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…error When a socket read holds valid chunks followed by a malformed chunk-size line, phr_decode_chunked returns -1 after it decoded those chunks. Both -1 arms in src/http/lib.rs dropped the decoded bytes, so a streaming reader lost body that node v26.3.0 delivers before it errors the stream. The -1 arms now keep what was decoded, and dispatch_result_and_reset reports it to a streaming consumer in a progress callback ahead of the failure. On the JS thread the two callbacks usually land in one on_progress_update. FetchTasklet now handles the bytes in that run and the failure in a second run on the next task, so the error does not overtake bytes that arrived before it. Aborts and timeouts are excluded.
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Included review availability: Your plan provides up to 10 included reviews per hour; 0 remain after this review. WalkthroughStreaming HTTP handling now delivers decoded body bytes before terminal failures. Chunked decoding preserves valid data before malformed chunk errors. FetchTasklet defers eligible failures until buffered bytes are consumed. Tests cover packet timing, gzip, large chunks, and response consumption methods. ChangesStreaming fetch error handling
Priority: ⬇️ Low Merge Risk: 🔵 Low · up to The streaming behavior changes appear covered, but the outstanding test-structure concern should be addressed or explicitly accepted before merge. 🚥 Pre-merge checks | ✅ 4✅ Passed checks (4 passed)
Comment |
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Status: fix verified locally on 5ff5415. The head approved earlier (c799f59) had two regressions that a self-review found. Both are fixed, see this comment. Reproduced with a raw 3 of the 9 new tests (one read, a chunk larger than one read, through a CONNECT tunnel) fail on canary Limit: when the failure reaches the JS thread before it built the Response, the bytes are still dropped, as on main. That needs #38003 first. CI: the only test that was red on every retry in builds 114094 and 114113 is |
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@robobun put a node v26.3 comparison vs main vs PR |
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@cirospaciari Here it is. Each cell is what a
Run on linux x64: compare.mjs and raw output// node compare.mjs | bun compare.mjs
// Raw TCP server. Each case: what a `res.body` reader sees before the read rejects.
import net from "node:net";
import zlib from "node:zlib";
const head = "HTTP/1.1 200 OK\r\nTransfer-Encoding: chunked\r\n";
const bad = "Connection: close\r\n\r\n"; // "C" is a hex digit: chunk-size 0xC + junk
const sleep = ms => new Promise(r => setTimeout(r, ms));
const show = b => (b.length > 40 ? `${b.length} bytes` : JSON.stringify(b.toString()));
async function run(label, { first, later, readDelay = 0, text = false }) {
let sock;
const accepted = Promise.withResolvers();
const srv = net.createServer(s => {
s.on("error", () => {});
s.once("data", () => { s.write(first); sock = s; accepted.resolve(); });
});
await new Promise(r => srv.listen(0, "127.0.0.1", r));
let out;
try {
const res = await fetch(`http://127.0.0.1:${srv.address().port}/`);
if (text) {
out = await res.text().then(t => `text() resolved ${JSON.stringify(t)}`, e => `text() rejected: ${e.code || e.cause?.code || e.name}`);
} else {
if (readDelay) await sleep(readDelay);
const reader = res.body.getReader();
const chunks = [];
let pending = reader.read();
if (later) { await accepted.promise; for (const part of later) { if (part === "WAIT_READ") { const r = await pending; chunks.push(Buffer.from(r.value)); pending = reader.read(); } else sock.write(part); } }
let end;
try { for (let r = await pending; !r.done; r = await reader.read()) chunks.push(Buffer.from(r.value)); end = "stream ended"; }
catch (e) { end = `read rejected: ${e.code || e.cause?.code || e.name}`; }
out = `body=${show(Buffer.concat(chunks))} then ${end}`;
}
} catch (e) { out = `fetch rejected: ${e.code || e.cause?.code || e.name}`; }
console.log(`${label.padEnd(46)} ${out}`);
sock?.destroy();
await new Promise(r => srv.close(r));
}
const one = `${head}\r\n1\r\nx\r\n${bad}`;
await run("1 head+chunk+bad line, one write", { first: one });
await run("2 same, reader attaches after 300 ms", { first: one, readDelay: 300 });
await run("3 head, then chunk+bad line in one write", { first: `${head}\r\n`, later: [`1\r\nx\r\n${bad}`] });
await run("4 head+chunk, then bad line after \"x\" was read", { first: `${head}\r\n1\r\nx\r\n`, later: ["WAIT_READ", bad] });
const big = Buffer.alloc(256 * 1024, "abcdefghijklmnopqrstuvwxyz").toString();
await run("5 head+256 KiB chunk+bad line, one write", { first: `${head}\r\n${big.length.toString(16)}\r\n${big}\r\n${bad}` });
const gz = zlib.gzipSync("hello hello hello hello");
await run("6 gzip member in one chunk+bad line, one write", { first: Buffer.concat([Buffer.from(`${head}Content-Encoding: gzip\r\n\r\n${gz.length.toString(16)}\r\n`), gz, Buffer.from(`\r\n${bad}`)]) });
await run("7 case 1 with await res.text()", { first: one, text: true });
process.exit(0); |
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I reviewed this PR and didn't find any bugs. Because it adds a new self-enqueued second on_progress_update run that carries the JS thread's ref through cleanup / the start_request_stream error exit, and threads an extra progress callback through dispatch_result_and_reset (shared by fail, fail_from_h2, and complete_connecting_process), a human familiar with the FetchTasklet refcount lifecycle should also look.
What was reviewed
report_body_decoded_before_failure: gated on streaming + non-emptydecoded_body+state.fail.is_some()and skips abort/timeout, so thecomplete_connecting_processand non-streaming (bun install) callers ofdispatch_result_and_resetsee no new callback.- Both
-1 | -2chunked arms: the-2path's return value is unchanged (Ok(processed)== the previousprocess_body_bufferresult when streaming,Ok(false)otherwise); aprocess_body_buffererror on the-1path propagates via?instead of being masked byInvalidHTTPResponse. hold_failure_behind_unseen_bodyis gated onhas_schedule_callback.swap(false)so the JS-thread-posted second run cannot re-hold the failure; when it triggers,has_more = truemakesis_done = false, so the ref transfers to the enqueued task rather than being deref'd incleanup.- Tests: local
net.createServeron127.0.0.1port 0,await usingon the server, no sleeps — reads are pending beforesend()writes.
Extended reasoning...
Overview
The PR changes three files. In src/http/lib.rs, the two chunked-transfer decode arms merge -1 (invalid) with -2 (needs more) so that already-decoded body bytes pass through process_body_buffer before InvalidHTTPResponse is returned, and dispatch_result_and_reset gains a report_body_decoded_before_failure prelude that emits one extra has_more = true progress callback carrying leftover decoded_body to streaming consumers ahead of the failure result. In src/runtime/webcore/fetch/FetchTasklet.rs, on_progress_update now detects the case where the HTTP thread posted both body bytes and a terminal failure before the JS thread ran: it strips the failure for this run, delivers the bytes, and in cleanup restores the failure and enqueues a second task (via enqueue_task(Task::init(ptr::from_mut(this)))) carrying this thread's ref; the start_request_stream VM-stopped error exit derefs when a failure was held back. test/js/web/fetch/fetch-chunked-size.test.ts adds a five-case describe block using a raw net server that writes valid chunks followed by a malformed chunk-size line.
Security risks
None identified. The change only affects how already-parsed body bytes are surfaced when a chunked response subsequently fails to parse; no new input is trusted, and picohttpparser's -1 remains the terminal condition. The extra callback is gated to streaming consumers, so buffered consumers (bun install, .text()) still see a single failure result.
Level of scrutiny
High. This touches cross-thread refcounted lifecycle code in FetchTasklet — exactly the class of change REVIEW.md flags as most-blocked ("Reference counts provably balanced on every terminal path"). The new self-enqueued task pattern relies on several invariants: that has_schedule_callback is set only by FetchTasklet::callback (so the second run's swap(false) yields false and cannot re-hold), that the HTTP thread sends nothing after a terminal failure (so no third callback races in between), and that every path out of the first run either reaches cleanup (which enqueues the ref-carrying task) or the start_request_stream error branch (which derefs). The PR description reasons through these carefully and lists an extensive suite run, but the invariants are non-local and a maintainer who owns this code should confirm them.
Other factors
dispatch_result_and_reset is shared by fail, fail_from_h2, and complete_connecting_process; the new prelude is a no-op for the last (no state.fail) and for non-streaming/redirect-pending cases, so scope looks contained, but the h2 path is not exercised by the new tests. The PR notes the CONNECT-tunnel path is untested. The five new tests are hermetic (local net server, port 0, await using, condition-driven — a pending read before send()), cover the same-read/separate-read/gzip/large-chunk matrix, and include the negative case (.text() still rejects). Given zero findings from the bug hunt (dry_streak) but non-trivial refcount-transfer changes, deferring to a human reviewer is the right call rather than approving.
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@robobun make row 6 match node.js plz #42261 (comment) |
…lformed chunk-size Node v26.3.0 delivers no bytes in this case: the error tears its decompressor down before it emits. The -1 arms now return the error for a compressed body before they keep the decoded bytes, so only an uncompressed body reports the chunks ahead of the malformed line.
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@robobun fix the row 6 bug and re-run it for me #42261 (comment) |
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@cirospaciari Done in ab12acd, and re-run on the current head. Row 6 now matches Node, and so does every other row. The two
The main column for row 5 changes from run to run (127946 and 196554 bytes in two runs). It depends on where the socket reads split the 256 KiB: main drops whatever part of the chunk shares the last read with the bad line. Run on linux x64: compare.mjs and raw output// node compare.mjs | bun compare.mjs
// Raw TCP server. Each case: what a `res.body` reader sees before the read rejects.
import net from "node:net";
import zlib from "node:zlib";
const head = "HTTP/1.1 200 OK\r\nTransfer-Encoding: chunked\r\n";
const bad = "Connection: close\r\n\r\n"; // "C" is a hex digit: chunk-size 0xC + junk
const sleep = ms => new Promise(r => setTimeout(r, ms));
const show = b => (b.length > 40 ? `${b.length} bytes` : JSON.stringify(b.toString()));
async function run(label, { first, later, readDelay = 0, text = false }) {
let sock;
const accepted = Promise.withResolvers();
const srv = net.createServer(s => {
s.on("error", () => {});
s.once("data", () => { s.write(first); sock = s; accepted.resolve(); });
});
await new Promise(r => srv.listen(0, "127.0.0.1", r));
let out;
try {
const res = await fetch(`http://127.0.0.1:${srv.address().port}/`);
if (text) {
out = await res.text().then(t => `text() resolved ${JSON.stringify(t)}`, e => `text() rejected: ${e.code || e.cause?.code || e.name}`);
} else {
if (readDelay) await sleep(readDelay);
const reader = res.body.getReader();
const chunks = [];
let pending = reader.read();
if (later) { await accepted.promise; for (const part of later) { if (part === "WAIT_READ") { const r = await pending; chunks.push(Buffer.from(r.value)); pending = reader.read(); } else sock.write(part); } }
let end;
try { for (let r = await pending; !r.done; r = await reader.read()) chunks.push(Buffer.from(r.value)); end = "stream ended"; }
catch (e) { end = `read rejected: ${e.code || e.cause?.code || e.name}`; }
out = `body=${show(Buffer.concat(chunks))} then ${end}`;
}
} catch (e) { out = `fetch rejected: ${e.code || e.cause?.code || e.name}`; }
console.log(`${label.padEnd(46)} ${out}`);
sock?.destroy();
await new Promise(r => srv.close(r));
}
const one = `${head}\r\n1\r\nx\r\n${bad}`;
await run("1 head+chunk+bad line, one write", { first: one });
await run("2 same, reader attaches after 300 ms", { first: one, readDelay: 300 });
await run("3 head, then chunk+bad line in one write", { first: `${head}\r\n`, later: [`1\r\nx\r\n${bad}`] });
await run("4 head+chunk, then bad line after \"x\" was read", { first: `${head}\r\n1\r\nx\r\n`, later: ["WAIT_READ", bad] });
const big = Buffer.alloc(256 * 1024, "abcdefghijklmnopqrstuvwxyz").toString();
await run("5 head+256 KiB chunk+bad line, one write", { first: `${head}\r\n${big.length.toString(16)}\r\n${big}\r\n${bad}` });
const gz = zlib.gzipSync("hello hello hello hello");
await run("6 gzip member in one chunk+bad line, one write", { first: Buffer.concat([Buffer.from(`${head}Content-Encoding: gzip\r\n\r\n${gz.length.toString(16)}\r\n`), gz, Buffer.from(`\r\n${bad}`)]) });
await run("6b gzip: head, then chunk+bad line in one write", { first: `${head}Content-Encoding: gzip\r\n\r\n`, later: [Buffer.concat([Buffer.from(`${gz.length.toString(16)}\r\n`), gz, Buffer.from(`\r\n${bad}`)])] });
await run("7 case 1 with await res.text()", { first: one, text: true });
process.exit(0); |
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@cirospaciari Please do not merge this yet. My self-review of the approved head found two regressions. I am reproducing them now and will push fixes with tests.
Two statements in the PR description are also wrong and I will correct them: |
…once the Response exists The flush in dispatch_result_and_reset reported any non-empty decoded_body, so a corrupted gzip body gave a reader inflater output ahead of ZlibError. The two -1 arms now set has_body_ahead_of_failure when they keep bytes (fetch only, uncompressed only), and the hook reports nothing without it. FetchTasklet held a failure back even before the Response existed. The Response was then built with a live body, and a body stream made before its first read dropped the error that arrived next, so the stream ended cleanly. The failure is now held only once the Response exists. With the response head in the same read the Response is built from the failure, as on main.
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@cirospaciari Both regressions are confirmed and fixed in 5a92cbd, each with a test that fails on the head you approved (c799f59) and passes on main and on the new head. Your approval was for c799f59, so please look again. The fix costs row 1 its Node parity for now. Details below. 1. Corrupted gzip body gave a reader wrong bytes. The flush in
Fix: the flush is opt-in. Only the two 2.
Cause: c799f59 held the failure back even when the Response did not exist yet. The Response was then built with a live body. A body stream made from it before its first read drops an error that arrives next ( Fix: What this costs. When the failure reaches the JS thread before it built the Response, the Response is built from the failure as on main, and the bytes are dropped. That is row 1. It can also be row 5b when the JS thread is slow.
Rows 3, 4, 5, 6, 6b and 7 match Node. Rows 1 and 5b match main, not Node. To get row 1 back the stored-error path has to be fixed first, which is what #38003 does (
I also corrected two wrong statements in the description: |
…e head was reported A failure that still carries the response head builds the Response from the failure. Reporting the chunks in a callback of their own ahead of it let the JS thread build a live body between the two callbacks, so the outcome depended on thread timing.
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@cirospaciari One more commit on top of the fixes above: 3db5d26. A review comment on 5a92cbd pointed out a timing window in the "head + chunk + bad line in one write" case. The HTTP thread sent the chunks in a callback of their own and then the failure. If the JS thread ran between the two, it built the Response with a live body, and a body stream made before its first read then dropped the failure (the same stored-error path as regression 2). main sends one failure callback there and always builds the Response from the failure. The |
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Actionable comments posted: 2
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Inline comments:
In `@test/js/web/fetch/fetch-chunked-size.test.ts`:
- Around line 133-166: Replace the parameterized it.each block with
describe.each, retaining the existing test cases and consume callbacks, then add
an inner it test containing the server setup, fetch, consumption, and assertion.
- Around line 82-89: Add a CONNECT-tunnel regression test alongside the existing
CONNECT cases, using a pending body reader that receives the chunked body byte
“x” followed by a malformed chunk size and asserting the body and
InvalidHTTPResponse error result through ProxyTunnel::receive. Preserve the
existing split-envelope and well-formed-body tests.
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src/http/InternalState.rssrc/http/lib.rssrc/runtime/webcore/fetch/FetchTasklet.rstest/js/web/fetch/fetch-chunked-size.test.ts
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2 participants
Follow-up to #34918 (request).
Problem
1\r\nx\r\nConnection: close\r\n). A reader that waits onres.bodythen gets no body, onlyInvalidHTTPResponse. Node v26.3.0 gives the reader"x", then rejects the next read. With a 256 KiB chunk ahead of the bad line the reader lost up to 134198 of 262144 bytes.phr_decode_chunkedreturns-1after it decoded the valid chunks. Both-1arms insrc/http/lib.rs(handle_response_body_chunked_encoding_from_single_packet,_from_multiple_packets) dropped those bytes.Fix
fetch(), an uncompressed body and a response head that was already reported, the-1arms keep the decoded bytes and sethas_body_ahead_of_failure.dispatch_result_and_resetthen reports them in their own progress callback (report_body_decoded_before_failure) before it sends the failure. A compressed body gets nothing, as in Node.on_progress_update. Once the Response exists,FetchTasklethandles the bytes in that run and the failure in a second run, on the next task (hold_failure_behind_unseen_body). Not for an abort.test/js/web/fetch/fetch-chunked-size.test.ts(9 new tests, 3 fail on canarye5f9986a4, 6 pin what must not change). Other suites: see Notes.Limit
"x"there.Background
fetch()parses responses on the HTTP thread. It reports body bytes toFetchTasklet::callback, which stores them and posts one task to the JS thread. Two callbacks before that task runs reach the JS thread as one update.on_progress_updateerrors the body and drops undelivered bytes.Node v26.3.0 vs main vs this PR
What a
res.body.getReader()loop collects before the read rejects. Bad line:Connection: close\r\n\r\n. Script: #42261 (comment)Transfer-Encoding: chunked)e5f9986a4)5ff541592a)1\r\nx\r\n+ bad line, one write, read at once"x", then rejects"", then rejects"", then rejects (Limit)"", then rejects"", then rejects"", then rejects1\r\nx\r\n+ bad line in one write"x", then rejects"", then rejects"x", then rejects1\r\nx\r\n, bad line only after"x"was read"x", then rejects"x", then rejects"x", then rejects"", then rejects"", then rejects"", then rejectsawait res.text()Notes
Regressions that review found on earlier heads of this PR (
c799f5915c,5a92cbd53f), fixed in5a92cbd53fand3db5d26cf8and pinned by tests:The flush reported any non-empty
decoded_body. A corrupted gzip body gave a reader inflater output, wrong bytes included, ahead ofZlibError. main and Node give nothing. The flush is now opt-in: only the two-1arms sethas_body_ahead_of_failure, and only forfetch()(signals.body_receive_mode) with an uncompressed body.bun installtarball streaming sets onlyResponseBodyStreaming, so it gets no new callback. An S3 download stream wires the same backpressure signals asfetch()(to_with_backpressure), so it is included. It already handles a progress callback that is followed by a failure.The failure was held back even before the Response existed. The Response was then built with a live body. A body stream made from it before its first read (
const body = res.body, read one task later) drops an error that arrives next:ByteStream::appendstores the error andon_startreportsStart::Empty, so the stream ended cleanly with no error. main builds that Response from the failure (BodyValue::Error), which every consumer sees. The failure is now held only once the Response exists, where the outcome for such a stream is the same as on main. ByteStream: report a stored producer error and keep the taken prefix with the buffer #38003 fixes the stored-error path itself. With it in, the failure can be held in the first case too and row 1 can match Node.(Found in review of
5a92cbd53f.) With the head in the same read, the chunks went out in a callback of their own ahead of the failure. If the JS thread ran between the two callbacks it built a live body, with the same lost error as in 2. The-1arms now keep the chunks only when the head was already reported (state.cloned_metadata.is_none()), so that case sends one failure callback, as on main.Why the JS-thread part is needed. For row 3 the HTTP thread sends
"x"and then the failure before the JS thread runs.on_body_receivedsent the error to the stream and itsdefercleared the buffer. Now the first run delivers"x"to the pending read and the second run errors the stream. Node does the same: its parser error reaches the body one tick after the data.hold_failure_behind_unseen_bodyonly triggers whenhas_schedule_callbackwas set, which onlyFetchTasklet::callbackdoes. The second run is enqueued by the JS thread itself, so it cannot hold the failure again. The second run carries the JS thread's ref, the same as the task the HTTP thread posted. Ifstart_request_streamfails in the first run because the VM stops, the ref is dropped there. The hold applies to every failure kind except aborts, not only toInvalidHTTPResponse: a connection that closes early no longer overtakes the bytes that arrived before it once the Response exists (test/js/web/fetch/body.test.tsworks around that today with itsconsumedFirstChunkhandshake, and the test is intest/flaky-tests.txt). I did not change that test here.The flush lives in
dispatch_result_and_reset, so the CONNECT-tunnel path (ProxyTunnel::on_data->close_from_callback->fail) gets it with no change at the call sites. h2 and h3 do not use chunked encoding and never set the flag.Compressed bodies (row 6). Node delivers nothing from the read that holds the bad line, because the error tears its gunzip down before it emits. The
-1arms match that. Bytes that earlier reads already decompressed and reported are not affected.A late reader (row 2) sees no chunks in Node and in Bun. Erroring a stream discards what is queued, and by then the error has arrived.
Suites run with the debug build on
5a92cbd53f:fetch-chunked-size,body.test.ts,body-clone,body-mixin-errors,body-stream,body-async-iterator,fetch-gzip,fetch.brotli,fetch-retry-chunked,fetch-abort-stream-body,fetch-abort-socket-close-race,fetch-stream-cancel-leak,fetch-response-finalizer-sweep,fetch.stream,fetch-keepalive,fetch-redirect,fetch-http2-client,node-http.test.ts,node-fetch,client-timeout-error,node-http-transfer-encoding. The only failures were 5 s timeouts infetch.stream"Content-Length response works (multiple parts)" on a machine with load average 74. They pass when run alone and do not touch a failure path. An earlier head also ranfetch.test.ts, the othertest/js/node/http/client files and 27test-http-client-*/test-http-chunk*/test-http-abort*files fromtest/js/node/test/parallel/.The CONNECT-tunnel path has its own test (
through a CONNECT tunnel): an HTTP CONNECT proxy in front of a TLS origin that writes1\r\nx\r\nand the malformed line in one TLS record. It fails on the main canary and passes here.[human-review] gate passed · iteration 3 · 4 files touched
fails on main (without fix)
passes on PR (with fix)
diff hotspot
gate history · 2 passed · 0 rejected · iteration 3
evidence per changed file