# Two-machine deployment: lightweight map + processing worker

Two-machine architecture: the **map** (interface, XYZ tile pyramid, API) runs
on a Raspberry Pi; **tile generation** (IGN downloads, PDAL, GPU) runs on a
powerful machine. Both run the same server (`lidar_pipeline.mapserve`, image
`lidar-maps`), the powerful machine in its full version (pipeline included).

```
Browser ──HTTP──▶ Raspberry Pi (lightweight lidar-maps image, port 8975)
                    │  serves the map + the pyramid (cache-only + background
                    │  maintenance, LIDAR_TILE_CACHE_ONLY / LIDAR_TILE_BACKGROUND)
                    │  /api/generate, /api/preview, /api/status
                    │     └─ forwarded to ──▶ processing worker
                    │  tiles fetched back from the worker (LIDAR_SOURCE_URL:
                    │     /api/tiles inventory + versioned static assets)
                    ▼
               Processing worker (full image,
               docker-compose.worker.yml service `worker`):
               IGN download + GPU pipeline (tile generator)
               + tile pyramid + tile inventory
```

See also `docs/MAPS.md` for the map/tile-pyramid internals referenced below.

## Processing worker (tile generator)

The `worker` service acts as the generator: it accepts generation requests
sent by remote maps (IGN download + PDAL/GPU processing), serves its own tile
pyramid and tile inventory (`/api/tiles` + static `visualisations/`,
`index_thumbs/`, `index_subtiles/`) that lightweight machines fetch on demand.

```bash
docker compose -f docker-compose.worker.yml up -d --build   # API at http://<worker-ip>:8973
docker compose -f docker-compose.worker.yml logs -f worker
```

One-off batch processing of tiles already present in `input/`:

```bash
docker compose -f docker-compose.worker.yml run --rm --build process [-r 0.2 | --force]
```

On a machine without a GPU: remove the `gpus: all` lines (CPU processing,
slower). Optional but recommended if the network isn't trusted: protect the
API with a shared token — uncomment in `docker-compose.worker.yml`:

```yaml
environment:
  - LIDAR_API_TOKEN=a-secret-to-share
```

## Raspberry Pi (lightweight map)

### 0. Prerequisites on the Pi

- **Architecture**: the image is built natively on the machine (ARM64 or
  x86_64, check with `uname -m`). The build happens on the Pi itself
  (`Dockerfile.maps`: `python:3.12-slim` base, ~200 MB, no PDAL/GDAL).
- **Docker + compose plugin**: official install
  [docs.docker.com/engine/install](https://docs.docker.com/engine/install/)
  (verify with `docker compose version`).
- **Disk space**: plan for the cache size (fetched tiles + rendered tiles;
  use the size of `output/` on the processing machine as a reference).

### 1. Copy the code onto the Pi (git clone)

```bash
git clone https://github.com/<you>/lidar_rendu.git lidar
cd lidar
```

`output/` and `input/` are git-ignored: the repository only holds the code,
the cache fills on demand from the processing machine.

### 2. Start the map

`docker-compose.maps.yml` (versioned) serves as the base; the Pi's local
configuration lives in an **override** file `docker-compose.maps.override.yml`
(not versioned). Start from the provided template:

```bash
cp docker-compose.maps.override.yml.example docker-compose.maps.override.yml
```

It looks like this (adapt addresses, cache folder and Traefik routing):

```yaml
name: lidar-maps
services:
  maps:
    volumes: !override            # Compose >= 2.24 (replaces ./output)
      - /srv/lidar/output:/data/output
    mem_limit: 1g
    memswap_limit: 1g
    environment:
      - TZ=Europe/Paris
      - LIDAR_SOURCE_URL=http://192.168.1.50:8973      # worker (tiles + inventory)
      - LIDAR_GENERATION_URL=http://192.168.1.50:8973  # worker (delegated generation)
      # - LIDAR_REMOTE_TOKEN=a-secret-to-share         # if LIDAR_API_TOKEN is set on the worker
      - LIDAR_TILE_WORKERS=1
      - LIDAR_TILE_SOURCE_CACHE_MB=64
      - LIDAR_TILE_CACHE_ONLY=1        # browsing renders NOTHING
      - LIDAR_TILE_BACKGROUND=1        # the pyramid is maintained as a background task
      - LIDAR_TILE_BACKGROUND_PAUSE=1.0
    networks: [webapp, proxy]
    labels:                           # optional Traefik routing
      - "traefik.enable=true"
      - "traefik.http.routers.lidar-maps.rule=Host(`lidar.example.fr`)"
      - "traefik.http.routers.lidar-maps.entrypoints=websecure"
      - "traefik.http.routers.lidar-maps.tls.certresolver=myresolver"
      - "traefik.http.services.lidar-maps.loadbalancer.server.port=8975"

networks:
  webapp:
    name: lidar_rendu_default
    external: true
  proxy:
    name: proxy
    external: true
```

```bash
mkdir -p /srv/lidar/output   # owned by uid 1000 (container)
docker compose -f docker-compose.maps.yml -f docker-compose.maps.override.yml up -d --build
```

The map is available at `http://<pi-host>:8975/` (and via Traefik if
configured).

`LIDAR_TILE_CACHE_ONLY=1` + `LIDAR_TILE_BACKGROUND=1` flip the load pattern on
a small Pi: browsing renders nothing (a missing tile is served transparent,
with `X-Tile-Pending`), and a background task watches for new or regenerated
tiles and maintains the pyramid at low priority — see `docs/MAPS.md`, section
"Cache-only + background maintenance".

### 3. Generating tiles from the map

The **Generation** tab (**＋ Area**: draw a rectangle → IGN download + run on
the worker; **⤒ Complete**: already-downloaded but incomplete tiles) and the
**↻ Generate this tile** button (Tile tab, after clicking a tile) are hidden
if:

- the browser's IP is outside `LIDAR_REGEN_CIDR` (default: loopback + private
  RFC1918 ranges; a comma-separated list of CIDRs, or an empty string to lift
  the restriction). The IP is the one seen on the connection (preserved by
  Docker's DNAT for LAN clients); behind a local reverse proxy (itself inside
  the allowed network), `X-Forwarded-For` designates the real client;
- the worker is unreachable AND no local pipeline exists.

A request submitted while a run is already in progress is placed in a
**queue** on the worker side (an in-progress job is never interrupted);
progress is displayed tile by tile (orange/blue/red frames on the map) and the
**Stop** button sends a SIGTERM to the pipeline. At the end of the
run, the map refreshes and pyramid maintenance resumes automatically.

### 4. Centering the map on the GPS position (phone)

Browsers only expose the Geolocation API in a **secure context** (HTTPS):
serve the map behind Traefik (TLS) as above, or, as a last resort, directly
over HTTPS (the standalone entry point `python -m lidar_pipeline.mapserve`
honors `LIDAR_SSL_CERTFILE` / `LIDAR_SSL_KEYFILE`).

## Updating

### Processing machine

```bash
cd <checkout> && git pull && docker compose -f docker-compose.worker.yml up -d --build
```

### Pi

```bash
ssh <pi-host> "cd <checkout> && git pull && docker compose -f docker-compose.maps.yml -f docker-compose.maps.override.yml up -d --build"
```

The interface code is baked into the image (`Dockerfile.maps`): **ANY**
interface change requires a rebuild (`--build`) — without it, the old code
keeps running.