A few corrections on Prometheus:
> an AlertManager which handles generating and transmitting alerts
Alerts are generated in Prometheus, the Alertmanager then groups, deduplicates and transmits them. See https://www.robustperception.io/prometheus-and-alertmanager-...
> Data Storage Model: Prometheus uses LevelDB as the storage backend
LevelDB is only used for metadata (we used to use LevelDB for everything, that didn't work out too well). The primary timeseries storage is a custom format, which you can find more details about in https://www.youtube.com/watch?v=HbnGSNEjhUc&index=6&list=PLo...
> It has an active community but no enterprise support.
There's several providers of support, my company being one of them. See https://prometheus.io/community/
And some others:
> InfluxDB supports ingesting data via a CLI, client libraries and an HTTP API.
It also accepts a custom TCP protocol, the graphite protocol and the OpenTSDB protocol.
> Influxdb .. supports GroupBy but not TopN queries.
https://docs.influxdata.com/influxdb/v0.13/query_language/fu...