fix: honor node streaming backpressure#8557
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wmertens
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Apr 19, 2026
wmertens
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LGTM! But I'd like to see the comment?
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| const writePromise = writer.write(new Uint8Array([1, 2, 3])); | ||
| await Promise.resolve(); | ||
| expect(res.listenerCount('drain')).toBe(0); |
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could you add a comment explaining when the drain listeners are attached?
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This PR makes Qwik SSR honor downstream backpressure during Node streaming. The core renderer now waits for pending async flushes before emitting the next chunk, and the Node middleware translates ServerResponse.write() / drain semantics into an awaitable stream signal instead of fire-and-forget writes.
It also adds a regression test in render-api.spec.tsx to ensure a second chunk is not emitted while the first async write is still pending, plus Node middleware regression coverage so handled errors are not rethrown after headers were already sent.
Performance testing shows time drops from ~250ms to ~40ms for response