MQTT Live Updates¶

For real-time data push — IoT sensors, live monitoring, streaming data.

When to Use MQTT vs Polling¶

	Polling	MQTT
Latency	Seconds (interval-based)	Milliseconds (push)
Infrastructure	None (just HTTP)	MQTT broker required
Use case	Dashboards, reports	IoT, live monitoring
Complexity	Simple	Moderate

Use polling unless you need sub-second updates or already have an MQTT broker.

Setup¶

1. Enable in Django settings¶

# settings.py
D3_BRIDGE = {
    "MQTT": True,
}

2. Create a live chart¶

from d3_bridge import LineChart

chart = LineChart(
    data=SensorReading.objects.last_hour().values("timestamp", "temperature"),
    x="timestamp",
    y="temperature",
    title="Temperature (Live)",
    live=True,
    mqtt_broker="ws://your-broker:8083/mqtt",
    mqtt_topic="sensors/+/temperature",
    mqtt_window=100,  # keep last 100 data points
)

3. MQTT message format¶

The broker should publish JSON matching your chart's data fields:

{"timestamp": "2026-03-17T14:30:00", "temperature": 23.5}

How It Works¶

Django View (initial data) ──→ Chart renders
                                   ↑
MQTT Broker (WebSocket) ──→ mqtt.js ──→ chart.update(newPoint)

Chart renders with initial data from the Django view
JavaScript connects to the MQTT broker via WebSocket
On each message, chart.update() is called with the new data point
The chart re-renders with a D3 transition

Connection Status¶

A live indicator appears in the top-right corner of the chart:

LIVE (green) — connected and receiving
LIVE (red) — disconnected, attempting to reconnect

Parameters¶

Parameter	Type	Default	Description
`live`	bool	`False`	Enable MQTT
`mqtt_broker`	str	`None`	WebSocket URL (`ws://` or `wss://`)
`mqtt_topic`	str	`None`	MQTT topic (supports `+` and `#` wildcards)
`mqtt_window`	int	`100`	Max data points to keep
`mqtt_qos`	int	`0`	MQTT QoS level (0, 1, or 2)

Compatible Brokers¶

Any MQTT broker with WebSocket support:

EMQX — default WebSocket on port 8083
Mosquitto — with WebSocket listener configured
HiveMQ
Cloud services (AWS IoT, Azure IoT Hub, etc.)