---
title: "loki.relabel | Grafana Agent documentation"
description: "Learn about loki.relabel"
---

# loki.relabel

The `loki.relabel` component rewrites the label set of each log entry passed to its receiver by applying one or more relabeling `rule`s and forwards the results to the list of receivers in the component’s arguments.

If no labels remain after the relabeling rules are applied, then the log entries are dropped.

The most common use of `loki.relabel` is to filter log entries or standardize the label set that is passed to one or more downstream receivers. The `rule` blocks are applied to the label set of each log entry in order of their appearance in the configuration file. The configured rules can be retrieved by calling the function in the `rules` export field.

If you’re looking for a way to process the log entry contents, take a look at [the `loki.process` component](../loki.process/) instead.

Multiple `loki.relabel` components can be specified by giving them different labels.

## Usage

Alloy ![Copy code to clipboard](/media/images/icons/icon-copy-small-2.svg) Copy

```alloy
loki.relabel "LABEL" {
  forward_to = RECEIVER_LIST

  rule {
    ...
  }

  ...
}
```

## Arguments

The following arguments are supported:

Expand table

| Name             | Type             | Description                                                    | Default | Required |
|------------------|------------------|----------------------------------------------------------------|---------|----------|
| `forward_to`     | `list(receiver)` | Where to forward log entries after relabeling.                 |         | yes      |
| `max_cache_size` | `int`            | The maximum number of elements to hold in the relabeling cache | 10,000  | no       |

## Blocks

The following blocks are supported inside the definition of `loki.relabel`:

Expand table

| Hierarchy | Name                | Description                                        | Required |
|-----------|---------------------|----------------------------------------------------|----------|
| rule      | [rule](#rule-block) | Relabeling rules to apply to received log entries. | no       |

### rule block

The `rule` block contains the definition of any relabeling rules that can be applied to an input log. The transformations are applied in top-down order if more than one `rule` block is defined.

You can use the following arguments to configure a `rule`. All arguments are optional. Omitted fields take their default values.

Expand table

| Name            | Type           | Description                                                                                                                                                                                                                                   | Default | Required |
|-----------------|----------------|-----------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------|---------|----------|
| `action`        | `string`       | The relabeling action to perform.                                                                                                                                                                                                             | replace | no       |
| `modulus`       | `uint`         | A positive integer used to calculate the modulus of the hashed source label values.                                                                                                                                                           |         | no       |
| `regex`         | `string`       | A valid RE2 expression with support for parenthesized capture groups. Used to match the extracted value from the combination of the `source_label` and `separator` fields or filter labels during the `labelkeep/labeldrop/labelmap` actions. | `(.*)`  | no       |
| `replacement`   | `string`       | The value against which a regular expression replace is performed if the regular expression matches the extracted value. Supports previously captured groups.                                                                                 | `"$1"`  | no       |
| `separator`     | `string`       | The separator used to concatenate the values present in `source_labels`.                                                                                                                                                                      | ;       | no       |
| `source_labels` | `list(string)` | The list of labels whose values are to be selected. Their content is concatenated using the `separator` and matched against `regex`.                                                                                                          |         | no       |
| `target_label`  | `string`       | Label to which the resulting value is written to.                                                                                                                                                                                             |         | no       |

You can use the following actions:

- `drop` - Drops logs where `regex` matches the string extracted using the `source_labels` and `separator`.
- `dropequal` - Drop targets for which the concatenated `source_labels` do match `target_label`.
- `hashmod` - Hashes the concatenated labels, calculates its modulo `modulus`, and writes the result to the `target_label`.
- `keep` - Keeps logs where `regex` matches the string extracted using the `source_labels` and `separator`.
- `keepequal` - Drop targets for which the concatenated `source_labels` do not match `target_label`.
- `labeldrop` - Matches `regex` against all label names. Any labels that match are removed from the log’s label set.
- `labelkeep` - Matches `regex` against all label names. Any labels that don’t match are removed from the log’s label set.
- `labelmap` - Matches `regex` against all label names. Any labels that match are renamed according to the contents of the `replacement` field.
- `lowercase` - Sets `target_label` to the lowercase form of the concatenated `source_labels`.
- `replace` - Matches `regex` to the concatenated labels. If there’s a match, it replaces the content of the `target_label` using the contents of the `replacement` field.
- `uppercase` - Sets `target_label` to the uppercase form of the concatenated `source_labels`.

> Note
> 
> The regular expression capture groups can be referred to using either the `$CAPTURE_GROUP_NUMBER` or `${CAPTURE_GROUP_NUMBER}` notation.

## Exported fields

The following fields are exported and can be referenced by other components:

Expand table

| Name       | Type           | Description                                                  |
|------------|----------------|--------------------------------------------------------------|
| `receiver` | `receiver`     | The input receiver where log lines are sent to be relabeled. |
| `rules`    | `RelabelRules` | The currently configured relabeling rules.                   |

## Component health

`loki.relabel` is only reported as unhealthy if given an invalid configuration. In those cases, exported fields are kept at their last healthy values.

## Debug information

`loki.relabel` does not expose any component-specific debug information.

## Debug metrics

- `loki_relabel_entries_processed` (counter): Total number of log entries processed.
- `loki_relabel_entries_written` (counter): Total number of log entries forwarded.
- `loki_relabel_cache_misses` (counter): Total number of cache misses.
- `loki_relabel_cache_hits` (counter): Total number of cache hits.
- `loki_relabel_cache_size` (gauge): Total size of relabel cache.

## Example

The following example creates a `loki.relabel` component that only forwards entries whose ’level’ value is set to ’error'.

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```alloy
loki.relabel "keep_error_only" {
  forward_to = [loki.write.onprem.receiver]

  rule {
    action        = "keep"
    source_labels = ["level"]
    regex         = "error"
  }
}
```

## Compatible components

`loki.relabel` can accept arguments from the following components:

- Components that export [Loki `LogsReceiver`](../../compatibility/#loki-logsreceiver-exporters)

`loki.relabel` has exports that can be consumed by the following components:

- Components that consume [Loki `LogsReceiver`](../../compatibility/#loki-logsreceiver-consumers)

> Note
> 
> Connecting some components may not be sensible or components may require further configuration to make the connection work correctly. Refer to the linked documentation for more details.