Socket.io fs.readFileSync for many connections at same time - node.js

Question

This is not really a question, but I wonder to know if what I did is correct because its working!
So, lets to the question, I`m monitoring many interfaces (PPPoE clients) at same to know its traffic reading the statistics from linux.
I`m using npm packages: express, socket.io and socket.io-stream.
Client:
var sessionsAccel = $('table.accel').DataTable([]);
sessionsAccel.on('preDraw', function() {
$('.interfaceAccel').each(function(i) {
var t = $(this).data();
sockets['socket' + t.id].disconnect();
delete speeds['tx_bytes' + t.id];
delete speeds['rx_bytes' + t.id];
});
})
.on('draw', function() {
$('.interfaceAccel').each(function(i) {
var t = $(this).data();
sockets['socket' + t.id] = io.connect('http://172.16.101.2:3000/status', {
query: 'interface=' + t.interface,
'forceNew': true
});
sockets['socket' + t.id].on("connect", function() {
ss(sockets['socket' + t.id]).on('sendStatus', function(stream, data) {
if (typeof speeds['tx_bytes' + t.id] != 'undefined') {
var speedtx = (data.tx_bytes - speeds['tx_bytes' + t.id]) * 8 / 1000;
var speedrx = (data.rx_bytes - speeds['rx_bytes' + t.id]) * 8 / 1000;
if (speedtx > 1000) {
speedtx = speedtx / 1000;
speedtx = speedtx.toFixed(2);
speedtx_info = speedtx + ' Mbps';
} else {
speedtx = speedtx.toFixed(2);
speedtx_info = speedtx + ' kbps';
}
if (speedrx > 1000) {
speedrx = speedrx / 1000;
speedrx = speedrx.toFixed(2);
speedrx_info = speedrx + ' Mbps';
} else {
speedrx = speedrx.toFixed(2);
speedrx_info = speedrx + ' kbps';
}
$('.tx_' + t.id).html(speedtx_info);
$('.rx_' + t.id).html(speedrx_info);
}
speeds['tx_bytes' + t.id] = data.tx_bytes;
speeds['rx_bytes' + t.id] = data.rx_bytes;
});
});
});
})
Server:
const app = require('express')();
const http = require('http').createServer(app);
const io = require('socket.io')(http);
const ss = require('socket.io-stream');
const path = require('path');
const fs = require('fs');
function getIntInfo(interface) {
if(fs.existsSync('/sys/class/net/'+ interface +'/statistics/tx_bytes')) {
var tx_bytes = fs.readFileSync('/sys/class/net/'+ interface +'/statistics/tx_bytes').toString();
var rx_bytes = fs.readFileSync('/sys/class/net/'+ interface +'/statistics/rx_bytes').toString();
var tx_packets = fs.readFileSync('/sys/class/net/'+ interface +'/statistics/tx_packets').toString();
var rx_packets = fs.readFileSync('/sys/class/net/'+ interface +'/statistics/rx_packets').toString();
return {tx_bytes : tx_bytes, rx_bytes : rx_bytes, tx_packets: tx_packets, rx_packets: rx_packets};
}else
return false;
}
io.of('/status').on('connection', function(socket) {
var query = socket.handshake.query['interface'];
var timer = setInterval(function() {
var stream = ss.createStream();
var info = getIntInfo(query);
ss(socket).emit('sendStatus', stream, info);
}, 1000);
socket.on('disconnect', function(){
socket.disconnect(true);
//console.info('disconnected user (id=' + socket.id + ').');
});
})
http.listen(3000, function(){
console.log('listening on *:3000');
});
That's it, every row from Datatable (which is the interface) open a socket connection and retrieve the statistics.
My question is, this will mess up my server with many I/O reading these files?

Answer 1

Since you're doing this every second for every connected client, it seems like you should probably cache this data so it doesn't have to be read from the disk or sent over the wire when it hasn't changed to save both server load and bandwidth usage. But, the details of how to best do that depend upon knowledge about your particular application that you haven't included.
You can at least use asynchronous I/O like this:
const util = require('util');
const fs = require('fs');
const readFile = util.promisify(fs.readFile);
function getIntInfo(interface) {
function readInfo(name) {
return readFile('/sys/class/net/'+ interface +'/statistics/' + name).then(data => data.toString());
}
return Promise.all(
readFile('tx_bytes'),
readFile('rx_bytes'),
readFile('tx_packets'),
readFile('rx_packets')
).then(([tx_bytes, rx_bytes, tx_packets, rx_packets]) => {
return {tx_bytes, rx_bytes, tx_packets, rx_packets};
}).catch(err => {
console.log(err);
return false;
});
}
And, you have to stop the interval any time a client disconnects and change how it calls getIntInfo():
io.of('/status').on('connection', function(socket) {
var query = socket.handshake.query['interface'];
var timer = setInterval(function() {
getIntInfo(query).then(info => {
var stream = ss.createStream();
ss(socket).emit('sendStatus', stream, info);
});
}, 1000);
socket.on('disconnect', function(){
// stop the timer for this connection
clearInterval(timer);
});
});
Now that I think about it a bit more, you could improve scalability quite a bit by having just one interval timer that was reading the data and then sending that one set of data to all listening clients that had connected to the /status namespace. You would reduce the file reading from once per second for every client to just once per second for no matter how many clients.