node.js - Keeping open a MongoDB database connection

Question

In so many introductory examples of using MongoDB, you see code like this:

var MongoClient = require('mongodb').MongoClient;
MongoClient.connect("mongodb://localhost:port/adatabase", function(err, db)
{
    /* Some operation... CRUD, etc. */
    db.close();
});

If MongoDB is like any other database system, open and close operations are typically expensive time-wise.

So, my question is this: Is it OK to simply do the MongoClient.connect("... once, assign the returned db value to some module global, have various functions in the module do various database-related work (insert documents into collections, update documents, etc. etc.) when they're called by other parts of the application (and thereby re-use that db value), and then, when the application is done, only then do the close.

In other words, open and close are done once - not every time you need to go and do some database-related operation. And you keep re-using that db object that was returned during the initial openconnect, only to dispose of it at the end, with the close, when you're actually done with all your database-related work.

Obviously, since all the I/O is asynch, before the close you'd make sure that the last database operation completed before issuing the close. Seems like this should be OK, but i wanted to double-check just in case I'm missing something as I'm new to MongoDB. Thanks!

Answer 1

Yes, that is fine and typical behavior. start your app, connect to db, do operations against the db for a long time, maybe re-connect if the connection ever dies unexpectedly, and then just never close the connection (just rely on the automatic close that happens when your process dies).