As part of my course I'm learning mongodb and now Mongoose. I've written the code exactly as done in the lesson but when trying to start it with node app.js I get the following error:
$ node app.js (node:25772) UnhandledPromiseRejectionWarning: MongoNotConnectedError: MongoClient must be connected to perform this operation
at Object.getTopology (C:\Users\donal\OneDrive\Desktop\Udemy Web Development\FruitsProject\node_modules\mongoose\node_modules\mongodb\lib\utils.js:391:11) at Collection.insertOne (C:\Users\donal\OneDrive\Desktop\Udemy Web Development\FruitsProject\node_modules\mongoose\node_modules\mongodb\lib\collection.js:150:61) at NativeCollection.<computed> [as insertOne] (C:\Users\donal\OneDrive\Desktop\Udemy Web Development\FruitsProject\node_modules\mongoose\lib\drivers\node-mongodb-native\collection.js:200:33) at NativeCollection.Collection.doQueue (C:\Users\donal\OneDrive\Desktop\Udemy Web Development\FruitsProject\node_modules\mongoose\lib\collection.js:135:23) at C:\Users\donal\OneDrive\Desktop\Udemy Web Development\FruitsProject\node_modules\mongoose\lib\collection.js:82:24 at processTicksAndRejections (internal/process/task_queues.js:77:11) (Use node --trace-warnings ...to show where the warning was created) (node:25772) 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(). To terminate the node process on unhandled promise rejection, use the CLI flag--unhandled-rejections=strict (see https://nodejs.org/api/cli.html#cli_unhandled_rejections_mode). (rejection id: 1) (node:25772) [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.
I have mongosh running in a separate tab in the terminal and I've tried several searches to look for similar problems. Any help very welcome!
Here's my app.js code in full:
mongoose.connect("mongodb://localhost:27017/fruitsDB");
const fruitSchema = new mongoose.Schema({
name: String,
rating: Number,
review: String
});
const Fruit = mongoose.model("Fruit", fruitSchema);
const fruit = new Fruit({
name: "Apple",
rating: 7,
review: "Pretty solid as a fruit"
});
fruit.save();
mongoose.connection.close();
const findDocuments = function(db, callback) {
const collection = db.collection('fruits');
collection.find({}).toArray(function(err, fruits) {
assert.equal(err, null);
console.log("Found the following records");
console.log(fruits)
callback(fruits);
});
}
mongoose.connect is async, so you're trying to execute the code before a connection is established with the database.
const connectToMongo = async() => {
await mongoose.connect("mongodb://localhost:27017/fruitsDB", {
useNewUrlParser: true,
useUnifiedTopology: true,
useFindAndModify: false,
});
return mongoose;
};
You can now use async/await or .then() to wait till a connection is established
(async function () {
await connecToMongo();
const fruitSchema = new mongoose.Schema({
name: String,
rating: Number,
review: String
});
const Fruit = mongoose.model("Fruit", fruitSchema);
const fruit = new Fruit({
name: "Apple",
rating: 7,
review: "Pretty solid as a fruit"
});
fruit.save();
mongoose.connection.close();
const findDocuments = function (db, callback) {
const collection = db.collection('fruits');
collection.find({}).toArray(function (err, fruits) {
assert.equal(err, null);
console.log("Found the following records");
console.log(fruits)
callback(fruits);
});
}
})
i ran into the same issue and the culprit is calling mongoose.connection.close(); in the body of your javascript. as @AnanthDev mentioned, mongoose is asynchronous and ends up closing the connection before it's able to perform the actions.
the following works because mongoose.connection.close() is in a callback function and does not run until after the actions is performed.
Fruit.insertMany([kiwi, orange, banana], function(err) {
if (err) {
console.log(err);
} else {
mongoose.connection.close();
console.log("Successfully saved all the fruits to fruitsDB");
}
})