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[cfcromn]

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[gemini-code-assist]

Code Review

This pull request refactors the SSE subscription logic to use an event-driven approach by introducing AvatarSseSubscribedEvent and publishing it asynchronously upon subscription. It also simplifies connection tracking and cleanup logic, and reduces the heartbeat interval. The review feedback highlights a potential connection leak in the asynchronous onAvatarSseSubscribed event listener if a database error occurs, and suggests wrapping the logic in a runCatching block to guarantee proper cleanup.

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[gemini-code-assist]

In onAvatarSseSubscribed, if findAvatarChanges() throws an exception (e.g., due to a database connection timeout or query failure), the exception will propagate out of the @Async method. Because send is never called, the cleanup method is never invoked, leaving the SseEmitter in the emitters list indefinitely (until it eventually times out, which is set to 30 minutes). This can leak connection slots and quickly exhaust maxConnections under database error conditions.

We should wrap the execution in a runCatching block and ensure cleanup is called with complete = true if an exception occurs.

    @Async
    @EventListener
    @Transactional(readOnly = true)
    fun onAvatarSseSubscribed(event: AvatarSseSubscribedEvent) {
        runCatching { findAvatarChanges() }
            .onSuccess { send(event.emitter, it) }
            .onFailure { e ->
                logger.error("Failed to send initial avatar changes", e)
                cleanup(event.emitter, "initial send failed", complete = true)
            }
    }