高效同城配送系统架构揭秘

同城配送系统架构设计

采用Spring Boot作为基础框架，结合Redis实现高速缓存，利用RabbitMQ处理异步任务。系统采用微服务架构，分为订单服务、配送服务、支付服务和通知服务四大模块。订单服务处理用户下单逻辑，配送服务管理骑手调度，支付服务对接第三方支付平台，通知服务负责短信和推送。

数据库设计采用分库分表策略，订单表按用户ID哈希分片，配送表按地理位置分片。Redis缓存热点数据如骑手实时位置和配送费计算规则。RabbitMQ队列分为即时队列和延迟队列，分别处理普通订单和预定订单。

核心功能实现

订单创建流程

@PostMapping("/orders")
public ResponseEntity<Order> createOrder(@RequestBody OrderDTO orderDTO) {
    // 1. 校验库存
    inventoryService.checkStock(orderDTO.getItems());
    
    // 2. 计算配送费
    BigDecimal deliveryFee = deliveryService.calculateFee(
        orderDTO.getPickupAddress(), 
        orderDTO.getDeliveryAddress());
    
    // 3. 创建订单（分布式事务）
    Order order = orderService.createOrder(
        orderDTO, 
        deliveryFee);
    
    // 4. 触发配送任务
    rabbitTemplate.convertAndSend(
        "delivery.queue", 
        new DeliveryTask(order.getId()));
    
    return ResponseEntity.ok(order);
}

骑手调度算法 采用改进的遗传算法实现智能调度，适应度函数考虑以下因素：

距离系数：$D = \sqrt{(x_1-x_2)^2 + (y_1-y_2)^2}$
负载因子：$L = \frac{current_orders}{max_capacity}$
时效权重：$T = e^{-0.1 \cdot remaining_time}$

Redis存储骑手实时位置数据：

GEOADD riders 116.404 39.915 "rider_1001"
GEORADIUS riders 116.404 39.915 5 km

消息队列设计

RabbitMQ配置多个Exchange：

order.direct：处理即时订单路由
order.delayed：处理预定订单（使用插件实现延迟）
dead.letter：处理失败消息

队列绑定策略：

rabbitmq:
  queues:
    immediate: 
      exchange: order.direct
      routingKey: order.new
    scheduled:
      exchange: order.delayed  
      routingKey: order.scheduled
      ttl: 3600000

性能优化方案

缓存穿透防护 采用布隆过滤器+空值缓存策略：

public Order getOrderWithCache(Long id) {
    // 1. 布隆过滤器检查
    if (!bloomFilter.mightContain(id)) {
        return null;
    }
    
    // 2. 查询缓存
    Order order = (Order)redisTemplate.opsForValue().get("order:"+id);
    if (order == null) {
        // 3. 查询数据库并设置空值过期
        order = orderRepository.findById(id);
        redisTemplate.opsForValue().set(
            "order:"+id, 
            order != null ? order : new NullOrder(),
            5, TimeUnit.MINUTES);
    }
    return order instanceof NullOrder ? null : order;
}

配送状态同步 使用WebSocket+Redis Pub/Sub实现实时更新：

@EventListener
public void handleDeliveryEvent(DeliveryStatusEvent event) {
    redisTemplate.convertAndSend(
        "delivery.update", 
        event.getOrderId() + ":" + event.getStatus());
    
    // WebSocket推送
    simpMessagingTemplate.convertAndSend(
        "/topic/orders/" + event.getOrderId(),
        new StatusMessage(event.getStatus()));
}

容灾与监控

降级策略

支付服务降级：启用本地记账模式
地图服务降级：切换至离线路径库
通知服务降级：转存至本地队列

监控指标

Prometheus采集的JVM指标
Grafana展示的配送时效看板
ELK收集的业务日志

系统通过Spring Cloud Sleuth实现全链路追踪，关键业务操作记录操作日志至MongoDB。采用Hystrix实现熔断机制，当骑手接单超时率达到阈值时自动触发系统告警。

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