The Recorder (recorder) node publishes start_recording / stop_recording to a twin’s webrtc-command MQTT topic so the media service persists the already-running WebRTC stream to its configured bucket. The node never carries the media itself — the camera or microphone must already be streaming.
Palette category: Actuation. Edge-only. Toggles persistence on the media service; it does not create the stream.
The Recorder node, the audio widget’s REC button in the environment view, and the microphone driver’s fallback relay all publish the exact same payload on cyberwave/twin/{uuid}/webrtc-command. The three paths converge on the same media-service handler and the same webrtc-command/status ACK, so you can mix and match without changing the consumer. | Field | Type | Required | Description |
|---|
twin_uuid | string | Yes | Twin whose stream should be recorded. Defaults to the workflow’s bound twin. |
command | string | Yes | start_recording or stop_recording. Wire from an upstream Conditional / Fuzzy Matcher to toggle dynamically, or pin a literal in the inspector. |
frontend_type | string | Yes | video or audio. The media service treats this as audio when unset. |
sensor | string | Yes | Sensor identifier (e.g. camera, mic). Required by the media-service start_recording handler — commands without it are refused. |
stream_source | string | No | Optional producer hint (e.g. camera). |
stream_instance_id | string | No | Optional disambiguator when a twin publishes multiple streams under the same sensor. |
MQTT payload
Published to {prefix}cyberwave/twin/{twin_uuid}/webrtc-command with QoS 1:
{
"command": "start_recording",
"source_type": "edge",
"sensor": "camera",
"frontend_type": "video",
"stream_source": "camera",
"stream_instance_id": "primary"
}
"command": "stop_recording". Status is published back by the media service on {prefix}cyberwave/twin/{twin_uuid}/webrtc-command/status.
Outputs
| Field | Type | Description |
|---|
command | string | Recording command that was published. |
topic | string | Full MQTT topic the command was published to. |
payload | object | Payload sent to the media service. |
sent | boolean | Whether the broker accepted the publish. |
Execution targets
| Target | Behavior |
|---|
| Edge | Emitter renders a client.mqtt.publish against the twin-scoped webrtc-command topic in the generated worker. |
| Cloud | Not supported — the node raises at compile time for cloud workflows. |
