fix(server): add backpressure to SSE event queues#19423
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BYK wants to merge 1 commit intoanomalyco:devfrom
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fix(server): add backpressure to SSE event queues#19423BYK wants to merge 1 commit intoanomalyco:devfrom
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This was referenced Mar 28, 2026
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AsyncQueue is unbounded — when SSE clients fall behind (slow network, stalled browser tab), JSON-serialized bus events accumulate without limit. This caused 187GB RSS in production (anomalyco#16697). Add optional capacity parameter to AsyncQueue with drop-oldest behavior. Set to 1024 items (~2MB) for both SSE endpoints. TUI queues remain unbounded (1:1 request/response, never accumulate).
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Issue for this PR
Closes #16697
Type of change
What does this PR do?
Adds backpressure to the
AsyncQueueused by SSE endpoints to prevent unbounded memory growth when clients fall behind.Root cause:
AsyncQueuehas no size limit. When an SSE client stalls (slow network, backgrounded tab, stalled proxy),Bus.subscribeAllkeeps pushingJSON.stringify'd events into the queue without bound. In production this caused 187GB RSS (forensic report).Fix: Add optional
capacityparameter toAsyncQueuewith drop-oldest behavior. When the queue exceeds capacity, oldest items are discarded. Set to 1024 items (~2MB at ~2KB avg event size) for both SSE endpoints (event.tsandglobal.ts). TUI queues remain unbounded since they are 1:1 request/response pairs that never accumulate.The web UI already handles reconnection gracefully (full state reload on
server.connected), so dropped events during a stall are recovered naturally.3 files changed, ~7 lines.
How did you verify your code works?
Checklist