feat(routing-policy): size the adaptive forward mux on upload (bidirectional sizing) - #4138
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…ctional sizing) The adaptive preset's on_tick controller sized only the reverse (download) direction: it read RecvBytes deltas and widened/collapsed the mux under sustained download load, while the forward (upload) width was pinned at one leg. SentBytes was never read, so an upload-heavy flow could not grow the send mux. Add a forward controller that mirrors the reverse one, driven by SentBytes: the same EWMA smoothing, peak decay, saturated/idle thresholds, hysteresis and cooldown constants (reused, not duplicated). On sustained upload saturation it emits a new RotationAction.AddForwardLeg that the router actuates forward-only (appendRouteAsymmetric addFwd=true/addRev=false, via addOneAuxSendLeg), so the extra send capacity does not enlarge the reverse/download set; it collapses back to the lean single forward leg when the upload goes idle. A combined desiredActive target folds the forward growth in so the reverse park/drop-recovery rules never tear down a forward-grown leg. When SentBytes is flat the whole forward machine stays dormant, so a download-only or idle flow evolves byte-identically to before. Rebuilt the preset wasm bundle so native and wazero make identical decisions; extended the parity harness with an upload sequence and added engine tests for upload-widen / download-regression / idle-collapse.
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The adaptive preset's on_tick controller sized only the reverse (download) direction: it read
RecvBytesdeltas and widened/collapsed the mux under sustained download load, while the forward (upload) width stayed pinned at one leg.SentByteswas never read, so an upload-heavy flow could not grow its send mux.This adds a forward controller that mirrors the reverse one, driven by
SentBytes, reusing (not duplicating) the same EWMA smoothing, peak decay, saturated/idle thresholds, hysteresis and cooldown constants. On sustained upload saturation it emits a newRotationAction.AddForwardLeg; the router actuates it forward-only (appendRouteAsymmetric(addFwd=true, addRev=false)via a newaddOneAuxSendLeg), so the extra send capacity does not enlarge the reverse/download set. It collapses back to the lean single forward leg when the upload goes idle. A combineddesiredActivetarget folds the forward growth into the convergence target so the reverse park / drop-recovery rules never tear down a forward-grown leg.When
SentBytesis flat the whole forward machine stays dormant, so download-only and idle flows evolve byte-identically to before — the validated steady shape (fwd=1, rev=1 active + 2 standby) is unchanged.Native/wazero parity: the preset wasm bundle was rebuilt with TinyGo so the native and wazero engines make identical decisions; the parity harness gained an upload sequence (
AddForwardLegverified to fire and round-trip the wire), andgo test ./pkg/router/policy/...passes. New engine tests cover upload-widen, download-regression (unchanged), and idle-collapse.Caveat surfaced in the report: the warm-standby pool is full-duplex, so a forward-only widen must dial a fresh send leg rather than promote a spare; and a send-only leg would black-hole any download the far end mis-spreads onto it — acceptable for an upload-dominant flow and pruned by the existing leg-dataprogress/liveness guards.