Adds a read-only diagnostic surface that lets a test (or any caller)
read the peer's transport parameters, the live connection-level send
credit / consumed counters, the current peer-granted MAX_STREAMS_*
values, and the total bytes sitting in stream send buffers but not
yet handed to STREAM frames.
Goal: pin which budget runs out at the production "stream cliff"
described in nestsClient/plans/2026-05-01-quic-stream-cliff-investigation.md.
The plan flagged three candidates — connection-level MAX_DATA, per-
stream MAX_STREAM_DATA, or the relay's MAX_STREAMS_UNI extension
policy. The snapshot makes it possible to attribute the stall by
reading the diff between the pre-pump, post-pump, and post-grace
snapshots from the test's stdout.
QuicConnection:
- flowControlSnapshot(): suspend, lock-protected, returns
QuicFlowControlSnapshot (new data class) — peer TPs + live
accounting + sum of enqueued-not-sent bytes across streams.
QuicWebTransportSession (jvmAndroid adapter):
- quicFlowControlSnapshot() passthrough so the test can downcast
its WebTransportSession and read the underlying connection's
state without poking through the common transport interface.
SendTraceScenario:
- Optional flowControlSnapshot lambda parameter; when supplied,
logs three checkpoints — fc-pre, fc-post-pump, fc-post-grace —
each on a single line with the full snapshot.
NostrnestsProdAudioTransmissionTest + NostrNestsSustainedSendOutcomesInteropTest:
- withProdSpeakerAndListeners / withHarnessSpeakerAndListeners now
yield a snapshot lambda to the scenario block. Every sweep test
automatically dumps fc-* lines to the JUnit XML system-out.
FlowControlSnapshotTest:
- Pre-handshake: peer TP fields are null, counters zero.
- Post-handshake: every TP field reflects what the in-process TLS
server advertised; sendConnectionFlowCredit equals
initial_max_data; consumed = 0.
- Post-allocate-and-enqueue: nextLocalUni/BidiIndex advance,
totalEnqueuedNotSentBytes sums the buffered chunks, and
streamsWithPendingBytes counts only streams with > 0 pending.
Reading the production sweep output after this commit:
- fc-pre dumps what the relay grants on handshake (initial_max_data,
initial_max_stream_data_uni, initial_max_streams_uni).
- fc-post-pump shows whether sendConnectionFlowConsumed has
plateaued at the cap (peer didn't extend MAX_DATA) or whether
bytes are stuck in stream send buffers.
- The diff between fc-post-pump and fc-post-grace tells us
whether the relay's eventual MAX_DATA / MAX_STREAMS update did
or didn't arrive during the 30-60 s grace window.
Claude
a0e5e04964