Resilient MongoDb Connection using Promises and Levee

0db-middleware.js

'use strict';

var DbConn = require('./conn');
var Levee = require('levee');


module.exports = function (options) {
    var conn, breaker;
    
    conn = new DbConn(options.uri);
    breaker = Levee.createBreaker(conn, { maxFailures: 1, resetTimeout: 5000 });

    return function db(req, res, next) {
        breaker.run(null, function (err, db) {
            req.db = db;
            next(err);
        });
    };
};

1conn.js

'use strict'

var Promise = require('promise');
var Mongo = require('mongodb');


function Connection(uri) {
    this.uri = uri || Mongo.Db.DEFAULT_URL;
    this.promise = undefined;
    this.connect();
}

Connection.prototype.connect = function connect() {
    var self, uri;

    self = this;
    uri = this.uri;

    this.promise = new Promise(function (resolve, reject) {
        Mongo.Db.connect(uri, { server: { auto_reconnect: true } }, function (err, db) {
            if (err) {
                reject(err);
                return;
            }

            db.on('close', function (server, db) {
                self.promise = Promise.reject(new Error('mongodb server disconnected.'));

                server.once('reconnect', function () {
                    self.promise = Promise.resolve(db);
                });
            });

            resolve(db);
        });
    });
};

Connection.prototype.execute = function execute(_, callback) {
    var self = this;
    this.promise.then(function (db) {
        callback(null, db);
    }, function (err) {
        self.connect();
        callback(err);
    });
};

module.exports = Connection;