From the zpool_influxdb.8 manual page:
  zpool_influxdb produces InfluxDB-line-protocol-compatible metrics from
  zpools.  Like the zpool command, zpool_influxdb reads the current pool
  status and statistics.  Unlike the zpool command which is intended for
  humans, zpool_influxdb formats the output in the InfluxDB line protocol.
  The expected use is as a plugin to a metrics collector or aggregator,
  such as Telegraf.

zpool_influxdb is installed into /usr/libexec/zfs/

Differential revision:	https://reviews.freebsd.org/D31094

(cherry picked from commit 48b4fe0503282f03d25e23f44109c5cb6d450f7c)