# Routing

Routing is a core feature that lets you route your data through filters and then to one or multiple destinations. The router relies on the concept of [Tags](https://docs.fluentbit.io/manual/4.1/concepts/key-concepts) and [Matching](https://docs.fluentbit.io/manual/4.1/concepts/key-concepts) rules.

{% @mermaid/diagram content="graph LR
accTitle: Fluent Bit data pipeline
accDescr: A diagram of the Fluent Bit data pipeline, which includes input, a parser, a filter, a buffer, routing, and various outputs.
A\[Input] --> B\[Parser]
B --> C\[Filter]
C --> D\[Buffer]
D --> E((Routing))
E --> F\[Output 1]
E --> G\[Output 2]
E --> H\[Output 3]
style E stroke:darkred,stroke-width:2px;" %}

There are two important concepts in Routing:

* Tag
* Match

When data is generated by an input plugin, it comes with a `Tag`. A Tag is a human-readable indicator that helps to identify the data source. Tags are usually configured manually.

To define where to route data, specify a `Match` rule in the output configuration.

Consider the following configuration example that delivers `CPU` metrics to an Elasticsearch database and Memory (`mem`) metrics to the standard output interface:

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

```yaml
pipeline:
  inputs:
    - name: cpu
      tag: my_cpu

    - name: mem
      tag: my_mem

  outputs:
    - name: es
      match: my_cpu

    - name: stdout
      match: my_mem
```

{% endtab %}

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

```
[INPUT]
  Name cpu
  Tag  my_cpu

[INPUT]
  Name mem
  Tag  my_mem

[OUTPUT]
  Name   es
  Match  my_cpu

[OUTPUT]
  Name   stdout
  Match  my_mem
```

{% endtab %}
{% endtabs %}

Routing reads the `Input` `Tag` and the `Output` `Match` rules. If data has a `Tag` that doesn't match at routing time, the data is deleted.

## Routing with wildcards

Routing is flexible enough to support wildcards in the `Match` pattern. The following example defines a common destination for both sources of data:

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

```yaml
pipeline:
  inputs:
    - name: cpu
      tag: my_cpu

    - name: mem
      tag: my_mem

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

{% endtab %}

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

```
[INPUT]
  Name cpu
  Tag  my_cpu

[INPUT]
  Name mem
  Tag  my_mem

[OUTPUT]
  Name   stdout
  Match  my_*
```

{% endtab %}
{% endtabs %}

The match rule is set to `my_*`, which matches any Tag starting with `my_`.

## Routing with regular expressions

Routing also provides support for regular expressions with the `Match_Regex` pattern, allowing for more complex and precise matching criteria. The following example demonstrates how to route data from sources based on a regular expression:

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

```yaml
pipeline:
  inputs:
    - name: temperature_sensor
      tag: temp_sensor_A

    - name: humidity_sensor
      tag: humid_sensor_B

  outputs:
    - name: stdout
      match_regex: '.*_sensor_[AB]'
```

{% endtab %}

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

```
[INPUT]
  Name temperature_sensor
  Tag  temp_sensor_A

[INPUT]
  Name humidity_sensor
  Tag  humid_sensor_B

[OUTPUT]
  Name         stdout
  Match_regex  .*_sensor_[AB]
```

{% endtab %}
{% endtabs %}

In this configuration, the `Match_regex` rule is set to `.*_sensor_[AB]`. This regular expression matches any `Tag` that ends with `_sensor_A` or `_sensor_B`, regardless of what precedes it. This approach provides a more flexible and powerful way to handle different source tags with a single routing rule.