Mongoose 4.11 introduced an important new option to work around a major deprecation. The
useMongoClient option is the source of the '
open() is deprecated in mongoose' deprecation warning that has caused so much discussion. This option opts you in to using Mongoose 4.11's simplified initial connection logic and allows you to avoid getting a deprecation warning from the underyling MongoDB driver.
Mongoose 4.11 was released last week and includes several neat new features. It also has one very important deprecation, so before you upgrade please read about the
useMongoClient option in the docs. I'll write more about
useMongoClient and why it is necessary another time. But first, mongoose 4.11 enables a new plugin, mongoose-lean-virtuals, which lets you apply virtuals to query results even if you use the
lean() function. This plugin is a more general version of mongoose-lean-id.
You might remember locking from your undergrad systems programming class. Locks help when multiple threads that can be interrupted at any time access a shared resource. In distributed programming (like building a Node.js server that talks to a database) you have a similar problem: parallel operations can mutate documents in the database in conflicting ways. In particular, enforcing uniqueness, such as making sure only one user has a given email, is tricky.
Mongoose setters have always had the limitation that they only work for
save(), not for queries. For example, let's say you have a schema that enforces your emails are always lowercase:
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One great perk of async/await in Node.js is how well it integrates with existing libraries. By now, most popular Node.js libraries support some sort of promise-based API, so they integrate nicely with async/await. You might even have the pleasure of removing a few dependencies from your
package.json if you start using async/await instead of co. In this article, I'll show you how async/await works with mocha tests, express routes and middleware, and mongoose queries and cursors.