Redis-聊天室和秒杀

jason_yang
366 阅读2分钟

Redis

基于内存的键值数据结构，用于数据库，缓存，消息代理。

1.特点

  1. 保存在内存速度快
  2. Redis支持持久化，断电不丢数据，对数据的更新异步保存到磁盘上
  3. 支持类型多
  4. 支持事务，所有操作都是原子性。
  5. 场景丰富，(1)消息处理，按key设置过期事件，(2)过期自动删除

2.场景

  1. 缓存
  2. 分布式锁：支持多台服务器横向部署，共用一份数据
  3. 自动过期
  4. 计数器和排行榜
  5. 秒杀的缓冲层
  6. 处理签到和其他状态（大数据处理）
  7. 发布/订阅

3.例子

1.聊天室实现

#注意该代码只使用的订阅发布，不能实现多服务器部署
const Koa = require('koa');
const app = new Koa();
const Router = require('koa-router');
const fs = require('fs');
const server = require('http').createServer(app.callback());
const io = require('socket.io')(server);
const redis = require('redis')

// 首页路由
const router = new Router();
router.get('/', ctx => {
    ctx.response.type = 'html';
    ctx.response.body = fs.createReadStream('./index.html');
});
app.use(router.routes());

const rclient = redis.createClient(6379, '127.0.0.1')
rclient.on("ready", err => {
    console.log('client ready ....');
})

const publish = redis.createClient(6379, 'localhost')
publish.on('ready', err => {
    console.log('publish ready ...')
})

// socket连接
io.on('connection', (socket) => {
    // redis模式
    // 订阅
    rclient.subscribe('chat')
    // 收到redis的发布，开始处理消息给客户端
    rclient.on('message', (channel, msg) => {
        io.emit('chat message', msg)//通过socket发送消息给客户端
    })
    socket.on('chat message', msg => {
        console.log('receive message:' + msg)
        publish.publish('chat', msg)//这里通过redis发布消息
    })
    socket.on('disconnect', () => {
        console.log('user disconnected');
    })
});

// 监听端口
server.listen(3000, () => {
    console.log('listening on *:3000');
});

测试地址:

2.实现秒杀

index.js

//该代码可以用于多服务器部署
const Koa = require("koa");
const app = new Koa();
const Router = require("koa-router");
const redis = require("redis");
const redisClient = redis.createClient(6379, "localhost");

const wrapper = require("co-redis");
const client = wrapper(redisClient);

client.on("ready", () => {
  console.log("redis ready ...");
});

// 首页路由
const router = new Router();
router.get("/", (ctx) => {
  ctx.response.type = "html";
  ctx.response.body = fs.createReadStream("./index.html");
});

router.get("/create", async (ctx) => {

  // 清空商品
  await client.ltrim("goods", -1, 0);

  // 添加30个商品
  new Array(30).fill().forEach(async (v, i) => {
    await client.rpush("goods", i);
    console.log("添加商品:", i);
  });

  // redis llen
  const num = await client.llen("goods");
  console.log("抢购商品数量:", num);

  ctx.body = {
    ok: 1,
  };
});

/**
 * 秒杀
 */
router.get("/buy", async (ctx) => {
  // 产生一个随机数当做用户id
  const uid = (Math.random() * 9999999).toFixed();
  let pid = await client.lpop("goods");

  // 判断库存
  if (pid) {
    await client.hset("orders", pid, uid);
    console.log("订单生成", pid, uid);
  }else {
    console.log('已抢光')
  }

  ctx.body = { ok: 1 };
});

router.get("/order", async (ctx) => {
  const keys = await client.hkeys("orders");
  console.log('订单列表')
  console.log('===========')
  const orders = await client.hgetall('orders')
  for (k of keys) {
    console.log(`${k} => ${await client.hget("orders", k)}`);
  }

  ctx.body = {
    orders
  };
});

router.get('/order/clear',async ctx => {
  const keys = await client.hkeys("orders");
  for (k of keys) {
    console.log(`删除订单: ${k} => ${await client.hdel("orders", k)}`);
  }
  ctx.body = {ok : 1}
})

app.use(router.routes());

// 监听端口
app.listen(3000, () => {
  console.log("listening on *:3000");
});

// node index.js //启动服务

test.js 测试代码 ,使用autocannon创建100个buy请求

(async () => {
  const autocannon = require("autocannon");
  const result = await autocannon({
    url: "http://localhost:3000/buy",
    connections: 100, //default
    pipelining: 1, // default
    duration: 1, // default
  });
  console.log('秒杀完成');
})()
// node test.js //启动测试代码

测试地址:

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