如何使用nodejs和mongodb正確處理promise

Question

我已將我的 nodejs 應用程序配置為使用 mongodb。 我可以成功連接並將數據添加到我的 mongodb 實例。 我的應用程序配置如下（敏感信息已編輯）：

// mongoDB configs
const MongoClient = require('mongodb').MongoClient;
const uri = "mongodb+srv://<username>:<password>@codigoinitiative.3klym.mongodb.net/<collection>?retryWrites=true&w=majority";
const client = new MongoClient(uri, { useNewUrlParser: true });

//express configs
const app = express();
const express = require('express');

//mongo endpoint
app.get('/mongo', (req, res) => {
    invoke().then(() => res.send('all good')).catch(err => console.log('invoke error:', err))
});


//mongodb access/logic
async function invoke() {
    console.log('connecting')

    return new Promise((resolve, reject) => {
        client.connect(err => {
            if(err) return reject(err)

            console.log('connected.');
            const collection = client.db("CodigoInitiative").collection("Registered");
            //create document to be inserted
            const pizzaDocument = {
            name: "Pizza",
            shape: "round",
            toppings: [ "Pepperoni", "mozzarella di bufala cheese" ],
            };
        
            // perform actions on the collection object
            const result = collection.insertOne(pizzaDocument);
            console.log(result.insertedCount);
        
            // //close the database connection
            client.close();
        });
    });

}

如果我點擊/mongo端點，披薩文檔會在數據庫上創建就好了，但我注意到連接永遠不會關閉； 意思是， /node端點永遠不會發送“all good”字符串作為響應。 此外，對/node的任何后續請求都會引發以下錯誤：

connecting
the options [servers] is not supported
the options [caseTranslate] is not supported
the options [dbName] is not supported
the options [srvHost] is not supported
the options [credentials] is not supported
connected.
undefined
(node:94679) UnhandledPromiseRejectionWarning: MongoError: topology was destroyed
    at executeWriteOperation (/Users/vismarkjuarez/Documents/GitLab/CodigoInitiative/node_modules/mongodb/lib/core/topologies/replset.js:1183:21)
    at ReplSet.insert (/Users/vismarkjuarez/Documents/GitLab/CodigoInitiative/node_modules/mongodb/lib/core/topologies/replset.js:1252:3)
    at ReplSet.insert (/Users/vismarkjuarez/Documents/GitLab/CodigoInitiative/node_modules/mongodb/lib/topologies/topology_base.js:301:25)
    at insertDocuments (/Users/vismarkjuarez/Documents/GitLab/CodigoInitiative/node_modules/mongodb/lib/operations/common_functions.js:259:19)
    at InsertOneOperation.execute (/Users/vismarkjuarez/Documents/GitLab/CodigoInitiative/node_modules/mongodb/lib/operations/insert_one.js:26:5)
    at executeOperation (/Users/vismarkjuarez/Documents/GitLab/CodigoInitiative/node_modules/mongodb/lib/operations/execute_operation.js:77:17)
    at Collection.insertOne (/Users/vismarkjuarez/Documents/GitLab/CodigoInitiative/node_modules/mongodb/lib/collection.js:517:10)
    at /Users/vismarkjuarez/Documents/GitLab/CodigoInitiative/node.js:154:39
    at /Users/vismarkjuarez/Documents/GitLab/CodigoInitiative/node_modules/mongodb/lib/utils.js:677:5
    at /Users/vismarkjuarez/Documents/GitLab/CodigoInitiative/node_modules/mongodb/lib/mongo_client.js:226:7
(node:94679) UnhandledPromiseRejectionWarning: Unhandled promise rejection. This error originated either by throwing inside of an async function without a catch block, or by rejecting a promise which was not handled with .catch(). To terminate the node process on unhandled promise rejection, use the CLI flag `--unhandled-rejections=strict` (see https://nodejs.org/api/cli.html#cli_unhandled_rejections_mode). (rejection id: 1)
(node:94679) [DEP0018] DeprecationWarning: Unhandled promise rejections are deprecated. In the future, promise rejections that are not handled will terminate the Node.js process with a non-zero exit code.

看來我沒有正確處理 promise 和異步調用，並且在某處缺少.catch() ，但我不確定在哪里。 我在哪里搞砸了？

Answer 1

你沒有看到all good原因是因為這個塊

return new Promise((resolve, reject) => {

從來沒有真正解決。 您應該通過調用resolve(...)來解決它。 只有這樣你的invoke().then(() =>...才會被觸發。

所以我會讓那個塊看起來像這樣：

...
...
        
      // perform actions on the collection object
      const result = collection.insertOne(pizzaDocument);
      console.log(result.insertedCount);
        
      // //close the database connection
      client.close();
      resolve('ok')
...
...

但更一般地說，您當然希望 mongo 連接在請求到來時准備好，而不是每次都打開一個新連接。

另外，就個人而言，我會像這樣簡化您的代碼。

//mongo endpoint
app.get('/mongo', invoke);


//mongodb access/logic
const invoke = (req, res) => {
        client.connect(err => {
            if(err) return res.json(err)

            console.log('connected.');
            const collection = client.db("CodigoInitiative").collection("Registered");
            //create document to be inserted
            const pizzaDocument = {
                name: "Pizza",
                shape: "round",
                toppings: [ "Pepperoni", "mozzarella di bufala cheese" ],
            };

            // perform actions on the collection object
            const result = collection.insertOne(pizzaDocument);
            console.log(result.insertedCount);

            // //close the database connection
            client.close();
            res.json({msg: 'all good'})
        });
}