是什么导致 AWS Lambda 上的 Mongodb 超时错误？

Question

我有一个使用 mongoose 查询 mongoDb 的节点 lambda 函数。

大约 20% 的时间，似乎是随机的，我在尝试连接时收到以下错误： MongoNetworkTimeoutError: 连接超时

虽然 MongoDb 似乎建议使用 context.callbackWaitsForEmptyEventLoop = false 并尝试在调用之间重用相同的连接，但我读到其他帖子说解决此问题的方法是每次都主动重新打开连接。我试过了，但它仍然在发生。有人有什么想法吗？

这是我的代码：

let  conn = mongoose.createConnection(process.env.MONGO_URI, {
        bufferCommands: false, // Disable mongoose buffering
        bufferMaxEntries: 0, // and MongoDB driver buffering
        useNewUrlParser: true,
        useUnifiedTopology: true,
        socketTimeoutMS: 45000,
        keepAlive: true,
        reconnectTries: 10
      })

      try {
        await conn
        console.log('Connected correctly to server')

      } catch (err) {
        console.log('Error connecting to DB')
        console.log(err)
        console.log(err.stack)
      }

  await conn 

以下是 Cloudwatch 的完整错误输出：

{
    "errorType": "Runtime.UnhandledPromiseRejection",
    "errorMessage": "MongoNetworkTimeoutError: connection timed out",
    "reason": {
        "errorType": "MongoNetworkTimeoutError",
        "errorMessage": "connection timed out",
        "name": "MongoNetworkTimeoutError",
        "stack": [
            "MongoNetworkTimeoutError: connection timed out",
            "    at connectionFailureError (/var/task/node_modules/mongodb/lib/core/connection/connect.js:342:14)",
            "    at TLSSocket.<anonymous> (/var/task/node_modules/mongodb/lib/core/connection/connect.js:310:16)",
            "    at Object.onceWrapper (events.js:420:28)",
            "    at TLSSocket.emit (events.js:314:20)",
            "    at TLSSocket.EventEmitter.emit (domain.js:483:12)",
            "    at TLSSocket.Socket._onTimeout (net.js:484:8)",
            "    at listOnTimeout (internal/timers.js:554:17)",
            "    at processTimers (internal/timers.js:497:7)"
        ]
    },
    "promise": {},
    "stack": [
        "Runtime.UnhandledPromiseRejection: MongoNetworkTimeoutError: connection timed out",
        "    at process.<anonymous> (/var/runtime/index.js:35:15)",
        "    at process.emit (events.js:326:22)",
        "    at process.EventEmitter.emit (domain.js:483:12)",
        "    at processPromiseRejections (internal/process/promises.js:209:33)",
        "    at processTicksAndRejections (internal/process/task_queues.js:98:32)",
        "    at runNextTicks (internal/process/task_queues.js:66:3)",
        "    at listOnTimeout (internal/timers.js:523:9)",
        "    at processTimers (internal/timers.js:497:7)"
    ]
}

Answer 1

我遇到了同样的问题（我有一个快速应用程序，但这没关系）。解决方案是将数据库连接对象移到处理程序方法之外并缓存/重用它。

'use strict'
const serverless = require('serverless-http')
const MongoClient = require('mongodb').MongoClient

const api = require('./modules/api')
const SecureConfig = require('./modules/secureConfig')

let dbObject = null
const getDBConnection = async (event, context) => {
    try {
        if (dbObject && dbObject.serverConfig.isConnected()) return dbObject

        const client = await MongoClient.connect(SecureConfig.mongodb.host, SecureConfig.mongodb.mongoConfig)
        dbObject = client.db(SecureConfig.mongodb.db)
        return dbObject
    } catch(err) {
        throw(err)
    }
}

module.exports.handler = async (event, context) => {
  const db = await getDBConnection()
  const server = serverless(api.default(db));
  try {
    /**
     * Lambda’s context object exposes a callbackWaitsForEmptyEventLoop property,
     * that effectively allows a Lambda function to return its result to the caller
     * without requiring that the MongoDB database connection be closed.
     * This allows the Lambda function to reuse a MongoDB connection across calls.
     */
    context.callbackWaitsForEmptyEventLoop = false

    return await server(event, context)
  } catch (error) {
    console.error('Lambda handler root error.')
    throw error
  }
}

您可以在此处找到更多详细信息：https://www.mongodb.com/blog/post/optimizing-aws-lambda-performance-with-mongodb-atlas-and-nodejs