Bun.serve(http3): do not re-enter lsquic when stop() runs inside a request handler - #42619
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…quest handler server.stop() and server.stop(true) from an HTTP/3 request handler, or from a microtask the handler resolved, run inside lsquic_engine_process_conns. Both paths entered the engine again (cooldown, send_unsent_packets), which lsquic asserts against. On a release build the abrupt path closed the UDP fd before the running tick packed the CONNECTION_CLOSE, so every peer waited for its idle timer. The graceful path on a connection that had already served a request left the process spinning at 100% CPU with the request in the handler never answered. One enter/leave pair now brackets every engine call that can run callbacks. While it is held, us_quic_socket_context_shutdown and us_quic_listen_socket_close only record the request, and leave finishes it: GOAWAY or CONNECTION_CLOSE, flush, then the fd. A new QUIC listener releases a pending fd before it binds, so a same-port rebind in the same turn still works.
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Status Reproduced on release 1.4.3-canary.1 (6a92015) and on main (a22b2aa). The script needs a self-signed pair ( // bun repro.mjs abrupt | graceful
import fs from "node:fs";
const tls = { key: fs.readFileSync("key.pem", "utf8"), cert: fs.readFileSync("cert.pem", "utf8") };
const abrupt = process.argv[2] !== "graceful", t0 = performance.now();
const inHandler = Promise.withResolvers(), proceed = Promise.withResolvers();
const server = Bun.serve({ port: 0, hostname: "127.0.0.1", tls, http3: true, http1: false,
async fetch(req) {
if (req.url.endsWith("/warm")) return new Response("warm");
inHandler.resolve();
await proceed.promise;
return new Response("late");
} });
const h3 = { protocol: "http3", tls: { rejectUnauthorized: false } };
const origin = "https://127.0.0.1:" + server.port;
await fetch(origin + "/warm", h3).then(r => r.text());
const body = new ReadableStream({ start(c) { c.enqueue("x"); c.close(); } });
const inflight = fetch(origin + "/", { ...h3, method: "POST", body }).then(r => r.text(), e => e.code);
await inHandler.promise; // this continuation runs inside the handler's microtask drain
server.stop(abrupt);
proceed.resolve();
console.log(await inflight, "@" + Math.round(performance.now() - t0) + " ms");
process.exit(0);
Tests: |
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No actionable comments were generated in the recent review. 🎉 ℹ️ Recent review info⚙️ Run configurationConfiguration used: Path: .coderabbit.yaml Review profile: ASSERTIVE Plan: Essentials Run ID: 📒 Files selected for processing (2)
Included review availability: Your plan provides up to 10 included reviews per hour; 1 remains after this review. WalkthroughThe QUIC engine now defers shutdown and listener-close work requested during engine processing. HTTP/3 tests cover forceful stops, stream resets, same-port rebinding, implicit disposal, and graceful stops. ChangesQUIC lifecycle handling
Suggested reviewers: Priority: ➖ Normal Merge Risk: ⚪ Minimal · up to The HTTP/3 shutdown lifecycle changes have no supported unresolved merge-blocking risk. 🚥 Pre-merge checks | ✅ 4✅ Passed checks (4 passed)
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Inline comments:
In `@packages/bun-usockets/src/quic.c`:
- Around line 935-937: Restrict us_quic_finish_pending_closes during
us_quic_socket_context_listen to listeners whose cached ls->local bound port
matches the requested port, so unrelated pending closes remain queued. Compare
the effective port populated by getsockname rather than only the raw requested
value, preserving correct behavior when the requested port is 0.
In `@test/js/bun/http/serve-http3.test.ts`:
- Around line 995-998: Replace the plain parameterized for-loops in both new
test suites with describe.each: use the four boolean combinations for the
graceful-stop matrix and the two label/setup pairs for the stop(true) cases.
Preserve the existing generated case names, grouping, and test behavior while
applying the parameter values through each suite’s callbacks.
- Line 1015: Update the child script’s stdin handling around the process.stdin
end listener to explicitly start flowing before waiting for "end", such as by
calling resume() or another existing acquisition path. Preserve the clean
process.exit(0) behavior once stdin closes.
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review. Visit https://docs.coderabbit.ai/cli?utm_source=ghpr.
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packages/bun-usockets/src/quic.ctest/js/bun/http/serve-http3.test.ts
Included review availability: Your plan provides up to 10 included reviews per hour; 1 remains after this review.
…port A bind to another port, or to port 0, cannot collide with the pending fd, so it stays open and its CONNECTION_CLOSE still goes out. The in-handler stop tests use test.each, and their fixture starts stdin so that it exits when the test closes it.
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The three review comments are addressed in 5679b3e.
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Updated 8:48 AM PT - Sep 13th, 2026
✅ @robobun, your commit eaca956d6b55ae419a5557027cb12162049e11a6 passed in 🧪 To try this PR locally: bunx bun-pr 42619That installs a local version of the PR into your bun-42619 --bun |
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…quest handler (oven-sh#42619) ### Problem - `server.stop()` or `server.stop(true)` from an HTTP/3 request handler, or from a microtask the handler resolved (the end of a `using server` scope counts), runs inside `lsquic_engine_process_conns` and enters the engine again. lsquic forbids that. A debug build aborts: `lsquic_engine_send_unsent_packets(lsquic_engine_t *): Assertion '!((engine)->pub.enp_flags & ENPUB_PROC)' failed.` - Release, `stop(true)`: `us_quic_listen_socket_close` (`packages/bun-usockets/src/quic.c:917`) closes the UDP fd before the running tick packs the CONNECTION_CLOSE. Every peer waits for its idle timer (10 s to 30 s). - Release, `stop()` on a connection that already served a request: the process spins at 100% CPU and the request in the handler never completes. ### Fix - One enter/leave pair brackets every engine call that can run callbacks (`process_conns`, `send_unsent_packets`). While it is held, `us_quic_socket_context_shutdown` and `us_quic_listen_socket_close` only record the request. `leave` finishes it: GOAWAY or CONNECTION_CLOSE, flush, then the fd. - `us_quic_socket_context_listen` releases a pending fd before it binds to the same port, so `stop(true)` then `Bun.serve` on that port in one turn still works. A stop from a timer is unchanged. - Verified: `test/js/bun/http/serve-http3.test.ts` (9 new tests, release main fails 6, debug main fails 9). - Self-reviewed: the review asked for the graceful path in the same PR. Done. Supersedes oven-sh#34447. ### Background - lsquic drives every connection from `lsquic_engine_process_conns`. Request handlers and the microtasks they resolve run inside it. - `lsquic_conn_abort` only sets a flag. The connection's tick sees it after the handler returns and packs the CONNECTION_CLOSE. The engine sends it before `process_conns` returns. - `ctx->processing` in `quic.c` is set while the engine is on the stack. <details><summary>Notes</summary> **Where this comes from.** No user report and no CI incident. oven-sh#34038 made an abrupt stop send CONNECTION_CLOSE for an idle connection when the caller is off the stack. A probe of the same stop with a request in the handler found the cases above. **Timings, release 1.4.3-canary.1, client and server in one process, request in the handler** | call | from a timer | from the handler, before | from the handler, after | | --- | --- | --- | --- | | `stop(true)`, streamed POST | `HTTP3StreamReset` at once | `HTTP3StreamReset` @10 s (warm connection) or @30 s (cold) | at once | | `stop(true)`, GET, old port dead | `HTTP3HandshakeFailed` @10 s | @20 s | @10 s | | `stop()`, cold connection | response arrives | response arrives | same | | `stop()`, warm connection | response arrives | 100% CPU, never completes (stopped after 60 s) | response arrives | The stall for `stop(true)` is the smaller of the server `idleTimeout` (30 s when it is 0) and the client's `max_idle_timeout`, and it hits every connection of the server. A client that re-sends the request adds its 10 s handshake timeout against the closed port. That retry is by design for an idempotent request (`fetch-http3-client.test.ts`, `retries on a fresh session when a pooled session is stale (port reuse)`). After the fix the client log shows `conn_close status=8` at once. **Why the `stop(true)` tests use a `ReadableStream` body.** The fetch client never re-sends a streamed body, so `HTTP3StreamReset` surfaces as soon as the client sees the connection close. With any other body the retry hides the difference behind a 10 s handshake timeout. **Why not keep the fd open in every case.** `stop(true)` promises that the port is free when it returns, and `server.stop(true); server = Bun.serve({ port })` is a common restart pattern. A deferred fd still holds the port, and these sockets do not set `SO_REUSEPORT`. The first version of this change failed that rebind inside a handler with `Failed to listen on UDP port N for HTTP/3`. One test pins it. Only in that case the stopped server's connections go silent, as they did before. A bind to another port leaves the pending fd alone (one more test). **Engine calls outside the pair.** `lsquic_engine_cooldown` (makes no callbacks), `lsquic_engine_packet_in` and `lsquic_engine_connect` (their callbacks stay in C), and `lsquic_engine_destroy` in `us_quic_socket_context_free`. **Excluded, not new.** `server.stop()` followed by `server.stop(true)`: the first call takes `h3_listener`, so the second never reaches `us_quic_listen_socket_close` for HTTP/3. **Relation to oven-sh#34447.** It wraps the abrupt path's engine calls in `if (!processing)` and defers the graceful path with its own latch and hook. It still closes the fd first on `stop(true)` (its test comment says the client then hangs), and it describes the graceful case as benign on release. This PR keeps one latch per call and one hook, and ports its two graceful tests with a warm-connection variant. **Relation to oven-sh#42579.** Its new client test stops a server after one `setImmediate` hop to stay off this path. After this PR the hop is not needed. **Suites run on the debug ASAN build:** `serve-http3` (62 pass), `fetch-http3-client` (56), `serve-protocols` (20), `fetch-http3-adversarial` (27), `fetch-http3-cold-post` (2), `fetch-http3-syscall-fault` (3). </details> <!-- robobun:evidence:begin --> --- **[human-review]** gate passed · iteration 0 · 2 files touched <details><summary>fails on main (without fix)</summary> ```console ASAN without fix: 11 FAILED $ BUN_DEBUG_QUIET_LOGS=1 bun scripts/build.ts --profile=debug --quiet test "--reporter=junit" "--reporter-outfile=/tmp/pr_gate.xml" "test/js/bun/http/serve-http3.test.ts" bun test v1.4.3 (6a92015) test/js/bun/http/serve-http3.test.ts: (node:1831379) ExperimentalWarning: quic is an experimental feature and might change at any time (Use `bun-debug --trace-warnings ...` to show where the warning was created) (pass) Bun.serve HTTP/3 > basic GET [1433.51ms] (pass) Bun.serve HTTP/3 > POST echoes body, status, request headers [1535.24ms] (pass) Bun.serve HTTP/3 > 204 with no body [1423.30ms] (pass) Bun.serve HTTP/3 > query string is preserved [1345.95ms] (pass) Bun.serve HTTP/3 > large response body crosses multiple QUIC packets [1369.07ms] (pass) Bun.serve HTTP/3 > concurrent requests across separate connections [1374.92ms] (pass) Bun.serve HTTP/3 > client abort mid-response does not crash the server [1562.40ms] (pass) Bun.serve HTTP/3 > http1: false rejects HTTP/1.1 but accepts HTTP/3 [1396.90ms] (pass) Bun.serve HTTP/3 > http1: false — url/address/stop see the QUIC listener [2251.74ms] (pass) Bun.serve HTTP/3 > maxRequestBodySize is enforced for H3 bodies without C ... (truncated) release without fix: 6 failed, 1 skipped bun test v1.4.3-canary.1 (b7616e5) test/js/bun/http/serve-http3.test.ts: (node:1832208) ExperimentalWarning: quic is an experimental feature and might change at any time (Use `bun --trace-warnings ...` to show where the warning was created) (pass) Bun.serve HTTP/3 > basic GET [133.48ms] (pass) Bun.serve HTTP/3 > POST echoes body, status, request headers [134.22ms] (pass) Bun.serve HTTP/3 > 204 with no body [132.61ms] (pass) Bun.serve HTTP/3 > query string is preserved [133.55ms] (pass) Bun.serve HTTP/3 > large response body crosses multiple QUIC packets [137.20ms] (pass) Bun.serve HTTP/3 > concurrent requests across separate connections [133.74ms] (pass) Bun.serve HTTP/3 > client abort mid-response does not crash the server [131.62ms] (pass) Bun.serve HTTP/3 > http1: false rejects HTTP/1.1 but accepts HTTP/3 [133.16ms] (pass) Bun.serve HTTP/3 > http1: false — url/address/stop see the QUIC listener [1029.34ms] (pass) Bun.serve HTTP/3 > maxRequestBodySize is enforced for H3 bodies without Content-Length [140.71ms] (pass) Bun.serve HTTP/3 > unknown route returns 404 [130.97ms] (pass) Bun.serve HTTP/3 > routes: handler with :params [131.55ms] (pass) Bun.serve HTTP/ ... (truncated) ``` </details> <details><summary>passes on PR (with fix)</summary> ```console ASAN with fix: all passed $ BUN_DEBUG_QUIET_LOGS=1 bun scripts/build.ts --profile=debug --quiet test "--reporter=junit" "--reporter-outfile=/tmp/pr_gate.xml" "test/js/bun/http/serve-http3.test.ts" bun test v1.4.3 (6a92015) test/js/bun/http/serve-http3.test.ts: (node:1834975) ExperimentalWarning: quic is an experimental feature and might change at any time (Use `bun-debug --trace-warnings ...` to show where the warning was created) (pass) Bun.serve HTTP/3 > basic GET [1367.83ms] (pass) Bun.serve HTTP/3 > POST echoes body, status, request headers [1318.78ms] (pass) Bun.serve HTTP/3 > 204 with no body [1425.18ms] (pass) Bun.serve HTTP/3 > query string is preserved [1385.53ms] (pass) Bun.serve HTTP/3 > large response body crosses multiple QUIC packets [1317.12ms] (pass) Bun.serve HTTP/3 > concurrent requests across separate connections [1423.12ms] (pass) Bun.serve HTTP/3 > client abort mid-response does not crash the server [1372.72ms] (pass) Bun.serve HTTP/3 > http1: false rejects HTTP/1.1 but accepts HTTP/3 [1330.87ms] (pass) Bun.serve HTTP/3 > http1: false — url/address/stop see the QUIC listener [2307.59ms] (pass) Bun.serve HTTP/3 > maxRequestBodySize is enforced for H3 bodies without C ... (truncated) release with fix: 1 skipped $ bun scripts/build.ts --profile=release [configured] bun-profile → bun (stripped) in 662ms (unchanged) ninja: Entering directory `/workspace/bun/build/release' [1/124] gen generated_host_exports.rs generated_host_exports.rs: 122 exports (host=5, lazy=10, generic=107, rust=0); 243 extern-C blocks audited [2/124] gen cpp.rs (cppbind) [2/124] cargo bun_runtime → libbun_runtime.a �[1m�[92m Compiling�[0m bun_core v0.0.0 (/workspace/bun/src/bun_core) �[1m�[92m Compiling�[0m bun_errno v0.0.0 (/workspace/bun/src/errno) �[1m�[92m Compiling�[0m bun_ptr v0.0.0 (/workspace/bun/src/ptr) �[1m�[92m Compiling�[0m bun_boringssl_sys v0.0.0 (/workspace/bun/src/boringssl_sys) �[1m�[92m Compiling�[0m bun_safety v0.0.0 (/workspace/bun/src/safety) �[1m�[92m Compiling�[0m bun_base64 v0.0.0 (/workspace/bun/src/base64) �[1m�[92m Compiling�[0m bun_cares_sys v0.0.0 (/workspace/bun/src/cares_sys) �[1m�[92m Compiling�[0m bun_zlib_sys v0.0.0 (/workspace/bun/src/zlib_sys) �[1m�[92m Compiling�[0m bun_zstd v0.0.0 (/workspace/bun/src/zstd) �[1m�[92m Compiling�[0m bun_picohttp v0.0.0 (/workspace/bun/src/picohttp) �[1m�[92m Compiling�[0m bun_brotli v0.0.0 (/workspace/bun/src/ ... (truncated) ``` </details> <details><summary>diff hotspot</summary> ``` packages/bun-usockets/src/quic.c | 116 +++++++++++++++++--- test/js/bun/http/serve-http3.test.ts | 199 +++++++++++++++++++++++++++++++++++ 2 files changed, 300 insertions(+), 15 deletions(-) ``` </details> **gate history** · 1 passed · 0 rejected · iteration 0 <details><summary>evidence per changed file</summary> ``` file reads edits tests packages/bun-usockets/src/quic.c 7 7 31 test/js/bun/http/serve-http3.test.ts 4 5 31 ``` </details> <!-- robobun:evidence:end -->
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Problem
server.stop()orserver.stop(true)from an HTTP/3 request handler, or from a microtask the handler resolved (the end of ausing serverscope counts), runs insidelsquic_engine_process_connsand enters the engine again. lsquic forbids that. A debug build aborts:lsquic_engine_send_unsent_packets(lsquic_engine_t *): Assertion '!((engine)->pub.enp_flags & ENPUB_PROC)' failed.stop(true):us_quic_listen_socket_close(packages/bun-usockets/src/quic.c:917) closes the UDP fd before the running tick packs the CONNECTION_CLOSE. Every peer waits for its idle timer (10 s to 30 s).stop()on a connection that already served a request: the process spins at 100% CPU and the request in the handler never completes.Fix
process_conns,send_unsent_packets). While it is held,us_quic_socket_context_shutdownandus_quic_listen_socket_closeonly record the request.leavefinishes it: GOAWAY or CONNECTION_CLOSE, flush, then the fd.us_quic_socket_context_listenreleases a pending fd before it binds to the same port, sostop(true)thenBun.serveon that port in one turn still works. A stop from a timer is unchanged.test/js/bun/http/serve-http3.test.ts(9 new tests, release main fails 6, debug main fails 9).Background
lsquic_engine_process_conns. Request handlers and the microtasks they resolve run inside it.lsquic_conn_abortonly sets a flag. The connection's tick sees it after the handler returns and packs the CONNECTION_CLOSE. The engine sends it beforeprocess_connsreturns.ctx->processinginquic.cis set while the engine is on the stack.Notes
Where this comes from. No user report and no CI incident. #34038 made an abrupt stop send CONNECTION_CLOSE for an idle connection when the caller is off the stack. A probe of the same stop with a request in the handler found the cases above.
Timings, release 1.4.3-canary.1, client and server in one process, request in the handler
stop(true), streamed POSTHTTP3StreamResetat onceHTTP3StreamReset@10 s (warm connection) or @30 s (cold)stop(true), GET, old port deadHTTP3HandshakeFailed@10 sstop(), cold connectionstop(), warm connectionThe stall for
stop(true)is the smaller of the serveridleTimeout(30 s when it is 0) and the client'smax_idle_timeout, and it hits every connection of the server. A client that re-sends the request adds its 10 s handshake timeout against the closed port. That retry is by design for an idempotent request (fetch-http3-client.test.ts,retries on a fresh session when a pooled session is stale (port reuse)). After the fix the client log showsconn_close status=8at once.Why the
stop(true)tests use aReadableStreambody. The fetch client never re-sends a streamed body, soHTTP3StreamResetsurfaces as soon as the client sees the connection close. With any other body the retry hides the difference behind a 10 s handshake timeout.Why not keep the fd open in every case.
stop(true)promises that the port is free when it returns, andserver.stop(true); server = Bun.serve({ port })is a common restart pattern. A deferred fd still holds the port, and these sockets do not setSO_REUSEPORT. The first version of this change failed that rebind inside a handler withFailed to listen on UDP port N for HTTP/3. One test pins it. Only in that case the stopped server's connections go silent, as they did before. A bind to another port leaves the pending fd alone (one more test).Engine calls outside the pair.
lsquic_engine_cooldown(makes no callbacks),lsquic_engine_packet_inandlsquic_engine_connect(their callbacks stay in C), andlsquic_engine_destroyinus_quic_socket_context_free.Excluded, not new.
server.stop()followed byserver.stop(true): the first call takesh3_listener, so the second never reachesus_quic_listen_socket_closefor HTTP/3.Relation to #34447. It wraps the abrupt path's engine calls in
if (!processing)and defers the graceful path with its own latch and hook. It still closes the fd first onstop(true)(its test comment says the client then hangs), and it describes the graceful case as benign on release. This PR keeps one latch per call and one hook, and ports its two graceful tests with a warm-connection variant.Relation to #42579. Its new client test stops a server after one
setImmediatehop to stay off this path. After this PR the hop is not needed.Suites run on the debug ASAN build:
serve-http3(62 pass),fetch-http3-client(56),serve-protocols(20),fetch-http3-adversarial(27),fetch-http3-cold-post(2),fetch-http3-syscall-fault(3).[human-review] gate passed · iteration 0 · 2 files touched
fails on main (without fix)
passes on PR (with fix)
diff hotspot
gate history · 1 passed · 0 rejected · iteration 0
evidence per changed file