# Plugin Helper: Event Emitter

The `event_emitter` plugin helper introduces the `router` method to the plugin.

Here is an example:

```ruby
require 'fluent/plugin/output'

module Fluent::Plugin
  class RelabelOutput < Output
    Fluent::Plugin.register_output('relabel', self)
    helpers :event_emitter

    def multi_workers_ready?
      true
    end

    def process(tag, es)
      router.emit_stream(tag, es)
    end
  end
end
```

## Methods

### `router`

This method returns a `Fluent::EventRouter` instance.

Code example:

```ruby
# emit event
router.emit(tag, time, record)

# emit event stream
router.emit_stream(tag, es)

# emit error event
begin
  # do something
rescue => error
  # Route event to @ERROR label or
  # log error message when @ERROR label is not defined in configuration
  router.emit_error_event(tag, time, record, error)
end
```

## Plugins using `event_emitter`

* All input plugins
* All filter plugins
* [`out_exec`](/output/exec.md)
* [`out_relabel`](/output/relabel.md)
* [`out_copy`](/output/copy.md)
* [`out_roundrobin`](/output/roundrobin.md)

If this article is incorrect or outdated, or omits critical information, please [let us know](https://github.com/fluent/fluentd-docs-gitbook/issues?state=open).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/plugin-helper-overview/api-plugin-helper-event_emitter.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.