如何使用nodejs和mongodb正确处理promise

Question

我已经将我的nodejs应用程序配置为使用MongoDB。我可以成功地连接和添加数据到我的mongodb实例。我的应用程序配置如下（敏感信息编辑）：

// 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();
        });
    });

}

如果我点击/mongoendpoint，那么pizza文档就会很好地在数据库中创建，但我注意到连接从未关闭；这意味着/nodeendpoint从不将“all good”字符串作为响应发送。而且，对/node的任何后续请求都会抛出以下错误：

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.

我似乎没有正确处理promise和async调用，并且在某个地方缺少.catch()，但我不确定是在哪里。我这是在搞什么鬼？

Answer 1

您没有看到all good的原因是这个块

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

从未真正解决过。您应该通过调用resolve(...)来解析它。只有这样，您的才会调用（）。然后(()=>...会被触发。

所以我会让这个块看起来像这样：

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

但更一般地说，您当然希望mongo连接在请求进入时就绪，而不是每次都打开一个新的连接。

另外，我个人也会这样简化您的代码。

//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'})
        });
}