Phase C3: ContentDeliveryLayerNode — the per-stream-part overlay node

[ptesavol]

Summary

Ports the content-delivery overlay node and its factory from the TS pin — the class that composes the C1/C2 classes (temporary connections, handshaking, neighbor finding/updating) with propagation, inspection (C7) and the discovery layer (C4) into the actual per-stream-part node. The test porting flushed out five real defects, each diagnosed with runtime evidence (crash-report stacks, rate comparisons) and verified fixed.

What's ported

• ContentDeliveryLayerNode — neighbor list + the four contact views (nearby/random/ring-left/ring-right) fed from discovery-layer events, broadcast with per-publisher duplicate detection, leave-notice handling with view eviction, temporary-connection and content-delivery RPC server wiring, suppressOwnMessageLoopback, and TS-parity stop(). Plumtree branches are milestone-E scope and omitted.
• createContentDeliveryLayerNode — defaults taken from the TS source (neighbor target 4, view size 20, min propagation targets 2, 150-message/10 s buffer, 10 s update interval); explicit shared-pointer ownership graph in place of TS garbage collection, with documented destruction order.
• DhtNodeDiscoveryLayer + DhtNode contact-event re-emission — TS passes a DhtNode wherever a DiscoveryLayerNode is expected (structural typing). DhtNode now re-emits the six PeerManager contact events as its own, exactly like TS (second event-emitter base with merged lookup), and the adapter provides the interface nominally. C6's NetworkStack will reuse it.

Five defects found by the ported tests

1. NodeList data race — worker threads iterated lists being mutated concurrently (64-node SetUp segfault; crash-report stack through getValuesOfIncludedKeys). All access mutex-guarded; NodeAdded/NodeRemoved emit outside the lock (their handlers make blocking RPC sends).
2. NodeList ordering parity — TS's Map is insertion-ordered and the interleave protocol depends on it (getLast = newest neighbor to hand over); the std::map port was id-ordered. Now an insertion-ordered vector; TS's ordering test ported.
3. Teardown lazy-task lifetime — stop()'s leave-notice coroutines captured remotes whose last references concurrent handlers could drop before the batch ran (the documented rpc-remote lazy-task trap). The batch pins the remotes; verified 0/3 → 8/8 on the crashing fixture.
4. previousMessageRef optionality — TS passes undefined when absent; the port forwarded the proto3 default instance, tripping the DuplicateMessageDetector invariant for (0, 0) refs. Optional through the whole chain now.
5. Synchronous propagation deadlock — sendToNeighbor ran blockingWait inside the RPC delivery path, so under broadcast fan-out nodes blocked sending to each other in cycles and propagation stalled (0/3 timeouts at 64 nodes). Propagation sends are now Task-returning bounded scope tasks (3/3 after); ProxyClient keeps its synchronous result-reporting API through a new awaitable collect variant.

Tests (all ported from the pin)

TS test	C++
unit/ContentDeliveryLayerNode.test.ts (incl. loopback-suppression cases)	ContentDeliveryLayerNodeTest (9 tests)
integration/ContentDeliveryLayerNode-Layer1Node.test.ts	ContentDeliveryLayerNodeLayer1Test (single node / 4 nodes + bidirectionality / 64 nodes) over real DhtNodes + simulator
integration/...-Latencies.test.ts	same fixture parameterized with 50 ms fixed latency (the TS files differ only in that)
integration/Propagation.test.ts	PropagationScaleTest at 64 nodes (TS runs 256; the C++ simulator's per-node cost makes that a ~16 min run, beyond CI budget — scale-up documented as follow-up)
unit/NodeList.test.ts (14 cases)	NodeListTest (stub → full port, incl. insertion order)

Results (local, arm64 mac)

trackerless-network 83/83 with verified clean process exit, streamr-dht 181/181 (regression for the DhtNode event additions), full-tree build green, both package lints and the repo-wide lint rc=0.

Remaining milestone-C phases after this: C5 (ContentDeliveryManager + proxy server side), C6 (NetworkStack/NetworkNode), C8 (full-node end-to-end + TS interop).

🤖 Generated with Claude Code