feat(net)!: leave subscriptions and fetches to flow control by kixelated · Pull Request #6467 · moq-dev/moq

kixelated · 2026-10-23T03:56:14Z

Summary

moq_net::session::Limits drops the subscriptions and fetches caps, which only refused at runtime what flow control already bounds, and gains requests for the one bound they also fed: the drafts 14 to 16 request window. The documented example now compiles (it is a doctest).

Proof that each removed cap is covered, per version:

Cap	moq-lite (all)	moq-transport 14 to 16	moq-transport 17+
inbound SUBSCRIBE / TRACK / TRACKS	one bidi stream each: QUIC stream credit	request window (MAX_REQUEST_ID, `live <= window`)	one bidi stream each: stream credit
inbound FETCH	one bidi stream each	request window	one bidi stream each
PUBLISHes we hold for a peer's SUBSCRIBE_TRACKS listing	n/a	n/a (no SUBSCRIBE_TRACKS)	not covered: kept, now bounded by `requests` (tracks past it are skipped as before)

Stream credit holds because every transport we accept on returns bidi credit only once both halves of a stream close: moq-quic (QUIC, WebTransport), Rust qmux (moq-quic's state machine), and iroh. A peer past it waits; it is not refused.

What stays:

announces: lite announces share one stream and IETF namespaces have no other bound.
requests: with announces it sizes the drafts 14 to 16 window (2 * (announces + requests)), the draft 17+ skipped-ID history, and the listing PUBLISH bound above. Defaults keep the window where it was: 100,000 + 20,000 in moq-net and on relay peers.
The subscriptions_peak stat. Subscriptions are still counted (uncapped) so the peak keeps reporting. On moq-lite it now counts SUBSCRIBE streams only, rather than TRACK, SUBSCRIBE, and TRACKS streams deduplicated per track; that per-track Interests map existed only for the cap and is deleted.

Test: request_caps::flow_control_bounds_the_subscriptions_a_peer_holds asks for 24 subscriptions against a window of 8 and 8 bidi streams, on drafts 14, 15, 16, 17 and lite-06, and checks the server holds at most 8 while the session stays open. It fails (24 held) with both bounds lifted. To express bidi credit, transport::memory::Config gains max_concurrent_bi_streams, mirroring max_concurrent_uni_streams; a bidi stream holds credit until the peer is done with both halves.

Deleted tests that only exercised the removed caps: fetch_caps.rs, held_tracks_share_the_cap_with_their_subscriptions, the lite and IETF "past the cap closes the session" unit tests, coalesced_fetches_each_hold_their_own_slot, and the Interests unit test.

Also aligned IETF join after finish, whose recommendation charged finished entries to the removed subscription limit.

Dropped: the JS mirror. @moq/net keeps its internal subscription and FETCH caps, because @moq/qmux returns MAX_STREAMS credit on accept rather than on close, so stream credit does not bound open streams there. Its comments now say so.

Public API and wire impact

moq_net::session::Limits: subscriptions and fetches removed, requests added (unreleased type; the MIGRATE.md entry for feat(net)!: bound peer-declared lengths and per-session requests #4820 is rewritten).
moq_net::transport::memory::Config::max_concurrent_bi_streams added (non-exhaustive struct).
moq-relay config: [session]/[peer] subscriptions and fetches (--session-subscriptions, --session-fetches, --peer-subscriptions, --peer-fetches, and their env vars) replaced by requests (--session-requests, --peer-requests, MOQ_SESSION_REQUESTS, MOQ_PEER_REQUESTS). Unreleased; old keys fail loud via deny_unknown_fields.
Behavior: a peer past what the old caps admitted now waits on flow control instead of losing the session with TOO_MANY_REQUESTS. Relay clients on moq-lite or draft 17+ may hold up to [quic] max_streams (10,000 by default) subscriptions instead of 1,000.
Wire: none.

Decisions

Remaining field name: requests, since the relay needs a lower bound for untrusted draft 14 to 16 clients than for peers. Rejected: window (it also bounds listing PUBLISHes and ID history) and no field with a fixed window.
Relay [session] requests default: 10,000 (window 22,000), not 11,000 to keep the old 24,000 exactly.
Listing PUBLISH bound: kept with requests in this PR, since nothing else bounds the PUBLISH tasks a draft 17+ peer's listings spawn. Rejected for now: opening each PUBLISH only as the peer's stream credit admits.

Checks

just check: pass (lint and tests for the changed packages, including cargo test -p moq-net).
just test interop --all: pass.

🤖 Generated with Claude Code

(Written by Claude Opus 5.5)

Quest-Claim: 578f46a02720f2a0

`session::Limits` drops `subscriptions` and `fetches`: every moq-lite request and every draft 17+ moq-transport request holds a stream, so stream credit bounds them, and on drafts 14 to 16 the request window does. `requests` replaces them where they still fed a bound: the window, the draft 17+ skipped-ID history, and the PUBLISHes a peer's listings hold. The relay config follows, and the memory transport gains bidi stream credit so a test can prove the peer stays bounded. Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>

kixelated · 2026-10-23T06:31:28Z

Implementation is complete and local checks pass; this stays a draft for the three decisions in the description (field name requests, the relay [session] requests default, and keeping the listing PUBLISH bound).

Suggested follow-ups:

@moq/qmux returns MAX_STREAMS credit on accept rather than on close, so stream credit does not bound open streams there. Fixing that would let @moq/net drop its subscription and FETCH caps to mirror Rust.
Bound draft 17+ listing PUBLISHes by design (open each only as the peer's stream credit admits) instead of by Limits::requests.

(Written by Claude Opus 5.5)

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>

coderabbitai · 2026-10-23T08:03:11Z

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📒 Files selected for processing: 33

doc/bin/relay/config.md
doc/concept/stats.md
doc/lib/rs/moq-net.md
js/net/src/ietf/setup_options.ts
js/net/src/util/limits.ts
quest/m1/api-audit/README.md
quest/m1/api-audit/session-limits.md
quest/m1/js-qmux-credit.md
quest/m1/listing-credit.md
quest/m2/ietf-join-after-finish.md
rs/moq-net/MIGRATE.md
rs/moq-net/src/auth.rs
rs/moq-net/src/client.rs
rs/moq-net/src/error.rs
rs/moq-net/src/ietf/control.rs
rs/moq-net/src/ietf/publisher.rs
rs/moq-net/src/ietf/publisher/tracks.rs
rs/moq-net/src/ietf/session.rs
rs/moq-net/src/lite/publisher.rs
rs/moq-net/src/lite/session.rs
rs/moq-net/src/server.rs
rs/moq-net/src/session.rs
rs/moq-net/src/stats.rs
rs/moq-net/src/transport/memory.rs
rs/moq-net/tests/integration/fetch_caps.rs
rs/moq-net/tests/integration/main.rs
rs/moq-net/tests/integration/request_caps.rs
rs/moq-net/tests/integration/track_stream_demand.rs
rs/moq-relay/src/cluster.rs
rs/moq-relay/src/config.rs
rs/moq-relay/src/limits.rs
rs/moq-relay/src/settings.rs
rs/moq-tokio/src/client.rs

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chatgpt-codex-connector · 2026-10-23T08:03:17Z

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📝 Code Review	✅ Completed 2026-10-24T02:07:51.991435Z	`92423bf`	New commits

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kixelated · 2026-10-23T08:37:05Z

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Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>

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…ered A peer that cancels a SUBSCRIBE whose token the application already took now keeps the request stream (and so its stream credit or request window slot) until the application answers or drops the token. Without this, a peer could cancel and resubscribe to pile up verifications beyond its credit, which the removed subscription cap used to bound. Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>

kixelated · 2026-10-24T01:11:52Z

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# Conflicts: # rs/moq-net/src/ietf/publisher.rs # rs/moq-net/src/lite/publisher.rs

The earlier fix only covered the initial token. A peer could also cancel after the application took a REQUEST_UPDATE renewal, freeing the request's credit while the verification stayed in flight. The subscription's auth hold now carries a kio consumer, and the request stream closes, after PUBLISH_DONE, only once every token verification holding it has been answered or dropped. Demand is still released at once. This replaces the withdraw/poll_released verdict API. Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>

kixelated · 2026-10-24T02:12:58Z

Merge pass summary (head 92423bf):

Merged main three times. The conflicts were in rs/moq-relay/src/config.rs (main's test_env::Env isolation now applies to the requests limit vars) and in cap tests main had edited that this PR deletes. The new test was adapted to driver::Transport.
Docs (Codex P2): session::Limits, SessionError::TooManyRequests, and Error::TooManyRequests now name only the actual close cases: announcement overflow, and the drafts 14-16 request window or MAX_REQUEST_ID.
Quests: quest/m1/listing-credit.md and quest/m1/js-qmux-credit.md no longer link the finished session-limits quest. The Required entry on it was dropped, so listing-credit is now unblocked.
Auth credit (Codex P2 and P1): with the subscription cap gone, a peer could cancel a SUBSCRIBE after the application took its token, or a renewal's, and so pile up verifications beyond its credit. The subscription's auth Hold now carries a kio consumer, and the request stream closes only once every taken token has been answered or dropped. PUBLISH_DONE is still written at once, and track demand is still released at the cancel. Internal only; no public API or wire change.

Checks: just check and just test interop --all pass on the final tree. One earlier interop run had cpp-publisher audio timestamp-gap failures that did not reproduce on rerun.

(Written by Claude Opus 5.5)

kixelated and others added 2 commits October 22, 2026 20:56

chore(quest): claim quest/m1/api-audit/session-limits.md

efebd55

Quest-Claim: 578f46a02720f2a0

kixelated changed the title ~~Session limits only where needed~~ feat(net)!: leave subscriptions and fetches to flow control Oct 23, 2026

kixelated and others added 3 commits October 22, 2026 22:36

docs(net): unwrap a doc line clippy read as a list item

54868c1

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>

Merge origin/main into quest/m1/api-audit/session-limits

430e62f

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>

docs(net): keep the session count expression on one doc line

80252ab

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>

kixelated and others added 2 commits October 22, 2026 23:58

Merge quest/m1/api-audit/session-limits into the local branch

cae0a30

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>

Merge origin/main into quest/m1/api-audit/session-limits

d1f2e28

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>

kixelated marked this pull request as ready for review October 23, 2026 08:03

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Comment thread rs/moq-relay/src/settings.rs

Comment thread rs/moq-relay/src/limits.rs

Merge origin/main into quest/m1/api-audit/session-limits

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Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>

kixelated added this pull request to the merge queue Oct 23, 2026

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Comment thread rs/moq-net/src/session.rs Outdated

github-merge-queue Bot removed this pull request from the merge queue due to a conflict with the base branch Oct 23, 2026

kixelated and others added 2 commits October 23, 2026 16:15

Merge origin/main into quest/m1/api-audit/session-limits

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quest: drop links to the finished session-limits quest

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Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>

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Comment thread rs/moq-net/src/ietf/publisher.rs Outdated

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Comment thread rs/moq-net/src/ietf/publisher.rs Outdated

kixelated and others added 3 commits October 23, 2026 18:15

Merge remote-tracking branch 'origin/main' into merge-6467-a9fe

38ae1bd

# Conflicts: # rs/moq-net/src/ietf/publisher.rs # rs/moq-net/src/lite/publisher.rs

Merge remote-tracking branch 'origin/main' into merge-6467-a9fe

92423bf

kixelated added this pull request to the merge queue Oct 24, 2026

Merged via the queue into main with commit 164c1ad Oct 24, 2026
10 checks passed

kixelated deleted the quest/m1/api-audit/session-limits branch October 24, 2026 04:12

This was referenced Oct 24, 2026

refactor(relay)!: consolidate configuration loading and roles #6535

Merged

feat(net)!: dynamic tracks serve fills for misses #6171

Merged

fix(qmux)!: return stream credit once both halves of a bidi stream end #6644

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