NOTE: I have solved most of the problem, but am still encountering an issue with catching the disconnects as noted towards the bottom of this post in the Update section.
NOTE 2: As requested I have posted a more complete view of my setup. See the heading at the bottom of this post.
I am trying to set up a load balancer in Apache but it is not working for socket.io. My Apache code looks like this:
<VirtualHost *:80>
ServerAdmin webmaster@example.com
ServerName jpl.example.com
ProxyRequests off
Header add Set-Cookie "ROUTEID=.%{BALANCER_WORKER_ROUTE}e; path=/" env=BALANCER_ROUTE_CHANGED
<Proxy "balancer://mycluster">
BalancerMember "http://203.0.113.22:3000" route=1
BalancerMember "http://203.0.113.23:3000" route=2
</Proxy>
ProxyPass "/test/" "balancer://mycluster/"
ProxyPassReverse "/test/" "balancer://mycluster/"
</VirtualHost>
Problems with socket.io
The issue I am facing is that on the backend I have a node.js server that uses socket.io connections for long polling in both subdir1/index.html and subdir2.index.html. Unfortunately, socket.io likes to be only running from the root directory:
http://203.0.113.22:3000/socket.io/
It is unable to find it if I try running it from:
http://jpl.example.com/test/socket.io
The start of my index.js file on the server looks like this:
// Setup basic express server
var express = require('express');
var app = express();
var server = require('http').createServer(app);
var io = require('socket.io')(server);
Part of my /subdir1/index.html (also being loaded from the server) originally looked like this:
<script src="/socket.io/socket.io.js"></script>
<script>
var socket = io.connect();
socket.on('notification', function (data) {
But I was now getting an error when accessing it through the proxy. The error was:
http://jpl.example.com/socket.io/socket.io.js 404 (Not Found)
I have tried changing it to this:
<script src="/test/socket.io/socket.io.js"></script>
<script src="http://code.jquery.com/jquery-latest.min.js"></script>
<script>
var refresh_value = 0;
var refresh_time = 0;
//var socket = io.connect();
var socket = io.connect('http://example.com/', {path: "/test/"});
socket.on('notification', function (data) {
It no longer gives me an error, but there is no indication that it is communicating with the socket.
What am I doing wrong here and how can I get this to work?
Update
I have now mostly solved the problem with using:
var socket = io.connect('http://example.com/', {path: "/test/socket.io"});
instead of:
var socket = io.connect('http://example.com/', {path: "/test/"});
Final problem:
Things are now working but I am still experiencing the following issue:
It takes about a minute before it detects that a client has actually closed a page. Without a Proxy and Apache load balancer I do not have this issue. I have tried various things such as setting KeepAlive to "no" and modifying the VirtualHost at the top of this page with the following:
<Proxy "balancer://mycluster">
BalancerMember "http://203.0.113.22:3000" route=1 max=128 ttl=300 retry=60 connectiontimeout=5 timeout=300 ping=2
BalancerMember "http://203.0.113.23:3000" route=2 max=128 ttl=300 retry=60 connectiontimeout=5 timeout=300 ping=2
</Proxy>
But it still takes about a minute before it recognizes that a client has left the page. What can I do to solve this problem?
A more complete view of my setup
As requested, to help diagnose the problem I am posting a more complete view of my setup. I have eliminated as much as I thought I could while providing as much detail as I could:
My current Apache file:
<VirtualHost *:80>
# Admin email, Server Name (domain name), and any aliases
ServerAdmin webmaster@example.com
ServerName jpl.example.com
ProxyRequests off
Header add Set-Cookie "ROUTEID=.%{BALANCER_WORKER_ROUTE}e; path=/" env=BALANCER_ROUTE_CHANGED
<Proxy "balancer://mycluster">
BalancerMember "http://203.0.113.22:3000" route=1 keepalive=On smax=1 connectiontimeout=10 retry=600 timeout=900 ttl=900
BalancerMember "http://203.0.113.23:3000" route=2 keepalive=On smax=1 connectiontimeout=10 retry=600 timeout=900 ttl=900
ProxySet stickysession=ROUTEID
</Proxy>
<Proxy "balancer://myws">
BalancerMember "ws://203.0.113.22:3000" route=1 keepalive=On smax=1 connectiontimeout=10 retry=600 timeout=900 ttl=900
BalancerMember "ws://203.0.113.23:3000" route=2 keepalive=On smax=1 connectiontimeout=10 retry=600 timeout=900 ttl=900
ProxySet stickysession=ROUTEID
</Proxy>
RewriteEngine On
RewriteCond %{REQUEST_URI} ^/test/socket.io [NC]
RewriteCond %{QUERY_STRING} transport=websocket [NC]
RewriteRule /(.*) balancer://myws/$1 [P,L]
ProxyPass "/test/" "balancer://mycluster/"
ProxyPassReverse "/test/" "balancer://mycluster/"
</VirtualHost>
On each of those servers I have a node installation. The main index.js looks like this:
/************ Set Variables ******************/
// Setup basic express server
var express = require('express');
var app = express();
var server = require('http').createServer(app);
var io = require('socket.io')(server);
var port = process.env.PORT || 3000;
var fs = require('fs'),
mysql = require('mysql'),
connectionsArray = [],
connection = mysql.createConnection({
host : 'localhost',
user : 'myusername',
password : 'mypassword',
database : 'mydatabase',
port : 3306
}),
POLLING_INTERVAL = 5000;
server.listen(port, function () {
console.log("-----------------------------------");
console.log('Server listening at port %d', port);
});
// Routing
app.use(express.static(__dirname + "/public"));
/********* Connect to DB ******************/
connection.connect(function(err) {
if (err == null){
console.log("Connected to Database!");
}
else {
console.log( err );
process.exit();
}
});
/*********************** Looping *********************/
var pollingLoop = function () {
var query = connection.query('SELECT * FROM spec_table'),
specs = [];
query
.on('error', function(err) {
console.log( err );
updateSockets( err );
})
.on('result', function( spec ) {
specs.push( spec );
})
.on('end',function(){
pollingLoop2(specs);
});
};
var pollingLoop2 = function (specs) {
// Make the database query
var query = connection.query('SELECT * FROM info_table'),
infos = [];
// set up the query listeners
query
.on('error', function(err) {
console.log( err );
updateSockets( err );
})
.on('result', function( info ) {
infos.push( info );
})
.on('end',function(){
if(connectionsArray.length) {
setTimeout( pollingLoop, POLLING_INTERVAL );
updateSockets({specs:specs, infos:infos});
}
});
};
/*************** Create new websocket ****************/
//This is where I can tell who connected and who disconnected.
io.sockets.on('connection', function ( socket ) {
var socketId = socket.id;
var clientIp = socket.request.connection.remoteAddress;
var time = new Date();
console.log(time);
console.log("\033[32mJOINED\033[0m: "+ clientIp + " (Socket ID: " + socketId + ")");
// start the polling loop only if at least there is one user connected
if (!connectionsArray.length) {
pollingLoop();
}
socket.on('disconnect', function () {
var socketIndex = connectionsArray.indexOf( socket );
var time = new Date();
console.log(time);
console.log("\033[31mLEFT\033[0m: "+ clientIp + " (Socket ID: " + socketId + ")");
if (socketIndex >= 0) {
connectionsArray.splice( socketIndex, 1 );
}
console.log(' Number of connections: ' + connectionsArray.length);
});
connectionsArray.push( socket );
console.log(' Number of connections: ' + connectionsArray.length);
});
/********* Function updateSockets ************/
var updateSockets = function ( data ) {
connectionsArray.forEach(function( tmpSocket ){
tmpSocket.volatile.emit( 'notification' , data );
});
};
Finally, in my public/dir1/index.html file I have something that looks like this:
//HTML code here
<script src="/test/socket.io/socket.io.js"></script>
<script>
var socket = io.connect('', {path: "/test/socket.io"});
socket.on('notification', function (data) {
$.each(data.specs,function(index,spec){
//Other js code here
})
})
</script>
//More HTML code here
With this particular setup the connection works, but it takes over a minute before I can detect that a page is closed. Also, with this set up there is an error logged to the console:
WebSocket connection to 'ws://jpl.example.com/test/socket.io/?EIO=3&transport=websocket&sid=QE5aCExz3nAGBYcZAAAA' failed: Connection closed before receiving a handshake response
ws @ socket.io.js:5325
What am I doing wrong and how can I fix my code so that I can detect disconnects the moment they occur?
Note: It works just fine if I do not use a subdirectory /test/.
Please also note: this is only a subdirectory appearing in the URL. It does not exist in the file system anywhere.
Also, I am open to tips and suggestions if you notice areas in my code that I could be writing better.
