Mongodb timeout error on AWS Lambda

I have a node lambda function that queries mongoDb using mongoose.

About 50% of the time, seemingly randomly, I get the following error upon trying to connect: MongoNetworkTimeoutError: connection timed out

While MongoDb seems to recommend using context.callbackWaitsForEmptyEventLoop = false and trying to reuse the same connection between calls, I read other posts that said the fix for this would be to actively re-open a connection every time. I tried that but it’s still happening. I also tried playing with values for
socketTimeoutMS and connectTimeoutMS to no avail.
Does anyone have any ideas? This is a significant blocker for me right now - thanks!

Here’s my code:

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,

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

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

  await conn 

And here’s the full error output from Cloudwatch:

    "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)"
1 Like

@Boris_Wexler Did you get a solution for this? I am stuck in the same scenario. Already have tried connectionTimeout and socketTimeout, but that dosen’t seem to work. What next I am thinking is to give a try for is connection pooling.