Expresser: MongoDB Database

The Database module is a MongoDB wrapper and has 3 main methods: {{ get }}, {{ set }} and {{ del }}. There's also a {{ count }} helper that works with newer versions of MongoDB.

It also provides a super simple failover mechanism to switch to a backup database in case the main database fails repeatedly. This will be activated only if you set the {{ settings.database.connString2 }} value. Please note that Expresser won't keep the main and backup database in sync! If you wish to keep them in sync you'll have to implement this feature yourself - we suggest using background workers with IronWorker ([url:http://iron.io]).

If the {{ settings.app.cloud }} setting is enabled, the Database module will automatically figure out the connection details for the following MongoDB services: AppFog, MongoLab, MongoHQ.

If you're using Backbone.js or any other framework which uses "id" as the document identifier, you might want to leave the {{ settings.database.normalizeId }} true, so the Database module will parse results and convert {""_id""} to "id" on output documents and from "id" to {""_id""} when saving documents to the db.

Sample code

The following example illustrates how to get a document having "username = igor" from collection "users" and duplicate it to a document having "username = igor2". Errors will be logged using the Logger module.

var expresser = require("expresser");

var setCallback = function (err, result) {
    if (err) {
        expresser.logger.error("Can't save document with username igor2.", err);
    } else {
        expresser.logger.info("Document duplicated!", result);
    }
}

var getCallback = function (err, result) {
    if (err) {
        expresser.logger.error("Can't get document with username igor.", err);
    } else {
        user = result[0];
        user.username = "igor2"; // Update the username 'igor' to 'igor2'.
        delete user["id"]; // Delete the user ID so it's created as a new document.
        expresser.database.set("users", user, setCallback);
    }
}

expresser.database.mongo.get("users", {username: "igor"}, getCallback);

For detailed info on specific features, check the annotated source on /docs/database-mongo.html