The graphite exporter reports the broker metrics at a fixed interval (defined in milliseconds) to a graphite server. The necessary configuration is done inside the vernemq.conf.
You can further tune the connection to the Graphite server:
The above configuration parameters can be changed at runtime using the vmq-admin script.
Usage: vmq-admin set = ... [[--node | -n] | --all]
Example: vmq-admin set graphite_interval=20000 graphite_port=2003 -n VerneMQ@127.0.0.1