如何使用nodejs和mongodb正确处理promise
如何使用nodejs和mongodb正确处理promise
提问于 2021-02-05 11:31:47
我已经将我的nodejs应用程序配置为使用mongodb。我可以成功连接mongodb实例并将数据添加到mongodb实例中。我的app配置如下(敏感信息已被编辑)：
// 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();
});
});
}如果我命中/mongo端点，那么将在数据库上创建披萨文档，但是我注意到连接从未关闭；这意味着/node端点从不发送'all good‘字符串作为响应。此外，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.似乎我没有正确处理promise和async调用，并且在某个地方丢失了一个.catch()，但我不确定在哪里。我哪里搞砸了？
回答 1
Stack Overflow用户
发布于 2021-02-05 11:38:56
您看不到all good的原因是因为这个块
return new Promise((resolve, reject) => {从来没有真正解决过。您应该通过调用resolve(...)来解决此问题。只有到那时，你的invoke().then(() => ...才会被触发。
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')
...
...但更普遍的是，您肯定希望mongo连接在请求到来时准备就绪，而不是每次都打开一个新的连接。
另外，就我个人而言，我会这样简化你的代码。
//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'})
});
}页面原文内容由Stack Overflow提供。腾讯云小微IT领域专用引擎提供翻译支持
原文链接：
https://stackoverflow.com/questions/66057190
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