Zero-allocation connector boundary (design 054)

CHANGELOG.md

@@ -29,7 +29,7 @@ and this project adheres to [Semantic Versioning](https://semver.org/spec/v2.0.0
 
 ## [Unreleased]
 
-### Added — Design 055: wildcard inbound links
+### Added — wildcard inbound links
 
 - **One inbound link can feed many topics into one record.**
   `link_from("mqtt://sensors/{device}/temp")` matches every device;
@@ -60,6 +60,28 @@ is unchanged. ([aimdb-core](aimdb-core/CHANGELOG.md))
   withheld by the broker instead of reconnecting the client forever.
   ([aimdb-mqtt-connector](aimdb-mqtt-connector/CHANGELOG.md))
 
+### Changed (breaking) — zero-allocation connector boundary
+
+Each connector's own task now drives both directions; core runs no task per
+connector or per route, and a steady-state message crosses the boundary
+without allocating on a scratch serializer.
+
+- **Core** adds `OutboundRoutes` (one pull for every outbound link of a scheme,
+  with a lock-free ready set and per-route `RouteStats`) and `InboundDispatch`,
+  plus `Reader::poll_recv`. `pump_sink`, `pump_source`, `Source`, `Connector`,
+  `TopicProvider` and `collect_outbound_routes` are removed, and
+  `with_topic_provider` becomes `with_topic_writer` / `with_topic_fn`, which
+  write the topic into a bounded buffer. ([aimdb-core](aimdb-core/CHANGELOG.md))
+- **MQTT** encodes embedded packets into one `bbqueue` write ring, sized with
+  `with_write_buffer`, and the native backend moves the topic instead of
+  cloning it. ([aimdb-mqtt-connector](aimdb-mqtt-connector/CHANGELOG.md))
+- **KNX**: `KnxConnector::new` loses its `&'static Channels` argument.
+  ([aimdb-knx-connector](aimdb-knx-connector/CHANGELOG.md))
+- **WebSocket** runs one broadcast loop over `OutboundRoutes`.
+  ([aimdb-websocket-connector](aimdb-websocket-connector/CHANGELOG.md))
+- **Embassy adapter** drops `EmbassySink` and `EmbassySource`.
+  ([aimdb-embassy-adapter](aimdb-embassy-adapter/CHANGELOG.md))
+
 ## [2.0.0] - 2026-09-18
 
 ### Added

Makefile

@@ -249,10 +249,14 @@ test:
 	cargo test --package aimdb-mqtt-connector --no-default-features --features "_test-tokio-broker" --test tokio_broker
 	@printf "$(YELLOW)  → Testing MQTT connector (both backends, one broker, one process)$(NC)\n"
 	cargo test --package aimdb-mqtt-connector --no-default-features --features "_test-backend-parity" --test backend_parity
+	@printf "$(YELLOW)  → Testing MQTT connector (allocations per round trip, both backends)$(NC)\n"
+	cargo test --package aimdb-mqtt-connector --no-default-features --features "_test-backend-parity" --test alloc_round_trip
 	@printf "$(YELLOW)  → Testing MQTT connector (mqtts:// against a pinned self-signed root)$(NC)\n"
 	cargo test --package aimdb-mqtt-connector --no-default-features --features "_test-tls-broker" --test tls_broker
 	@printf "$(YELLOW)  → Testing MQTT connector (event-driven session: wake cadence, partial packets, QoS 1)$(NC)\n"
 	cargo test --package aimdb-mqtt-connector --no-default-features --features "_test-tokio-broker" --test session_loop
+	@printf "$(YELLOW)  → Testing MQTT connector (embedded packet-size limits against a fake broker)$(NC)\n"
+	cargo test --package aimdb-mqtt-connector --no-default-features --features "_test-tokio-broker" --test write_ring_proofs
 	@printf "$(YELLOW)  → Testing MQTT connector (the same criteria over mqtts://)$(NC)\n"
 	cargo test --package aimdb-mqtt-connector --no-default-features --features "_test-tls-broker" --test tls_session
 	@printf "$(YELLOW)  → Testing MQTT connector (no_std unit tests: framing, deadlines, TLS duplex)$(NC)\n"
@@ -398,10 +402,14 @@ clippy:
 	cargo clippy --package aimdb-mqtt-connector --no-default-features --features "_test-tokio-broker" --test tokio_broker -- -D warnings
 	@printf "$(YELLOW)  → Clippy on MQTT connector (backend parity)$(NC)\n"
 	cargo clippy --package aimdb-mqtt-connector --no-default-features --features "_test-backend-parity" --test backend_parity -- -D warnings
+	@printf "$(YELLOW)  → Clippy on MQTT connector (allocations per round trip)$(NC)\n"
+	cargo clippy --package aimdb-mqtt-connector --no-default-features --features "_test-backend-parity" --test alloc_round_trip -- -D warnings
 	@printf "$(YELLOW)  → Clippy on MQTT connector (mqtts:// host smoke)$(NC)\n"
 	cargo clippy --package aimdb-mqtt-connector --no-default-features --features "_test-tls-broker" --test tls_broker -- -D warnings
 	@printf "$(YELLOW)  → Clippy on MQTT connector (event-driven session criteria)$(NC)\n"
 	cargo clippy --package aimdb-mqtt-connector --no-default-features --features "_test-tokio-broker" --test session_loop -- -D warnings
+	@printf "$(YELLOW)  → Clippy on MQTT connector (embedded packet-size limits)$(NC)\n"
+	cargo clippy --package aimdb-mqtt-connector --no-default-features --features "_test-tokio-broker" --test write_ring_proofs -- -D warnings
 	@printf "$(YELLOW)  → Clippy on MQTT connector (the same criteria over mqtts://)$(NC)\n"
 	cargo clippy --package aimdb-mqtt-connector --no-default-features --features "_test-tls-broker" --test tls_session -- -D warnings
 	@printf "$(YELLOW)  → Clippy on MQTT connector (no_std unit tests)$(NC)\n"

README.md

@@ -205,6 +205,13 @@ docker compose up
 
 ## Under the hood
 
+<p align="center">
+  <picture>
+    <source media="(prefers-color-scheme: dark)" srcset="assets/aimdb-architecture-dark.svg">
+    <img src="assets/aimdb-architecture-light.svg" alt="AimDB architecture: inbound connectors push into typed records, outbound connectors pull from the same buffers, and the aimdb CLI and MCP server reach every record through one AimX server" width="900">
+  </picture>
+</p>
+
 - **The Rust type is the contract.** No IDL, no schema registry. CI cross-compiles the same contracts from Cortex-M to WASM. → [Data contracts](https://aimdb.dev/blog/data-contracts-deep-dive)
 - **Buffers decide how data moves.** SPMC Ring for streams, SingleLatest for state, Mailbox for commands. Zero allocations per message, [measured](aimdb-bench/data/baselines). → [Buffers](https://aimdb.dev/docs/getting-started)
 - **Optional persistence.** `.persist()` with a SQLite backend keeps history across restarts. → [`aimdb-persistence`](aimdb-persistence)

aimdb-bench/Cargo.toml

@@ -67,6 +67,12 @@ harness = false
 name = "b0_alloc_connector"
 harness = false
 
+# Outbound wake-up time per message, 1 to 256 routes.
+# Informational: not in `bench-gate`.
+[[bench]]
+name = "b1_outbound_wakeup"
+harness = false
+
 [features]
 default = ["std"]
 # Gates `profiles`/`reports`/`harness` and their criterion/serde_json/

aimdb-bench/README.md

@@ -26,10 +26,9 @@ Plus two informational benches that exercise the full runner-driven pipeline.
   `b1_b2_remote_json` (host). These compare issue #196's direct JSON bytes with
   the compatibility `serde_json::Value` tree through the real typed record,
   buffer, `Payload` and AimX envelope. Socket I/O and scheduling are excluded.
-- **connector boundary** — `b0_alloc_connector` (host). Baseline for design
-  054: `Router::route`, `pump_source` with a minimal `Source`, and the
-  per-message `recv_into` + `Connector::publish` calls of `pump_sink`, on a
-  no-op connector.
+- **connector boundary** — `b0_alloc_connector` (host). The connector
+  interfaces from design 054: `InboundDispatch::dispatch` and
+  `OutboundRoutes::next`, on a no-op connector.
 - **Embassy** — `b0_alloc_embassy`, `b1_b2_embassy`
   (host). These drive the real [`EmbassyBuffer`] backend via
   `futures::executor::block_on` over embassy-sync's poll methods — no
@@ -127,11 +126,11 @@ The committed baseline lives in `data/baselines/b0_alloc_tokio.json`. When a cha
 `b0_alloc_embassy` mirrors this against the Embassy buffer backend and writes `data/baselines/b0_alloc_embassy.json` — also **0 allocs/msg** across all three profiles, confirming the Embassy `poll_recv` path is allocation-free on the host. The on-target B3 bench (`examples/embassy-bench-stm32h5`) re-checks the same 0-alloc claim against the real embedded allocator.
 
 `b0_alloc_linkable` warms up for 1,000 iterations, then measures 10,000 generated-shape postcard `Linkable::encode_into` calls into one stack buffer.
-The required result is **0 allocation calls and 0 allocated bytes**. It isolates the codec seam: `SerializedReader` still returns a boxed future, dynamic topics may allocate and connector implementations may copy payload ownership after the core pump lends them the scratch slice.
+The required result is **0 allocation calls and 0 allocated bytes**. It isolates the codec seam: connector implementations may still copy the payload after `OutboundRoutes` lends them the scratch slice.
 
 `b0_alloc_remote_json` warms the production in-memory `record.get` and subscription-event paths, then compares 5000 tree/direct operations. Its gate is relative: direct JSON must reduce both allocation calls and allocated bytes. It does not require zero allocations because the owned JSON `Vec`, `Arc<[u8]>` payload and AimX envelope serialization still own storage.
 
-`b0_alloc_connector` measures what the connector interfaces cost per message, with no transport. It asserts today's values exactly (0 for `route`, 2 for `pump_source`, 2–3 outbound), so a regression *or* an improvement fails it until `EXPECTED` in the bench and `data/baselines/b0_alloc_connector.json` are updated together. The inbound `pump_source` row is the difference of two runs, so pump setup cancels out. See design 054 for where each allocation comes from.
+`b0_alloc_connector` measures what the connector interfaces cost per message, with no transport. It asserts its values exactly (0 everywhere except a new key, 1, and the owned serializer, 1), so a regression *or* an improvement fails it until `EXPECTED` in the bench and `data/baselines/b0_alloc_connector.json` are updated together. `make bench-gate` runs it. See design 054 for where each allocation comes from.
 
 > **Embassy eager registration (design 039 F8/F9).** An Embassy `SpmcRing` reader registers its embassy `Subscriber` eagerly, at `subscribe()` time — matching Tokio's `broadcast` — so no separate priming step is needed before the first `push`.