---
title: "Event Barrier"
slug: "dataflow-nodes-event-barrier"
updated: 2025-07-14T14:12:30Z
published: 2025-07-14T14:12:30Z
---

> ## Documentation Index
> Fetch the complete documentation index at: https://docs.knovvu.com/llms.txt
> Use this file to discover all available pages before exploring further.

# Event Barrier

Event Barrier node, makes sure crucial events of an utterance are sent before other events.

A **Key Event** is specified as a parameter. For each **Event Group** (*Utterance*), events are held in a queue until a Key Event for that group arrives. Once it does:

- The **Key Event** is emitted first.
- Then, all queued events from the same group are emitted in the order they arrived.

The **Key Event** only affects its own group—it does **not** trigger the release of events from other groups.

## Parameters

| name | description | default |
| --- | --- | --- |
| Key Event's Name | Name of the event that will be sent before any other event of the same group. |  |

          Example

          

For example, If we want to send an SR Milestone event only after the Language Detected event of the same utterance, we would assign `Language Detected` as the parameter.

## Inputs

### Audio

none

### Events

All

## Outputs

### Audio

none

### Events

All

## Remarks

          Additional behavior to note

          

- If a **Key Event** for a group arrives **before** any other events of that group, subsequent events will **pass through immediately** without being queued.
- **Multiple Key Events** can be received over time, each independently enabling a flush or pass-through for its specific group.

### Project Structure

In the figure below, you can see an example project.

- [**Sentiment**](/v1/docs/dataflow-nodes-sentiment) node config is prepared to send empty results.
- The Key Event Name of **Event Barrier** is set as `Sentiment`.

 <center data-tomark-pass="">
<p><img src="https://cdn.document360.io/9bca2910-6a3b-4224-9470-43f91f9a6d57/Images/Documentation/image-V3RZK2FG.png" alt="image.png"></p>
</center> 

![image.png](https://cdn.document360.io/9bca2910-6a3b-4224-9470-43f91f9a6d57/Images/Documentation/image-K0DYP0PG.png)

With this project, we make sure that every utterance, a [Sentiment](/v1/docs/events#sentiment) event is sent before the corresponding [SR Milestone](/v1/docs/events#sr-milestone) event.

### Supported flow types

Stream, Batch

## Release Notes

        

****v4.1.0****

            
            

- Introduced node.