# Event Streams API Preview **URL:** \ **Category:** Module Development\ **Created:** [November 19, 2024, 5:38pm UTC](https://forum.inductiveautomation.com/t/event-streams-api-preview/98796 "2024-11-19T17:38:29Z")\ **Posts on this page:** 8\ **Page:** 1
**Author:** ![cody.tamaki](https://avatars.discourse-cdn.com/v4/letter/c/b487fb/32.png) [@cody.tamaki](https://forum.inductiveautomation.com/u/cody.tamaki)\ **Post date:** [November 19, 2024, 5:38pm UTC](https://forum.inductiveautomation.com/t/event-streams-api-preview/98796/1 "2024-11-19T17:38:29Z")
Could somebody point me towards the classes we'd be using in 8.3 to publish events for the new event streams feature coming? I'm working on a feature right now that would probably utilize this in the future so I'd like to plan ahead if possible 🙂 ---
**Author:** ![jimender2](https://avatars.discourse-cdn.com/v4/letter/j/f05b48/32.png) [@jimender2](https://forum.inductiveautomation.com/u/jimender2)\ **Post date:** [December 2, 2024, 5:51am UTC](https://forum.inductiveautomation.com/t/event-streams-api-preview/98796/2 "2024-12-02T05:51:23Z")
You can look around in here though I dont see anything yet about it. > **[Overview](https://files.inductiveautomation.com/sdk/javadoc/earlyaccess/ignition83/8.3.0-SNAPSHOT/index.html)** > > package index ---
**Author:** ![cody.tamaki](https://avatars.discourse-cdn.com/v4/letter/c/b487fb/32.png) [@cody.tamaki](https://forum.inductiveautomation.com/u/cody.tamaki)\ **Post date:** [December 4, 2024, 5:18pm UTC](https://forum.inductiveautomation.com/t/event-streams-api-preview/98796/3 "2024-12-04T17:18:48Z")
Yeah I guess since there isn't anything here, is there any way of knowing what the API will look like from Inductive to publish a new event? I'm assuming we'll just need a namespace/topic and a payload? ---
**Author:** ![paul-griffith](https://sea1.discourse-cdn.com/inductiveautomation/user_avatar/forum.inductiveautomation.com/paul-griffith/32/37249_2.png) [@paul-griffith](https://forum.inductiveautomation.com/u/paul-griffith)\ **Post date:** [December 4, 2024, 6:11pm UTC](https://forum.inductiveautomation.com/t/event-streams-api-preview/98796/4 "2024-12-04T18:11:58Z")
It's not showing up because the event streams feature hasn't been merged in yet. It's going to be a new module, so once you've marked it as a dependency and pulled it in you'll be able to compile against it. On the gateway, you'll have to register your source and/or handler with a central registry, which will call a startup method on your hook that delivers you an `EventStreamSource.Subscriber` that you submit events to whenever your code deems it appropriate: ```java /** * Provides {@link EventPayload} to the Event Stream through the {@link Subscriber} interface. */ public interface EventStreamSource { /** * Registered with {@link EventStreamRegistry} to create concrete implementation of * {@link EventStreamSource} from the provided configuration. */ @FunctionalInterface interface Factory { /** * Called once when Event Stream is first created. * @param context {@link EventStreamContext} * @param config {@link EventStreamSource} configuration that defines its behavior * @return {@link EventStreamSource} */ EventStreamSource create(EventStreamContext context, JsonObject config); } /** * Interface for submitting events to the Event Stream. */ interface Subscriber { /** * Notifies Event Stream that events have arrived and are ready to process. *
* This call will never block. If blocking is desired, use the returned {@link CompletionStage} to wait for * the event to be processed. * * @param events List of events to pass Event Stream to start processing. * * @return Future of results that completes once all {@code events} have been processed. */ CompletionStage submitEvents(List events); /** * Notifies Event Stream that an event has arrived and are ready to process. If multiple events are available, * {@link Subscriber#submitEvents} should be used. *
* This call will never block. If blocking is desired, use the returned {@link CompletionStage} to wait for * the event to be processed. * * @param event Event to pass Event Stream to start processing. * * @return Future of results that completes once all {@code events} have been processed. */ default CompletionStage submitEvent(EventPayload event) { return submitEvents(List.of(event)).thenApply(results -> results.results().get(0)); } /** * Notifies Event Stream an error occurred. This is primarily used for diagnostics, the Event Stream will still * be considered running until Shutdown. If the error is resolved events can continue to be submitted * * @param throwable Throwable that caused the error. */ void onError(Throwable throwable); } /** * Called on Event Stream startup. Events can safely be sent to {@link Subscriber#submitEvents} or * {@link Subscriber#submitEvent}. */ void onStartup(Subscriber subscriber); /** * Called on {@link EventStreamSource} shutdown. No more events should be sent through {@link Subscriber}. If * events are submitted after, they'll immediately complete with Error result. */ void onShutdown(); } ``` You'll separately have to register different configuration (mostly for the sake of UI) in the designer to have a way to actually configure whatever settings make sense for your source, much like the way Perspective handles binding configuration. Disclaimer: This code isn't merged yet and obviously we're pre-public-beta here, so this API is potentially subject to change still. ---
**Author:** ![cody.tamaki](https://avatars.discourse-cdn.com/v4/letter/c/b487fb/32.png) [@cody.tamaki](https://forum.inductiveautomation.com/u/cody.tamaki)\ **Post date:** [December 4, 2024, 7:09pm UTC](https://forum.inductiveautomation.com/t/event-streams-api-preview/98796/5 "2024-12-04T19:09:27Z")
Thank you Paul! What's in an EventPayload if you don't mind me asking? ---
**Author:** ![paul-griffith](https://sea1.discourse-cdn.com/inductiveautomation/user_avatar/forum.inductiveautomation.com/paul-griffith/32/37249_2.png) [@paul-griffith](https://forum.inductiveautomation.com/u/paul-griffith)\ **Post date:** [December 4, 2024, 10:53pm UTC](https://forum.inductiveautomation.com/t/event-streams-api-preview/98796/6 "2024-12-04T22:53:42Z")
`EventPayload` is just a wrapper class that contains an arbitrary Object and optional 'metadata' in the form of a `Map`. Pretty maximally flexible. ---
**Author:** ![paul-griffith](https://sea1.discourse-cdn.com/inductiveautomation/user_avatar/forum.inductiveautomation.com/paul-griffith/32/37249_2.png) [@paul-griffith](https://forum.inductiveautomation.com/u/paul-griffith)\ **Post date:** [December 12, 2024, 11:54pm UTC](https://forum.inductiveautomation.com/t/event-streams-api-preview/98796/7 "2024-12-12T23:54:19Z")
Event streams has been merged and the Javadoc updated accordingly: > **[com.inductiveautomation.eventstream](https://files.inductiveautomation.com/sdk/javadoc/earlyaccess/ignition83/8.3.0-SNAPSHOT/com/inductiveautomation/eventstream/package-summary.html)** > > declaration: package: com.inductiveautomation.eventstream ---
**Author:** ![jimender2](https://avatars.discourse-cdn.com/v4/letter/j/f05b48/32.png) [@jimender2](https://forum.inductiveautomation.com/u/jimender2)\ **Post date:** [December 16, 2024, 11:29am UTC](https://forum.inductiveautomation.com/t/event-streams-api-preview/98796/8 "2024-12-16T11:29:27Z")
Looks awesome. I cant wait to get my hands on it. The module we are building is north of 200k loc and I can see Event streams helping simplify bits and pieces of it.