// MQTT连接报文结构分析
public class MQTTConnectPacket {
    private byte protocolLevel;    // 协议级别
    private boolean cleanSession;  // 清理会话标志
    private int keepAlive;         // 保活时间(秒)
    private String clientId;       // 客户端标识
    private String willTopic;      // 遗嘱主题
    private byte[] willMessage;    // 遗嘱消息

    // 连接标志位解析
    private byte connectFlags() {
        byte flags = 0;
        if (cleanSession) flags |= 0x02;
        if (willTopic != null) {
            flags |= 0x04;
            flags |= (willQos & 0x03) << 3;
            if (willRetain) flags |= 0x20;
        }
        if (username != null) flags |= 0x80;
        if (password != null) flags |= 0x40;
        return flags;
    }
}

// CoAP消息头结构体
struct coap_header_t {
    uint8_t ver : 2;      // 版本号
    uint8_t t : 2;        // 消息类型
    uint8_t tkl : 4;      // Token长度
    uint8_t code;         // 方法/响应码
    uint16_t id;          // 消息ID
    uint8_t token[8];     // Token值
    // 选项字段可变长度
};

// 观察者模式实现
class CoAPObserver {
private:
    std::map<std::string, std::vector<Endpoint>> resources;
    std::mutex observer_mutex;

public:
    void addObserver(const std::string& resource, const Endpoint& ep) {
        std::lock_guard<std::mutex> lock(observer_mutex);
        resources[resource].push_back(ep);
    }

    void notifyObservers(const std::string& resource, const uint8_t* payload, size_t len) {
        // 异步通知所有观察者
        for (const auto& ep : resources[resource]) {
            sendCoAPNotification(ep, payload, len);
        }
    }
};

// 分布式会话存储实现
public class DistributedSessionStore implements SessionStore {
    private final HazelcastInstance hazelcast;
    private final IMap<String, ClientSession> sessions;

    @Override
    public void storeSession(String clientId, ClientSession session) {
        // 异步写入，提高吞吐量
        sessions.putAsync(clientId, session)
                .thenAccept(result -> {
                    log.debug("Session stored for client: {}", clientId);
                });
    }

    @Override
    public ClientSession getSession(String clientId) {
        // 本地缓存优先，减少网络开销
        return sessions.getOrDefault(clientId, null);
    }

    // 会话迁移机制
    public void migrateSessions(String fromNode, String toNode) {
        Set<String> targetSessions = sessions.keySet().stream()
                .filter(key -> key.hashCode() % clusterSize == toNode.hashCode() % clusterSize)
                .collect(Collectors.toSet());

        // 批量迁移会话数据
        migrateInBatches(targetSessions, toNode);
    }
}

class ConsistentHashRouter:
    def __init__(self, nodes, virtual_nodes=150):
        self.virtual_nodes = virtual_nodes
        self.ring = {}
        self.sorted_keys = []

        for node in nodes:
            self.add_node(node)

    def add_node(self, node):
        for i in range(self.virtual_nodes):
            key = self.hash_function(f"{node}:{i}")
            self.ring[key] = node
            self.sorted_keys.append(key)

        self.sorted_keys.sort()

    def get_node(self, topic):
        if not self.ring:
            return None

        key = self.hash_function(topic)
        idx = bisect.bisect_right(self.sorted_keys, key) % len(self.sorted_keys)
        return self.ring[self.sorted_keys[idx]]

    def hash_function(self, key):
        return hashlib.md5(key.encode()).hexdigest()

mqtt:
  broker:
    host: "localhost"
    port: 1883
    ssl: false
  qos: 1
  retain: true
  keepalive: 60

automation:
  rules:

    - name: "夜间模式"
      trigger: "time/sunset"
      conditions:

        - "sensor/motion == false"
      actions:

        - "light/living_room/turn_off"
        - "security/arm"

# Kubernetes部署配置
apiVersion: apps/v1
kind: Deployment
metadata:
  name: mqtt-broker
spec:
  replicas: 10
  selector:
    matchLabels:
      app: mqtt-broker
  template:
    metadata:
      labels:
        app: mqtt-broker
    spec:
      containers:

      - name: emqx
        image: emqx/emqx:4.3.0
        ports:

        - containerPort: 1883
        - containerPort: 8083
        env:

        - name: EMQX_CLUSTER__DISCOVERY
          value: k8s

        - name: EMQX_NAME
          value: "emqx"
        resources:
          requests:
            memory: "1Gi"
            cpu: "500m"
          limits:
            memory: "2Gi"
            cpu: "1000m"

class EdgeAIProcessor:
    def __init__(self, model_path):
        self.model = tf.lite.Interpreter(model_path)
        self.input_details = self.model.get_input_details()
        self.output_details = self.model.get_output_details()

    def process_sensor_data(self, sensor_readings):
        # 预处理传感器数据
        input_data = self.preprocess(sensor_readings)

        # 边缘推理
        self.model.set_tensor(self.input_details[0]['index'], input_data)
        self.model.invoke()
        output = self.model.get_tensor(self.output_details[0]['index'])

        # 决策执行
        if output[0] > 0.8:  # 需要灌溉
            self.trigger_irrigation()

        return output

# Linux内核参数优化
net.core.somaxconn = 65535
net.ipv4.tcp_max_syn_backlog = 65535
net.core.netdev_max_backlog = 65535
net.ipv4.tcp_keepalive_time = 600
net.ipv4.tcp_keepalive_intvl = 60
net.ipv4.tcp_keepalive_probes = 3

# 针对物联网场景的特殊优化
net.ipv4.tcp_slow_start_after_idle = 0
net.ipv4.tcp_tw_reuse = 1
net.ipv4.tcp_fin_timeout = 30

// EMQX JVM优化配置
-Xms8g -Xmx8g 
-XX:+UseG1GC 
-XX:MaxGCPauseMillis=200
-XX:InitiatingHeapOccupancyPercent=35
-XX:ConcGCThreads=4
-XX:ParallelGCThreads=8
-XX:+ExplicitGCInvokesConcurrent
-XX:+HeapDumpOnOutOfMemoryError
-XX:HeapDumpPath=/var/log/emqx/heapdump.hprof

// Linux零拷贝技术应用
struct iovec iov[2];
iov[0].iov_base = header;
iov[0].iov_len = header_len;
iov[1].iov_base = payload;
iov[1].iov_len = payload_len;

// 使用writev减少系统调用
ssize_t n = writev(socket_fd, iov, 2);
if (n < 0) {
    // 错误处理
}

@Aspect
@Component
public class MQTTTracingAspect {

    @Around("execution(* org.eclipse.paho.client.mqttv3.MqttClient.publish(..))")
    public Object tracePublish(ProceedingJoinPoint joinPoint) throws Throwable {
        Span span = tracer.buildSpan("mqtt_publish")
                .withTag("topic", (String) joinPoint.getArgs()[0])
                .withTag("qos", joinPoint.getArgs()[1].toString())
                .start();

        try (Scope scope = tracer.scopeManager().activate(span)) {
            return joinPoint.proceed();
        } catch (Exception e) {
            span.log(e.getMessage());
            span.setTag("error", true);
            throw e;
        } finally {
            span.finish();
        }
    }
}