Unhandled Promise Rejection Warning: Mongoose Server Selection Error

UnhandledPromiseRejectionWarning: MongooseServerSelectionError Bug?*

What is the current behavior?

• hello there I am trying to connect mongoose with URL string included everything is fine but after console.log(“mongoDB database connection established successfully”) this is not showing this console’s text but an error is coming there

const express = require("express");
const cors = require("cors");
const mongoose = require("mongoose");
require("dotenv").config();
const app = express();
const port = process.env.PORT || 5000;

app.use(cors());
app.use(express.json());

const uri = process.env.ATLAS_URI;
mongoose.connect(uri,{useNewUrlParser:true,useCreateIndex:true,useUnifiedTopology:true} 
    );
const connection = mongoose.connection;
connection.once('open',() =>{
console.log("mongoDB database connection established successfully");
})
app.listen(port, () => {
  console.log(`server is running on port ${port}`);
});

server.js file code above and in .env the URI key is given

What is the expected behavior?

• the expected output is MongoDB database connection established successfully.

What are the versions of Node.js, Mongoose, and MongoDB you are using? Note that “latest” is not a version.

• “cors”: “^2.8.5”, “dotenv”: “^8.2.0”, “express”: “^4.17.1”, “mongoose”: “^5.11.14”,

[deistermatheus]

@krishnadevz , a few things that might help people troubleshoot your issue:

1 - Does the shell connect successfully from your system or is the issue specific to the node app? 2 - Can you post the connection string format you are using in your env config? ex: the connection string format that you have copied and pasted from MongoDB Atlas in the Connect option 3 - Have you double checked if your ip is whitelisted in the Atlas Network Access settings? Dynamic IPs are a usual source of connection problems in dev setups 4 - Consider adding a .catch block to mongoose.connect, to log the reason why the connection Promise was rejected and see if it complains about something in your Uri:

mongoose.connect(uri ,connectionOptions).catch(console.error); 

It looks like a malformed uri that the mongodriver cannot parse and use to connect, but I can’t tell exactly why from the info you posted

[krishnadevz]

the issue is resolved now