# Musson Industrial's Tag-Stream Module

**URL:** <https://forum.inductiveautomation.com/t/musson-industrials-tag-stream-module/92203>\
**Category:** 3rd Party Modules\
**Created:** [June 21, 2024, 11:53am UTC](https://forum.inductiveautomation.com/t/musson-industrials-tag-stream-module/92203 "2024-06-21T11:53:10Z")\
**Posts on this page:** 1\
**Page:** 1

<div class="post-metadata">

**Author:** ![bmusson](https://sea1.discourse-cdn.com/inductiveautomation/user_avatar/forum.inductiveautomation.com/bmusson/32/87530_2.png) [@bmusson](https://forum.inductiveautomation.com/u/bmusson)\
**Post date:** [June 21, 2024, 11:53am UTC](https://forum.inductiveautomation.com/t/musson-industrials-tag-stream-module/92203/1 "2024-06-21T11:53:10Z")

</div>

# Embr-Tag-Stream

**Musson Industrial** is excited to announce the release of `embr-tag-stream`, an Ignition module that provides an API for high-speed streaming of tag changes and alarms via [SSE (server-sent events)](https://javascript.info/server-sent-events).

## Motivation

SSE provides a simple API for one-way, push-only communication (server -\> client, think of a one-way websocket). Client code is simple, message overhead is low, reconnection is automatic, and security concerns are minimal due to the strict one-way nature of the connection.

## How to Use

The general flow goes like this:

1. `POST` to `/embr/tag/stream/subscribe` with a list of tags.
2. The server responds with a `session_id` (and some extra tag information).
3. Subscribe to the session at `/embr/tag/stream/session/{session_id}`.
4. Tag change and alarm events will be published as they happen, in the following formats:

#### Message Format

```js
event: tag_change
data: {"tag_id":0,"v":"Tag Value!","q": 192,"t":1717624491517}

event: alarm_event
data: {"tag_id":0,"count":1,"displayPath":"","eventData":{"eventValue":"false","name":"AlarmName","eventTime":"Thu Jun 20 13:17:37 EDT 2024","priority":"Critical","displayPath":""},"extension":{"isShelved":"false"},"id":"454d77c5-44f8-4e52-ab3c-e1ed5c950583","isAcked":false,"isCleared":false,"isShelved":false,"label":"AlarmName","name":"AlarmName","notes":"","priority":"Critical","source":"prov:default:/tag:Tag1:/alm:AlarmName","state":"Active, Unacknowledged","values":[{"isShelved":"false"}]}

```

## Example

An example client is included with the module and can be accessed at `http://{gatewayAddress}/res/embr-tag-stream/index.html`.

### Example Client Script

```js
let eventSource = null;
function createSession() {
    // Close the existing session, if it exists.
    if (eventSource) {
        eventSource.close();
    }

    // Create the body of the session request.
    const requestBody = JSON.stringify({
        "tagPaths": subscribedTags // List of tags to subscribe to.
    })
    console.log(`post-body: ${requestBody}`)

    // Create a new session.
    fetch("/embr/tag/stream/session", {
        method: "POST",
        mode: "cors",
        body: requestBody
    }).then( response => {
        // Get the response as JSON.
        return response.json()
    }).then( sessionInfo => {
        console.log(`post-response: ${sessionInfo}`)

        // Connect to the event source.
        const url = `/embr/tag/stream/session/${sessionInfo.data.session_id}`
        eventSource = new EventSource(url);

        // When a tag change occurs, display the tags new value.
        eventSource.addEventListener('tag_change', (e) => {
            const tagChangeData = JSON.parse(e.data)
            const tagPath = sessionInfo.data.tags[tagChangeData.tag_id].tag_path
            // ... Do something with the tag change information
        })

        // When the session is opened...
        eventSource.onopen = function (e) {
            console.log('EventSource opened.');
        }
    
        // If an error occurs...
        eventSource.onerror = function (e) {
            console.log('EventSource errored.');
        }
    })
}

```

## Disclaimer: Authentication

The current version of the module has no authentication requirements. If you install this module, anyone with access the the `/embr/tag/stream/session` path can subscribe to your tags.

Authentication isn't a requirement for me for this at the moment, but I would eventually like to have `BasicAuthentication` support on the session creation url, with a Gateway configuration page for selecting a `UserSource` and required roles. I will probably wait until 8.3 (I don't really want to mess with Wicket/persistence layer with 8.3 close around the corner).

Contributions are always welcome!

## Download

Full documentation and the latest release is available [here](https://github.com/mussonindustrial/embr/tree/main/modules/embr-tag-stream).

> **[embr-tag-stream · Releases · mussonindustrial/embr](https://github.com/mussonindustrial/embr/releases?q=embr-tag-stream&expanded=true)**
>
> 🔥 Open-source modules for Ignition by Inductive Automation. The home of Charts, Thermo, Periscope, and more. - mussonindustrial/embr

* * *

## Sponsorship

If you benefit from this module for commercial use, we ask you to consider sponsoring our efforts through [GitHub sponsors](https://github.com/sponsors/mussonindustrial). Your support will allow us to continue development of open-source modules and tools that benefit the entire community (plus there are some bonuses for sponsors 🙂).