I have a NextJs app built with mongodb database.
I was surprised to see that I quickly almost reached the threshhold of maximum connections:
This app used to be built with node and react and this was never the case.
But the logic of connecting to the database has changed.
I have this function that connects to the database:
// lib/mongodb.ts
import mongoose from "mongoose";
// #TODO
// I tried putting this in types/global.d.ts
// But, I kept getting the mongoose global error
// So I brought it here
// Not sure if it makes sense to keep this here
declare global {
var mongoose: {
conn: any;
promise: Promise<any> | null;
};
}
const MONGODB_URI = process.env.MONGODB_URI;
if (!MONGODB_URI) {
throw new Error("Please define the MONGODB_URI environment variable");
}
let cached = global.mongoose;
if (!cached) {
// conn: The established connection
// promise: Ongoing connection attempt
/**
* cached.promise: Prevents multiple concurrent connection attempts during the first request when the connection is not yet established.
cached.conn: Efficiently returns the active connection after it has been established.
*/
cached = global.mongoose = { conn: null, promise: null };
}
async function connectToDatabase() {
/**
* By storing the established connection in cached.conn, subsequent requests can
* skip the connection process below entirely, leading to faster response times.
*/
if (cached.conn) {
return cached.conn;
}
/**
* By checking cached.promise, we prevent redundant connection attempts.
* If a connection attempt (promise) has already been made, we don't need to initiate
* another one, we can reuse it, thus avoiding unnecessary load on the database.
*/
if (!cached.promise) {
/**
* The connection promise is stored in cached.promise so that any subsequent requests made
* before the connection resolves can await the same promise, preventing redundant connection
* attempts.
*/
cached.promise = mongoose
.connect(MONGODB_URI as string)
.then((mongoose) => {
return mongoose;
})
.catch((error) => {
console.error("🚀 ~ Error connecting to MongoDB:", error);
throw error; // Re-throw the error after logging
});
}
try {
cached.conn = await cached.promise;
} catch (error) {
throw error;
}
return cached.conn;
}
export default connectToDatabase;
