pg 4.4.3
I'm using socket.io to connect client-side to server. I've guessed, I suppose to connect server to database on server start, but there are a lot of warnings in pg "docs": 'use done() or bad things will happen'.
When should i use it? If i'm opening connection to the db and then creating socket.io server within it, and then using done() after each query, then i'm receiving error after 30 sec idle:
Error: This socket has been ended by the other party
May be I should create socket.io and then open connection to the db within each user session? or open connection to db on each query if it's not currently opened? Being honest, I don't get, why should i do this, why can't I just create single connection to the database on server start and send all queries through it instead of this open-close repetition.
Related
I use native mongodb driver with Expressjs, I don't want to open and close connections on a regular basis in my routes. I want to open once use one connection in all my next() functions and then close when done.
I saw that after opening a connection I can pass the db object to next() functions in request object and use it.
When I try to close the connection like var db=req.db; db.close(); it throws an error.
Inorder to solve this issue I have decided to use settimeout function to close my connection.
I can pass around and use the db obj and send response and the after 1-2 seconds db obj is closed by settimeout.
I'm worried if the requests are more will the settimeout functions effect the servers performance. If I use this trick to manage my db connections.
Sorry, I forgot to do:
db=client.db('test')
and:
db.close();
Change in later versions can't directly open db without getting the client, using native mongodb-nodejs driver.
I have developed an application with ReactJS, ExpressJS, MongoDB and SocketIO.
I have two servers:- Server A || Server B
Socket Server is hosted on the Server A and application is hosted on the Server B
I am using Server A socket on Server B as a client.
Mainly work of Server A socket is to emit the data after fetching from the MongoDB database of Server A
Everything is working as expected but after 4-5-6 hours stop emitting the data but the socket connection will work.
I have checked using
socket.on('connection',function(){
console.log("Connected")
)
I am not getting whats the wrong with the code.
My code : https://jsfiddle.net/ymqxo31d/
Can anyone help me out on this
I have some programming errors.
I am getting data from MongoDB inside the setInterval() so after a little while exhausts resources and database connection starts failing every time.
Firstly i have created a Single MongoDB connection and used every place where i needed.
2ndly i removed setInterval and used setTimeout as below. (NOTE: If i continue using setInterval it execute on defined interval. It doesn't have any status that the data is emitted or not [this also cause the heavy resource usages] but i need to emit the data to socket when successfully fetched.)
setTimeout(emitData,1000);
function emitData(){
db.collection.find({}).toArray(function(data){
socket.emit('updateData',data);
setTimeout(emitData,1000);
})
}
I'm writing a nodejs 5.10.1 application, and i connect to a redis-server.
i'm using the ioredis nodejs module from https://github.com/luin/ioredis.
I can't seem to figure out how to check if a connection was established to the server.
the code to connect to a redis server is pretty simple:
var Redis = require('ioredis');
var redis = new Redis();
the documentation states the following under Connection Events
You can also check out the Redis#status property to get the current connection status.
don't really understand what it means or how to work with it. any ideas ?
One of the properties of the redis object you started is the status:
console.log(redis.status) will give you the current , in my case it says : connecting
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 trying to use node.js with mongodb and following the tutorial at http://howtonode.org/express-mongodb
The code for opening the connection is
ArticleProvider = function(host, port) {
this.db= new Db('node-mongo-blog', new Server(host, port, {auto_reconnect: true}, {}));
this.db.open(function(){});
};
However i cannot see any connections being closed.
But when i see the logs on the mongo console, i can see that are connections which open and they close after some time.
Does the connection close automatically? Will it be a problem when a large no of clients try to access the server? Where should the connection be closed?
Thanks
Tuco
In that example application, only a single ArticleProvider object is created for the application to share when serving requests. That object's constructor opens a db connection that won't be closed until the application terminates (which is fine).
So what you should see is that you get a new mongo connection each time you start your app, but no additional connections made no matter how many clients access the server. And shortly after you terminate your app you should see its connection disappear on the mongo side.
node-mongodb-native provides a close method for Db objects and you can close your connection when you are finished by calling it.
var that = this;
this.db.open(function(){
// do db work here
// close the connection
that.db.close();
});
If you don't close your connection, event loop keeps the connection open and your process doesn't exit. If you are building a web server where your process will not be terminated, it's not necessary for you to close the connection.
A better reference for node-mongodb-native can be found on https://github.com/mongodb/node-mongodb-native.
Remember to put the db.close in the last callback that gets executed so the connection is open until all callbacks are finished. Otherwise, it gives an error like
/usr/local/lib/node_modules/mongodb/lib/utils.js:97
process.nextTick(function() { throw err; });
^
Error
at Error.MongoError (/usr/local/lib/node_modules/mongodb/node_modules/mongodb-core/lib/error.js:13:17)
at Server.destroy (/usr/local/lib/node_modules/mongodb/node_modules/mongodb-core/lib/topologies/server.js:629:47)
at Server.close (/usr/local/lib/node_modules/mongodb/lib/server.js:344:17)
at Db.close (/usr/local/lib/node_modules/mongodb/lib/db.js:267:19)