# Record modifier

The *Record Modifier* [filter](https://docs.fluentbit.io/manual/4.1/data-pipeline/filters/record-modifier) lets you append fields to a record, or exclude specific fields.

## Configuration parameters

The plugin supports the following configuration parameters:

| Key             | Description                                                                                    |
| --------------- | ---------------------------------------------------------------------------------------------- |
| `Record`        | Append fields. This parameter needs a key/value pair.                                          |
| `Remove_key`    | If the key is matched, that field is removed. You can use this or `Allowlist_key`.             |
| `Allowlist_key` | If the key isn't matched, that field is removed. You can use this or `Remove_key`.             |
| `Whitelist_key` | An alias of `Allowlist_key` for backwards compatibility.                                       |
| `Uuid_key`      | If set, the plugin appends UUID to each record. The value assigned becomes the key in the map. |

## Get started

To start filtering records, run the filter from the command line or through a configuration file.

This is a sample `in_mem` record to filter.

```
{"Mem.total"=>1016024, "Mem.used"=>716672, "Mem.free"=>299352, "Swap.total"=>2064380, "Swap.used"=>32656, "Swap.free"=>2031724}
```

### Append fields

The following configuration file appends a product name and hostname to a record using an environment variable:

{% tabs %}
{% tab title="fluent-bit.yaml" %}

```yaml
pipeline:
  inputs:
    - name: mem
      tag: mem.local

  filters:
    - name: record_modifier
      match: '*'
      record:
       - hostname ${HOSTNAME}
       - product Awesome_Tool

  outputs:
    - name: stdout
      match: '*'
```

{% endtab %}

{% tab title="fluent-bit.conf" %}

```
[INPUT]
  Name mem
  Tag  mem.local

[OUTPUT]
  Name  stdout
  Match *

[FILTER]
  Name record_modifier
  Match *
  Record hostname ${HOSTNAME}
  Record product Awesome_Tool
```

{% endtab %}
{% endtabs %}

You can run the filter from command line:

```shell
fluent-bit -i mem -o stdout -F record_modifier -p 'Record=hostname ${HOSTNAME}' -p 'Record=product Awesome_Tool' -m '*'
```

The output looks something like:

```
[0] mem.local: [1492436882.000000000, {"Mem.total"=>1016024, "Mem.used"=>716672, "Mem.free"=>299352, "Swap.total"=>2064380, "Swap.used"=>32656, "Swap.free"=>2031724, "hostname"=>"localhost.localdomain", "product"=>"Awesome_Tool"}]
```

### Remove fields with `Remove_key`

The following configuration file removes `Swap.*` fields:

{% tabs %}
{% tab title="fluent-bit.yaml" %}

```yaml
pipeline:
  inputs:
    - name: mem
      tag: mem.local

  filters:
    - name: record_modifier
      match: '*'
      remove_key:
       - Swap.total
       - Swap.used
       - Swap.free

  outputs:
    - name: stdout
      match: '*'
```

{% endtab %}

{% tab title="fluent-bit.conf" %}

```
[INPUT]
  Name mem
  Tag  mem.local

[OUTPUT]
  Name  stdout
  Match *

[FILTER]
  Name record_modifier
  Match *
  Remove_key Swap.total
  Remove_key Swap.used
  Remove_key Swap.free
```

{% endtab %}
{% endtabs %}

You can also run the filter from command line.

```shell
fluent-bit -i mem -o stdout -F  record_modifier -p 'Remove_key=Swap.total' -p 'Remove_key=Swap.free' -p 'Remove_key=Swap.used' -m '*'
```

The output looks something like:

```
[0] mem.local: [1492436998.000000000, {"Mem.total"=>1016024, "Mem.used"=>716672, "Mem.free"=>295332}]
```

### Retain fields with `Allowlist_key`

The following configuration file retains `Mem.*` fields.

{% tabs %}
{% tab title="fluent-bit.yaml" %}

```yaml
pipeline:
  inputs:
    - name: mem
      tag: mem.local

  filters:
    - name: record_modifier
      match: '*'
      Allowlist_key:
       - Mem.total
       - Mem.used
       - Mem.free

  outputs:
    - name: stdout
      match: '*'
```

{% endtab %}

{% tab title="fluent-bit.conf" %}

```
[INPUT]
  Name mem
  Tag  mem.local

[FILTER]
  Name record_modifier
  Match *
  Allowlist_key Mem.total
  Allowlist_key Mem.used
  Allowlist_key Mem.free

[OUTPUT]
  Name  stdout
  Match *
```

{% endtab %}
{% endtabs %}

You can also run the filter from command line:

```shell
fluent-bit -i mem -o stdout -F record_modifier -p 'Allowlist_key=Mem.total' -p 'Allowlist_key=Mem.free' -p 'Allowlist_key=Mem.used' -m '*'
```

The output looks something like:

```
[0] mem.local: [1492436998.000000000, {"Mem.total"=>1016024, "Mem.used"=>716672, "Mem.free"=>295332}]
```