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[BUG]: a slow SSE client can balloon server memory #231
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on Jun 11, 2026 Vetted 2026-07-17. Still count-based on main: mpsc::channel(streaming_buffer_size), default 400, with no per-item byte cap (handlers.rs:742). The memory arithmetic in this ticket holds. How hard it bites depends on the unbounded event fields tracked in #232. Description updated.
- changed the title
[-]Slow client backpressure cascade[/-][+][BUG]: a slow SSE client can balloon server memory[/+]on Jul 17, 2026
The outgoing SSE channel is bounded by item count, not bytes: mpsc::channel::<Result<Bytes, String>>(streaming_buffer_size), default 400 (handlers.rs:742, main.rs:65). There is no per-item size cap, and several event fields are unbounded (#232), so one slow client can hold up to 400 arbitrarily large chunks in memory while every producer upstream blocks on send().
Verified against main 2026-07-17. Severity scales directly with #232: once event fields are bounded this becomes a modest fixed buffer, but while they are unbounded the worst case is buffer_size times largest_event.