我正在跟随一个教程,我创建了一个cache.js文件,将mongoose查询和JSON.stringify转化为接收该查询的值的键。目标是缓存它,然后在app.js中添加.cache(),以便在mongoose.find()中使用。
如果缓存为空,我现在会从数据库中进行GET操作,然后将其存储在缓存中。
如果缓存为空,我现在会从数据库中进行GET操作,然后将其存储在缓存中。
console.log("CACHE VALUE #2");
console.log(cacheValue1);
确保数据存储并成功输出。这一行代码是有效的。但是加上这一行代码,
console.log("CACHE VALUE #1");
console.log(cacheValue);
cacheValue
是空的。
为什么呢?
它将值存储在底部,而键永远不会改变,所以我不明白为什么它不会返回数据而是 null。
因此 Cache Value #1
始终为 null,而 Cache Value #2
具有正确的数据。
控制台输出:
GRABBING FROM DB
CLIENT CONNECTION STATUS: true
Setting CACHE to True
ABOUT TO RUN A QUERY
{"$and":[{"auctionType":{"$eq":"publicAuction"}},{"auctionEndDateTime":{"$gte":1582903244869}},{"blacklistGroup":{"$ne":"5e52cca7180a7605ac94648f"}},{"startTime":{"$lte":1582903244869}}],"collection":"listings"}
CACHE VALUE #1
null
CACHE VALUE #2
(THIS IS WHERE ALL MY DATA SHOWS UP)
const mongoose = require('mongoose');
const redis = require('redis');
const util = require('util');
var env = require("dotenv").config({ path: './.env' });
const client = redis.createClient(6380, process.env.REDISCACHEHOSTNAME + '.redis.cache.windows.net', {
auth_pass: process.env.REDISCACHEKEY,
tls: { servername: process.env.REDISCACHEHOSTNAME + '.redis.cache.windows.net' }
});
client.get = util.promisify(client.get);
const exec = mongoose.Query.prototype.exec;
mongoose.Query.prototype.cache = function () {
this.useCache = true;
console.log("Setting CACHE to True")
return this;
}
mongoose.Query
.prototype.exec = async function () {
if (!this.useCache) {
console.log("GRABBING FROM DB")
console.log("CLIENT CONNECTION STATUS: " + client.connected);
return exec.apply(this, arguments);
}
console.log("ABOUT TO RUN A QUERY")
const key = JSON.stringify(Object.assign({}, this.getQuery(), {
collection: this.mongooseCollection.name
}));
//See if we have a value for 'key' in redis
console.log(key);
const cacheValue = await client.get(key);
console.log("CACHE VALUE #1");
console.log(cacheValue);
//If we do, return that
if (cacheValue) {
console.log("cacheValue IS TRUE");
const doc = JSON.parse(cacheValue);
return Array.isArray(doc)
? doc.map(d => new this.model(d))
: new this.model(doc);
}
//Otherwise, issue the query and store the result in redis
const result = await exec.apply(this, arguments);
let redisData = JSON.stringify(result);
//stores the mongoose query result in redis
await client.set(key, JSON.stringify(redisData)), function (err) {
console.error(err);
}
const cacheValue1 = await client.get(key);
console.log("CACHE VALUE #2");
console.log(cacheValue1);
return result;
}
.cache()
这样的方式调用的:https://pastebin.com/xW1Lzr82 - user6680