Introduction

VerneMQ can be monitored in several ways. We implemented native support for Graphite, MQTT $SYS tree, and Prometheus.

The metrics are also available via the command line tool:

vmq-admin metrics show

Or with:

vmq-admin metrics show -d

Which will output the metrics together with a short description describing what the metric is about. An example looks like:

# The number of AUTH packets received.
counter.mqtt_auth_received = 0
​
# The number of times a MQTT queue process has been initialized from offline storage.
counter.queue_initialized_from_storage = 0
​
# The number of PUBLISH packets sent.
counter.mqtt_publish_sent = 10
​
# The number of bytes used for storing retained messages.
gauge.retain_memory = 21184

Notice that the metrics:

mqtt_connack_not_authorized_sent
mqtt_connack_bad_credentials_sent
mqtt_connack_server_unavailable_sent
mqtt_connack_identifier_rejected_sent
mqtt_connack_unacceptable_protocol_sent
mqtt_connack_accepted_sent

Are no longer used (always 0) and will be removed in the future. They were replaced with mqtt_connack_sent using the return_code label. For MQTT 5.0 the reason_code label is used instead.

The output on the command line are aggregated by default, but details for a label can be shown as well, for example all metrics with the not_authorized label:

vmq-admin metrics show --return_code=not_authorized
counter.mqtt_connack_sent = 0

All available labels can be show using vmq-admin metrics show --help.