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limited-stock-rush.js
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106 lines (85 loc) · 3.22 KB
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const _ = require('lodash')
const AV = require('leanengine')
const Promise = require('bluebird')
const {redisClient} = require('../redis')
const RushStock = AV.Object.extend('RushStock')
/*
* 使用 LeanCache 实现秒杀抢购
*
* 在秒杀抢购活动中可能会在短时间内有大量的请求，如果每个请求都需要访问云存储会占用大量的工作线程数，
* 在这个例子中我们将秒杀活动的信息存到 LeanCache 中，并用 LeanCache 来维护秒杀结果，
* 一个 LeanCache 实例可以支持 10000 QPS 甚至更多的请求，
* 在秒杀活动期间不需要访问云存储，在活动结束后再将结果提交至云存储。
*
* 安装依赖：
*
* npm install lodash bluebird
*
*/
/*
* 供管理员创建一个秒杀活动
*
* quota 表示这个活动的配额，即有多少用户可以抢到；
* items 表示按顺序每个用户获得的商品，会在秒杀成功后提示给用户，你可以修改代码来生成这个字段的值。
*/
AV.Cloud.define('createRushStock', {internal: true}, async request => {
const name = request.params.name
const quota = parseInt(request.params.quota) || 20
const items = _.times(quota, String)
const rush = await new RushStock().save({
name: name,
quota: quota,
items: items,
status: 'opening'
})
const rushId = rush.objectId
await redisClient.hset('stockRushStocks', rushId, JSON.stringify({rushId, quota, items}))
return rush
})
/* 供用户获取当前开放的秒杀列表 */
AV.Cloud.define('getOpeningRushs', async request => {
return Promise.map(await redisClient.hgetall('stockRushStocks'), async (rushStringify, name) => {
const rushStock = JSON.parse(rushStringify)
const takedCount = await redisClient.llen(`stockRushStockTaked:${rushStock.rushId}`)
return {
name: name,
rushId: rushStock.rushId,
quota: rushStock.quota,
takedCount: takedCount
}
})
})
/* 供用户参与秒杀活动 */
AV.Cloud.define('rush', async request => {
const rushId = request.params.rushId
if (!request.currentUser) {
throw new AV.Cloud.Error('当前未登录用户', {status: 401})
}
const [rushStringify, takedCount] = await redisClient.multi()
.hget('stockRushStocks', rushId)
.llen(`stockRushStockTaked:${rushId}`)
.exec()
const rushStock = JSON.parse(rushStringify)
if (rushStock.quota < takedCount) {
throw new AV.Cloud.Error('红包已抢完')
}
const newTakedCount = await redisClient.rpsuh(`stockRushStockTaked:${rushId}`, request.currentUser.objectId)
if (takedCount < rushStock.quota) {
return {message: `恭喜抢到 ${rushStock.items[newTakedCount - 1]}`}
} else {
throw new AV.Cloud.Error('红包已抢完')
}
})
/* 供管理员将秒杀结果提交到云存储 */
AV.Cloud.define('commitRushStock', {internal: true}, async request => {
const rushId = request.params.rushId
const rush = await new AV.Query(RushStock).get(rushId)
const userIds = await redisClient.lrange(`stockRushStockTaked:${rushId}`, 0, rush.get('quota') - 1)
await rush.save({
status: 'closed',
users: userIds.map( userId => {
return AV.Object.createWithoutData('_User', userId)
})
})
await redisClient.del(`stockRushStockTaked:${rushId}`)
})