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Stamp a reuse deadline on each parked keep-alive socket: the session's idleTimeout, the response's Keep-Alive: timeout=N minus 2 s, or 4 s when the origin sends no hint. find_in closes a socket past its deadline instead of handing it out. An idle socket retires with a FIN.
…eck the deadline for h2 too, keep 300 s for bun install The 600 s cap on a Keep-Alive hint applies only when the session has no idleTimeout of its own. find_in checks the reuse deadline for HTTP/2 sessions as well, so a session idleTimeout is exact there too. The registry client keeps a 300 s window: every request is a GET and is retried on a closed connection. Tests observe the FIN from the server side, and cover each arm of the window computation.
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Updated 6:34 AM PT - Oct 21st, 2026
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WalkthroughHTTP connection pooling now uses response Keep-Alive hints and session settings to set reuse windows. Pooled sockets track deadlines and close normally after expiration. Tests and documentation cover the timeout behavior, and registry GET requests use a dedicated pool. ChangesHTTP Keep-Alive reuse
Suggested reviewers: Priority: ➖ Normal Severity of issue fixed: Medium Merge Risk: 🔵 Low · up to
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| Check name | Status | Explanation |
|---|---|---|
| Linked Issues check |  |
The description references issue #45138, and the implementation directly addresses stale pooled connections causing POST requests to fail with ECONNRESET. |
| Out of Scope Changes check | |
The code, documentation, tests, and registry-pool exception all support the stated fetch connection-pooling objective. No unrelated changes are evident. |
| Linked Issues check | |
Issue #45138 requires that POST requests do not fail because Bun reuses a stale idle connection. The PR gives parked sockets a reuse deadline based on idleTimeout, Keep-Alive: timeout=N minus two … |
| Out of Scope Changes check | |
The changes stay within the connection-reuse fix. Pool logic, timeout parsing, session behavior, timer handling, HTTP/2 handling, registry-pool preservation, API documentation, and regression tests su… |
| Title check | |
The title clearly summarizes the main change: preventing reuse of pooled keep-alive connections after the origin’s reuse window expires. |
| Description check | |
The description is detailed and covers the problem, implementation, verification, test limitations, and tradeoffs. It does not use the template headings exactly, but it provides the required informati… |
Full details: Linked Issues check
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Explanation
Issue
#45138requires that POST requests do not fail because Bun reuses a stale idle connection. The PR gives parked sockets a reuse deadline based onidleTimeout,Keep-Alive: timeout=Nminus two seconds, or four seconds without a hint.find_incloses expired sockets instead of reusing them. The existing idempotent retry gate remains unchanged. The added HTTP/1.1, session, and HTTP/2 tests cover the reuse and graceful-close behavior.
Full details: Out of Scope Changes check
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Explanation
The changes stay within the connection-reuse fix. Pool logic, timeout parsing, session behavior, timer handling, HTTP/2 handling, registry-pool preservation, API documentation, and regression tests support the fix or prevent related behavior changes. The current
bun.d.tsdiff only updatesFetchSessionInit.keepAlive.idleTimeoutdocumentation. No unrelated change is demonstrated.
Full details: Description check
-
Explanation
The description is detailed and covers the problem, implementation, verification, test limitations, and tradeoffs. It does not use the template headings exactly, but it provides the required information in equivalent sections.
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Inline comments:
Review comments at @src/install/NetworkTask.rs:
- Around line 26-29: Update the REGISTRY_POOL id in NetworkTask so registry
sockets use a reserved nonzero ID outside the IDs allocated by FetchSession,
preventing reuse by ordinary default-pool requests; leave the pool’s other
options unchanged.
Review comments at @src/runtime/webcore/fetch/FetchSession.rs:
- Around line 340-343: Update the idle-timeout handling in FetchSession so
fractional idleTimeout values preserve their configured reuse deadline,
including when find_in checks whether a connection is reusable; alternatively,
reject fractional values during validation and document the whole-second
restriction.
Review comments at @test/js/web/fetch/fetch-http2-client.test.ts:
- Line 389: Remove the per-test timeout argument from the test containing the
shown timeout in fetch-http2-client.test.ts, and retain the test’s reuse-window
checks. Do not modify the other tests.
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docs/runtime/networking/fetch.mdxpackages/bun-types/bun.d.tssrc/http/AsyncHTTP.rssrc/http/HTTPContext.rssrc/http/InternalState.rssrc/http/h2_client/ClientSession.rssrc/http/lib.rssrc/install/NetworkTask.rssrc/runtime/webcore/fetch/FetchSession.rstest/js/web/fetch/fetch-http2-client.test.tstest/js/web/fetch/fetch-keepalive.test.tstest/js/web/fetch/fetch-session.test.ts
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…ndici, widen the test windows The registry pool gets its own id so a POST through the default pool or a FetchSession never rides a connection parked under its 300 s window. The Keep-Alive timeout value is its leading run of digits, so a semicolon-separated parameter list still counts. The tests that assert reuse use a 2 s window, and the fixed per-test timeouts are gone.
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Inline comments:
Review comments at @packages/bun-types/bun.d.ts:
- Around line 9085-9089: Update the idle connection timeout documentation near
the `idleTimeout` declaration to remove the inaccurate `@default 4` tag, or
replace it with explicit protocol-specific defaults that account for HTTP/2 and
HTTP/1 `Keep-Alive` hints.
Review comments at @test/js/web/fetch/fetch-keepalive.test.ts:
- Around line 1013-1015: Remove the local deadline and timeout error from the
polling loop that checks server.closes.ended and server.closes.reset; keep
polling with the existing sleep until a connection closes or resets, and let the
test runner enforce the upper bound.
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docs/runtime/networking/fetch.mdxpackages/bun-types/bun.d.tssrc/http/lib.rssrc/install/NetworkTask.rstest/js/web/fetch/fetch-http2-client.test.tstest/js/web/fetch/fetch-keepalive.test.tstest/js/web/fetch/fetch-session.test.ts
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Nothing blocking. The comments below are optional suggestions. There is no need to push a fix for them before merging.
Beyond the inline finding, I re-checked the parts of 03a5101 that follow up on the earlier round: the leading-digit Keep-Alive: timeout= parser in src/http/lib.rs (empty or non-digit value falls to None via parse_content_length_strict, more than 10 digits saturates to u32::MAX before the u64 parse, so timeout=5; max=100 and oversized values both land where the doc comment says) and the reserved REGISTRY_POOL id in src/install/NetworkTask.rs (u64::MAX cannot collide with the default pool's 0 or FetchSession ids, which count up from 1 via NEXT_POOL_ID). Both look correct; the remaining behavior change (4 s no-hint default replacing 300 s for plain fetch) is a product decision a maintainer should still weigh.
Extended reasoning...
The newest commit reworks parse_keepalive_timeout to take the leading digit run and delegate to the shared strict decimal parser, moves REGISTRY_POOL to a reserved pool id, and drops the fixed per-test timeouts while widening the reuse-window tests to 2 s. No security-sensitive surface is touched beyond parsing an adversarial header value, which now fails closed to None or saturates. The change still alters the default idle reuse window for every plain fetch() and S3 caller from 300 s to 4 s, which is a user-visible default change on the HTTP client hot path, so it is not a candidate for automated approval.
Still open from earlier reviews (3):
- Unresolved: 3 minor or pre-existing.
…h-pool-reuse-deadline # Conflicts: # src/install/NetworkTask.rs
…s a timeout The 4 s wait plus two requests leaves too little of the 5 s default on a slow build. The JSDoc no longer carries a single default: the window depends on the protocol and on the server's hint.
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Inline comments:
Review comments at @src/http/lib.rs:
- Line 5125: Update the Keep-Alive timeout assignment to retain the minimum
valid timeout across header fields, rather than replacing a shorter value with a
later, longer one. Preserve the existing handling of valid timeout values and
use `self.state.keepalive_timeout_seconds` to compare each parsed `seconds`
value.
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Fixes #45138
Problem
POSTthroughfetch()fails withECONNRESET("The socket connection was closed unexpectedly") when the origin closes idle connections after a few seconds (Turso: 5 s, noKeep-Aliveheader).src/http/HTTPContext.rs) parks an idle socket for 300 s and hands it out as the origin closes it. Only idempotent methods are retried (fetch silently retries POST on keep-alive disconnect (ECONNRESET) and merges response streams #28706).Fix
release_socketstamps a reuse deadline on each parked socket: the session'sidleTimeout, orKeep-Alive: timeout=Nminus 2 s, or 4 s with no hint (undici's numbers).N - 2 <= 0closes the socket instead of parking it. An HTTP/2 session has noKeep-Aliveheader and keeps 300 s.find_incloses a candidate past its deadline and dials a new connection. Theis_idempotentgate is unchanged.bun installkeeps a 300 s window in a pool of its own: its requests are GETs, which are retried.keepAlive.idleTimeoutis exact at reuse: the 4 s timer-wheel padding (1.4.0 regression: numeric fetchtimeoutoption aborts the in-flight request on a fixed 4 s tick, and never acts as a deadline #39952) now only arms the close timer. A timed-out idle socket sends a FIN, not a RST.fetch-keepalive.test.ts(9 new),fetch-session.test.ts(4 new),fetch-http2-client.test.ts(1 new),regression/issue/28706,bun-addand the related fetch suites. Self-reviewed: 12 concerns raised, 11 addressed. Not taken: a MSG_PEEK probe for idle HTTP/2 sessions (a syscall per reuse, out of scope).Background
PooledSocketis one parked keep-alive connection.release_socketandfind_inare the pool's only writer and reader.Keep-Alive: timeout=N(RFC 9112 appendix C.2.2) is the origin's idle limit. Node'shttp.Serversendstimeout=5.POSTon a stale socket replays a request the origin may have run (fetch silently retries POST on keep-alive disconnect (ECONNRESET) and merges response streams #28706). An age check with the 300 s default leaves plainfetch()broken.Downsides
fetch()to an origin with noKeep-Aliveheader reconnects after 4 s idle, not 300 s, as in Node. AFetchSessionidleTimeoutwidens it. Afetch.preconnectconnection is kept 4 s too. Each idle close is now a FIN, so this side holds a TIME_WAIT entry per idle connection, as in Node.PooledSocket232 -> 240 B,InternalState400 -> 408 B. Per pool lookup: one clock read (vDSO), one compare per candidate. Binary size not measured (nobloatyhere).Notes
Server-observed idle close (node:net server, ms after the last response):
FetchSessionidleTimeout: 1ECONNRESET) at 8015fetch, no hintKeep-Alive: timeout=7Keep-Alive: timeout=2The close timer is still the coarse uSockets wheel: a socket stops being reused exactly at its deadline and is closed within one wheel step after (4 s up to four minutes, 60 s beyond).
Reporter's script (
repro.mjs POST, 30 requests at 4.994 to 5.000 s gaps against a server that destroys the socket at 5 s): 1.4.3{ ECONNRESET: 2 }, this PR{}.The hint applies to a CONNECT tunnel's origin response too: the tunnel rides on the proxy socket, and the origin closing it makes the parked socket useless. A successful CONNECT reply returns before the header loop, so the proxy's own
Keep-Alivenever reaches the parser.The
Keep-Aliveparse and the deadline field first appeared in #35817, which closed without review.The hint value is its leading run of digits, like undici's
timeout=(\d+), sotimeout=5; max=100counts as 5. A quoted value does not parse and gets the 4 s default. SeveralKeep-Alivefield lines keep the shortest timeout.The JSDoc has no single
@default: the window depends on the protocol and the server's hint, so the text spells each out.Review changes after the first push: the registry pool has a reserved id (
u64::MAX) so no POST through the default pool or aFetchSessioncan take one of its 300 s connections. The sessionidleTimeoutis documented as whole seconds, rounded up. The tests that assert reuse use a 2 s window so a slow runner cannot miss it. Not changed: a sessionidleTimeoutstill caps at the origin's hint minus 2 s (a registry that sendstimeout=5is reused for 3 s, and a stale GET is retried), andfetch.preconnecttakes the 4 s default (Chromium keeps an unused socket for 10 s, a used one for 300 s).#41891 kept the RST on the idle-timer path because no timer then bounded a graceful TLS close started from the timeout handler. uSockets now gives that wait
US_SSL_CLOSE_AFTER_SPILL_TIMEOUT(10 s,packages/bun-usockets/src/crypto/openssl.c), so the reason is gone.bun installwith the 4 s default: a 45-dependency install against the local registry opened 45 connections for 87 requests before and after. With one manifest delayed past 4 s, every dependent discovered after it re-dialed (64 to 124 connections in a 141-package tree). The registry client therefore keeps the 300 s window (REGISTRY_POOLinsrc/install/NetworkTask.rs).Other suites run:
test/js/web/fetch/fetch.test.ts(failures there are IPv6, public internet, and 150 ms abort timeouts under the ASAN build, all onConnection: closepaths that never reach the pool).no test proof · iteration 0 · platform-specific test(s) that do not run on this machine, deferring to CI, which covers all platforms: test/js/web/fetch/fetch-session.test.ts, test/js/web/fetch/fetch-keepalive.test.ts