Access same instance of db connection in different files in express js

Question

I have 4 files:

1) db.js - mongodb connection
2) socket.js - for all socket events
3) route.js - route for /
4) app.js - main start point for express app

I want to share same db instance from db.js in socket.js and route.js so that the connection to db is made only once.

I have tried 2 ways for this:

1) require db.js in both files, but this creates new connection every time require is called.
2) pass the collections in request object in db.js, but then how would I access the request object in socket.js in 

io.on("connection",function(socket){
 // request ??
})

How can it be solved?

Rob M. · Accepted Answer · 2023-04-11 21:35:44Z

2

You could move to a dependency injection setup rather than explicitly requiring db.js in each file, that would allow you to reuse your existing db connection:

main.js

// require and setup db like normal
var db = require('./db.js');
// require route, but now call it as a function and pass your db instance
var route = require('./route.js)(db);

route.js

module.exports = function(db, maybeOtherSharedResources) {
  // existing code from route.js
}

edited Apr 11, 2023 at 21:35

answered Apr 7, 2017 at 20:32

Rob M.

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3 Comments

Sahil Over a year ago

This works well for socket.js file but not for route.js. The previously defined API in route.js becomes 404. route.js now - var express = require('express'); var router = express.Router(); module.exports = function(model){ router.post('/save', function(req, res) { var myCollection = model().myCollection; if (myCollection) { //save } else { //error } });

Rob M. Over a year ago

You need to ensure that you are returning your routes/etc. from files you end up exporting as functions.

Sahil Over a year ago

Implemented and it is working, now the poblem is when I refresh on client side it gives error in route.js on line var myCollection = model().myCollection , says - Trying to open unclosed connection.

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