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SSE Subscription Push

This page describes how the platform supports both:

  • topic-based SSE subscription
  • all-topic SSE subscription

The goal is to let clients subscribe to one business topic precisely, or observe all pushed topics from one aggregated stream.

Current Capability​

The platform already exposes a topic subscription endpoint:

  • GET /subscribe/{topic}

It also reserves an all-topic endpoint:

  • GET /subscribe/topic/all

The latter needs to be fully implemented so that it can return a working SseEmitter instead of staying as a placeholder.

Design Goals​

Topic Subscription​

Keep and complete:

  • GET /subscribe/{topic}

Requirements:

  • returns text/event-stream
  • validates non-empty topic
  • cleans up the subscription automatically on lifecycle end

All-Topic Subscription​

Implement:

  • GET /subscribe/topic/all

Clients can consume it directly:

const source = new EventSource('/subscribe/topic/all');

This allows one connection to receive events from all topics.

Core Implementation Points​

Controller Layer​

The controller should explicitly declare:

produces = "text/event-stream"

and expose:

  • topic subscription: /subscribe/{topic}
  • all-topic subscription: /subscribe/topic/all

Manager Layer​

SseEmitterManager should add a global subscriber collection such as:

  • allSubscribers

and support:

  • subscribeAll()
  • lifecycle cleanup callbacks
  • removal of failed subscribers on send errors

Broadcast Strategy​

When sendToTopic(topic, message) is called, the message should be delivered to:

  • subscribers of the given topic
  • all-topic subscribers

This preserves current topic-based behavior while adding aggregated subscription naturally.

SseEmitterManager​

Responsible for:

  • managing topic -> emitters mapping
  • managing the all-topic subscriber set
  • registering onCompletion, onTimeout, and onError
  • reclaiming invalid subscribers on send failure

SseHelper​

Provides lightweight wrapping methods such as:

  • subscribe(String topic)
  • subscribeAll()

to keep the calling style consistent.

SseController​

Exposes HTTP endpoints:

  • GET /subscribe/{topic}
  • GET /subscribe/topic/all

and returns SseEmitter.

API Notes​

Topic Subscription​

  • path: GET /subscribe/{topic}
  • return type: text/event-stream
  • fit for listening to one business topic such as orders, notifications, or job status

Example:

const source = new EventSource('/subscribe/news');

All-Topic Subscription​

  • path: GET /subscribe/topic/all
  • return type: text/event-stream
  • fit for aggregated notifications, monitoring, or debugging

Example:

const source = new EventSource('/subscribe/topic/all');

Verification Suggestions​

Even without running the full site, these checks are still recommended.

Manager-Level Verification​

Validate SseEmitterManager by:

  • creating one topic subscriber
  • creating one all-topic subscriber
  • calling sendToTopic(topic, message)
  • confirming that both subscription paths receive the delivery

Code Review Checklist​

  • lifecycle callbacks clean up connections correctly
  • send failure removes only the invalid subscriber
  • empty collections are cleaned up to avoid memory growth

Compatibility​

This capability does not change the existing topic subscription path.

It only adds:

  • all-topic subscription
  • more complete cleanup and broadcast logic

So it is a compatible enhancement rather than a breaking change.