rename a metric tag, how ?

[StefanSa]

Hi there,
i get these metrics from the telegraf client.

{
  "fields": {
    "usage_guest": 0,
    "usage_guest_nice": 0,
    "usage_idle": 99.82499999983702,
    "usage_iowait": 0,
    "usage_irq": 0,
    "usage_nice": 0,
    "usage_softirq": 0,
    "usage_steal": 0,
    "usage_system": 0.024999999999977263,
    "usage_user": 0.14999999999986358
  },
  "name": "cpu",
  "tags": {
    "cpu": "cpu-total",
    "host": "os-dash01"
  },
  "timestamp": 1649056860
}

The array name fields would have to be renamed with the contents of the field name (cpu). What is the best way to do this ?

That would be the goal:

{
  "cpu": {
    "usage_guest": 0,
    "usage_guest_nice": 0,
    "usage_idle": 99.82499999983702,
    "usage_iowait": 0,
    "usage_irq": 0,
    "usage_nice": 0,
    "usage_softirq": 0,
    "usage_steal": 0,
    "usage_system": 0.024999999999977263,
    "usage_user": 0.14999999999986358
  },
  "name": "cpu",
  "tags": {
    "cpu": "cpu-total",
    "host": "os-dash01"
  },
  "timestamp": 1649056860
}

[jszwedko]

Hi @StefanSa ,

You can use remap with a VRL program like:

.cpu = del(.fields)

[StefanSa]

Hi @jszwedko , good evening from Germany.
Thank you for your quick reply. I already know this solution / example.
The field name is dynamic and can have different values like cpu, system, ram etc.
These different values of name should overwrite the name of fields.
How do i do this ?

[StefanSa]

@jszwedko
Perfect, I've thought of that too.
But my tests had not been successful.
Thanks for the competent and quick help, but especially for vector.

[jszwedko]

No worries! I neglected the error handling as well. This function requires error handling because VRL can't be sure that .name is a string or integer (or doesn't exist at all). I guess my question would be: what do you want to have happen if .name is not a string or is not set? If you want the remap to fail completely, you can just do set!(., [.name], del(.fields)). If you want to skip the rename, you could do:

name, err = string(.name)
if err != null {
   set(., [name], del(.fields)) # note that name lacks the `.` here since we are referring to the variable now
}

This will only do the rename if .name is set and is a string (or integer, technically).

[StefanSa]

@jszwedko
set!(., [.name], del(.fields)).
is unfortunately not the solution.
fields is completely deleted, but not renamed as wanted.

{
  "@timestamp": "2022-04-04T19:57:10Z",
  "name": "cpu",
  "tags": {
    "cpu": "cpu-total",
    "host": "os-dash01"
  }
}

[jszwedko]

Apologies, I also forgot set operates by-value. So you'll need to do . = set!(., [.name], del(.fields)).

[StefanSa]

@jszwedko
Perfect, now everything OK.
Thanks again !