Here is a list of the $SYS topics in the DataHub MQTT broker. You can also get a live
view of the $SYS topics by creating a DataHub MQTT client connection in a DataHub instance
that connects to the MQTT broker in the same DataHub instance. Subscribe to the topic
pattern $SYS/# to see all $SYS topics.
$SYS/broker/bytes/received
The total number of bytes received since the broker started.
$SYS/broker/bytes/sent
The total number of bytes sent since the broker started.
$SYS/broker/clients/active
Deprecated: see $SYS/broker/clients/connected
$SYS/broker/clients/connected
The number of currently connected clients.
$SYS/broker/clients/maximum
The maximum number of clients that have been connected to the broker at the same time.
$SYS/broker/clients/total
The total number of active and inactive clients currently connected and registered on the broker.
$SYS/broker/load/bytes/received/+
The moving average of the number of bytes received by the broker over
different time intervals. The final
+1min, 5min or
15min, like this:
$SYS/broker/load/bytes/received/15min. The value
returned represents the number of bytes received in 1 minute, averaged
over 1, 5 or 15 minutes.
$SYS/broker/load/bytes/sent/+
The moving average of the number of bytes sent by the broker over
different time intervals. The final
+1min, 5min or
15min, like this:
$SYS/broker/load/bytes/sent/15min. The value
returned represents the number of bytes sent in 1 minute, averaged over
1, 5 or 15 minutes.
$SYS/broker/load/connections/+
The moving average of the number of CONNECT packets
received by the broker over different time intervals. The final
+1min, 5min or
15min, like this:
$SYS/broker/load/connections/15min. The value
returned represents the number of connections received in 1 minute,
averaged over 1, 5 or 15 minutes.
$SYS/broker/load/messages/received/+
The moving average of the number of all types of MQTT messages
received by the broker over different time intervals. The final
+1min, 5min or
15min, like this:
$SYS/broker/load/messages/received/15min. The
value returned represents the number of MQTT messages received in 1
minute, averaged over 1, 5 or 15 minutes.
$SYS/broker/load/messages/sent/+
The moving average of the number of all types of MQTT messages sent by
the broker over different time intervals. The final
+1min, 5min or
15min, like this:
$SYS/broker/load/messages/sent/15min. The value
returned represents the number of MQTT messages sent in 1 minute,
averaged over 1, 5 or 15 minutes.
$SYS/broker/load/publish/sent/+
The moving average of the number of all types of
PUBLISH messages sent by the broker over
different time intervals. The final
+1min, 5min or
15min, like this:
$SYS/broker/load/publish/sent/15min. The value
returned represents the number of PUBLISH messages
sent in 1 minute, averaged over 1, 5 or 15 minutes.
$SYS/broker/load/sockets/+
The moving average of the number of socket connections opened to the
broker over different time intervals. The final
+1min, 5min or
15min, like this:
$SYS/broker/load/publish/sent/15min. The value
returned represents the number of socket connections in 1 minute,
averaged over 1, 5 or 15 minutes.
$SYS/broker/messages/received
The total number of messages of any type received since the broker started.
$SYS/broker/messages/sent
The total number of messages of any type sent since the broker started.
$SYS/broker/messages/stored
The number of messages currently held in the message store. This includes retained messages and messages queued for durable clients.
$SYS/broker/publish/bytes/sent
The total number of bytes in PUBLISH messages sent
since the broker started.
$SYS/broker/publish/messages/sent
The total number of PUBLISH messages sent since the
broker started.
$SYS/broker/retained messages/count
The total number of retained messages active on the broker.
$SYS/broker/store/messages/bytes
The number of bytes currently held by message payloads in the message store. This includes retained messages and messages queued for durable clients.
$SYS/broker/store/messages/count
The number of messages currently held in the message store. This includes retained messages and messages queued for durable clients.
$SYS/broker/subscriptions/count
The total number of subscriptions active on the broker.
$SYS/broker/uptime
The amount of time that the broker has been running, in a human-readable form.
$SYS/broker/version
The version of the broker. Static.