从0到1搭建外卖跑腿配送系统全流程解析

CREATE TABLE orders (
    id BIGINT PRIMARY KEY AUTO_INCREMENT,
    user_id BIGINT,
    merchant_id BIGINT,
    rider_id BIGINT,
    status VARCHAR(20),
    total_amount DECIMAL(10,2),
    create_time DATETIME,
    update_time DATETIME
);

app.post("/order/create", async (req, res) => {
    const { userId, merchantId, items } = req.body;

    // 1. 计算金额
    const total = items.reduce((sum, item) => {
        return sum + item.price * item.count;
    }, 0);

    // 2. 创建订单
    const order = await db.orders.create({
        user_id: userId,
        merchant_id: merchantId,
        total_amount: total,
        status: "PENDING"
    });

    // 3. 写入Redis用于派单
    await redis.lpush("order_queue", order.id);

    res.json({
        success: true,
        orderId: order.id
    });
});

// 骑手上线（存位置）
await redis.geoadd(
    "riders_location",
    longitude,
    latitude,
    riderId
);

const riders = await redis.georadius(
    "riders_location",
    orderLng,
    orderLat,
    3,          // 3公里范围
    "km",
    "WITHDIST",
    "COUNT",
    5
);

async function dispatchOrder(orderId, orderLng, orderLat) {
    const riders = await redis.georadius(
        "riders_location",
        orderLng,
        orderLat,
        5,
        "km",
        "WITHDIST"
    );

    if (!riders.length) {
        throw new Error("暂无可用骑手");
    }

    // 按距离排序
    riders.sort((a, b) => a[1] - b[1]);

    const selectedRider = riders[0][0];

    // 更新订单
    await db.orders.update({
        where: { id: orderId },
        data: {
            rider_id: selectedRider,
            status: "DISPATCHED"
        }
    });

    // 通知骑手（WebSocket/MQTT）
    notifyRider(selectedRider, orderId);

    return selectedRider;
}

const WebSocket = require("ws");

const wss = new WebSocket.Server({ port: 8080 });

wss.on("connection", (ws) => {
    ws.on("message", (msg) => {
        const data = JSON.parse(msg);

        if (data.type === "rider_login") {
            ws.riderId = data.riderId;
        }
    });
});

// 推送订单
function notifyRider(riderId, orderId) {
    wss.clients.forEach(client => {
        if (client.riderId === riderId) {
            client.send(JSON.stringify({
                type: "NEW_ORDER",
                orderId
            }));
        }
    });
}

app.post("/rider/accept", async (req, res) => {
    const { riderId, orderId } = req.body;

    const order = await db.orders.findById(orderId);

    if (order.status !== "DISPATCHED") {
        return res.json({ success: false, msg: "订单已被接单" });
    }

    await db.orders.update({
        where: { id: orderId },
        data: {
            status: "ACCEPTED",
            rider_id: riderId
        }
    });

    res.json({ success: true });
});

setInterval(() => {
    navigator.geolocation.getCurrentPosition(async (pos) => {
        await fetch("/rider/location/update", {
            method: "POST",
            body: JSON.stringify({
                riderId,
                lng: pos.coords.longitude,
                lat: pos.coords.latitude
            })
        });
    });
}, 5000);

app.post("/rider/location/update", async (req, res) => {
    const { riderId, lng, lat } = req.body;

    await redis.geoadd("riders_location", lng, lat, riderId);

    res.json({ success: true });
});

const lock = await redis.set("order_lock_" + orderId, riderId, "NX", "EX", 10);
if (!lock) {
    return "订单已被抢";
}