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The idle timer is re-armed by writes and by writable events only. The kernel raises a writable event once a good part of its send buffer has drained, so a peer that reads steadily but slower than that buffer drains can sit between two writable events for longer than idleTimeout. The request was then aborted and the socket closed mid-body. When the timer is armed with outgoing bytes pending (a short write, or a remainder in the uWS buffer), remember the kernel's delivery mark (Linux SIOCOUTQNSD/SIOCOUTQ, macOS SO_NWRITE, Windows SIO_TCP_INFO BytesOut). On timeout, a changed mark means the peer took bytes since: re-arm for one more period. A peer that took nothing for a whole period closes as before.
…sendfile A peer that takes one byte per period is idle. Re-arm only when the kernel delivered at least HTTP_RECEIVE_THROUGHPUT_BYTES * idleTimeout since the mark, the same floor the receive side applies. Http2Connection::touch and Http2Context::onTimeout take part in the same rule. The sendfile path arms its writable wait outside of any uWS write, so mark_needs_more re-arms the timer to record the pending bytes.
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Status: ready for review. Reproduced on 1.4.3 with a 12 MB body read at 100 KB/s (aborted at 12 s, 4.2 MB delivered, no chunked terminator). With this branch the same transfer completes, for stream, Blob, CI on 8fc1424 (build 111994) is green for this diff. What remains red there is unrelated: Windows x64 agents that Azure failed to create, one darwin shard that timed out downloading the build artifact, and the pre-existing Two revision notes for reviewers. The first version measured the unsent-queue depth (SIOCOUTQ); a producer that refills the send buffer as fast as the peer drains it holds that depth constant, so it read as no progress on a live HTTP/2 reader, and the mark is now a cumulative delivered-bytes counter ( |
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Included review availability: Your plan provides up to 10 included reviews per hour; 1 remains after this review. WalkthroughThe change adds platform-specific socket delivery marks and uses them to keep HTTP and HTTP/2 connections open while slow clients continue receiving response data. It also updates write-path timeout resets and adds regression tests for slow and stalled readers. ChangesSocket send-progress API
HTTP timeout handling
Regression coverage
Suggested reviewers: Merge Risk: ⚪ Minimal · up to This change adds slow-reader timeout coverage for HTTP/1 and HTTP/2 responses, including stalled-peer behavior. No concrete current-head merge-blocking risk remains. 🚥 Pre-merge checks | ✅ 4✅ Passed checks (4 passed)
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Updated 7:34 PM PT - Sep 7th, 2026
❌ @Jarred-Sumner, your commit 9584615 has 4 failures in
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🟡 (optional) The HTTP/2 side gets only the positive slow-reader case; the negative contract — a fully-stalled peer is still aborted within one period — is tested for HTTP/1 (serve.test.ts "still times out a reader that stops") but not here, even though Http2Context::onTimeout gained the same extension logic. Fix: add the h2 twin of the stalled-reader test so a regression that lets us_socket_send_progressed keep re-arming a dead h2 connection would be caught.
Extended reasoning...
REVIEW.md: "Cover the variant matrix, not just the repro … the negative contract" and "Fix the whole class in the same PR … HTTP/1 and HTTP/2." Http2Context::onTimeout (Http2Context.h:966-972) now calls us_socket_send_progressed and, when it returns 1, re-arms us_socket_timeout instead of aborting streams. Nothing in the added tests exercises the branch where an h2 peer opens a wide window, receives one burst, then stops reading entirely — the HTTP/1 suite proves that path still aborts, but a future change to the shared us_socket_send_progressed (or to how h2's touch() records the mark) that made a stalled h2 peer read as "progressed" would ship without a failing test. On the base branch there was no extension logic to under-cover; this is new surface added without its negative test.
Verification: nit — The claim is accurate. Http2Context::onTimeout gained the same re-arm-on-progress branch as HTTP/1 (packages/bun-uws/src/Http2Context.h:966-972: if (conn->sendProgressMarked && us_socket_send_progressed(...)) { us_socket_timeout(s, conn->idleTimeoutS); return s; }), so the negative contract — a peer that stops reading entirely must still abort — is now a live regression risk on the h2…
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The stalled-peer contract is shared code: both HttpContext::onTimeout and Http2Context::onTimeout call the same us_socket_send_progressed with the same floor, and the HTTP/1 case "still times out a reader that stops" exercises it. An h2 twin would add another 16 s plus case for the same function. Leaving this one open for a maintainer to weigh.
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A producer that refills the kernel send buffer as fast as the peer drains it holds the unsent-queue depth constant. A depth delta then reads as no progress even while the peer reads steadily, so the idle timer still aborted an HTTP/2 slow reader. Read a monotonic delivered-bytes counter instead (Linux TCP_INFO tcpi_bytes_acked, macOS tcpi_txbytes, Windows SIO_TCP_INFO BytesOut). Its growth is real throughput, so onTimeout re-arms a reader that took at least the minimum rate and closes one that took nothing.
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A long pause plus scheduler jitter under ASAN made a live reader look idle for a whole period on slow CI machines. Read at a fixed low rate instead (below the rate that frees a writable event, above the receive floor), run past one idle period, and assert the request is still open and bytes kept arriving rather than waiting for the whole body. The negative test asserts a reader that stops is still aborted, with a generous deadline.
With receive buffer autotuning a kernel can grow the client's buffer past 8 MB, and then one read frees less than a sixteenth of it and the peer window stays closed. The server then sees no acked bytes for a whole period on that host and aborts a reader that is in fact draining. Pin the buffer through setsockopt so every read reopens the window, and read at 64 KB/s so the old code still runs out of writable events within idleTimeout.
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Actionable comments posted: 1
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Inline comments:
In `@test/js/bun/http/serve.test.ts`:
- Around line 3194-3196: Import beforeAll and move the temp directory and
big.bin fixture creation into a beforeAll hook, retaining the resulting dir and
bigFile references for the tests and keeping the existing afterAll cleanup.
Ensure skipped suites do not allocate the 64 MiB buffer or create the temporary
file during collection.
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packages/bun-usockets/src/bsd.cpackages/bun-usockets/src/internal/networking/bsd.hpackages/bun-usockets/src/libusockets.hpackages/bun-usockets/src/socket.cpackages/bun-uws/src/Http2Context.hpackages/bun-uws/src/HttpContext.hpackages/bun-uws/src/HttpResponse.hpackages/bun-uws/src/HttpResponseData.hsrc/uws_sys/libuwsockets.cpptest/js/bun/http/serve-http2.test.tstest/js/bun/http/serve.test.ts
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…-timeout-slow-reader
Pausing len/RATE after every data event let one large event (Linux doubles SO_RCVBUF, so up to 256 KB with a 128 KB pin) cost a 4 s pause, equal to the shortest idle window of an 8 s timeout, and a late timer lowered the rate. Pace against bytes-so-far / RATE instead, so a late timer shortens the next pause, and pin 64 KB so one event is at most a 2 s pause.
On macOS the loopback stack serves a slow reader in persist-timer bursts about 4 s apart and hands the client chunks of up to 512 KB, so the server can observe nothing for several seconds even while the client reads steadily. uSockets rounds idleTimeout 8 to a 4 to 8 s window, which can expire between two such bursts; 10 (the default the report is about) gives 8 to 12 s. Cap any single read pause at 4 s so an oversized chunk cannot open a long gap, halve the rate to 32 KB/s so the unfixed server still misses its writable event on Linux, and shrink the body to 16 MiB, which is still far more than the paced window plus kernel buffers absorb.
Problem
Bun.serveaborts a response while the client is still reading it, when the client reads slower than the kernel send buffer drains. AfteridleTimeout(default 10 s)req.signalfires, a stream body getscancel(), and the socket closes mid-body. In development mode:warn: Bun.serve() timed out a request after 10 seconds. Pass idleTimeout to configure.A 12 MB body read at 100 KB/s on Linux loopback is cut at 12 s with 4.2 MB delivered. Plainnew Response(bytes), streams,Bun.fileandhttp2: trueare all affected.HttpResponse::resetTimeout,HttpContext::onWritable). Linux raises a writable event once about a third of the send buffer (4 MB autotuned) is free, so a steady reader below about 150 KB/s goes more than one period with no event.HttpContext::onTimeout(packages/bun-uws/src/HttpContext.h) then closes without looking at the bytes in flight.Fix
resetTimeoutrecords a kernel delivery mark:us_socket_send_progress_markreads a monotonic count of bytes delivered toward the peer. That istcpi_bytes_ackedfromTCP_INFOon Linux,tcpi_txbytesfromTCP_CONNECTION_INFOon macOS, andBytesOutfromSIO_TCP_INFOon Windows.us_socket_send_progressedcompares. If the counter grew by at leastHTTP_RECEIVE_THROUGHPUT_BYTES * idleTimeout(16 KB/s, the floor the receive side already applies to uploads) the timer gets one more period. A peer that took nothing, or a trickle, closes as before. A stalled peer still aborts within about one to two periods.Http2Connection::touchandHttp2Context::onTimeoutapply the same rule. The sendfile path arms its writable wait outside of any uWS write, sous_socket_mark_needs_more_not_sslre-arms the timer to record the pending bytes.test/js/bun/http/serve.test.ts("idleTimeout and a slow reader": bytes, stream, file, and a stalled peer that must still abort) andtest/js/bun/http/serve-http2.test.ts("idleTimeout keeps a slow reader alive"). The slow reader cases fail on 1.4.3 and pass here, on Linux (ASAN debug) and on macOS 14 x64 and 26 arm64. Also ranserve.test.ts,bun-server.test.ts,bun-serve-file.test.ts, theserve-http2*suites and the node http suites.Background
idleTimeout: 10fires 8 to 12 s after the last re-arm.send()setslast_write_failedand armsEPOLLOUT.us_socket_is_awaiting_writableexposes that flag. The remainder either stays inAsyncSocketData::buffer(end(),write()) or with the caller (tryEnd, the sendfile loop), which re-armsonWritable.close(), so only the remainder above was lost.Notes
tcp_wmem(4 MB max): readers at 50 to 150 KB/s were aborted, 400 KB/s survived. Behind nginx or caddy on the same host with proxy buffering off, the upstream socket drains at the WAN client's rate.getsockopt(orWSAIoctl) per re-arm, only while the socket is backpressured.tcpi_bytes_ackedis absent and the old behavior stays.idleTimeoutto 4 s ticks, so a value of 8 (a 4 to 8 s window) can expire between two bursts there, while 10 (8 to 12 s) always spans one. The tests use 10, pace against a byte schedule, cap any single pause at 4 s, and pin a smallSO_RCVBUFso Linux hands the client chunks of at most ~128 KB. Measured on the CI minis (macOS 14 x64 and 26 arm64) with a C probe and a standalone copy of the test.idleTimeout: 0was and is a full workaround. Node'shttp.createServerhas no idle timeout on the response side.