如何在mongoose中使用async/await

Question

在node.js中，我有以下代码：

mongoose.connect(dbURI, dbOptions)
.then(() => {
        console.log("ok");
    },
    err => { 
        console.log('error: '+ err)
    }
);

现在我想使用async/await语法来完成它。所以我可以开始使用var mcResult = await mongoose.connect(dbURI, dbOptions);，据我所知，它会等待操作，直到以任何结果结束（就像在同步模式下调用C函数read()或fread()一样）。

但是我应该写什么呢？那返回给mcResult变量的是什么，如何检查错误或成功？基本上，我想要一个类似的片段，但是用适当的async/await语法编写。

另外，我想知道，因为我有自动重新连接功能，在dbOptions中：

dbOptions: {
  autoReconnect: true,
  reconnectTries: 999999999,
  reconnectInterval: 3000
}

如果数据库连接不可用，await会一直卡住吗？希望您能给我一个提示，告诉我会发生什么以及如何解决。

- xakepp35

Answer 1

基本上，我想要一个类似的代码片段，但使用适当的async/await语法编写。

(async () => {
  try {
    await mongoose.connect(dbURI, dbOptions)
  } catch (err) {
    console.log('error: ' + err)
  }
})()

- john-goldsmith

---

@xakepp35 是的。如果你跟随Connection.prototype.openUri的逻辑，你会发现它最终会被拒绝。 - john-goldsmith

Answer 2

请尝试这个，下面的代码包含了数据库连接和查询的基础：

const mongoose = require('mongoose');
const Schema = mongoose.Schema;

let url = 'mongodb://localhost:27017/test';

const usersSchema = new Schema({
    any: {}
}, {
    strict: false
});

const Users = mongoose.model('users', usersSchema, 'users');

/** We've created schema as in mongoose you need schemas for your collections to do operations on them */

const dbConnect = async () => {
    let db = null;
    try {
        /** In real-time you'll split DB connection(into another file) away from DB calls */
        await mongoose.connect(url, { useNewUrlParser: true }); // await on a step makes process to wait until it's done/ err'd out.
        db = mongoose.connection;

        let dbResp = await Users.find({}).lean(); /** Gets all documents out of users collection. 
                                   Using .lean() to convert MongoDB documents to raw Js objects for accessing further. */

        db.close(); // Needs to close connection, In general you don't close & re-create often. But needed for test scripts - You might use connection pooling in real-time. 
        return dbResp;
    } catch (err) {
        (db) && db.close(); /** Needs to close connection -
                   Only if mongoose.connect() is success & fails after it, as db connection is established by then. */

        console.log('Error at dbConnect ::', err)
        throw err;
    }
}

dbConnect().then(res => console.log('Printing at callee ::', res)).catch(err => console.log('Err at Call ::', err));

既然我们正在讨论async/await，那么我想提到一些事情 - await需要其函数声明为async，否则会抛出一个错误。而且建议将async/await代码封装在try/catch块中。

- whoami - fakeFaceTrueSoul

Answer 3

const connectDb = async () => {
    await mongoose.connect(dbUri, dbOptions).then(
        () => {
            console.info(`Connected to database`)
        },
        error => {
            console.error(`Connection error: ${error.stack}`)
            process.exit(1)
        }
    )
}

connectDb().catch(error => console.error(error))

假设禁止使用 then()，你可以采用以下方法...

const connectDb = async () => {
    try {
        await mongoose.connect(dbConfig.url, dbConfigOptions)

        console.info(`Connected to database on Worker process: ${process.pid}`)
    } catch (error) {
        console.error(`Connection error: ${error.stack} on Worker process: ${process.pid}`)
        process.exit(1)
    }
}

- itssadon