Kill fork on windows throws "write EPIPE" - node.js

Question

I would like to kill forks after a specific amount of time. However, in my codebase, I sometimes get the following error (only on windows) :
events.js:85
throw er; // Unhandled 'error' event
^
Error: write EPIPE
at exports._errnoException (util.js:746:11)
at ChildProcess.target._send (child_process.js:484:28)
at ChildProcess.target.send (child_process.js:416:12)
at sendHelper (cluster.js:676:8)
at send (cluster.js:512:5)
at cluster.js:488:7
at SharedHandle.add (cluster.js:99:3)
at queryServer (cluster.js:480:12)
at Worker.onmessage (cluster.js:438:7)
at ChildProcess.<anonymous> (cluster.js:692:8)
This error seems to happen whenever a worker is not yet completely started and is killed (eg takes 1 second to start and is killed before having started)
Here's a minimal example so that you can reproduce.
var cluster = require('cluster');
var http = require('http');
var numCPUs = require('os').cpus().length;
var workers=[];
if (cluster.isMaster) {
// Fork workers.
for (var i = 0; i < numCPUs; i++) {
workers[i] = cluster.fork();
console.log('forking');
}
cluster.on('exit', function(worker, code, signal) {
console.log('worker ' + worker.process.pid + ' died');
});
setTimeout(function(){
workers.forEach(function(worker){
worker.kill();
})
},1)
} else {
// Workers can share any TCP connection
// In this case its a HTTP server
http.createServer(function(req, res) {
res.writeHead(200);
res.end("hello world\n");
}).listen(8000);
}
If I change the http.createServer to something like console.log, I don't have the problem, so I suspect it is because my worker hasn't finished "starting".
Strangely enough, I also get sometimes an AssertionError instead (they doesn't seem to be any kind of pattern, I have sometimes had 10s in a row of the same error, sometimes it toggles between the two errors : it seems random between EPIPE and ASSERTION error).
assert.js:86
throw new assert.AssertionError({
^
AssertionError: Resource leak detected.
at removeWorker (cluster.js:346:9)
at ChildProcess.<anonymous> (cluster.js:366:34)
at ChildProcess.g (events.js:199:16)
at ChildProcess.emit (events.js:110:17)
at Process.ChildProcess._handle.onexit (child_process.js:1074:12)

Answer 1

The reason for the error is that the daemon is not yet listening when we send it the SIGTERM signal:
The solution is to wait for the listening event before killing the fork.
var cluster = require('cluster');
var http = require('http');
var numCPUs = require('os').cpus().length;
var workers=[];
if (cluster.isMaster) {
// Fork workers.
for (var i = 0; i < numCPUs; i++) {
workers[i] = cluster.fork();
console.log('forking');
}
cluster.on('listening', function(worker, code, signal) {
setTimeout(function(){
worker.kill();
},1)
});
cluster.on('exit', function(worker, code, signal) {
console.log('worker ' + worker.process.pid + ' died');
});
} else {
// Workers can share any TCP connection
// In this case its a HTTP server
http.createServer(function(req, res) {
res.writeHead(200);
res.end("hello world\n");
}).listen(8000);
}

Answer 2

Here is my workaround...
As said by edi9999, worker process is busy in something and you can't kill it while it not listening.
So instead of killing the worker from main process, send a message from main process to worker and use process.exit() statement in the worker to kill itself.
This way, worker would finish the current work and listen to the message from main process and kill itself.
UPDATE
in this Repository of mine, there is an example code which you can try. This is a command line tool. If you cd in to the folder and type node se and press enter. You will get instructions on how to use it.
If you just wanna see code. Look following two files simultaneously.
1. se.js
2. functions.js
hope it helps!!