docs: align wire-spec and mark implemented vs proposed
Keep the 45-byte pose frame consistent across docs, simulator, and prototype, clarify MinIO is not peer sync, and state clearly that the repo is a from-scratch platform sketch with options rather than mandates.
This commit is contained in:
@@ -17,6 +17,25 @@ This repository describes how to build, deliver, test, and operate that platform
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7. **SQL is the contract.** Peer data access is read-only DuckDB SQL over SSH forced commands — the query language already lives on both ends, so no service, port, or protocol is invented for it.
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8. **No debug API.** The bench and the flight use the same channel: an engineer debugging on the ground runs the identical query through the identical wrapper, permissions, and output format a peer drone would use. What you test is what flies.
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None of the concrete tool picks above are mandates. This repo is a **from-scratch platform sketch**: enough structure to hire and build against, with every decision recorded so the team can replace a piece when a better fit appears.
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## Implemented now vs proposed next
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Honest map so a reader knows what runs today versus what is design intent.
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| Area | Implemented in this repo (runnable PoC) | Proposed for a production air-gapped fleet |
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| --- | --- | --- |
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| On-board layout | Hive-partitioned Parquet writer, seal step, DuckDB views | Same contract; Compose services under systemd |
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| Pose path | Fixed **45-byte** UDP frame + 2D bandwidth visualisation | Zenoh pub/sub (UDP kept as degraded minimal profile) |
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| Peer query | Read-only SQL **gate** over HTTP explorer (keyword allow-list) | Same gate idea via **SSH forced command** + OS/engine hardening |
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| Bulk sync | Visualised opportunistic transfer volume | rsync/rclone over persistent SSH between peers |
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| Mesh trust | Ansible templates for WireGuard + ed25519 forced commands | Provisioned per-device keys; nothing joins at runtime |
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| Ground segment | k3d/Terraform sim: lake, Grafana, offload CronJob, optional MinIO | k3s warehouse, GitOps overlays, post-flight mirror |
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| CI / delivery | GitHub Actions: pytest, smoke flight, Trivy, semver release + fleet manifest artifact | Self-hosted GitLab + registry inside the air gap (same stages) |
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| Docs | Problem, architecture, ADRs, design journey, open questions | Living ADRs owned by the team |
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Start from the [design journey](docs/12-design-journey.md) for the story; use the table above when reviewing scope.
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## Documentation
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| Document | Contents |
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+11
-8
@@ -20,8 +20,9 @@ graph TB
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subgraph serving [Layer 3 — Serving and sync]
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HOOK["event hook<br/>fires on new derived data"]
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PUB["state publisher<br/>pub/sub broadcast"]
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MINIO["MinIO<br/>derived datasets bucket"]
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QAPI["query API<br/>peer data requests"]
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BULK["bulk sync<br/>rsync over SSH"]
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MINIO["MinIO<br/>optional derived bucket"]
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QAPI["query API<br/>SQL-over-SSH"]
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end
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end
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@@ -33,12 +34,14 @@ graph TB
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WRITER -->|derived rows| HOOK
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HOOK --> PUB
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HOOK --> MINIO
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HOOK --> BULK
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QAPI --> DUCK
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PUB -.->|mesh| PEERS["peer drones"]
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MINIO -.->|replication| PEERS
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PUB -.->|mesh pose| PEERS["peer drones"]
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BULK -.->|sealed partitions| PEERS
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QAPI -.->|on demand| PEERS
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```
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MinIO stays available where an S3 API helps (on-board derived datasets, ground warehouse). **In-flight peer bulk sync is SSH/rsync**, not object-store replication — see [04 — Swarm sync](04-swarm-sync.md).
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### Layer 1 — Ingestion
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- `sensor-ingest` subscribes to sensor sources (ROS 2 topics where available, raw drivers otherwise) and normalizes them into typed streams: IMU, barometer, temperature, LiDAR, RSSI, power, and so on.
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@@ -53,10 +56,10 @@ graph TB
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### Layer 3 — Serving and sync
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- The **event hook** is the on-board "lambda": when the writer lands new *derived* rows (state, detections), it triggers registered actions — broadcast, MinIO upload, or a local mission-logic callback. Nothing polls.
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- The **state publisher** broadcasts compact position/attitude/detection payloads over the mesh pub/sub (transport analysis in [04 — Swarm sync](04-swarm-sync.md)).
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- **Bulk sync** pulls sealed derived partitions from peers over persistent SSH (rsync delta transfer); MinIO remains optional where an S3 API is wanted.
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- **Peer queries** are read-only DuckDB SQL over SSH forced commands — SELECT-only gate, read-only OS user, columnar responses (the design decision and its reasoning are in [04](04-swarm-sync.md)).
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- The **event hook** is the on-board "lambda": when the writer lands new *derived* rows (state, detections), it triggers registered actions — broadcast, optional MinIO put, bulk-sync hint, or a local mission-logic callback. Nothing polls.
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- The **state publisher** broadcasts compact position/attitude/detection payloads over the mesh pub/sub (UDP in the PoC; Zenoh proposed — [04](04-swarm-sync.md)).
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- **Bulk sync** pulls sealed derived partitions from peers over persistent SSH (rsync delta transfer). MinIO is optional where an S3 API is wanted; it is **not** the in-flight peer replication path.
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- **Peer queries** are read-only DuckDB SQL — HTTP explorer gate in the PoC; **SSH forced commands** proposed for flight (SELECT-only gate, read-only OS user, columnar responses — [04](04-swarm-sync.md)).
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## Communication planes
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+23
-13
@@ -16,19 +16,27 @@ Bandwidth is the scarcest resource in the system. Every message class gets an ex
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## Broadcast payload: small on the wire, precise at rest
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The `state` broadcast is a fixed compact frame:
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The `state` broadcast is a fixed compact frame. The runnable PoC encodes it as
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**45 bytes** little-endian (`simulator/virtual_drone/broadcast.py`); that size is
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what the prototype uses for bandwidth estimates.
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| Field | Type | Notes |
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| Field | Wire type (PoC) | Notes |
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| --- | --- | --- |
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| `drone_id` | uint16 | Fleet-scoped registry |
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| `magic` + `version` | 2s + uint8 | `b"SH"`, version `1` |
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| `drone_id` | 8s ascii | Zero-padded; a fleet `uint16` registry id is a natural production swap |
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| `ts_ns` | int64 | Epoch nanoseconds, same clock domain as storage |
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| `pos_x/y/z` | int32 | **Millimeters** in the mission frame — quantized only here, storage keeps full float precision |
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| `att_roll/pitch/yaw` | int16 | Centi-degrees |
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| `vel_x/y/z` | int16 | cm/s |
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| `pos_x/y/z` | 3 × int32 | **Millimeters** in the **mission frame** — quantized on the wire only; storage keeps full float precision |
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| `att_roll/pitch/yaw` | 3 × int16 | Centi-degrees — attitude stays on the wire so peers need no local shape model |
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| `vel_x/y/z` | 3 × int16 | cm/s |
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| `frame_ref` | uint8 | Frame of reference id (GPS-denied: local/visual-odometry frames must be explicit) |
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| `flags` | uint8 | Battery-low, returning, degraded-sensors, … |
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~40 bytes per frame → a 50-drone swarm at 5 Hz is ~10 KB/s of pose traffic before transport overhead. Trivial even on a congested mesh.
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45 bytes × 5 Hz × 50 drones ≈ 11 KB/s of pose traffic before transport overhead — still trivial on a congested mesh.
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An earlier sketch used relative coordinates and a bounding sphere (no attitude).
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It was dropped: mission-frame pose + attitude is simpler to fuse post-flight and
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costs almost nothing at this frame size. Relative localization remains a
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consumer concern when `frame_ref` differs across peers ([09](09-open-questions.md)).
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`detections` events are slightly larger (class, confidence, bounding volume, ego-pose) but event-shaped and rare by comparison.
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@@ -51,25 +59,27 @@ graph LR
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SB -->|"store-and-forward relay"| SC
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```
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### Recommended: Zenoh
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### Recommended (proposal): Zenoh
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- Designed exactly for constrained, dynamic networks: built-in peer discovery, brokerless peer-to-peer mode, store-and-forward, and a query layer on top of pub/sub.
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- First-class robotics citizenship: an official ROS 2 RMW implementation exists, so the ingestion side and the sync side can share one middleware.
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- Tiny footprint, ARM64-native.
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**PoC today:** the simulator and the 2D prototype exercise the **raw UDP** pose path only — the minimal degraded profile below. Zenoh is the proposed production pub/sub, not yet wired into the runnable stack.
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### Alternatives considered
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| Option | Verdict |
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| --- | --- |
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| **DDS multicast** (ROS 2 default) | Works, battle-tested; but discovery storms and tuning pain on lossy wireless meshes are well documented. Keep as fallback since ROS 2 speaks it natively |
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| **MQTT** | Needs a broker — a per-drone broker bridge is possible but adds moving parts for no gain over Zenoh |
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| **Raw UDP multicast** | Perfect as a last-resort minimal profile for the pose broadcast alone (fixed frame, no discovery); no query layer, no reliability — documented as the degraded mode |
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| **MinIO bucket replication** | Wrong tool for the 5 Hz pose path, right tool for bulk derived datasets — see below |
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| **Raw UDP multicast** | **Implemented in the PoC** for pose broadcast (fixed frame, no discovery); no query layer, no reliability — also the documented degraded mode |
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| **MinIO bucket replication** | Wrong tool for the 5 Hz pose path; optional on board for derived datasets and primary on the ground warehouse — not the in-flight bulk path |
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## Two sync mechanisms, deliberately separate
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1. **Fast path — pub/sub (Zenoh):** pose frames and detection events. Fire-and-forget with bounded staleness; consumers keep a peer-state cache.
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2. **Bulk path — rsync over persistent SSH:** sealed `detections`/`state` Parquet partitions are pulled opportunistically between drones when links allow. This is how a drone that was out of range catches up on mission history without anyone re-sending events.
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1. **Fast path — pub/sub (Zenoh proposed; UDP in the PoC):** pose frames and detection events. Fire-and-forget with bounded staleness; consumers keep a peer-state cache.
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2. **Bulk path — rsync over persistent SSH (proposed):** sealed `detections`/`state` Parquet partitions are pulled opportunistically between drones when links allow. This is how a drone that was out of range catches up on mission history without anyone re-sending events. The PoC visualises bulk volume; it does not yet run real rsync between virtual drones.
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Why SSH-based bulk sync over object-store replication:
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@@ -105,7 +115,7 @@ SQL access must not become a write channel. A single "read-only connection" flag
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| Layer | Mechanism | What it stops |
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| --- | --- | --- |
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| 1. Key = operation | Forced command: the query key can only invoke the query wrapper, nothing else | Arbitrary exec, lateral movement |
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| 2. Statement gate | Wrapper accepts a single statement, parses it, rejects anything but `SELECT` (no `COPY`, `ATTACH`, `INSTALL`, `SET`, multi-statements); parameters bound, not interpolated | SQL-as-a-write-channel, config tampering |
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| 2. Statement gate | Wrapper accepts a single statement, rejects anything but `SELECT`/`WITH`/… (no `COPY`, `ATTACH`, `INSTALL`, `SET`, multi-statements); production should prefer a real parser + bound parameters, not keywords alone | SQL-as-a-write-channel, config tampering |
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| 3. OS permissions | Wrapper runs as a dedicated user with **read-only filesystem access** to the data root and write access to nothing | Any write that slips past layer 2 |
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| 4. Engine hardening | `:memory:` database, external access disabled except the data-root glob, extension loading off | Reaching outside the store |
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| 5. Resource caps | Timeout, memory cap, niced CPU (flight software always wins), response size budget | Denial of service via expensive queries |
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+15
-10
@@ -1,9 +1,12 @@
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# 12 — Design journey
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How this design came together, told in the order the thinking actually happened.
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It is a walk-through, not a report. The formal decisions, with options and
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trade-offs, live as [Architecture Decision Records](adr/README.md). This is the
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story behind them, and each chapter links straight into the code it produced.
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It is a walk-through, not a report — and **not a mandate**. The goal is a
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from-scratch platform sketch that shows how the pieces fit; every concrete
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choice is an option with trade-offs recorded as
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[Architecture Decision Records](adr/README.md). Replace any piece if a better
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fit shows up. This is the story behind the decisions, and each chapter links
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straight into the code it produced.
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---
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@@ -70,15 +73,17 @@ stored and in which structure, not to step into that work.
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## 5. What actually needs to sync
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The most time-critical item is where each peer is, so every unit has time to
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react. The choice was to broadcast [relative pose](04-swarm-sync.md) (x, y, z and
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time) instead of absolute coordinates. Relative is cheaper and enough for
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coordination. To avoid sending orientation, a unit is modelled as a **sphere**
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that bounds its extent. That trades a little compute for much less data, and no
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per-shape encoding. If the units are identical, their 3D model can be provisioned
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ahead instead of transmitted.
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react. The wire frame carries **mission-frame position** (millimetres on the
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wire, full float at rest), **attitude**, **velocity**, a `frame_ref`, and flags —
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45 bytes at 5 Hz. That is cheap enough that shrinking further is not worth the
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fusion pain. An earlier sketch used relative coordinates and a bounding sphere
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with no orientation; it was dropped. When peers disagree on frames,
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`frame_ref` makes the mismatch explicit for consumers
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([09 — Open questions](09-open-questions.md)).
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> **Read the code**
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> - [`simulator/virtual_drone/broadcast.py`](https://git.produktor.io/eSlider/swarm-house/src/branch/main/simulator/virtual_drone/broadcast.py#L1-L40) — the 46-byte pose frame, position quantized on the wire only
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> - [`simulator/virtual_drone/broadcast.py`](https://git.produktor.io/eSlider/swarm-house/src/branch/main/simulator/virtual_drone/broadcast.py#L1-L45) — the 45-byte pose frame, position quantized on the wire only
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> - [`prototype/src/sim.ts`](https://git.produktor.io/eSlider/swarm-house/src/branch/main/prototype/src/sim.ts#L60-L63) — `POSE_BYTES = 45` drives the volume estimate
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> - [`prototype/src/sim.ts`](https://git.produktor.io/eSlider/swarm-house/src/branch/main/prototype/src/sim.ts#L260-L277) — pose broadcasts at 5 Hz and opportunistic bulk sync, made visible
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## 6. Security as nested layers, not one wall
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@@ -32,10 +32,15 @@ wrapper, permissions, and output format a peer drone would use.
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## Consequences
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- One access path is built, secured, and tested — "what you test is what
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- One access path is designed for flight and bench — "what you test is what
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flies".
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- The SQL gate is safety-critical and is covered by unit tests
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(`simulator/tests/test_sql_gate.py`).
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- The explorer and the prototype's live mode are *just another read-only
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consumer* of this same contract ([`../04-swarm-sync.md`](../04-swarm-sync.md)).
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- The statement gate in the PoC (`simulator/explorer/server.py`, covered by
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`simulator/tests/test_sql_gate.py`) is a **first layer**: keyword allow/deny
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over HTTP for the explorer. Production still needs the remaining layers in
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[04 — Swarm sync](../04-swarm-sync.md) (forced-command key, read-only OS user,
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engine hardening, resource caps) and a real SQL parser rather than keywords
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alone.
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- The explorer and the prototype's live mode are *stand-in consumers* of the
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same read-only contract over HTTP today; the proposed flight path is
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SQL-over-SSH ([`../04-swarm-sync.md`](../04-swarm-sync.md)).
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- Design principles 7 and 8 in [`../../README.md`](../../README.md) restate this.
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@@ -268,7 +268,7 @@ export default function App(): JSX.Element {
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{busiest.length === 0 && <div style={styles.dim}>no links in range</div>}
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</Section>
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<Section title="Legend">
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<div style={styles.dim}>blue line — pose broadcast (5 Hz, ~46 B)</div>
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<div style={styles.dim}>blue line — pose broadcast (5 Hz, 45 B)</div>
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<div style={styles.dim}>green line — bulk sync (sealed partitions)</div>
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<div style={styles.dim}>flash — broadcast event delivered</div>
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<div style={styles.dim}>red circle — transit object crossing the area</div>
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@@ -57,7 +57,7 @@ export function areaWidth(): number {
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export const LINK_RANGE = 320;
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const CRUISE = 28;
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const SEPARATION = 55;
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const POSE_BYTES = 46;
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const POSE_BYTES = 45;
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const POSE_HZ = 5;
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// Steady per-link broadcast throughput (both directions), bytes/s
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export const POSE_RATE_BYTES = POSE_BYTES * POSE_HZ;
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@@ -9,7 +9,7 @@ from virtual_drone.flight import Pose
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def test_frame_size_matches_wire_spec() -> None:
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# Documented as 46 B in docs/04; struct packs to FRAME.size (45 B on this layout).
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# Keep docs/04, the journey, and prototype/src/sim.ts POSE_BYTES in lockstep.
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assert FRAME.size == 45
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@@ -1,12 +1,13 @@
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"""State broadcast over UDP: the compact pose frame from the sync design.
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Frame layout (little-endian, 46 bytes):
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Frame layout (little-endian, 45 bytes) — source of truth for docs and the
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prototype bandwidth estimate:
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magic 2s b"SH"
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version B
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drone_id 8s zero-padded ascii
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drone_id 8s zero-padded ascii (PoC; production may switch to uint16 registry)
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ts_ns q epoch nanoseconds
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pos_mm 3i position, millimeters (quantized on the wire only)
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pos_mm 3i position in the mission frame, millimeters (wire quantization only)
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att_cdeg 3h roll/pitch/yaw, centi-degrees
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vel_cms 3h velocity, cm/s
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frame_ref B
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Reference in New Issue
Block a user