0xharryriddle/domain-iot

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 |

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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

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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

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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;
            }
        }
    }
}

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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 |

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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 |

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Related Skills

| When | See | |------|-----| | Embedded patterns | domain-embedded | | Async patterns | m07-concurrency | | Error recovery | m13-domain-error | | Performance | m10-performance |