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 time
WHY: Wireless, remote locations
RUST: Local queue, retry with backoff
Power Management
RULE: Minimize power consumption
WHY: Battery life, energy costs
RUST: Sleep modes, efficient algorithms
Device Security
RULE: All communication encrypted
WHY: Physical access possible
RUST: TLS, signed messages
Trace 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 levels
Environment 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
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 |