Phase 4 lays the telemetry foundation for distinguishing DRED recoveries
from classical PLC in production: a new SignalMessage variant, two new
per-session Prometheus counters on the relay side, and a highlighted
loss-recovery section in the Android DebugReporter.
The periodic emitter (client → relay) and Grafana panel are deferred to
Phase 4b — this commit ships the protocol surface, the relay sink, and
the immediate user-visible debug output. Once 4b lands the full path
(emitter → relay → Prometheus → Grafana), the metrics here will
automatically start receiving data.
Scope decision — why not extend QualityReport instead:
The existing wire-format QualityReport is a fixed 4-byte media packet
trailer. Adding counter fields to it would shift the binary layout and
break backward compatibility (old receivers would parse the last 4
bytes of the extended trailer as QR, corrupting audio). Using a
new SignalMessage variant on the reliable QUIC signal stream sidesteps
the wire-format problem entirely — serde JSON enums tolerate unknown
variants gracefully on old receivers, and the signal channel is the
right layer for periodic telemetry aggregates.
Changes:
wzp-proto/src/packet.rs:
- New SignalMessage::LossRecoveryUpdate variant carrying:
* dred_reconstructions: u64 (monotonic since call start)
* classical_plc_invocations: u64 (monotonic)
* frames_decoded: u64 (for rate calculation)
- All three fields tagged #[serde(default)] for forward compat.
wzp-client/src/featherchat.rs:
- Added a match arm so signal_to_call_type() handles the new
variant (treat as Offer for featherChat bridging purposes).
wzp-relay/src/metrics.rs:
- Two new IntCounterVec metrics on the relay, labeled by session_id:
* wzp_relay_session_dred_reconstructions_total
* wzp_relay_session_classical_plc_total
- New method update_session_loss_recovery(session_id, dred, plc)
applies monotonic deltas: if the incoming totals exceed the
current counter, the difference is inc_by'd. If the incoming
totals are LOWER (client restart or counter reset), the
Prometheus counter holds steady until the client catches up.
This matches the existing update_session_buffer delta pattern.
- remove_session_metrics() now cleans up the two new labels.
- New test session_loss_recovery_monotonic_delta exercises:
* initial population (10 DRED, 2 PLC)
* forward advance (25, 5 → delta +15, +3)
* lower values ignored (client reset → counters unchanged)
* client catches up (30, 8 → advances to new max)
- Existing session_metrics_cleanup test extended to cover the
new counters.
android/app/src/main/java/com/wzp/debug/DebugReporter.kt:
- Phase 4 users — and incident responders — need to quickly see
whether DRED is actually firing during a call. The stats JSON
already carries the counters (after Phase 3c), but they were
buried in the trailing JSON dump. Added a dedicated
"=== Loss Recovery ===" section to the meta preamble that
extracts dred_reconstructions, classical_plc_invocations,
frames_decoded, and fec_recovered from the JSON and displays
them plainly, plus computed percentages when frames_decoded > 0.
- New extractLongField helper: tiny hand-rolled JSON integer
extractor. We don't want to pull in a full JSON parser for this
single use case and CallStats has a flat, well-known schema.
Verification:
- cargo check --workspace: zero errors
- cargo test -p wzp-proto --lib: 63 passing
- cargo test -p wzp-codec --lib: 68 passing
- cargo test -p wzp-client --lib: 35 passing (+1 ignored probe)
- cargo test -p wzp-relay --lib: 68 passing (+1 new Phase 4 test)
- cargo check -p wzp-android --lib: zero errors
- Android APK build verified earlier today (unridden-alfonso.apk
via the remote Docker builder) — Phase 0–3c confirmed to compile
end-to-end on the NDK target.
Phase 4b remaining (not blocking this commit):
- Periodic LossRecoveryUpdate emitter in wzp-client/src/call.rs and
wzp-android/src/engine.rs (every ~5 s)
- Relay-side handler in main.rs that matches the new variant and
calls metrics.update_session_loss_recovery
- Grafana "Loss recovery breakdown" panel in docs/grafana-dashboard.json
Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>
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