nvme: add monitor plugin

[dwsuse]

Add a monitor plugin combining NVMe and OCP spec-compliant operations to simplify fleet monitoring.

Fixes: #2189

$ nvme monitor smart /dev/nvme0 -o json
{
  "device":"nvme0",
  "ocp_supported":false,
  "smart_log":{
    "critical_warning":0,
    "temperature":331,
    "avail_spare":100,
    "spare_thresh":10,
    "percent_used":19,
    "endurance_grp_critical_warning_summary":0,
    "data_units_read":182094536,
    "data_units_written":118624708,
    "host_read_commands":4971578062,
    "host_write_commands":3689075088,
    "controller_busy_time":3261,
    "power_cycles":1226,
    "power_on_hours":6028,
    "unsafe_shutdowns":134,
    "media_errors":0,
    "num_err_log_entries":0,
    "warning_temp_time":0,
    "critical_comp_time":0,
    "temperature_sensor_1":331,
    "temperature_sensor_2":361,
    "thm_temp1_trans_count":43,
    "thm_temp2_trans_count":0,
    "thm_temp1_total_time":766,
    "thm_temp2_total_time":0,
    "op_lifetime_energy_consumed":0,
    "interval_power_measurement":0
  }
}

[ikegami-t]

Looks good. To make let me confirm below.
Still monitoring feature like as nvme top command not required for this command also as since we can use the watch command instead?

[igaw]

FWIW, I was considering moving the code around nvme top to this new monitor plugin and just have a trampoline command.

Anyway, the nvme top does something different to this monitor smart would do. nvme top shows more the
fabric side, while the monitor smart shows you the medium health part.

I don't mind making monitor smart a bit more flexible, e.g. monitor smart --update 2s -o json | some-program-consuming-the-data (or any better name for the argument name).

Is this what you are asking?

[ikegami-t]

Understood. Yes thank you for your answering. Just I thought about the command naming monitor as monitoring the smart information but confirmed as just output the smart information as snap shot without the monitoring then asked. Now cleared the situation. Thank you.

[igaw]

I am not sure if we actually want to add the monitor plugin after all (see the discussion in #2189)

[ikegami-t]

I see. Thank you.