NodeJS -> Error: write after end (only after first request) - node.js

Question

In my express app i have the route below:
router.get('/generatedData', function (req, res) {
res.setHeader('Connection' , 'Transfer-Encoding');
res.setHeader('Content-Type' , 'text/html; charset=utf-8');
res.setHeader('Transfer-Encoding' , 'chunked');
var Client = someModule.client;
var client = Client();
client.on('start', function() {
console.log('start');
});
client.on('data', function(str) {
console.log('data');
res.write(str);
});
client.on('end', function(msg) {
client.stop();
res.end();
});
client.on('err', function(err) {
client.stop();
res.end(err);
});
client.on('end', function() {
console.log('end');
});
client.start();
});
On first call everything works fine (console)
We've got ourselves a convoy on port 3000
start
data
data
data
data
data
...
data
end
GET /generatedData 200 208.426 ms - -
I get all the data and res.end() is being called and successfully closes the request.
The problem starts after first request. I make the exact same request (new one of course) and i get the following error (console):
start
data
data
data
events.js:160
throw er; // Unhandled 'error' event
^
Error: write after end
at ServerResponse.OutgoingMessage.write (_http_outgoing.js:439:15)
at Client.<anonymous> (/Users/xxxx/projects/xxxx/routes/index.js:33:17)
at emitOne (events.js:96:13)
at Client.emit (events.js:188:7)
at FSWatcher.<anonymous> (/Users/xxxx/projects/xxxx/lib/someModule.js:116:32)
at emitTwo (events.js:106:13)
at FSWatcher.emit (events.js:191:7)
at FSEvent.FSWatcher._handle.onchange (fs.js:1412:12)
[nodemon] app crashed - waiting for file changes before starting...
This happens without res.end() being called.
I manage to get some data before the crash.
How can i get this error without res.end() being called at all?
Do i somehow save the previous res instance?
Thanks,
Asaf

Answer 1

Have the same problem. My module was extened by EventEmitter and each time i catch event in router - it stays there, end on second call there are two eventlisteners not one. Setting "once" instead of "on" - worked for me.
client.once('start', function() {
console.log('start');
});
instead of
client.on('start', function() {
console.log('start');
});