Depot Services Review

Depot Services Review Skill

Reviews Rust microservices in the depot/ directory that provide base station infrastructure for rover fleet operations.

Overview

The depot consists of 5 Rust-based microservices that handle rover discovery, mission dispatch, mapping, and GPS infrastructure:

Services Covered

Shared Technology Stack

All services use a consistent technology stack:

Runtime & Async:

• Rust Edition 2021
• Tokio 1.41+ (async runtime with rt-multi-thread, macros, net)
• Futures 0.3 (async utilities)

Web Framework:

• Axum 0.7-0.8 (web server, routing, WebSocket)
• Tower-HTTP 0.6 (middleware: CORS, compression, tracing)
• Hyper (underlying HTTP implementation)

Database (dispatch only):

• SQLx 0.8 (async PostgreSQL client)
• PostgreSQL 16+ (database server in Docker)
• JSON/JSONB for flexible schema fields

Serialization:

• Serde 1.0 (derive macros)
• serde_json 1.0 (JSON encoding/decoding)

Error Handling:

• thiserror 2.0 (library error types)
• anyhow (application-level error handling)

Logging:

• tracing 0.1 (structured logging)
• tracing-subscriber 0.3 (log formatting, env filtering)

Other:

• UUID 1.0 (unique identifiers with v4 generation)
• chrono 0.4 (timestamps with serde support)

Architecture Pattern

All services follow a consistent structure:

depot/<service>/
├── Cargo.toml           # Dependencies and metadata
├── Dockerfile           # Multi-stage build (alpine-based)
├── src/
│   └── main.rs          # Single-file service (300-1200 LOC)
└── migrations/          # SQL migrations (dispatch only)
    └── 001_initial.sql

Code Structure (main.rs):

//! Service documentation

// Imports
use axum::{...};
use tokio::...;

// Type definitions
struct AppState { ... }
type SharedState = Arc<AppState>;

// Main function
#[tokio::main]
async fn main() {
    // 1. Initialize logging
    // 2. Load configuration from env vars
    // 3. Initialize state (DB connection, channels, etc.)
    // 4. Create router with routes
    // 5. Bind to port and serve
}

// Handler functions
async fn endpoint_handler(...) -> impl IntoResponse { ... }

// Helper functions
fn utility_function(...) { ... }

Shared Patterns Review Checklist

1. Axum Web Server Setup

• Tokio runtime is configured correctly
  • Uses #[tokio::main] macro for async main
  • Runtime features include at least: rt-multi-thread, macros, net
  • No blocking operations in async contexts

❌ BAD:

fn main() {
    let rt = tokio::runtime::Runtime::new().unwrap();
    rt.block_on(async { ... });
}

✅ GOOD:

#[tokio::main]
async fn main() {
    // Tokio runtime handles everything
}

• Router is created with all routes defined
  • Uses Router::new() with chained .route() calls
  • Groups related routes together (RESTful patterns)
  • WebSocket routes use get() method with ws.on_upgrade()
  • State is attached with .with_state()

✅ GOOD:

let app = Router::new()
    // CRUD for zones
    .route("/zones", post(create_zone))
    .route("/zones", get(list_zones))
    .route("/zones/{id}", get(get_zone))
    .route("/zones/{id}", put(update_zone))
    .route("/zones/{id}", delete(delete_zone))
    // WebSocket
    .route("/ws", get(ws_handler))
    // Health check
    .route("/health", get(health))
    .layer(CorsLayer::permissive())
    .with_state(state);

• CORS is configured appropriately
  • Uses CorsLayer::permissive() for internal services
  • Applied as layer via .layer(CorsLayer::permissive())
  • Enables cross-origin requests from console

✅ GOOD:

use tower_http::cors::CorsLayer;

Router::new()
    .route("/endpoint", get(handler))
    .layer(CorsLayer::permissive())  // Allows all origins for internal services

• Server binds to correct address
  • Port loaded from PORT env var with sensible default
  • Binds to 0.0.0.0 (all interfaces) for Docker compatibility
  • Uses tokio::net::TcpListener for async binding

✅ GOOD:

let port: u16 = std::env::var("PORT")
    .ok()
    .and_then(|p| p.parse().ok())
    .unwrap_or(4860);  // Service-specific default

let addr = SocketAddr::from(([0, 0, 0, 0], port));
let listener = tokio::net::TcpListener::bind(addr).await.unwrap();
axum::serve(listener, app).await.unwrap();

Reference: See api-design-patterns.md for more Axum patterns.

2. State Management

• AppState struct contains all shared state
  • Database pool (dispatch only)
  • Broadcast channels for WebSocket updates
  • Configuration (directories, URLs, etc.)
  • Connected client tracking (if applicable)

✅ GOOD:

struct AppState {
    db: PgPool,  // Database connection pool
    rovers: RwLock<HashMap<String, ConnectedRover>>,  // Mutable state
    broadcast_tx: broadcast::Sender<BroadcastMessage>,  // Update channel
}

• State is wrapped in Arc for sharing
  • Uses Arc<AppState> for clone-on-share semantics
  • Type alias SharedState = Arc<AppState> for convenience
  • Handlers receive State<SharedState> extractor

✅ GOOD:

type SharedState = Arc<AppState>;

let state = Arc::new(AppState::new(pool));

async fn handler(State(state): State<SharedState>) -> impl IntoResponse {
    // Access state here
}

• Concurrent state access uses appropriate synchronization
  • Immutable state: direct access via Arc
  • Mutable state: RwLock for many readers, few writers
  • Channels: broadcast for fan-out, mpsc for point-to-point
  • Never use Mutex around async operations

❌ BAD:

let rovers = state.rovers.lock().await;  // Mutex in async = deadlock risk
tokio::time::sleep(Duration::from_secs(5)).await;  // Holding lock across await!
drop(rovers);

✅ GOOD:

// Read
let rovers = state.rovers.read().await;
let count = rovers.len();
drop(rovers);  // Release lock quickly

// Write
let mut rovers = state.rovers.write().await;
rovers.insert(id, rover);
drop(rovers);  // Release lock quickly

3. Database Patterns (Dispatch Service)

• SQLx connection pool is created correctly
  • Uses PgPoolOptions::new() to configure pool
  • Sets max_connections appropriately (10-20 for services)
  • Connection URL from DATABASE_URL env var
  • Handles connection errors gracefully

✅ GOOD:

let database_url = std::env::var("DATABASE_URL")
    .expect("DATABASE_URL must be set");

let pool = PgPoolOptions::new()
    .max_connections(10)
    .connect(&database_url)
    .await
    .expect("Failed to connect to database");

• Migrations are applied on startup
  • Migration SQL files in migrations/ directory
  • Applied manually in run_migrations() function
  • Checks if migration already applied before running
  • Logs migration status

✅ GOOD:

async fn run_migrations(pool: &PgPool) {
    let migration = include_str!("../migrations/001_initial.sql");

    // Check if already migrated
    let table_exists: bool = sqlx::query_scalar(
        "SELECT EXISTS (SELECT FROM information_schema.tables WHERE table_name = 'zones')"
    )
    .fetch_one(pool)
    .await
    .unwrap_or(false);

    if !table_exists {
        info!("Running migration...");
        sqlx::raw_sql(migration).execute(pool).await.expect("Migration failed");
    }
}

• Database queries use parameterized queries
  • NEVER use string concatenation for SQL
  • Always use .bind() for parameters
  • Prevents SQL injection vulnerabilities

❌ BAD (SQL injection vulnerability):

let query = format!("SELECT * FROM zones WHERE id = '{}'", user_input);
sqlx::query(&query).fetch_one(&pool).await?;

✅ GOOD:

sqlx::query_as::<_, Zone>(
    "SELECT * FROM zones WHERE id = $1"
)
.bind(id)  // Parameterized - safe!
.fetch_one(&pool)
.await?

• Query results use appropriate methods
  • .fetch_one() - exactly one row expected, error if zero or multiple
  • .fetch_optional() - zero or one row, returns Option<T>
  • .fetch_all() - multiple rows, returns Vec<T>
  • .execute() - for INSERT/UPDATE/DELETE, returns rows affected

✅ GOOD:

// Get by ID - must exist
let zone: Zone = sqlx::query_as("SELECT ... WHERE id = $1")
    .bind(id)
    .fetch_one(&state.db)
    .await
    .map_err(|e| (StatusCode::INTERNAL_SERVER_ERROR, e.to_string()))?;

// Get by ID - may not exist
let zone: Option<Zone> = sqlx::query_as("SELECT ... WHERE id = $1")
    .bind(id)
    .fetch_optional(&state.db)
    .await?;

• JSONB fields are handled correctly
  • Use #[sqlx(json)] attribute on struct fields
  • Serialize/deserialize with serde
  • Type must be serde_json::Value in database model
  • Cast to concrete types when needed

✅ GOOD:

#[derive(FromRow, Serialize)]
struct Zone {
    pub id: Uuid,
    #[sqlx(json)]
    pub waypoints: serde_json::Value,  // Stored as JSONB
}

// When parsing
let waypoints: Vec<Waypoint> = serde_json::from_value(zone.waypoints)?;

Reference: See database-patterns.md for comprehensive database guidance.

4. Error Handling

• Handler errors use Result with IntoResponse
  • Return type: Result<impl IntoResponse, (StatusCode, String)>
  • Errors map to HTTP status codes
  • Error messages are user-friendly (not debug strings)

✅ GOOD:

async fn get_zone(
    State(state): State<SharedState>,
    Path(id): Path<Uuid>,
) -> Result<impl IntoResponse, (StatusCode, String)> {
    let zone = sqlx::query_as("...")
        .bind(id)
        .fetch_optional(&state.db)
        .await
        .map_err(|e| (StatusCode::INTERNAL_SERVER_ERROR, e.to_string()))?
        .ok_or((StatusCode::NOT_FOUND, "Zone not found".to_string()))?;

    Ok(Json(zone))
}

• Custom error types implement IntoResponse
  • Derive from thiserror::Error for libraries
  • Implement IntoResponse for Axum handlers
  • Map error variants to appropriate HTTP status codes

✅ GOOD:

use thiserror::Error;

#[derive(Error, Debug)]
pub enum ApiError {
    #[error("Not found: {0}")]
    NotFound(String),
    #[error("IO error: {0}")]
    Io(#[from] std::io::Error),
}

impl IntoResponse for ApiError {
    fn into_response(self) -> axum::response::Response {
        let (status, message) = match &self {
            ApiError::NotFound(msg) => (StatusCode::NOT_FOUND, msg.clone()),
            ApiError::Io(e) => (StatusCode::INTERNAL_SERVER_ERROR, e.to_string()),
        };
        (status, Json(serde_json::json!({ "error": message }))).into_response()
    }
}

• Database errors are handled appropriately
  • .map_err() converts SQLx errors to HTTP responses
  • Use .ok_or() to convert Option to Result with NOT_FOUND
  • Log errors before returning them

✅ GOOD:

let zone: Zone = sqlx::query_as("SELECT ... WHERE id = $1")
    .bind(id)
    .fetch_optional(&state.db)
    .await
    .map_err(|e| {
        warn!(error = %e, "Database query failed");
        (StatusCode::INTERNAL_SERVER_ERROR, "Database error".to_string())
    })?
    .ok_or_else(|| {
        warn!(zone_id = %id, "Zone not found");
        (StatusCode::NOT_FOUND, "Zone not found".to_string())
    })?;

5. WebSocket Communication

• WebSocket upgrade is handled correctly
  • Handler accepts WebSocketUpgrade extractor
  • Returns ws.on_upgrade(|socket| handler_fn(socket, state))
  • Handler function is async fn taking WebSocket and state

✅ GOOD:

async fn ws_handler(
    ws: WebSocketUpgrade,
    State(state): State<SharedState>,
) -> impl IntoResponse {
    ws.on_upgrade(|socket| handle_ws(socket, state))
}

async fn handle_ws(socket: WebSocket, state: SharedState) {
    let (mut sender, mut receiver) = socket.split();
    // ... WebSocket logic
}

• WebSocket messages are properly parsed
  • Use serde_json::from_str() to parse text messages
  • Handle parse errors gracefully (don't crash connection)
  • Implement message protocol with tagged enum

✅ GOOD:

#[derive(Deserialize)]
#[serde(tag = "type", rename_all = "lowercase")]
enum RoverMessage {
    Register { rover_id: String },
    Progress { task_id: Uuid, progress: i32 },
}

// In handler
while let Some(msg) = receiver.next().await {
    let msg = match msg {
        Ok(Message::Text(text)) => text,
        Ok(Message::Close(_)) => break,
        _ => continue,
    };

    match serde_json::from_str::<RoverMessage>(&msg) {
        Ok(RoverMessage::Register { rover_id }) => { ... },
        Ok(RoverMessage::Progress { task_id, progress }) => { ... },
        Err(e) => warn!(error = %e, "Failed to parse message"),
    }
}

• Broadcast channels are used correctly
  • Create channel with broadcast::channel(capacity)
  • Subscribe with .subscribe() in each WebSocket handler
  • Send updates with .send() (returns Result)
  • Handle lagged receivers (broadcast can drop messages)

✅ GOOD:

// In AppState
struct AppState {
    broadcast_tx: broadcast::Sender<BroadcastMessage>,
}

impl AppState {
    fn new() -> Self {
        let (broadcast_tx, _rx) = broadcast::channel(256);  // Drop receiver
        Self { broadcast_tx }
    }

    fn broadcast(&self, msg: BroadcastMessage) {
        let _ = self.broadcast_tx.send(msg);  // Ignore if no receivers
    }
}

// In WebSocket handler
let mut rx = state.broadcast_tx.subscribe();
loop {
    tokio::select! {
        Ok(msg) = rx.recv() => {
            // Send to client
        }
        msg = receiver.next() => {
            // Handle incoming message
        }
    }
}

• WebSocket cleanup is handled on disconnect
  • Remove client from tracking map
  • Abort spawned tasks
  • Broadcast disconnect event if needed
  • No panics in cleanup code

✅ GOOD:

async fn handle_ws(socket: WebSocket, state: SharedState) {
    let mut rover_id: Option<String> = None;

    // WebSocket loop
    while let Some(msg) = receiver.next().await {
        // ... handle messages
        if let RoverMessage::Register { rover_id: id } = parsed {
            rover_id = Some(id.clone());
            // Register rover
        }
    }

    // Cleanup on disconnect
    if let Some(id) = rover_id {
        info!(rover_id = %id, "Client disconnected");
        let mut rovers = state.rovers.write().await;
        rovers.remove(&id);
        drop(rovers);

        state.broadcast(BroadcastMessage::Disconnected { rover_id: id });
    }
}

Reference: See websocket-patterns.md for detailed WebSocket guidance.

6. Logging and Observability

• Tracing is initialized early
  • Use tracing_subscriber::fmt() in main()
  • Set env filter with fallback: RUST_LOG env var or default level
  • Initialize before any other operations

✅ GOOD:

#[tokio::main]
async fn main() {
    tracing_subscriber::fmt()
        .with_env_filter(
            tracing_subscriber::EnvFilter::try_from_default_env()
                .unwrap_or_else(|_| "discovery=info,sqlx=warn".into())
        )
        .init();

    info!("Service starting...");
    // ... rest of main
}

• Log statements use structured logging
  • Use info!, warn!, error!, debug! macros
  • Include context with key-value pairs
  • Use % for Display, ? for Debug formatting
  • Log important events: startup, requests, errors, shutdown

✅ GOOD:

info!(
    rover_id = %rover.id,
    address = %rover.address,
    "Rover registered"
);

warn!(
    task_id = %task_id,
    error = %error,
    "Task failed"
);

• Health check endpoint exists
  • Endpoint at /health returning JSON
  • Includes service status and metrics
  • Returns 200 OK if service is healthy
  • Used by Docker healthcheck

✅ GOOD:

async fn health(State(state): State<SharedState>) -> impl IntoResponse {
    let rover_count = state.rovers.read().await.len();
    Json(serde_json::json!({
        "status": "ok",
        "rovers": rover_count
    }))
}

7. Configuration and Environment

• Configuration loaded from environment variables
  • Use std::env::var() for required config
  • Provide sensible defaults for optional config
  • Validate configuration early (fail fast)
  • Log configuration values (except secrets)

✅ GOOD:

// Required
let database_url = std::env::var("DATABASE_URL")
    .expect("DATABASE_URL must be set");

// Optional with default
let port: u16 = std::env::var("PORT")
    .ok()
    .and_then(|p| p.parse().ok())
    .unwrap_or(4860);

let sessions_dir = std::env::var("SESSIONS_DIR")
    .map(PathBuf::from)
    .unwrap_or_else(|_| PathBuf::from("/data/sessions"));

info!(
    port = port,
    sessions_dir = %sessions_dir.display(),
    "Configuration loaded"
);

• Paths use PathBuf for cross-platform compatibility
  • Never hardcode paths with / or \
  • Use PathBuf::from() to convert from env vars
  • Use .join() to build paths
  • Use .display() for logging paths

✅ GOOD:

let base_dir = PathBuf::from(std::env::var("DATA_DIR").unwrap_or("/data".into()));
let sessions_path = base_dir.join("sessions").join(&rover_id);

info!(path = %sessions_path.display(), "Session path");

8. Docker Build and Deployment

• Dockerfile uses multi-stage build
  • Stage 1: rust:1.83-alpine for building
  • Stage 2: alpine:3.21 for runtime
  • Minimizes final image size (typically 10-20 MB)

✅ GOOD:

# Build stage
FROM rust:1.83-alpine AS builder
RUN apk add --no-cache musl-dev
WORKDIR /app
COPY Cargo.toml Cargo.lock* ./
# Dummy build for caching
RUN mkdir src && echo "fn main() {}" > src/main.rs
RUN cargo build --release 2>/dev/null || true
# Real build
COPY src ./src
RUN touch src/main.rs
RUN cargo build --release

# Runtime stage
FROM alpine:3.21
RUN apk add --no-cache ca-certificates
COPY --from=builder /app/target/release/[service] /usr/local/bin/[service]
ENV PORT=4860
EXPOSE 4860
CMD ["[service]"]

• Release profile is optimized
  • lto = true - Link-time optimization
  • opt-level = "z" - Optimize for size
  • strip = true - Remove debug symbols

✅ GOOD in Cargo.toml:

[profile.release]
lto = true
opt-level = "z"
strip = true

• Docker Compose service is configured correctly
  • Container name follows pattern: depot-<service>
  • Restart policy: unless-stopped
  • Ports mapped correctly (host:container)
  • Environment variables passed from .env
  • Healthcheck defined
  • Dependencies declared with depends_on

✅ GOOD in docker-compose.yml:

discovery:
  build:
    context: ./discovery
    dockerfile: Dockerfile
  container_name: depot-discovery
  restart: unless-stopped
  ports:
    - "4860:4860"
  environment:
    - PORT=4860
    - RUST_LOG=discovery=info
  healthcheck:
    test: ["CMD", "wget", "-q", "-O-", "http://localhost:4860/health"]
    interval: 10s
    timeout: 3s
    retries: 3

Reference: See docker-deployment.md for comprehensive Docker patterns.

Service-Specific Reviews

Discovery Service (depot/discovery)

Purpose: Rover registration, heartbeat tracking, session file serving

Key Files:

• src/main.rs - Main service implementation (~600 LOC)
• Dockerfile - Multi-stage build

Endpoints:

• POST /register - Register rover with metadata
• POST /heartbeat/{id} - Update rover status with telemetry
• GET /rovers - List all registered rovers (HTTP fallback)
• GET /ws - WebSocket for live rover updates to operators
• GET /api/sessions - List recorded sessions
• GET /api/sessions/{rover_id}/{session_dir}/session.rrd - Serve session file
• GET /health - Health check

Specific Concerns:

• Rover timeout is implemented correctly

  • Constant ROVER_TIMEOUT = Duration::from_secs(10)
  • Background task checks for stale rovers every 2 seconds
  • Online status computed on-the-fly in get_rovers()

• Session file serving is secure

  • Path traversal attacks prevented (no .. in paths)
  • Files served from configured SESSIONS_DIR only
  • Tries both direct and nested session structures
  • Returns 404 if file doesn't exist

• WebSocket updates are efficient

  • Initial rover list sent on connection
  • Updates only sent when state changes
  • Broadcast channel prevents blocking on slow clients

Common Issues:

• Forgetting to call state.notify() after state changes
• Not dropping read locks before broadcasting (potential deadlock)
• Not handling both session directory structures (direct vs nested)

Dispatch Service (depot/dispatch)

Purpose: Mission planning, zone management, task assignment to rovers

Key Files:

• src/main.rs - Main service implementation (~1200 LOC)
• migrations/001_initial.sql - Database schema
• Dockerfile - Multi-stage build

Database Tables:

• zones - Geographic areas (routes, polygons, points)
• missions - Scheduled work definitions
• tasks - Execution instances with progress tracking

Endpoints:

• POST/GET/PUT/DELETE /zones - Zone CRUD
• POST/GET/PUT/DELETE /missions - Mission CRUD
• POST /missions/{id}/start - Start mission (creates task, assigns to rover)
• POST /missions/{id}/stop - Stop mission (cancels active task)
• GET/POST /tasks - Task management
• GET /ws - WebSocket for rover connections
• GET /ws/console - WebSocket for console updates
• GET /health - Health check

Specific Concerns:

• Task lifecycle is managed correctly

  • States: pending → assigned → active → done/failed/cancelled
  • started_at set on first progress update
  • ended_at set when task completes/fails/cancelled
  • Rover's current_task cleared when task ends

• WebSocket protocol is implemented correctly

  • Two WebSocket endpoints: /ws (rovers), /ws/console (operators)
  • Rover messages: Register, Progress, Complete, Failed
  • Dispatch messages: Task, Cancel
  • Broadcast messages: TaskUpdate, RoverUpdate, ZoneUpdate, MissionUpdate

• Task assignment logic is correct

  • Check if mission has preferred rover, verify connected
  • If no preference, find any available rover (no current task)
  • Create task in database with status=assigned
  • Update rover's current_task in memory
  • Send task to rover via WebSocket
  • Rollback if send fails

• JSONB fields are validated

  • zones.waypoints contains array of {x, y, theta?} objects
  • missions.schedule contains {trigger, cron?, loop} object
  • Validate structure before inserting (prevent invalid data)

Common Issues:

• Not clearing rover.current_task when task ends (rover stuck)
• Forgetting to broadcast updates to console clients
• Not rolling back database changes if WebSocket send fails
• Race condition between task creation and rover disconnect

Map API Service (depot/map-api)

Purpose: Serve processed maps and 3D assets to console and other clients

Key Files:

• src/main.rs - Main service implementation (~450 LOC)
• Dockerfile - Multi-stage build

Endpoints:

• GET /maps - List all maps
• GET /maps/{id} - Get map manifest (metadata)
• GET /maps/{id}/{asset} - Download asset (splat.ply, pointcloud.laz, mesh.glb, thumbnail.jpg)
• GET /sessions - List all sessions
• GET /sessions/{id} - Get session metadata
• GET /maps/{id}/sessions - Get sessions used to build map
• GET /health - Health check

Specific Concerns:

• Map manifest loading is efficient

  • Reads maps/index.json for map list
  • Lazily loads manifests from maps/{name}/manifest.json
  • Caches manifests in RwLock<HashMap<Uuid, MapManifest>>
  • Reloads on each list/get request (eventual consistency)

• Asset serving is correct

  • Validates asset exists in manifest before serving
  • Sets correct Content-Type header for each asset type
  • Reads entire file into memory (acceptable for small assets)
  • Returns 404 if asset file missing

• File paths are constructed safely

  • Uses PathBuf::join() to build paths
  • Validates file exists before serving
  • No path traversal vulnerabilities

Common Issues:

• Serving assets not listed in manifest (security issue)
• Not setting Content-Type header (browser confusion)
• Not handling missing files gracefully

GPS Status Service (depot/gps-status)

Purpose: Monitor RTK base station status and broadcast to console

Key Files:

• src/main.rs - Main service implementation (~400 LOC)
• Dockerfile - Multi-stage build

Endpoints:

• GET /status - Current RTK base station status
• GET /ws - WebSocket for live status updates to console
• GET /health - Health check

Specific Concerns:

• RTK status is polled correctly

  • Background task polls base station via serial/TCP
  • Parses RTCM3/NMEA messages for status
  • Broadcasts status updates via WebSocket
  • Handles base station disconnection gracefully

• WebSocket updates are throttled

  • Status sent at reasonable interval (1-5 seconds)
  • Prevents overwhelming clients with updates
  • Initial status sent on connection

Common Issues:

• Not handling base station disconnection
• Sending updates too frequently (CPU/bandwidth waste)
• Not validating RTCM3 message checksums

Mapper Service (depot/mapper)

Purpose: Orchestrate map processing pipeline (batch job, not always running)

Key Files:

• src/main.rs - Main orchestrator (~1000 LOC)
• Dockerfile - Multi-stage build

Operation:

• Runs as batch job (not a long-running service)
• Scans sessions directory for new sessions
• Queues sessions for processing
• Invokes splat-worker for 3D reconstruction
• Generates map manifests and assets
• Updates index.json

Specific Concerns:

• Session discovery is efficient

  • Scans filesystem for new sessions
  • Reads metadata.json from each session
  • Filters by GPS bounds, frame counts, etc.
  • Deduplicates sessions already processed

• Processing pipeline is fault-tolerant

  • Tracks session status (pending, processing, processed, failed)
  • Retries failed sessions with exponential backoff
  • Logs errors for manual intervention
  • Doesn't block on failed sessions

• Map manifest generation is correct

  • Calculates GPS bounds from all sessions
  • Lists all available assets (splat, pointcloud, mesh, thumbnail)
  • Includes session references
  • Updates index.json atomically

Common Issues:

• Not handling concurrent mapper invocations (file conflicts)
• Not validating session metadata before processing
• Not cleaning up temporary files on failure

Quick Commands

Development

# Check code (no build)
cargo check -p discovery
cargo check -p dispatch

# Build service
cargo build -p discovery --release

# Run tests
cargo test -p dispatch

# Run service locally (requires dependencies)
cd depot/discovery
PORT=4860 cargo run

# Run with logging
RUST_LOG=discovery=debug cargo run

Docker

# Build service image
cd depot/discovery
docker build -t depot-discovery .

# Run service container
docker run -p 4860:4860 -e RUST_LOG=info depot-discovery

# Build all services via Docker Compose
cd depot
docker compose build

# Start all services
docker compose up -d

# View logs
docker compose logs -f discovery

# Restart service
docker compose restart dispatch

# Stop all services
docker compose down

Database (Dispatch Only)

# Connect to PostgreSQL
docker compose exec postgres psql -U postgres -d dispatch

# View tables
\dt

# Query zones
SELECT id, name, zone_type FROM zones;

# Query tasks
SELECT id, status, rover_id, progress FROM tasks ORDER BY created_at DESC LIMIT 10;

# Reset database (DESTRUCTIVE)
docker compose down -v  # Removes volumes
docker compose up -d postgres
docker compose restart dispatch  # Migrations run on startup

References

• database-patterns.md - SQLx, migrations, queries, transactions
• api-design-patterns.md - Axum routing, middleware, error handling
• websocket-patterns.md - WebSocket protocols, broadcast channels
• docker-deployment.md - Multi-stage builds, Docker Compose, healthchecks
• CLAUDE.md - Project-wide conventions
• depot/README.md - Depot architecture overview