Current topology does not support sessions in aws lambda

Hi! I’m using mongoose with the following connection setup:

let conn = null

async function connectToDatabase () {
  if (conn === null) {
    const database = await mongoose.connect(MONGO_CONNECT_STRING, {
      useUnifiedTopology: true,
      useNewUrlParser: true,
      useCreateIndex: true,
      serverSelectionTimeoutMS: 5000
    })
    conn = database.connections[0].readyState
  }
}

And, about 30% of the time I get an error when starting a transaction:

{
    "errorType": "MongoError",
    "errorMessage": "Current topology does not support sessions",
    "name": "MongoError",
    "stack": [
        "MongoError: Current topology does not support sessions",
        "    at MongoClient.startSession (/var/task/node_modules/mongodb/lib/mongo_client.js:459:11)",
        "    at NativeConnection.startSession (/var/task/node_modules/mongoose/lib/connection.js:440:31)",
        "    at /var/task/node_modules/mongoose/lib/connection.js:582:16",
        "    at processTicksAndRejections (internal/process/task_queues.js:75:11)"
    ]
}

What am I doing wrong?

Serverless AWS Lambda Node 14.x Mongoose 5.11.15 MongoDB - Atlas 4.4.3

[michaelgutierrez0]

Looks similar to my issue: https://github.com/Automattic/mongoose/issues/9943

[harveyconnor]

Thanks @vkarpov15 for the insight, we’ll take a deeper look and see if we can get more information.