The problem: (node.js application + mongodb Native driver)
I have a JSON file with more than 60000 Json Documents.the documents always a creation date and unique id called vid. and I need to insert in a MongoDB collection.
I need to insert the new vid or update the ones already existing with another document more recent.
What I already did:
https://github.com/TelmoIvo/PFC/blob/master/cfginit.js
What is happening:
After inserting/updating like 500 times and getting 287 documents in collection I get this error:
AssertionError: null == { [MongoError: connect EADDRINUSE] name : 'MongoError', message: 'connect EADDRINUSE' } at the line assert.equal (null, err);
from what I read, it's saying I have the connection to DB already in use. but I close after I insert/update everytime.
Any advice?
I wouldn't be calling MongoClient.connect every time. That's causing a ton of connections to open and close all the time which is overloading mongo. You should let the MongoClient manage the connection pool. Change it so that you store the db object from MongoClient.connect maybe in your init file add something like
//store this outside your init so its accessible to other functions
//this is what you will use to access the database
var db;
//add this to your init function
MongoClient.connect(url, function(err, database){
db = database;
}
Then in your functions to add and update use the db object you stored to update your collections and you won't need to keep opening connections. You can drop all the MongoClient.connect code and don't call db.close() since your connections are being shared to the object so let MongoClient manage them.
Related
In my application, I have different projects as db in MongoDB. So whenever an API call is happening I connect the db by its projectId and once the query fetching has happened I will disconnect the current db. It takes 5 to 10 seconds to reconnect the db with respective project ids. Because of that API calls are not happening as expected.
Here, I'm trying to make dynamic db connections, which will always connected to the respective project db and it disconnects once the db state is inactive.
I didn't get any reference to connect dynamic DB's, Can anyone pls suggest me some solution to this?
Connection Method
const connectionString = env.MONGO_DB_URL + projectId + env.MONGO_DB_OPTIONS
mongoose.connect(connectionString,{
useNewUrlParser: true,
useUnifiedTopology: true,
});
This projectId in the connection string will be a dynamic one.
I created a MEAN project in heroku.
In MongoDB I have a DB / Collection like this:
db == content / collection == android_main
I have verified that the collection is in the proper database (and not in admin) via the following MongoSH exchange:
Atlas atlas-xxxxxx-shard-0 [primary] content> use admin
switched to db admin
Atlas atlas-xxxxxx-shard-0 [primary] admin> show collections
Atlas atlas-xxxxxx-shard-0 [primary] admin> use content
switched to db content
Atlas atlas-xxxxxx-shard-0 [primary] content> show collections
android_main
In MongoDB I also have a user w/ specific privs to read this db/collection.
In the code (Node.js) I use the following connection string:
mongodb+srv://<USER>:<PASS>#<MONGO URL>/content?retryWrites=true&w=majority
The connection completes successfully. I pass in the user I mentioned above, e.g. the user with just the specific read privs on the database (content) and collection (android_main).
In the code, the mechanism I use to get the database variable via the connection and connection string specifically is:
mongodb.MongoClient.connect(process.env.MONGODB_URI, function (err, database) {
Now, in the code, in response to an `HTTP GET` I issue the following:
db.collection("android_main").find({}).toArray(function(err, docs) {
...
}
I get back this error:
ERROR: user is not allowed to do action [find] on [admin.android_main]
Question: how can I modify my code a/o setup to ensure the db.collection.find() call references the proper database? I would have thought this was taken care of in the connection, where the database is explicitly called out.
I'm going to post the following answer which solves the issue above.
I found it by just playing around with random ideas.
I'd like to thank Heroku and their pathetic documentation for turning a 30 minute task into a 3 day ordeal.
client.connect(
process.env.MONGODB_URI,
function (err, database) {
console.log("CONNECT...");
if (err) {
console.log(err);
process.exit(1);
}
db = database.db(DATABASE);
var server = app.listen(process.env.PORT || 8080,
function () {
var port = server.address().port;
console.log("CONNECT App now running on port", port);
}
);
console.log("CONNECT Done.");
}
);
Apparently, to properly set the variable db (the one which you will use in the queries later) you should note that the database you receive in the connection callback is the admin database (that which was used for auth), and from that you make the db() request passing in the database you intend to use. All of this is utterly redundant b/c we pass the database we intend to use in the connection string. What a complete CF; but it's certainly not the 1st one. Enjoy.
In the MongoDB Nodejs driver, I see some confusion in what the connection URI can be.
On one hand, in the page describing the URI (https://docs.mongodb.com/manual/reference/connection-string/) it says the the path parameter is the "authentication database".
On the other hand, in many of the official examples (http://mongodb.github.io/node-mongodb-native/driver-articles/mongoclient.html#mongoclient-connect) it seems they are using the path parameter as the active database to use (they call db.collection() straight away, without calling .database().
Am I missing something?
TL;DR:
Calling db.collection() immediately after connection only works in versions of the driver less than 3.0.
Details:
Firstly, the official examples you sighted were from MongoDB driver at version 1.4.9, the driver is now at version 3.5.8, I would suggest you check out the latest documentation and examples here.
To clarify the confusion, the database path specified in the connection URI is the authentication database i.e the database used to log in, this is true even for the 1.4.9 version of the driver - reference.
However, the reason for the difference you mentioned, i.e being able to call db.collection() immediately after a connection in some cases is a result of the change in the MongoClient class in version 3 of the driver - reference.
Before version 3, MongoClient.connect would return a DB instance to its call back function and this instance would be referencing the database specified in the path of the connection URI, so you could call db.collection() straight away:
MongoClient.connect("<connection_URI>", function(err, db) {
// db is a DB instance, so I can access my collections straight away:
db.collection('sample_collection').find();
});
However, an update was made at version 3 such that, MongoClient.connect now returns a MongoClient instance not a DB instance anymore - reference:
MongoClient.connect("<connection_URI>", function(err, client) {
// client is a MongoClient instance, you would have to call
// the Client.db() method to access your database
const db = client.db('sample_database');
// Now you can access your collections
db.collection('sample_collection').find();
});
I have an Express App which connects to a MongoDB server at startup and serves requests on-demand (I don't disconnect - it's a single threaded server so no pooling - fairly simple stuff)
Problem is that it's possible the MongoDB server will be unavailable for periods of time (it's not on-site) and whilst the Express App doesn't crash, it seems that any requests made to the server will run indefinately until the connection is restored!
I'd like to limit that (e.g. throw an error back after a period of time) but I can't seem to make that happen...
I'm using connect options "{server: {auto_reconnect: true}}" which seems to ensure that once the MongoDB server reappears, requests complete (without it, requests made during downtime seem to run forever...) - and I don't have access to the client code so I can't fix it there...
I'd assumed a combination of 'connectTimeoutMS' or 'socketTimeoutMS' would allow me to terminate requests when MongoDB is unavailable for longer periods, but I just can't get those to work (I've tried them as connect options, passing them in the URI etc. etc.)
Any attempt to open a Collection and Find/Insert/Update just 'hangs' until the MongoDB reappears - I've left it over 30 mins and everything was just sitting these (and completed AOK when the network was restored!)
What's the best way around this? Should I open a connection specifically for each request (not really a performance issue - it's not a high volume app) or is there something else I'm missing?
Updated to add the connect code
var myDB
var mongodb = require('mongodb')
var uri = // some env vars and stuff
mongodb.MongoClient.connect(uri, {server: {auto_reconnect: true}}, function (err, db) {
myDB = db
})
myDB is then used elsewhere to open collections - and the handle from that is used to find/insert etc.
If the connection to the DB is interrupted, myDB.collection() calls (or calls to find/insert on their handles) will simply hang until the connection is restored - nothing I've tried will cause them to 'time out' sooner!?
I assume that you are using mongoose as a driver.
You'd catch the error by this.
var db = require('domain').create();
db.on('error', function(err) {
console.log('DB got a problem');
});
db.run(function() {
mongoose.connect(config, options);
});
or you can directly access
mongoose.connection.readyState
to check the statement of your DB.
Connection ready state
0 = disconnected
1 = connected
2 = connecting
3 = disconnecting
Each state change emits its associated event name.
http://mongoosejs.com/docs/api.html
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)