# Routing Examples

This article shows configuration samples for typical routing scenarios.

## Simple: `Input -> Filter -> Output`

```
<source>
  @type forward
</source>

<filter app.**>
  @type record_transformer
  <record>
    hostname "#{Socket.gethostname}"
  </record>
</filter>

<match app.**>
  @type file
  # ...
</match>
```

## Two Inputs: `forward` and `tail`

```
<source>
  @type forward
</source>

<source>
  @type tail
  tag system.logs
  # ...
</source>

<filter app.**>
  @type record_transformer
  <record>
    hostname "#{Socket.gethostname}"
  </record>
</filter>

<match {app.**,system.logs}>
  @type file
  # ...
</match>
```

If you want to separate the data pipelines for each source, use Label.

## With Label: `Input -> Filter -> Output`

Label reduces complex `tag` handling by separating data pipelines.

```
<source>
  @type forward
</source>

<source>
  @type dstat
  @label @METRICS # dstat events are routed to <label @METRICS>
  # ...
</source>

<filter app.**>
  @type record_transformer
  <record>
    # ...
  </record>
</filter>

<match app.**>
  @type file
  # ...
</match>

<label @METRICS>
  <match **>
    @type elasticsearch
    # ...
  </match>
</label>
```

## Reroute Event by Tag

Use [fluent-plugin-route](https://github.com/tagomoris/fluent-plugin-route) plugin. This plugin rewrites `tag` and re-emit events to other `match` or Label.

```
<match worker.**>
  @type route
  remove_tag_prefix worker
  add_tag_prefix metrics.event

  <route **>
    copy # For fall-through. Without copy, routing is stopped here. 
  </route>
  <route **>
    copy
    @label @BACKUP
  </route>
</match>

<match metrics.event.**>
  @type stdout
</match>

<label @BACKUP>
  <match metrics.event.**>
    @type file
    path /var/log/fluent/backup
  </match>
</label>
```

## Re-route Event by Record Content

Use [fluent-plugin-rewrite-tag-filter](https://github.com/fluent/fluent-plugin-rewrite-tag-filter).

```
<source>
  @type forward
</source>

# event example: app.logs {"message":"[info]: ..."}
<match app.**>
  @type rewrite_tag_filter
  <rule>
    key message
    pattern ^\[(\w+)\]
    tag $1.${tag}
  </rule>
  # more rules
</match>

# send mail when receives alert level logs
<match alert.app.**>
  @type mail
  # ...
</match>

# other logs are stored into a file
<match *.app.**>
  @type file
  # ...
</match>
```

See also: [out\_rewrite\_tag\_filter](https://docs.fluentd.org/output/rewrite_tag_filter)

## Re-route Event to Other Label

Use [out\_relabel](https://docs.fluentd.org/output/relabel) plugin. This plugin simply emits events to Label without rewriting the `tag`.

```
<source>
  @type forward
</source>

<match app.**>
  @type copy
  <store>
    @type forward
    # ...
  </store>
  <store>
    @type relabel
    @label @NOTIFICATION
  </store>
</match>

<label @NOTIFICATION>
  <filter app.**>
    @type grep
    regexp1 message ERROR
  </filter>

  <match app.**>
    @type mail
  </match>
</label>
```

If this article is incorrect or outdated, or omits critical information, please [let us know](https://github.com/fluent/fluentd-docs-gitbook/issues?state=open). [Fluentd](http://www.fluentd.org/) is an open-source project under [Cloud Native Computing Foundation (CNCF)](https://cncf.io/). All components are available under the Apache 2 License.


---

# 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.fluentd.org/configuration/routing-examples.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.