Javascript 如何使用统一的拓扑和承诺从NodeJS连接到MongoDB
我是MongoDB的新手-提前为任何pebkac道歉 根据,统一拓扑范式不再使用“连接”的概念,而是简单地设置一个连接字符串并开始执行操作。然后,每个操作都会失败或成功,具体取决于驱动程序在执行操作时是否能够到达服务器 我试图实现以下示例代码,以在测试机器上建立到本地MongoDB服务器的“连接”,但它不起作用:节点抛出未捕获的承诺拒绝消息,显然是因为它在某个地方出错 然而,示例代码没有显示如何使用承诺实现新的范例。我假设这是主要的问题,所以我尝试了下面显示的第二个代码,但仍然没有得到允许我检索记录的对象。你能告诉我我做错了什么,以及在Express应用程序中建议/最好的方法来确保它尽可能稳定吗 第一次尝试: index.js:Javascript 如何使用统一的拓扑和承诺从NodeJS连接到MongoDB,javascript,node.js,mongodb,database-connection,Javascript,Node.js,Mongodb,Database Connection,我是MongoDB的新手-提前为任何pebkac道歉 根据,统一拓扑范式不再使用“连接”的概念,而是简单地设置一个连接字符串并开始执行操作。然后,每个操作都会失败或成功,具体取决于驱动程序在执行操作时是否能够到达服务器 我试图实现以下示例代码,以在测试机器上建立到本地MongoDB服务器的“连接”,但它不起作用:节点抛出未捕获的承诺拒绝消息,显然是因为它在某个地方出错 然而,示例代码没有显示如何使用承诺实现新的范例。我假设这是主要的问题,所以我尝试了下面显示的第二个代码,但仍然没有得到允许我检索
async function init(){
console.log("Starting...");
const MongoClient = require('mongodb');
const client = MongoClient('mongodb://test:test@localhost:27017', { useUnifiedTopology: true });
const coll = client.db('test').collection('foo');
await coll.insert({ test: 'document' });
const docs = coll.find({ test: 1 }, { readPreference: 'secondary' }).toArray();
console.dir({ docs });
await client.close();
}
init();
错误:
Starting...
(node:15328) UnhandledPromiseRejectionWarning: TypeError: client.db is not a function
at init (index.js:5:22)
at Object.<anonymous> (index.js:13:1)
at Module._compile (internal/modules/cjs/loader.js:1128:30)
at Object.Module._extensions..js (internal/modules/cjs/loader.js:1167:10)
at Module.load (internal/modules/cjs/loader.js:983:32)
at Function.Module._load (internal/modules/cjs/loader.js:891:14)
at Function.executeUserEntryPoint [as runMain] (internal/modules/run_main.js:71:12)
at internal/main/run_main_module.js:17:47
(node:15328) 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(). (rejection id: 1)
(node:15328) [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.
输出:
Starting...
Connected: result = MongoClient {
_events: [Object: null prototype] { newListener: [Function (anonymous)] },
_eventsCount: 1,
_maxListeners: undefined,
s: {
url: 'mongodb://test:test@localhost:27017',
options: {
servers: [Array],
caseTranslate: true,
useUnifiedTopology: true,
checkServerIdentity: true,
sslValidate: true,
auth: [Object],
authSource: 'admin',
dbName: 'test',
socketTimeoutMS: 360000,
connectTimeoutMS: 30000,
retryWrites: true,
useRecoveryToken: true,
readPreference: [ReadPreference],
credentials: [MongoCredentials],
promiseLibrary: [Function: Promise]
},
promiseLibrary: [Function: Promise],
dbCache: Map {},
sessions: Set {},
writeConcern: undefined,
namespace: MongoDBNamespace { db: 'admin', collection: undefined }
},
topology: NativeTopology {
_events: [Object: null prototype] {
authenticated: [Function (anonymous)],
error: [Function (anonymous)],
timeout: [Function (anonymous)],
close: [Function (anonymous)],
parseError: [Function (anonymous)],
fullsetup: [Function],
all: [Function],
reconnect: [Function (anonymous)],
serverOpening: [Function (anonymous)],
serverDescriptionChanged: [Function (anonymous)],
serverHeartbeatStarted: [Function (anonymous)],
serverHeartbeatSucceeded: [Function (anonymous)],
serverHeartbeatFailed: [Function (anonymous)],
serverClosed: [Function (anonymous)],
topologyOpening: [Function (anonymous)],
topologyClosed: [Function (anonymous)],
topologyDescriptionChanged: [Function (anonymous)],
commandStarted: [Function (anonymous)],
commandSucceeded: [Function (anonymous)],
commandFailed: [Function (anonymous)],
joined: [Function (anonymous)],
left: [Function (anonymous)],
ping: [Function (anonymous)],
ha: [Function (anonymous)]
},
_eventsCount: 24,
_maxListeners: Infinity,
s: {
id: 0,
options: [Object],
seedlist: [Array],
state: 'connected',
description: [TopologyDescription],
serverSelectionTimeoutMS: 30000,
heartbeatFrequencyMS: 10000,
minHeartbeatFrequencyMS: 500,
Cursor: [Function: Cursor],
bson: BSON {},
servers: [Map],
sessionPool: [ServerSessionPool],
sessions: Set {},
promiseLibrary: [Function: Promise],
credentials: [MongoCredentials],
clusterTime: null,
iterationTimers: Set {},
connectionTimers: Set {},
clientInfo: [Object]
}
}
}
Caught error: TypeError: result is not a function
at index.js:8:15
at processTicksAndRejections (internal/process/task_queues.js:97:5)
下面是使用统一拓扑范例(无显式
connect
命令)从Node.JS连接到MongoDB数据库的完整示例。感谢@MaheshBhatnagar指出我的错误
本例使用承诺,在建立连接后,开始以每5秒插入一条记录的频率插入记录。如果禁用或断开MongoDB数据库,它将缓存插入,直到(a.超时,默认为30秒,或b.连接恢复)。如果超时,插入将丢失,但如果服务器重新联机,后续请求将得到正确处理
如果我做错了,或者有什么建议,请告诉我
index.js:
async function init(){
console.log("Starting...");
const MongoClient = require('mongodb');
const client = MongoClient('mongodb://test:test@localhost:27017', { useUnifiedTopology: true });
const coll = client.db('test').collection('foo');
await coll.insert({ test: 'document' });
const docs = coll.find({ test: 1 }, { readPreference: 'secondary' }).toArray();
console.dir({ docs });
await client.close();
}
init();
async function init(){
console.log("Starting...");
const MongoClient = require('mongodb');
const client = MongoClient('mongodb://test:test@localhost:27017', { useUnifiedTopology: true })
.then(async (result) => {
console.log("Connected: result = ", result);
const db = result('test'); // Get the 'test' database
const coll = db.collection('foo'); // Ge the 'foo' collection
await coll.insert( { test: 'document' }); // Create a new document
const docs = coll.find({}, { readPreference: 'secondary'}) // Retrieve all docs
.then((results) => {
const data = results.toArray();
console.log('Results: ', data);
});
await client.close();
})
.catch((err) => {
console.log('Caught error: ', err);
});
}
init();
const url = 'mongodb://test:test@localhost:27017';
async function init(){
console.log("init...");
const MongoClient = require('mongodb');
return MongoClient(url, { useUnifiedTopology: true}); // Return a Promise
}
async function go(db_result) {
// Do an insert and output the last-inserted document.
console.log("Go...");
const db = db_result.db('test'); // Get the 'test' database
const coll = db.collection('foo'); // Ge the 'foo' collection
// Create a new document:
await coll.insertOne({ test: 'document' }, (err, response) => {
if (err) {
console.log("Error inserting", err);
}
else
{
console.log("New record: ", response.ops[0]) // Output newly inserted record (thanks to https://stackoverflow.com/questions/40766654)
}
});
}
// Sleep for a specified time:
function sleep(ms) {
return new Promise( resolve => {
setTimeout(resolve,ms)
})
}
init() // Set up connection, then start doing inserts.
.then( async (db_result) => {
// When MongoClient is instantiated:
while(true) {
console.log("Going...")
go(db_result)
console.log("Sleeping")
await sleep(5000);
}
})
.catch((err) => {
console.log("Caught error: ", err)
})
为什么不使用mongoose?@MaheshBhatnagar mongoose是行业最佳实践吗?我真的不想要一个完整的ORM,只需要基本的CRUD访问。好的,我们可以连接gmail hangout吗?当然,你的联系方式是什么感谢@MaheshBhatnagar,我在第二个例子中弄乱了一行:
const db=result('test');//获取“test”数据库
应该是const db=result.db('test');//获取“测试”数据库
没有理由将init
设置为async
。//returna Promise
注释具有误导性,因为MongoClient()<代码>MongoClient
;由于async
关键字,您只能得到一个Promise
。