Mode	Old Format (5-field)	New Format (6-field)
Every 5 seconds	N/A	*/5 * * * * *
Every 5 minutes	*/5 * * * *	0 */5 * * * *
Every 2 hours	0 */2 * * *	0 0 */2 * * *
Daily at 10:15:30	15 10 * * *	30 15 10 * * *
Weekly Sun 12:00:30	0 12 * * 0	30 0 12 * * 0
Monthly 15th 09:45:20	45 9 15 * *	20 45 9 15 * *

User Experience Flow

Creating a New Cron Job (Default)

1. User creates a new Cron Timer node
2. Opens the dialog
3. Sees “Every N seconds” pre-selected with “5”
4. Generated expression: */5 * * * * *
5. Executes every 5 seconds

Upgrading Existing Cron Jobs

1. User opens existing cron job with old 5-field expression
2. Dialog automatically parses and converts to appropriate mode
3. Legacy expressions like */5 * * * * are recognized as “Every 5 minutes”
4. User can add seconds precision by switching modes or using custom

Fine-tuning Time-based Schedules

1. User selects “Daily at time”
2. Sets Hour: 14, Minute: 30, Second: 15
3. Expression: 15 30 14 * * *
4. Executes daily at exactly 14:30:15

Backward Compatibility

✅ Old 5-field expressions continue to work:

• */5 * * * * → Interpreted as every 5 minutes at second 0
• 0 9 * * 1 → Interpreted as Monday 09:00:00

✅ Expression parsing handles both formats automatically

Default Behavior

Scenario	Default Expression	Executes
New cron job	*/5 * * * * *	Every 5 seconds
Blank expression	*/5 * * * * *	Every 5 seconds

Common Use Cases

High-Frequency Monitoring

Mode: Every N seconds
Seconds: 1
Expression: */1 * * * * *
Result: Executes every second (max frequency)

Regular Sensor Polling

Mode: Every N seconds
Seconds: 10
Expression: */10 * * * * *
Result: Executes every 10 seconds

Precise Daily Task

Mode: Daily at time
Hour: 3
Minute: 30
Second: 0
Expression: 0 30 3 * * *
Result: Executes at 3:30:00 AM daily

Weekly Backup with Offset

Mode: Weekly on days
Days: Sunday selected
Hour: 2
Minute: 0
Second: 30
Expression: 30 0 2 * * 0
Result: Executes at 2:00:30 AM every Sunday

Field Constraints

Field	Range	Description
Second	0-59	Seconds within the minute
Minute	0-59	Minutes within the hour
Hour	0-23	Hour of the day (24-hour)
Day	1-31	Day of the month
Month	1-12	Month of the year
Day of Week	0-6	Sunday (0) through Saturday (6)

Custom Expression Format

For advanced users, custom 6-field cron expressions are supported:

[second] [minute] [hour] [day] [month] [day_of_week]

Examples:
*/30 * * * * *           - Every 30 seconds
0,30 * * * * *           - At 0 and 30 seconds each minute
15 0,30 * * * *          - At 15 seconds past 0 and 30 minutes
0 0 12 * * 1-5           - 12:00:00 PM on weekdays
*/5 0-30 9-17 * * 1-5    - Every 5 seconds, minutes 0-30, hours 9 AM-5 PM, weekdays

UI Screenshots

Default View (Every N seconds)

Default view showing “Every N seconds” selected with 5 seconds

Daily Schedule

Daily schedule with seconds precision

Custom Expression

Custom 6-field cron expression

Tips for Users

1. Start simple: Use “Every N seconds” for most monitoring tasks
2. Be precise: Add seconds to daily/weekly tasks for exact timing
3. Test first: Use a test node to verify your cron timing
4. Check logs: Monitor execution logs to confirm schedule
5. Use custom: Advanced patterns require custom expression mode

Related Documents

• Cron Seconds Implementation
• Compute Processor Refactoring

Summary

The updated cron UI provides:

• ✅ Second-level precision for all scheduling modes
• ✅ Intuitive “Every N seconds” as default
• ✅ Full backward compatibility with existing cron jobs
• ✅ Clear visual feedback with generated expression display
• ✅ Support for both simple and complex scheduling needs

This makes Krill’s scheduler one of the most flexible and user-friendly in the IoT automation space.