# 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](/manual/4.1/concepts/key-concepts.md) and [Matching](/manual/4.1/concepts/key-concepts.md) 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.


---

# Agent Instructions: Querying This Documentation

If you need additional information that is not directly available in this page, you can query the documentation dynamically by asking a question.

Perform an HTTP GET request on the current page URL with the `ask` query parameter:

```
GET https://docs.fluentbit.io/manual/4.1/data-pipeline/router.md?ask=<question>
```

The question should be specific, self-contained, and written in natural language.
The response will contain a direct answer to the question and relevant excerpts and sources from the documentation.

Use this mechanism when the answer is not explicitly present in the current page, you need clarification or additional context, or you want to retrieve related documentation sections.