Feature request: publish detailed health metrics

[pavilalopes]

Currently, only the overall zpool health status is published. It would be useful if the individual vdev and disk status were also published.

For example, this status

$ zpool status
...
config:
        NAME                        STATE     READ WRITE CKSUM
        zpool1                      ONLINE       0     0     0
          raidz1-0                  ONLINE       0     0     0
            wwn-0x5000c500b3b2f8c0  ONLINE       0     0     0
            wwn-0x5000c500b3b53463  ONLINE       0     0     0
            wwn-0x5000c500b3b33354  ONLINE       0     0     0

could lead to these metrics being published:

zfs_pool_health{pool="zpool1"} 0
zfs_pool_vdev_health{pool="zpool1", vdev="raidz1-0"} 0
zfs_pool_disk_health{pool="zpool1", vdev="raidz1-0" disk="wwn-0x5000c500b3b2f8c0"} 0
zfs_pool_disk_health{pool="zpool1", vdev="raidz1-0" disk="wwn-0x5000c500b3b53463"} 0
zfs_pool_disk_health{pool="zpool1", vdev="raidz1-0" disk="wwn-0x5000c500b3b33354"} 0

This would make it possible to build more informative dashboards. With only the pool health status, the operator still has to log into the server to find out which/how many devices are faulted.

[pdf]

Unfortunately the ZFS library we use does not provide access to this information, most likely because the zpool command does not provide a flag to enable machine-parseable output. I'd consider exporting this data if it was available upstream, however I don't expect to contribute this functionality myself in the foreseeable future.

[HubbeKing]

OpenZFS has now added an "influxdb" command to provide machine-parseable output, which may be useful for this.
openzfs/zfs#10786

[pdf]

We no longer rely on an upstream ZFS library, however I'm not certain that we can rely on the influxdb output as that is ZFS version-dependent, and I'd like to maintain good host version compatibility. The alternative though is ugly text parsing, and I'm not eager to tackle this any time soon, though it's certainly doable.