How can I access the mongo db connection variable globally in loopback. Currently it is done by executing the async:
Alerts.getDataSource().connector.connect(function (err, db) {
db.collection("dbname");
......................//other code
});
Is it possible make this db variable directly accessible from everywhere inside a model instead than calling connector.connect everywhere? Thanks in advance!
All you need is connection pooling. Here you go!
// This is a global variable to use for handing the MongoDB client
var mongodb;
// Connection URL
var url = '[connectionString]';
// Create the db connection
Alerts.getDataSource().connector.connect(function (err, db) {
mongodb = db
......................//other code
});
Here is a better explanation on Mongodb Connection Pooling
Related
I'm always connecting to the "admin" DB, which is a fixed bug.
Using Mongoose 5.0.6 MongoDb 3.6 and trying to connect to Atlas.
My question, what driver Mongoose 5.0.6 depend on?
How can I find out when Mongoose will have that fix?
On a different direction, is there a way to connect with MongoDB then use this connection with
Mongoose?
Cheers
Basically you should try connecting with your url link, and specify the DB name on the mongoose connect method
so if your cluster link is:
mongodb+srv://userName:Passwrod#clustor.mongodb.net/
and your DB name is:
testDB
then you should call the mongoose.connect method as follows:
mongoose.connect('mongodb+srv://userName:Passwrod#cluster.mongodb.net/', {dbName: 'testDB'});
Connection is established when you use this connection string for (MongoShell 3.6+) :
var connDB = "mongodb+srv://<username>:<password>#cluster-fax0w.mongodb.net/test"
However, you will not be able to read/write data without entering the DBName in the mongoose.connect().
mongoose.connect(uri, { dbName: <your DB name> })
.then( () => {
console.log('Connection to the Atlas Cluster is successful!')
})
.catch( (err) => console.error(err));
Just a side note if you ever get an error connecting to the MongoDB Atlas make sure:
You've whitlisted our IP address / all (0.0.0.0/0)
Your credentials are right
Firewall / anti-virus are disabled
And if all fails
Make sure your DNS is a public one. Or maybe change it to Google's public DNS.
Throwing a link for the same:
https://www.youtube.com/watch?v=F9u5ULrRt3Y
Goodluck!
I am working on a project that requires a dedicated database per registered user. I prefer working with MongoDB so I'm using that for the same (Am I Right?). The app uses a REST API as the backend (written in Node Express) and an AngularJS App. So, what I think of doing is whenever a user makes a request to some API endpoint say, a GET request to api/user/mydata, I would create a connection to his particular database, fetch the required data, close the connection and return the fetched data as the response. Is this approach correct? Also, I'm using Mongoose as the ODM and PassportJS for user Authentication. Moreover, users of my app are mutually exclusive. There is no data connection between a user with any other registered user.
There's a way to do that but only without using Mongoose. You would have to create a root connection to your MongoDB server (mind it, not to a particular database on that server) using the mongodb node module and then you can switch between the database as per your query requirement without creating a new connection per database as shown below:
const MongoClient = require('mongodb').MongoClient;
const assert = require('assert');
// URL to the root of MongoDB Server and not a particular db
const url = 'mongodb://localhost:27017';
// Database Names
const dbName1 = 'myproject1';
const dbName2 = 'myproject2';
// Use connect method to connect to the server
MongoClient.connect(url, function(err, client) {
assert.equal(null, err);
console.log("Connected successfully to server");
const db1 = client.db(dbName1);
const db2 = client.db(dbName2);
client.close();
});
You can't do this through mongoose, as mongoose and its models require connection to be made to a particular database and not to just the root db server. Anyways, I didn't want to give up mongoose for my own project so I just had to resort to initializing the db connection and its models per HTTP request by the user and closing the connection upon response.
I have a node program connecting to a MongoDB. Theres a production server where we do proper authentication to connect to the db, but during development on our local machines it's just more tedious to keep track of authentication, especially because most of the time we completely wipe the db often. So resetting up authentication becomes even more tedious. So my solution was to attempt to connect to the db securely, and then if it fails then try to connect to the db in the dev fashion. Heres the code:
var db = require('monk')('username:password#localhost/TESTR', {authSource:'admin'});
db.catch(function(err) {
clog.i("MONGO AUTHENTICATION FAILED, USING NO AUTH CLIENT");
db = require('monk')('localhost/TESTR')
});
The problem is that this doesn't work. The rest of the app just complains about the authentication failure the first attempt had. Is there a better solution to this? Or am I just a moron?
var monk = require('monk');//layer used to connect mongodb
var db = monk('*****:27017/TESTR');
var collection = db.get('collection_name');
//you can access your collection using the mongo query
//simple controller action
module.exports = function(req, res){
collection.find({}, function(err, cb){
if(err) {res.json("db exception");}
else{res.json(cb)//it returns the db collections}
};
}
I've read this tutorial:
http://cwbuecheler.com/web/tutorials/2013/node-express-mongo/
in part 3, the author explains how to connect to MongoDB, but his way requires running of separate command windows.
I want to know if there is a way to connect the DB i've created, from the application code, without running other command windows.
Thanks a lot.
The mongod command is used to start the Mongo server. To connect a db client to it from your application, you can take a look at this example from the official MongoDB documentation (scroll to "Connect to MongoDB"). You simply need to do something like
var MongoClient = require('mongodb').MongoClient;
// Connection URL
var url = 'mongodb://localhost:27017/nodetest1';
// Use connect method to connect to the server
MongoClient.connect(url, function(err, db) {
console.log("Connected succesfully to server");
db.close();
});
I am using mongodb-native-driver in express.js app. I have around 6 collections in the database, so I have created 6 js files with each having a collection as a javascript object (e.g function collection(){}) and the prototypes functions handling all the manipulation on those collections. I thought this would be a good architecture.
But the problem I am having is how to connect to the database? Should I create a connection in each of this files and use them? I think that would be an overkill as the connect in mongodb-native-driver creates a pool of connections and having several of them would not be justified.
So how do I create a single connection pool and use it in all the collections.js files? I want to have the connection like its implemented in mongoose. Let me know if any of my thought process in architecture of the app is wrong.
Using Mongoose would solve these problems, but I have read in several places thats it slower than native-driver and also I would prefer a schema-less models.
Edit: I created a module out of models. Each collection was in a file and it took the database as an argument. Now in the index.js file I called the database connection and kept a variable db after I got the database from the connection. (I used the auto-reconnect feature to make sure that the connection wasn't lost). In the same index.js file I exported each of the collections like this
exports.model1 = require('./model1').(db)
exprorts.model2 = require('./model2').(db)
This ensured that the database part was handled in just one module and the app would just call function that each model.js file exported like save(), fincdbyid() etc (whatever you do in the function is upto you to implement).
how to connect to the database?
In order to connect using the MongoDB native driver you need to do something like the following:
var util = require('util');
var mongodb = require('mongodb');
var client = mongodb.MongoClient;
var auth = {
user: 'username',
pass: 'password',
host: 'hostname',
port: 1337,
name: 'databaseName'
};
var uri = util.format('mongodb://%s:%s#%s:%d/%s',
auth.user, auth.pass, auth.host, auth.port, auth.name);
/** Connect to the Mongo database at the URI using the client */
client.connect(uri, { auto_reconnect: true }, function (err, database) {
if (err) throw err;
else if (!database) console.log('Unknown error connecting to database');
else {
console.log('Connected to MongoDB database server at:');
console.log('\n\t%s\n', uri);
// Create or access collections, etc here using the database object
}
});
A basic connection is setup like this. This is all I can give you going on just the basic description of what you want. Post up some code you've got so far to get more specific help.
Should I create a connection in each of this files and use them?
No.
So how do I create a single connection pool and use it in all the collections.js files?
You can create a single file with code like the above, lets call it dbmanager.js connecting to the database. Export functions like createUser, deleteUser, etc. which operate on your database, then export functionality like so:
module.exports = {
createUser: function () { ; },
deleteUser: function () { ; }
};
which you could then require from another file like so:
var dbman = require('./dbmanager');
dbman.createUser(userData); // using connection established in `dbmanager.js`
EDIT: Because we're dealing with JavaScript and a single thread, the native driver indeed automatically handles connection pooling for you. You can look for this in the StackOverflow links below for more confirmation of this. The OP does state this in the question as well. This means that client.connect should be called only once by an instance of your server. After the database object is successfully retrieved from a call to client.connect, that database object should be reused throughout the entire instance of your app. This is easily accomplished by using the module pattern that Node.JS provides.
My suggestion is to create a module or set of modules which serves as a single point of contact for interacting with the database. In my apps I usually have a single module which depends on the native driver, calling require('mongodb'). All other modules in my app will not directly access the database, but instead all manipulations must be coordinated by this database module.
This encapsulates all of the code dealing with the native driver into a single module or set of modules. The OP seems to think there is a problem with the simple code example I've posted, describing a problem with a "single large closure" in my example. This is all pretty basic stuff, so I'm adding clarification as to the basic architecture at work here, but I still do not feel the need to change any code.
The OP also seems to think that multiple connections could possibly be made here. This is not possible with this setup. If you created a module like I suggest above then the first time require('./dbmanager') is called it will execute the code in the file dbmanager.js and return the module.exports object. The exports object is cached and is also returned on each subsequent call to require('./dbmanager'), however, the code in dbmanager.js will only be executed the first require.
If you don't want to create a module like this then the other option would be to export only the database passed to the callback for client.connect and use it directly in different places throughout your app. I recommend against this however, regardless of the OPs concerns.
Similar, possibly duplicate Stackoverflow questions, among others:
How to manage mongodb connections in nodejs webapp
Node.JS and MongoDB, reusing the DB object
Node.JS - What is the right way to deal with MongoDB connections
As accepted answer says - you should create only one connection for all incoming requests and reuse it, but answer is missing solution, that will create and cache connection. I wrote express middleware to achieve this - express-mongo-db. At first sight this task is trivial, and most people use this kind of code:
var db;
function createConnection(req, res, next) {
if (db) { req.db = db; next(); }
client.connect(uri, { auto_reconnect: true }, function (err, database) {
req.db = db = databse;
next();
});
}
app.use(createConnection);
But this code lead you to connection-leak, when multiple request arrives at the same time, and db is undefined. express-mongo-db solving this by holding incoming clients and calling connect only once, when module is required (not when first request arrives).
Hope you find it useful.
I just thought I would add in my own method of MongoDB connection for others interested or having problems with different methods
This method assumes you don't need authentication(I use this on localhost)
Authentication is still easy to implement
var MongoClient = require('mongodb').MongoClient;
var Server = require('mongodb').Server;
var client = new MongoClient(new Server('localhost',27017,{
socketOptions: {connectTimeoutMS: 500},
poolSize:5,
auto_reconnect:true
}, {
numberOfRetries:3,
retryMilliseconds: 500
}));
client.open(function(err, client) {
if(err) {
console.log("Connection Failed Via Client Object.");
} else {
var db = client.db("theDbName");
if(db) {
console.log("Connected Via Client Object . . .");
db.logout(function(err,result) {
if(!err) {
console.log("Logged out successfully");
}
client.close();
console.log("Connection closed");
});
}
}
});
Credit goes to Brad Davley which goes over this method in his book (page 231-232)