telegraf/plugins/processors/defaults/README.md

Defaults Processor

The Defaults processor allows you to ensure certain fields will always exist with a specified default value on your metric(s).

There are three cases where this processor will insert a configured default field.

1. The field is nil on the incoming metric
2. The field is not nil, but its value is an empty string.
3. The field is not nil, but its value is a string of one or more empty spaces.

Configuration

## Set default fields on your metric(s) when they are nil or empty
[[processors.defaults]]

## This table determines what fields will be inserted in your metric(s)
  [processors.defaults.fields]
    field_1 = "bar"
    time_idle = 0
    is_error = true

Example

Ensure a status_code field with N/A is inserted in the metric when one it's not set in the metric be default:

[[processors.defaults]]
  [processors.defaults.fields]
    status_code = "N/A"

- lb,http_method=GET cache_status=HIT,latency=230
+ lb,http_method=GET cache_status=HIT,latency=230,status_code="N/A"

Ensure an empty string gets replaced by a default:

- lb,http_method=GET cache_status=HIT,latency=230,status_code=""
+ lb,http_method=GET cache_status=HIT,latency=230,status_code="N/A"