Type prefix

[WangHL0927]

I found that emq-exporter's own data type has no prefix. It is recommended to add a uniform type prefix to prevent confusion. Uniform prefixes can also be retrieved in the Grafana Dashboard.

emq_nodes_stats_topics_max 6
# HELP emq_up Was the last scrape of EMQ successful
# TYPE emq_up gauge
emq_up 1
# HELP go_gc_duration_seconds A summary of the GC invocation durations.
# TYPE go_gc_duration_seconds summary
go_gc_duration_seconds{quantile="0"} 0.000201694
go_gc_duration_seconds{quantile="0.25"} 0.000232821
go_gc_duration_seconds{quantile="0.5"} 0.00026052
go_gc_duration_seconds{quantile="0.75"} 0.000269629