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Daemon setTimeout in js

I am writing a node.js library that requires setup in order to run. I have used setTimeout to show a warning if the setup function isn't run within 5 seconds.
However, this makes the program wait for 5 seconds before exiting, even if all the other code is finished.
I want to show a warning message iff the setup function hasn't been called and the program is still running after 5 seconds. Is there a way to do this with vanilla JS?
const done = new Event(); // Event is a simple class I made for a one-time event multicast
function setup() {
done.emit();
}
const timeoutHandle = setTimeout(() => showWarning(), 5000);
done.subscribe(() => {
clearTimeout(timeoutHandle);
});
console.log("The program should end here");
// The program keeps going for 5 seconds even after the last statement

However, this makes the program wait for 5 seconds before exiting, even if all the other code is finished.
You can utilize timeout.unref():
When called, the active Timeout object will not require the Node.js event loop to remain active. If there is no other activity keeping the event loop running, the process may exit before the Timeout object's callback is invoked. Calling timeout.unref() multiple times will have no effect.
So const timeoutHandle = setTimeout(() => showWarning(), 5000); timeoutHandle.unref();
This will prevent the setTimeout to keep the process active.

SailsJS test if process is already running

say I have a long task that starts running when a person connects to InitializeDB. (Of course with authorization in the future, but left that out for now).
'post /initializeDB':'OrderController.initializeAll',
Now the problem is: the initialize function should never be run twice. - I know ideally I set up a taskmanager which just starts a task in the background which I could poll.
However for current simplicity, (and to show a proof of concept) is it possible for a sails route to "know" that another connection/route is already running? So that if I connect twice to /initializeDB it won't try to initialize the database twice?

You can use a variable in your controller - just toggle it to true when the process is running, something like that. So, in OrderController.js:
var initializeRunning = false;
module.exports = {
initializeAll: function(req, res) {
// return benign result if already running
if (initializeRunning) {
return res.send({alreadyRunning: true});
}
// start running
initializeRunning = true;
// using setTimeout as a stand-in for a long async process
setTimeout(function() {
// finished the process
res.send({complete: true});
// if you want to allow this method to run again later, unset your toggle
initializeRunning = false;
}, 3000);
},
};

Nodejs manage different threads

I'm a little bit newbie with Nodejs.
I'm working in a Nodejs - express solution.
I want to send and e-mail when some information is added to a MSSSQL database.
This is working well for me. The problem is that I want to check every five minutes that this information added to the database is modified or not, and if not, send another e-mail.
The call to add information to the db is this route:
router.post('/postlinevalidation', function(req, res) {
//insert function into mssql
silkcartCtrl.sendMail(req, res);
});
The controller part for sending the e-mail:
exports.sendMail = function(req, res) {
var emails = "";
fs.readFile('./config/email.conf', 'utf8', function (err,data) {
if (err) {
return logger.error(err);
}
emails = data;
});
var minutes = 5, the_interval = minutes * 60 * 1000;
var refreshId = setInterval(function() {
logger.info("I am doing my 5 minutes check FL_PENDIENTE");
var request = new sql.Request(req.dbsqlserver);
var sqlpendinglinesvalidation = "SELECT [FK_IDCHECK],[FK_IDPEDIDO],[BK_IDPROVEEDOR],[DE_PROVEEDOR]"+
",[FK_FAMILIA],[BK_FAMILIA],[FK_SUBFAMILIA],[BK_SUBFAMILIA],[FK_ARTICULO]"+
",[BK_ARTICULO],[FL_VALIDAR],[DT_FECHA],[FL_PENDIENTE],[DES_CHECK],[QNT_PROPUESTA],[FECHA]"+
"FROM TABLE"+
" WHERE [FL_PENDIENTE] = 1";
request.query(sqlpendinglinesvalidation, function (err, recordset) {
if (recordset.length > 0) {
var transporter = nodemailer.createTransport('smtps://user%40gmail.com:pwd#smtp.gmail.com');
var mailOptions = {
from: '"Mailer" <mail#mail.com>', // sender address
to: emails, // list of receivers
subject: 'Tienes compras pendientes de validar', // Subject line
text: 'Tienes compras pendientes de validar', // plaintext body
html: '<b>Tienes compras pendientes de validar.</b>' // html body
};
// send mail with defined transport object
transporter.sendMail(mailOptions, function(error, info){
if(error){
return logger.error(error);
}
logger.info('Message sent: ' + info.response);
});
} else {
clearInterval(refreshId);
return true;
}
});
}, the_interval);
};
As I said this is working well.
I control the five minutes withsetInterval
But I supossed every time the route postlinevalidation is called, a new thread is open, so I will have several setInterval processes running.
I want to know how to manage it. If the controller function exports.sendMail is running, when the route is called again, "kill this process", and start again exports.sendMail
Thanks in advance

But I supossed every time the route postlinevalidation is called, a
new thread is open, so I will have several setInterval processes
running.
No, this is not how node.js works. You don't get multiple threads because of multiple setInterval() timers.
node.js by itself is single threaded. So, each time a route is called, it just creates an event in the node.js event queue and they are served FIFO, one at a time. At any point that one of the route handlers makes an async call, it essentially "yields" control back and the next item in the event queue gets to run until it yields or finishes.
Timers like setInterval() also use the event queue so no additional threads are creates by setInterval(). It is possible that node.js modules that use native code may themselves use threads and node.js uses a small thread pool that it uses for disk managemnet, but neither of those have anything to do with setInterval().
If you explicitly want to create another execution context for a long running operation in node.js to separate it from the single node.js thread, then that is usually done with the child process module that is part of node.js. You create a new process (which can be a node.js process or some other program running in the process) and you can then communicate with that other process.
If the controller function exports.sendMail is running, when the route
is called again, "kill this process", and start again
exports.sendMail
This is something that would need to be an explicit feature of the nodemailer module in order for you to cancel an operation in process. How "in process" asynchronous operations are implemented and controlled is not a generic node.js thing, but is specific to how that specific module implements things and keeps track of things.
Looking into the code for the node-mailer and more specifically the smtp-connection module, it looks like it uses plain async node.js socket code. That means it does not create any new threads or processes on its own.
As for your setInterval() calls, you need to make sure that any body of code that creates a setInterval() keeps track of the interval timer ID and eventually clears the interval so it stops and you don't keep piling up more and more interval timers. Another possibility is that you have only one interval and it does checking for all outstanding operations (rather than have a separate interval for each one).

From a quick look, I think you don't really need to put the sendMail function inside postlinevalidation. If you want to control it, you could run it in a different script from the express app. You can use something like pm2 or parallelshell to run multiple scripts at the same time.

If you are using setInterval then you can use clearInterval to stop the setInterval based on your condition. Whenever you call a setInterval function, it returns an id using which you can stop the setInterval.
var interval = setInterval(doStuff, 5000);
function doStuff() {
if(your_condition) {
clearInterval(interval);
}
}

Calling socket.disconnect in a forEach loop doesn't actually call disconnect on all sockets

I am new to javascript world. Recently I was working on a chat application in nodejs. So I have a method called gracefulshutdown as follows.
var gracefulShutdown = function() {
logger.info("Received kill signal, shutting down gracefully.");
server.close();
logger.info('Disconnecting all the socket.io clients');
if (Object.keys(io.sockets.sockets).length == 0) process.exit();
var _map = io.sockets.sockets,
_socket;
for (var _k in _map) {
if (_map.hasOwnProperty(_k)) {
_socket = _map[_k];
_socket.disconnect(true);
}
}
...code here...
setTimeout(function() {
logger.error("Could not close connections in time, shutting down");
process.exit();
}, 10 * 1000);
}
Here is what is happening in the disconnect listener.The removeDisconnectedClient method simply updates an entry in the db to indicate the removed client.
socket.on('disconnect', function() {
removeDisconnectedClient(socket);
});
So in this case the disconnect event wasn't fired for all sockets. It was fired for only a few sockets randomly from the array. Although I was able to fix it using setTimeout(fn, 0) with the help of a teammate.
I read about it online and understood only this much that setTimeout defers the execution of of code by adding it to end of event queue. I read about javascript context, call stack, event loop. But I couldn't put together all of it in this context. I really don't understand why and how this issue occurred. Could someone explain it in detail. And what is the best way to solve or avoid them.

It is hard to say for sure without a little more context about the rest of the code in gracefulShutdown but I'm surprised it is disconnecting any of the sockets at all:
_socket = _map[ _k ];
socket.disconnect(true);
It appears that you are assigning an item from _map to the variable _socket but then calling disconnect on socket, which is a different variable. I'm guessing it is a typo and you meant to call disconnect on _socket?
Some of the sockets might be disconnecting for other reasons and the appearance that your loop is disconnecting some but not all the sockets is probably just coincidence.
As far as I can tell from the code you posted, socket should be undefined and you should be getting errors about trying to call the disconnect method on undefined.

From the method name where you use it I can suppose that application exits after attempts to disconnect all sockets. The nature of socket communication is asynchronous, so given you have a decent amount of items in _map it can occur that not all messages with disconnect will be sent before the process exits.
You can increase chances by calling exit after some timeout after disconnecting all sockets. However, why would you manually disconnect? On connection interruption remote sockets will automatically get disconnected...
UPDATE
Socket.io for Node.js doesn't have a callback to know for sure that packet with disconnect command was sent. At least in v0.9. I've debugged that and came to conclusion that without modification of sources it is not possible to catch that moment.
In file "socket.io\lib\transports\websocket\hybi-16.js" a method write is called to send the disconnect packet
WebSocket.prototype.write = function (data) {
...
this.socket.write(buf, 'binary');
...
}
Whereas socket.write is defined in Node.js core transport "nodejs-{your-node-version}-src\core-modules-sources\lib\net.js" as
Socket.prototype.write = function(chunk, encoding, cb)
//cb is a callback to be called on writeRequest complete
However as you see this callback is not provided, so socket.io will not know about the packet having been sent.
At the same time when disconnect() is called for websocket, member disconnected is set to true, and "disconnect" event is broadcasted, indeed. But synchronously. So .on('disconnect' handler on server socket doesn't give and valuable information about whether the packet was sent or not.
Solution
I can make a general conclusion from this. If it is so critical to make sure that all clients are immediately informed (and not wait for a heartbeat timeout or if heartbeat is disabled) then this logic should be implemented manually.
You can send an ordinary message which will mean for the client that server is shutting down and call socket disconnect as soon as the message is received. At the same time server will be able to accept all acknowledgements
Server-side:
var sockets = [];
for (var _k in _map) {
if (_map.hasOwnProperty(_k)) {
sockets.push(_map[_k]);
}
}
sockets.map(function (socket) {
socket.emit('shutdown', function () {
socket.isShutdown = true;
var all = sockets.every(function (skt) {
return skt.isShutdown;
});
if (all) {
//wrap in timeout to let current tick finish before quitting
setTimeout(function () {
process.exit();
});
}
})
})
Clients should behave simply
socket.on('shutdown', function () {
socket.disconnect();
});
Thus we make sure each client has explicitly disconnected. We don't care about server. It will be shutdown shortly.

In the example code it looks like io.sockets.sockets is an Object, however, at least in the library version I am using, it is a mutable array which the socket.io library is free to modify each time you are removing a socket with disconnect(true).
Thus, when you call disconnect(true); if the currently iterated item from index i is removed, this effect like this happens:
var a = [1,2,3,4];
for( var i in a) {
a.splice(i,1); // remove item from array
alert(i);
}
// alerts 0,1
Thus, the disconnect(true) call will ask the socket.io to remove the item from the array - and because you are both holding reference to the same array, the contents of the array are modified during the loop.
The solution is to create a copy of the _map with slice() before the loop:
var _map = io.sockets.sockets.slice(); // copy of the original
It would create a copy of the original array and thus should go through all the items in the array.
The reason why calling setTimeout() would also work is that it would defer the removal of the items from the array, allowing the whole loop iterate without modifying the sockets -Array.

The problem here is that sockjs and socket.io use asynchronous "disconnect" methods. IE. When you call disconnect, it is not immediately terminated. It is just a promise that it WILL be terminated. This has the following effect (assuming 3 sockets)
Your for loop grabs the first socket
The disconnect method is called on the first socket
Your for loop grabs the second socket
The disconnect method is called on the second socket
The disconnect method on the first socket finishes
Your for loop grabs the third socket
The disconnect method is called on the third socket
Program kills itself
Notice, that sockets 2 and 3 haven't necessarily finished yet. This could be for a number of reasons.
Finally, setTimeout(fn, 0) is, as you said, blocking the final call, but it may not be consistent (I haven't dug into this too much). By that I mean, you've set the final termination to be AFTER all your sockets have disconnected. The setTimeout and setInterval methods essentially act more like a queue. Your position in the queue is dictated by the timer you set. Two intervals set for 10s each, where they both run synchronously will cause one to run AFTER the other.

After Socket.io 1.0, the library does not expose you an array of the connected sockets. You can check that io.socket.sockets.length, is not equal to the open socket objects. Your best bet is that you broadcast a 'disconnect' message to all the clients that you want to off, and on.'disconnect' on the client side close the actual WebSocket.

setTimeout from a web worker

What if I want to put a web worker on pause if I cannot proceed processing data, and try a second later? Can I do that in this manner inside a web worker?
var doStuff = function() {
if( databaseBusy() ) {
setTimeout(doStuff, 1000);
} else {
doStuffIndeed();
}
}
I'm getting Uncaught RangeError: Maximum call stack size exceeded and something tells me it's because of the code above.

If by "pause" you mean "further calls to worker.postMessage() will get queued up and not processed by the worker", then no, you cannot use setTimeout() for this. setTimeout() is not a busywait, but rather an in-thread mechanism for delaying work until a later scheduled time. The web worker will still receive a new onmessage event from the main queue as soon as it is posted.
What you can do, however, is queue them up manually and use setTimeout to try to process them later. For example:
worker.js
var workQueue = [];
addEventListener('message',function(evt){
workQueue.push(evt.data);
doStuff();
},false);
function doStuff(){
while (!databaseBusy()) doStuffIndeed(workQueue.shift());
if (workQueue.length) setTimeout(doStuff,1000);
}
Each time a message is received the worker puts it into a queue and calls tryToProcess.
tryToProcess pulls messages from the queue one at a time as long as the database is available.
If the database isn't available and there are messages left, it tries again in 1 second.