IoT Domain
Layer 3: Domain Constraints
Domain Constraints → Design Implications
| Domain Rule | Design Constraint | Rust Implication |
|---|---|---|
| Unreliable network | Offline-first | Local buffering |
| Power constraints | Efficient code | Sleep modes, minimal alloc |
| Resource limits | Small footprint | no_std where needed |
| Security | Encrypted comms | TLS, signed firmware |
| Reliability | Self-recovery | Watchdog, error handling |
| OTA updates | Safe upgrades | Rollback capability |
Critical Constraints
Network Unreliability
RULE: Network can fail at any timeWHY: Wireless, remote locationsRUST: Local queue, retry with backoffPower Management
RULE: Minimize power consumptionWHY: Battery life, energy costsRUST: Sleep modes, efficient algorithmsDevice Security
RULE: All communication encryptedWHY: Physical access possibleRUST: TLS, signed messagesTrace Down ↓
From constraints to design (Layer 2):
"Need offline-first design" ↓ m12-lifecycle: Local buffer with persistence ↓ m13-domain-error: Retry with backoff
"Need power efficiency" ↓ domain-embedded: no_std patterns ↓ m10-performance: Minimal allocations
"Need reliable messaging" ↓ m07-concurrency: Async with timeout ↓ MQTT: QoS levelsEnvironment Comparison
| Environment | Stack | Crates |
|---|---|---|
| Linux gateway | tokio + std | rumqttc, reqwest |
| MCU device | embassy + no_std | embedded-hal |
| Hybrid | Split workloads | Both |
Key Crates
| Purpose | Crate |
|---|---|
| MQTT (std) | rumqttc, paho-mqtt |
| Embedded | embedded-hal, embassy |
| Async (std) | tokio |
| Async (no_std) | embassy |
| Logging (no_std) | defmt |
| Logging (std) | tracing |
Design Patterns
| Pattern | Purpose | Implementation |
|---|---|---|
| Pub/Sub | Device comms | MQTT topics |
| Edge compute | Local processing | Filter before upload |
| OTA updates | Firmware upgrade | Signed + rollback |
| Power mgmt | Battery life | Sleep + wake events |
| Store & forward | Network reliability | Local queue |
Code Pattern: MQTT Client
rust
use rumqttc::{AsyncClient, MqttOptions, QoS};
async fn run_mqtt() -> anyhow::Result<()> { let mut options = MqttOptions::new("device-1", "broker.example.com", 1883); options.set_keep_alive(Duration::from_secs(30));
let (client, mut eventloop) = AsyncClient::new(options, 10);
// Subscribe to commands client.subscribe("devices/device-1/commands", QoS::AtLeastOnce).await?;
// Publish telemetry tokio::spawn(async move { loop { let data = read_sensor().await; client.publish("devices/device-1/telemetry", QoS::AtLeastOnce, false, data).await.ok(); tokio::time::sleep(Duration::from_secs(60)).await; } });
// Process events loop { match eventloop.poll().await { Ok(event) => handle_event(event).await, Err(e) => { tracing::error!("MQTT error: {}", e); tokio::time::sleep(Duration::from_secs(5)).await; } } }}Common Mistakes
| Mistake | Domain Violation | Fix |
|---|---|---|
| No retry logic | Lost data | Exponential backoff |
| Always-on radio | Battery drain | Sleep between sends |
| Unencrypted MQTT | Security risk | TLS |
| No local buffer | Network outage = data loss | Persist locally |
Trace to Layer 1
| Constraint | Layer 2 Pattern | Layer 1 Implementation |
|---|---|---|
| Offline-first | Store & forward | Local queue + flush |
| Power efficiency | Sleep patterns | Timer-based wake |
| Network reliability | Retry | tokio-retry, backoff |
| Security | TLS | rustls, native-tls |
Related Skills
| When | See |
|---|---|
| Embedded patterns | domain-embedded |
| Async patterns | m07-concurrency |
| Error recovery | m13-domain-error |
| Performance | m10-performance |
