Backfill Queue

Store and replay tag data during MQTT broker outages.

What is Backfill?

When MQTT broker is unavailable, tags with backfill enabled store values locally. When connection restores, stored values are published in batches.

Benefits: - No data loss during outages - Historical accuracy maintained - Automatic replay on reconnection

Configuration

Enable on Tags

1. Edit tag
2. Enable Backfill
3. Save

Queue Settings

Configure per Sparkplug group: - Batch Size: Records per publish - Publish Delay: Milliseconds between batches

How It Works

1. MQTT connection lost
2. Tag values stored in queue
3. Connection restored
4. Publish NBIRTH/DBIRTH
5. Replay queued values in batches
6. Resume normal operation

Monitoring

View queue status: - Total records queued - Records per device - Playback progress - Estimated completion time

Best Practices

• Enable for critical historical data
• Don't enable on all tags (storage)
• Monitor queue size
• Test with planned outages

Next Steps

• Tag Configuration
• Broker Redundancy