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WalkthroughChangesSocket timeout handling now tracks native write-queue progress. Tests cover timeouts during stalled lookups, buffered writes, and paused peer reads. Socket timeout progress tracking
Merge Risk: ⚪ Minimal · up to The change makes HTTP and socket timeouts fire during stalled connection setup and adds regression coverage; the remaining issue is limited to test-comment style and introduces no actionable merge-blocking risk after normal checks. 🚥 Pre-merge checks | ✅ 4✅ Passed checks (4 passed)
Full details: Description checkExplanation The description explains the problem, reproduction, cause, implementation, and verification results. Although it uses headings different from the template, it provides the required information and is sufficiently complete. Comment |
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Updated 4:23 AM PT - Sep 2nd, 2026
❌ @robobun, your commit 0a5f804 has 1 failures in
🧪 To try this PR locally: bunx bun-pr 35813That installs a local version of the PR into your bun-35813 --bun |
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Found 1 issue this PR may fix:
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Re #25453: |
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Inline comments:
In `@src/js/node/net.ts`:
- Around line 1808-1826: Update Socket.prototype._onTimeout to mirror Node’s
reset-based gate: remove the kwriteCallback proxy and explanatory comment, and
gate timeout suppression on this[kLastWriteQueueSize] > 0 && handle. Add
this[kLastWriteQueueSize] = 0 at every async write completion and error path,
including the relevant drain handlers, so the value is reset consistently when
writes finish.
In `@test/js/node/http/client-timeout-error.test.ts`:
- Around line 130-151: Update the manual promise in the “socket.setTimeout()
emits socket 'timeout' before connect” test to reject when the request or socket
emits an error, while retaining resolution through socket.setTimeout. Ensure the
error is observed before awaiting the promise so failures reject promptly
instead of hanging.
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LGTM — the kwriteCallback gate addresses the 2×-interval regression I flagged earlier, and the pre-connect emit path now matches Node.
Checked: kwriteCallback is cleared at every drain/error/close/_write-reentry site, so the gate is equivalent to Node's post-kAfterAsyncWrite check without a second marker to keep in sync. The connecting and TLS-upgrade-pending _write branches both leave _handle null, so _onTimeout falls through to emit as intended. Tests are hermetic (stalling lookup never resolves, no DNS/network), wire errors to rejection via once(), and clean up in finally.
Extended reasoning...
Overview
Rewrites Socket.prototype._onTimeout in src/js/node/net.ts to match Node's write-progress check: instead of suppressing whenever _pendingData or the native buffer is non-empty (which swallowed the event during connect and never re-armed on a stalled buffer), it now gates on this[kwriteCallback] && handle and compares kLastWriteQueueSize to the current buffered amount, re-arming via _unrefTimer() only when the queue is actively moving. Adds a new kLastWriteQueueSize symbol, initializes it in the constructor, and records it in _write's async-backpressure branch. Three new tests in test/js/node/http/client-timeout-error.test.ts cover options.timeout, socket.setTimeout(), and bare net.Socket with a pre-connect buffered write.
Security risks
None. This is idle-timer bookkeeping on an existing socket; no new input parsing, no credential/TLS handling, no allocation sizing driven by external data.
Level of scrutiny
Medium-high — net.ts backs every node:net / node:http client socket. But the change is ~15 production lines, closely mirrors Node's lib/net.js _onTimeout, and the one design divergence (gating on Bun's existing kwriteCallback marker instead of scattering kLastWriteQueueSize = 0 resets across ~10 completion sites) was debated in-thread and is sound: I grep-verified kwriteCallback is set alongside kLastWriteQueueSize in _write's async branch and cleared at every drain (~431, ~1296), error (~474, ~1011, ~1049, ~1412), close (~668, ~1369), upgrade-close (~173), and failWrite (~201) path, plus the top of _write (~2805).
Other factors
- My earlier review found a real regression (post-drain idle timeout firing at 2× interval because
kLastWriteQueueSizewas never reset). The author fixed it by gating onkwriteCallback, which is cleared on completion — verified equivalent to Node'skAfterAsyncWritereset. - The two
_writebranches that setkwriteCallbackwithoutkLastWriteQueueSize(connecting at 2774, TLS-upgrade-pending at 2795) both have_handlenull, so the&& handleguard skips the comparison and emits — the intended fix. - Tests: fail-before on
main(hang), pass with fix, pass on Node v26.3.0 per PR body. Hermetic (stallinglookupnever invokes the callback, so no DNS or connect attempt).once()wires socket errors to rejection;finallydestroys and unblocks the deferred lookup. - All prior review threads (mine, comment-cop, CodeRabbit) are resolved; CodeRabbit explicitly withdrew its
kAfterAsyncWritemirroring suggestion.
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LGTM — the kwriteCallback gate resolves the 2× interval regression I flagged, and the new stalled-peer test covers the second guard.
Reviewed: _onTimeout now matches Node's write-progress heuristic (suppress + re-arm only while the queue moves; emit when stalled or no handle). Traced every kwriteCallback set/clear site — it's cleared on both drain success branches, failWrite, all error/close handlers, and onUpgradeWriteClose, so the gate is equivalent to Node's kLastWriteQueueSize > 0 post-kAfterAsyncWrite. Checked the pre-connect _write branch (line 2747): kwriteCallback set but handle null → guard skipped → 'timeout' fires. The four new tests are hermetic (stalling lookup, local loopback server), use once() so errors reject, and CI is green on all test lanes.
Extended reasoning...
Overview
Fixes net.Socket._onTimeout in src/js/node/net.ts (~20 lines of logic) so 'timeout' fires while the socket is still connecting with queued writes — the standard node:http dead-host guard. The old code had two guards that swallowed the event without re-arming: if (this._pendingData) return (always true for HTTP clients pre-connect) and if (getBufferedAmount(handle) > 0) return (dropped the one-shot timer on a stalled write). The new code ports Node's kLastWriteQueueSize progress check: suppress and re-arm only while the write queue is moving, otherwise emit. Adds 4 tests to test/js/node/http/client-timeout-error.test.ts.
Security risks
None. Pure JS-side timer/event logic in the Node compat layer; no parsing of untrusted input, no auth/crypto/permissions. If anything this is a security improvement — dead-host requests now surface at the configured timeout instead of hanging until kernel SYN-retransmit exhaustion.
Level of scrutiny
Medium. net.Socket is a hot Node compat surface, but this is a narrow, well-understood change that mirrors Node's lib/net.js _onTimeout verbatim modulo one substitution. My earlier review found a real regression (stale kLastWriteQueueSize after drain → 2× interval); the author fixed it by gating on this[kwriteCallback] — Bun's existing async-write-in-flight marker, set in the same _write branch as kLastWriteQueueSize and already cleared by every drain/error/close/upgrade-close path. I re-traced all ~12 kwriteCallback read/write sites this run and the invariant holds: whenever kwriteCallback is truthy with a handle, either the write is still buffered (progress check meaningful) or the queue just drained and the drain handler is about to clear it. CodeRabbit's suggestion to instead reset kLastWriteQueueSize = 0 at ~10 completion sites was discussed and withdrawn; the kwriteCallback gate is equivalent with less bookkeeping to keep in sync.
Other factors
- Fail-before verified in CI evidence: 3 new tests hang on
main, pass with fix, pass on Node v26.3.0. - 4th test (stalled connected write) covers the second removed guard; without the fix the timer is dropped with no re-arm.
- All prior review threads (mine, comment-cop, CodeRabbit ×2) resolved; comment-cop's paragraph-comment complaint led to the comment being removed entirely.
- Tests are hermetic: stalling
lookupcallback for the connecting case, localnet.createServerwiths.pause()for the stalled-peer case; all useonce()so socket errors reject rather than hang. - CI 195/196 green; the only red is
binary-sizeagainst a stale canary baseline (#79916), unrelated to a ~20-line JS builtin change. - Related Node parallel tests (
test-http-client-timeout-on-connect.js,test-net-socket-timeout*.js) reported passing.
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Issue #41133 reports this same bug: the node:http timeout option never fires when the connect stalls with the request queued. The reporter hits it through @opentelemetry/otlp-exporter-base. I verified on main that both guards in _onTimeout still swallow the timer with no re-arm, and that this diff is the same fix. Consider adding "Fixes #41133" on the next push. The branch currently conflicts with main (src/js/node/net.ts moved under the write path). |
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@robobun fix conflicts |
Socket._onTimeout was suppressing the 'timeout' event whenever _pendingData was non-null. _pendingData is only populated while the socket is still connecting (or mid-TLS-upgrade), which meant any write() before the handle existed would swallow the idle timer. node:http always queues the request headers into _pendingData before connect, so options.timeout and socket.setTimeout() were both inert against a host that never answers the SYN: the request sat until the kernel's SYN retransmit budget ran out. Node.js only suppresses the event when an in-flight write to the handle is making progress (kLastWriteQueueSize in lib/net.js). Match that: track the buffered amount captured when a write goes async, and on _onTimeout compare it to the current handle buffer. If the queue is draining, re-arm the timer and wait; otherwise emit. With no handle yet (still connecting), the event always fires, restoring Node parity for the dead-host guard.
kLastWriteQueueSize is captured when _write goes async but nothing zeroed it when the drain handler completed the write, so the first idle timeout after a backpressured write saw (stale N) != (current 0), suppressed, and re-armed, doubling the interval. Node zeroes it in kAfterAsyncWrite. Bun's equivalent completion marker is kwriteCallback (cleared by every drain/error/close path), so gate on that instead of scattering a reset across the dozen completion sites. kLastWriteQueueSize is set in the same branch as kwriteCallback in _write, so it is always fresh while the gate is open.
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Rebased onto main (1f6d2db). The one conflict was in |
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…ut the fix The 1 MiB loop stopped at the first write() that returned false, which left at most one partially sent chunk in the native queue. On a host whose loopback send buffer had autotuned past that residual, the kernel absorbed it within the 200 ms window and the old getBufferedAmount() guard saw an empty queue, so the case passed without the fix. Write one 64 MiB chunk instead. That is above any loopback socket-buffer capacity, so the native queue never drains and the old guard suppresses the timer for good: the case now hangs without the fix on every run.
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LGTM — both earlier concerns are addressed: the kwriteCallback gate on _onTimeout makes the stale-snapshot-after-drain path unreachable (every drain/error handler nulls kwriteCallback before the timer can fire), and the stalled-peer test now writes a single 64 MiB chunk so the native queue cannot drain into loopback kernel buffers.
What was reviewed:
_onTimeoutrewrite against Node'slib/net.jsshape — write-progress check is gated on an in-flight callback, re-arms via_unrefTimer(), and the pre-connect_pendingDatasuppression is gone.- All
kwriteCallback = nullsites (drain, failWrite, close, error, upgrade) — each clears the gate, sokLastWriteQueueSizestaleness cannot delay a post-drain idle timeout. - New tests:
port: 0/127.0.0.1only,once()awaits with error handlers wired, cleanup infinallybefore assertions complete, no sleeps.
Extended reasoning...
Overview
The PR rewrites Socket.prototype._onTimeout in src/js/node/net.ts to match Node's write-progress heuristic: instead of unconditionally suppressing 'timeout' when _pendingData is set or the handle has any buffered bytes (and never re-arming), it now suppresses only when there is an in-flight write callback and the handle's buffered amount has moved since the last snapshot, re-arming via _unrefTimer() in that case. A kLastWriteQueueSize symbol slot is introduced, initialized in the constructor and snapshotted in _write when a write goes async. Four tests in test/js/node/http/client-timeout-error.test.ts cover pre-connect options.timeout, pre-connect socket.setTimeout(), a bare net.Socket with a buffered write pre-connect, and a connected socket whose write is stalled by a paused peer.
Security risks
None. This is idle-timer emission logic in the Node compat layer; no auth, crypto, path handling, or untrusted-input parsing is touched. The tests use a stalling custom lookup and 127.0.0.1 — no external network.
Level of scrutiny
Medium. node:net timeout semantics are user-visible and the previous behavior (silently dropping the one-shot timer) was subtle, so I traced the new invariant end-to-end. My first-round concern (stale kLastWriteQueueSize causing a 2× idle-timeout after a drained backpressured write) was addressed by commit dd765a9, which gates the whole progress check on this[kwriteCallback]; I verified every drain/error/close path in net.ts nulls kwriteCallback, so a completed write cannot enter the suppression branch and Node's separate kAfterAsyncWrite zeroing is unnecessary here. My second-round concern (the stalled-peer test passing on release without the fix because the 1 MiB loop's residual fit in autotuned loopback buffers) was addressed by commit 5857545, which writes one 64 MiB chunk that cannot drain while the peer is paused.
Other factors
The _onTimeout shape is a close port of Node's reference (lastWriteQueueSize !== writeQueueSize → snapshot + _unrefTimer() + return; else emit). The tests follow harness conventions: once() awaits with 'error' listeners attached so failures reject rather than hang, port: 0, cleanup in finally, no setTimeout/sleep waits, and no per-test timeout overrides. The PR evidence shows all four new tests hang on main and pass with the fix under both debug+ASAN and release. No outstanding CHANGES_REQUESTED reviews; the coderabbit inline threads were resolved by a non-author.
winsock accepts the whole non-blocking send() into the kernel on loopback (send() returned all 64 MiB on both Windows CI lanes), so the write never goes async and the native queue the case exercises is never populated.
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Actionable comments posted: 1
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Inline comments:
In `@test/js/node/http/client-timeout-error.test.ts`:
- Line 209: Update the test around socket.write and the timeout event to track
whether the write callback has executed, then assert it remains uncalled after
await once(socket, "timeout"). Preserve the existing timeout assertions while
ensuring the test specifically covers a still-pending native write queue.
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minimal, and validate.
Inline comments:
In `@test/js/node/http/client-timeout-error.test.ts`:
- Around line 211-212: Remove the inline implementation-detail comments near the
stalled-queue timeout test while leaving its setup, action, and assertions
unchanged; retain the test behavior and expectations without embedding the
regression rationale in the test body.
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LGTM — both earlier concerns are addressed: gating the progress check on this[kwriteCallback] (which every drain/error path already nulls) makes the missing kLastWriteQueueSize = 0 reset unnecessary, and the stalled-peer test now writes a single 64 MiB chunk so the native queue can't drain into loopback buffers.
Re-checked that the two _write branches which set kwriteCallback without kLastWriteQueueSize (the connecting and TLS-upgrade paths) both have no usable _handle, so the && handle guard falls through to emit — the pre-connect fix holds.
Extended reasoning...
Overview
The PR replaces Socket.prototype._onTimeout's unconditional suppression (_pendingData present, or any nonzero getBufferedAmount) with Node's write-progress heuristic: track the buffered amount when a write goes async, and on timer expiry suppress-and-re-arm only if the queue has moved since the last check. Runtime change is ~15 lines in src/js/node/net.ts; four new tests in test/js/node/http/client-timeout-error.test.ts cover pre-connect options.timeout, pre-connect setTimeout(), a raw net.Socket with a buffered pre-connect write, and a stalled post-connect write to a paused peer.
Security risks
None identified. This is idle-timer bookkeeping on net.Socket; no parsing of untrusted input, no auth/crypto/TLS-verification changes. The tests use a stalling lookup callback with a .invalid host and a local net.createServer on port: 0 — no external network contact.
Level of scrutiny
Medium — node:net timeout behavior sits under every node:http client request. The two concerns raised on earlier pushes were both addressed: (1) the initial port gated on lastWriteQueueSize > 0 without ever zeroing it on drain, which would have doubled the first idle timeout after a backpressured write drained; commit dd765a9 switched the gate to this[kwriteCallback], which is nulled at every drain-success and error site (lines 206, 437, 481, 701, 1036, 1074, 1295, 1366, 1409, 2782), making the reset unnecessary. (2) The stalled-peer test originally stopped writing at the first false return, leaving too little in the native queue to survive 200 ms of loopback autotuning on a release build; commit 5857545 replaced it with one Buffer.alloc(64 << 20) write and asserts write() returned false, writableLength > 0, and the callback hasn't fired when 'timeout' arrives. I also verified the two _write paths that set kwriteCallback without touching kLastWriteQueueSize (the connecting branch at line 2751 and the TLS-upgrade branch at line 2772) both lack a live _handle, so _onTimeout's && handle guard falls through to emit — no stale-value hazard there.
Other factors
The implementation is a close port of Node's lib/net.js _onTimeout, with the kwriteCallback gate as a Bun-appropriate substitute for Node's kAfterAsyncWrite reset (avoids touching ~10 existing drain sites). Tests await events via once() with error listeners attached, use port: 0, gate the loopback-buffer test with isWindows from harness, and were added to the existing module test file. No outstanding CHANGES_REQUESTED from other reviewers; hunt exit reason was dry_streak.
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This diff also fixes the hang in The test calls I applied this PR's
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This PR also fixes #42398. The report there has the same cause: |
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Closing in favour of #42399 and #42404 by @thatdoogieguy. Those two PRs fix the same two early returns in
The merge of the two also matches Node's timing on a stalled write: it fires after two idle periods. This PR fires after one. The findings of this PR are now on those PRs: #41133 as a duplicate of #42398, the ASAN hang, the network-free tests and the Windows note. See #42399 (comment) and #42404 (comment). The branch stays. Reopen this PR if the other two stall. |
What
node:httpclientoptions.timeoutandsocket.setTimeout()never fired while the underlying socket was still connecting. Against a host that drops SYNs (firewalled / black-holed), the documented dead-host guardwas inert: the request sat until the kernel's SYN-retransmit budget ran out (~130s on Linux) before failing with
ECONNREFUSED. Node.js fires'timeout'at the requested interval.Repro
A
lookupcallback that is never invoked keeps the socket inconnectingwith no native handle, which is observationally the same as a SYN that is never ACKed:Bare
net.connect({ timeout })did fire mid-connect (nothing writes to that socket), which pointed at the write-queued path.Cause
Socket.prototype._onTimeoutswallowed the event whenever_pendingDatawas non-null:_pendingDatais only populated whileconnectingis true (or during a pending TLS upgrade):_write()parks the chunk there until the handle arrives.node:httpalways writes the request headers before the socket connects, so every HTTP client request had_pendingDataset for the entire connect window and the idle timer was silently dropped.The second guard (
getBufferedAmount(handle) > 0) also suppressed without re-arming, so a stalled post-connect write buffer would eat the only timer firing.Fix
Match Node's
lib/net.js_onTimeout: trackkLastWriteQueueSizewhen a write goes async, and on timer expiry compare it to the current handle buffer. If the queue moved, the socket is still draining, so re-arm (_unrefTimer()) and wait; otherwise emit'timeout'. With no handle yet (still connecting) the check is skipped and'timeout'always fires.Verification
All four hang on
mainwaiting for an event that never arrives. The same assertions pass under Node v26.3.0. The fourth test covers the second guard directly: a loopback peer thatpause()s, and one 64 MiB write so the client's native send queue is above any loopback socket-buffer capacity andgetBufferedAmount()stays nonzero for good. Node fires'timeout'once the queue stops moving (400 ms); the old guard suppressed it with no re-arm, so the case hangs 3/3 against a build with main'snet.ts.test-http-client-timeout-on-connect.js,test-net-socket-timeout*.js, andnode-http-server-timeouts.test.tscontinue to pass.no test proof · iteration 7 · platform-specific test(s) that do not run on this machine, deferring to CI, which covers all platforms: test/js/node/http/client-timeout-error.test.ts