Develop Reference

How to return memory of terminated web worker safely?

I made to use web workers to upload files.
It handle with small size files.
But with large size file, the speed is getting very slow and my script causes web page collapse.
It does not return memory of web workers.
See the attachment.
The Dedicated Workers keep being accumulated and consume GB memory, when large file is being uploaded.
And I see this warning accumulating whenever web worker call close()
Scripts may close only the windows that were opened by them.
I throttled threadsQuantity as 5.
I think the number of web workers should not be exceeded more than 5.
class Queue {
constructor() {
this.timestamp = new Date().getTime();
this.activeConnections = {};
this.threadsQuantity = 5;
}
async sendNext() {
const activeConnections = Object.keys(this.activeConnections).length;
if (activeConnections >= this.threadsQuantity) {
return;
}
if (!this.chunksQueue.length) {
if (!activeConnections) {
this.complete();
}
return;
}
let chunkId = this.chunksQueue.pop();
this.activeConnections[chunkId] = true;
this.sendChunk( chunkId) ;
}
sendChunk( chunkId) {
if (window.Worker) {
let chunk = this.getChunk( chunkId)
const myWorker = new Worker("/assets/js/worker.js?v=" + this.timestamp);
myWorker.postMessage([this.timestamp, chunkId, chunk]);
myWorker.onmessage = (e) => {
var obj = JSON.parse(e.data)
if( obj.success) {
delete this.activeConnections[chunkId];
this.sendNext()
close();
} else {
sendChunk( chunkId);
}
}
}
}
}
I tried with close() , self.close() but all got same warning and failed.
I tried with this.close(), but it cause this error.
app.0a4dcc55.js:32 Uncaught TypeError: this.close is not a function
at _.onmessage
How can I kill terminated web workers safely during process ?

socket.io router, assign to one of multiple instances

I am trying to overcome a limitation placed on how many connections TCP protocol can have opened on a single port. So i thought of a way to create multiple instances of my server running on different ports for example:
instance 1 (3001) server_i1.js
instance 2 (3002) server_i2.js
instance 3 (3003) server_i3.js
instance 4 (3004) server_i4.js
then i could have one additional file server_route.js that would check how many connections are established on each instance and forward user to less populated instance. I tried build something using cluster but it only seems to create new processes on the same port. How it can be done to have all users connect for example to http://exmaple.com:3000 and then forward them to one of four possible ports [3001, 3002, 3003, 3004]?
current server approach:
var cluster = require('cluster');
var numCPUs = require('os').cpus().length;
if(cluster.isMaster) {
for (var i = 0; i < numCPUs; i++) {
cluster.fork();
}
cluster.on('exit', function(worker, code, signal) {
console.log('worker ' + worker.process.pid + ' died');
});
} else {
var http = require('http'),
_io = require('socket.io'),
server = http.createServer();
server.listen('3000', 'example.com');
var io = _io.listen(server);
var connections = {},
msg_sent = 0;
io.on('connection', function(socket) {
connections[socket.id] = new Date().getTime();
socket.on('client-request', function(msg) {
msg_sent++;
});
socket.on('disconnect', function() {
delete connections[socket.id];
});
});
setInterval(function() {
console.log( 'Active connections: ', Object.keys(connections).length, 'Messages sent: ', msg_sent );
}, 1000);
}

Maybe use round robin? A sample implementation would look like this:
const ports = ["3001"," 3002", "3003"];
var current = 0;
io.on('connection', function(socket) {
socket.emit("redirect",ports[current]);
current = (current + 1) % ports.length;
});
On clientside one would do
(function start(port){
const socket = io("http://localhost:"+port);
socket.on("redirect", port => (socket.close(), start(port)));
//whatever
})(3000);

How to pass socket to cluster in node

I would like to get a multi-process node. Workers are listening clients connections. I need pass sockets to master process because master process emit message to clients. Workers also need socket to emit message to clients.
Socket is a circular object and can't pass to a master process.
My code:
const cluster = require('cluster');
const http = require('http');
var io = require('socket.io');
var users;
var clients = {};
if (cluster.isMaster) {
function messageHandler(msg) {
if (msg.usersarray) {
usersarray = msg.usersarray;
console.log(usersarray);
}else if(msg.socket){
clients[usersarray["manu"][0]] = msg.socket;
clients[usersarray["manu"][0]].emit("hola","hola");
}
}
// Start workers and listen for messages containing notifyRequest
const numCPUs = require('os').cpus().length;
for (var i = 0; i < numCPUs; i++) {
cluster.fork();
}
Object.keys(cluster.workers).forEach((id) => {
cluster.workers[id].on('message', messageHandler);
});
}else {
// Create server & socket
var server = http.createServer(function(req, res){
// Send HTML headers and message
res.writeHead(404, {'Content-Type': 'text/html'});
res.end('<h1>Aw, snap! 404</h1>');
});
server.listen(3000);
io = io.listen(server);
// Add a connect listener
io.sockets.on('connection', function(socket) {
var hs = socket.handshake;
console.log("socket connected");
if(users == undefined){
users = {};
}
if(hs.query.usuario != undefined){
if(users[hs.query.usuario] == undefined){
users[hs.query.usuario] = new Array();
}
users[hs.query.usuario].push(socket.id); // connected user with its socket.id
clients[socket.id] = socket; // add the client data to the hash
process.send({ usersarray: users});
process.send({ socket: socket});
}
// Disconnect listener
socket.on('disconnect', function() {
console.log('Client disconnected.');
});
});
}
in line process.send({ socket: socket}); Node js get error "TypeError: Converting circular structure to JSON"
-I used some module to transform circular object but don't working.
-I tried to pass socket id and then in master process, created new socket with this id but I didn't know to use it.
There is any posibility to pass socket from worker to master process?
Node js version: v5.5.0

Hm, I don't think it is possible what you are trying to do. When you create a cluster it means that you create separate processes (master + workers) which can only talk over the pipe.
Talking over the pipe means they can only send strings to each other. process.send tries to serialize a Javascript object as JSON (--> making a string out of it) using JSON.stringify. JSON for example cannot have functions, circles, etc. I just checked the socket object, it is very complex and contains functions (such as socket.emit()), so you cannot just serialize it and send it over the pipe.
Maybe you can check this or this on how to use clustered WebSockets.
It doesn't seem very trivial.. Maybe you can just pass CPU intensive tasks to some worker processes (via cluster or just spawning them yourself), send the results back to the master and let him do all the communication with the client?

I understand your purpose of broadcasting to all the node worker processes in a cluster, although you can not send socket component as such but there is a workaround for the purpose to be served. I will try an explain with an example :
Step 1: When a client action requires a broadcast :
Child.js (Process that has been forked) :
socket.on("BROADCAST_TO_ALL_WORKERS", function (data)
{
process.send({cmd : 'BROADCAST_TO_ALL_WORKERS', message :data.message});
})
Step 2: On the cluster creation side
Server.js (Place where cluster forking happens):
if (cluster.isMaster) {
for (var i = 0; i < numCPUs; i++) {
var worker = cluster.fork();
worker.on('message', function (data) {
if (data.cmd === "BROADCAST_TO_ALL_WORKERS") {
console.log(server_debug_prefix() + "Server Broadcast To All, Message : " + data.message + " , Reload : " + data.reload + " Player Id : " + data.player_id);
Object.keys(cluster.workers).forEach(function(id) {
cluster.workers[id].send({cmd : "BROADCAST_TO_WORKER", message : data.message});
});
}
});
}
cluster.on('exit', function (worker, code, signal) {
var newWorker = cluster.fork();
newWorker.on('message', function (data) {
console.log(data);
if (data.cmd === "BROADCAST_TO_ALL_WORKERS") {
console.log(data.cmd,data);
Object.keys(cluster.workers).forEach(function(id) {
cluster.workers[id].send({cmd : "BROADCAST_TO_WORKER", message : data.message});
});
}
});
});
}
else {
//Node Js App Entry
require("./Child.js");
}
Step 3: To Broadcast in the child process
-> Put this before io.on("connection") in Child.js
process.on("message", function(data){
if(data.cmd === "BROADCAST_TO_WORKER"){
io.sockets.emit("SERVER_MESSAGE", { message: data.message, reload: data.reload, player_id : data.player_id });
}
});
I hope its clear. Please comment if its confusing ... I will try and make it clear.

RabbitMQ for NodeJS with Express routing

My server is running NodeJS and uses the amqplib api to request data from another application. The NodeJS server is receiving the information successfully but there's a noticable delay and I'm trying to determine whether I am doing this in the most efficient manner. Specifically I'm concerned with the way that I open and close connections.
Project Layout
I have two controller files that handle receiving and requesting the data, request.img.server.controller.js and receive.img.server.controller.js. Finally the routes handle the controller methods when a button on the front end is pushed, oct.server.routes.js.
request.img.server.controller.js
'use strict';
var amqp = require('amqplib/callback_api');
var connReady = false;
var conn, ch;
amqp.connect('amqp://localhost:5672', function(err, connection) {
conn = connection;
connReady = true;
conn.createChannel(function(err, channel) {
ch = channel;
});
});
exports.sendRequest = function(message) {
console.log('sending request');
if(connReady) {
var ex = '';
var key = 'utils';
ch.publish(ex, key, new Buffer(message));
console.log(" [x] Sent %s: '%s'", key, message);
}
};
receive.img.server.controller.js
var amqp = require('amqplib/callback_api');
var fs = require('fs');
var wstream = fs.createWriteStream('C:\\Users\\yako\\desktop\\binarytest.txt');
var image, rows, cols;
exports.getResponse = function(resCallback) {
amqp.connect('amqp://localhost:5672', function(err, conn) {
conn.createChannel(function(err, ch) {
var ex = '';
ch.assertQueue('server', {}, function(err, q) {
console.log('waiting for images');
var d = new Date();
var n = d.getTime();
ch.consume(q.queue, function(msg) {
console.log(" [x] %s: '%s'", msg.fields.routingKey, msg.content.toJSON());
rows = msg.content.readInt16LE(0);
cols = msg.content.readInt16LE(2);
console.log("rows = %s", msg.content.readInt16LE(0));
console.log("cols = %s", msg.content.readInt16LE(2));
image = msg.content;
var currMax = 0;
for (var i = 4; i < image.length; i+=2) {
if (image.readInt16LE(i) > currMax) {
currMax = image.readInt16LE(i);
}
wstream.write(image.readInt16LE(i) + ',');
}
console.log('done writing max is', currMax);
//console.log(image);
resCallback(rows, cols, image);
}, {
noAck: true
});
});
});
});
};
oct.server.routes.js
'use strict';
module.exports = function(app) {
var request_img = require('../../app/controllers/image-tools/request.img.server.controller.js');
var receive_img = require('../../app/controllers/image-tools/receive.img.server.controller.js');
// oct routes
app.get('/load_slice', function(req, res) {
console.log('load slice hit');
receive_img.getResponse(function (rows, cols, image) {
res.end(image);
});
request_img.sendRequest('123:C:\\Users\\yako\\Documents\\Developer\\medicaldiag\\test_files\\RUS-01-035-09M-21.oct');
});
};

The way you're opening connections is bad, and is at least part of the performance problem.
Connections are expensive to open. They open a new TCP/IP connection on a TCP/IP port between the client and rabbitmq server. This takes time, and uses up a limited resource on both the client and server.
Because of this, a single connection to RabbitMQ should be created and used within each of your node.js processes. This one connection should be shared by all of the code in that process.
Whenever you need to do something with RabbitMQ, open a new channel on the shared connection and do your work. Channels are cheap and are meant to be opened and closed as needed, within a connection.
More specifically in your code, the receive.img.server.controller.js file is the major problem. This opens a new connection to RabbitMQ every time you call the getResponse method.
If you have 10 users hitting the site, you'll have 10 open RabbitMQ connections when 1 would be sufficient. If you have thousands of users hitting the site, you'll have thousands of open RabbitMQ connections when 1 would be sufficient. You also run the risk of exhausting your available TCP/IP connections on the RabbitMQ server or client.
Your receive.img.server.controller.js should look more like your request.img.server.controller.js - one connection open, and re-used all the time.
Also, FWIW - I recommend using the wascally library for RabbitMQ w/ node.js. This library sits on top of amqplib, but makes things significantly easier. It will manage your one connection for you, and make it easier for you to send and receive messages.
I also have some training material available for RabbitMQ and node.js that covers the basics of amqplib and then moves in to using wascally for real application development.

Node.js TCP/IP server queue not working

I'm writing a TCP/IP queue that's supposed to limit maximum connected users to 3 and make any others wait until user disconnects. These are the functions I'm using:
var maxClients = 3;
var currentClients = 0;
var _pending = [];
function process_pending()
{
if (_pending.length > 0) {
var client = _pending.shift();
currentClients++;
client(function()
{
currentClients--;
process.nextTick(process_pending);
});
}
}
function client_limit(client)
{
if (currentClients < maxClients) {
currentClients++;
client(function()
{
currentClients--;
process.nextTick(process_pending);
});
}
else
{
console.log('Overloaded, queuing clients...');
_pending.push(client);
}
}
Whenever three clients are connected and then fourth one tries to connect it displays the Overloaded message and that's okay, but if an existing client disconnects, nobody else can connect. Looks like the
client(function()
{
currentClients--;
process.nextTick(process_pending);
});
Doesn't work properly, how do I fix it?