How to "emitter.setMaxListeners()"?

Question

When I do a GET on a certain URI using the node.js 'request' module;

var options = {uri:"aURI", headers:headerData};
request.get(options, function (error, response, body) {
}

The error message is:

[Error: Exceeded maxRedirects. Probably stuck in a redirect loop.]

and there is also the following message:

"(node) warning: possible EventEmitter memory leak detected. 11 listeners added. Use emitter.setMaxListeners() to increase limit."

How do I setMaxListeners?

score 113 · Accepted Answer · edited Jul 19 '18 at 06:03

113

I strongly advice NOT to use the code:

process.setMaxListeners(0);

The warning is not there without reason. Most of the time, it is because there is an error hidden in your code. Removing the limit removes the warning, but not its cause, and prevents you from being warned of a source of resource leakage.

If you hit the limit for a legitimate reason, put a reasonable value in the function (the default is 10).

Also, to change the default, it is not necessary to mess with the EventEmitter prototype. you can set the value of defaultMaxListeners attribute like so:

require('events').EventEmitter.defaultMaxListeners = 15;

edited Jul 19 '18 at 06:03

bschlueter

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answered May 23 '17 at 19:06

Félix Brunet

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3

How to identify the cause of the resource leakage? – Brent Washburne Feb 05 '18 at 18:29
1

in short : debugging. Their is many things that can cause resource leakage. and there is some tools that can help detect them. but their is not magic way to find any bug. – Félix Brunet Feb 07 '18 at 14:28
5

You might use `require('events').defaultMaxListeners = 15;` directly. – Mohammed Essehemy Mar 02 '19 at 00:30
where to use it in react native – Anuj Sharma Mar 04 '20 at 13:08
I even more strongly advise to use it :D – danday74 Oct 21 '21 at 16:35
Where should I use this code, I have the same problem, I need to edit a file or what? – Domuta Marcel Sep 28 '22 at 22:28

score 32 · Answer 2 · answered Aug 17 '15 at 12:14

32

I use the code to increase the default limit globally: require('events').EventEmitter.prototype._maxListeners = 100;

answered Aug 17 '15 at 12:14

zag2art

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Had this problem in jenkins running a casperjs script, added this line at top of script and it works!. Thanks var y = require('events').EventEmitter.prototype._maxListeners = 100; – user2908957 Sep 29 '16 at 15:03
this don't work for me. The bellow is working: require('events').defaultMaxListeners = 15; – Debashis Chowdhury Dec 30 '20 at 07:26

score 7 · Answer 3 · answered Aug 28 '12 at 08:17

7

Although adding something to nodejs module is possible, it seems to be not the best way (if you try to run your code on other computer, the program will crash with the same error, obviously).

I would rather set max listeners number in your own code:

var options = {uri:headingUri, headers:headerData, maxRedirects:100};
request.setMaxListeners(0);
request.get(options, function (error, response, body) {
}

answered Aug 28 '12 at 08:17

Mariya Davydova

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This gives `request.setMaxListeners is not a function` error. You have to chain it on `request.get(…, function(){…}).setMaxListeners(0)` ([related ques](http://stackoverflow.com/questions/16093457/has-no-method-setmaxlisteners-error)) – laggingreflex Jul 22 '15 at 18:24

score 6 · Answer 4 · answered Nov 30 '11 at 14:59

6

This is how I solved the problem:

In main.js of the 'request' module I added one line:

Request.prototype.request = function () {
  var self = this
  self.setMaxListeners(0); // Added line

This defines unlimited listeners http://nodejs.org/docs/v0.4.7/api/events.html#emitter.setMaxListeners

In my code I set the 'maxRedirects' value explicitly:

var options = {uri:headingUri, headers:headerData, maxRedirects:100};

answered Nov 30 '11 at 14:59

camden_kid

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'Request' is client request. Am I right ? can you elaborate a bit more ? – Riz Mar 19 '12 at 10:15
@dev Yes, it's client request. It's the node module 'request'. – camden_kid Mar 19 '12 at 10:31
added request module. Now can I put that code in callback function of http.createServer ? I tried but warning is still there. – Riz Mar 19 '12 at 10:49
2

process.setMaxListeners(0); doesn't solve my problem. node version: v9.4.0. And also, its not a good practice to edit the code in node_modules rt? Can anyone tells any other solution? – Sanjay Kumar N S Aug 10 '18 at 06:53
This isn't advisable unless you're _deliberately_ creating all those listeners. – Slbox Sep 03 '21 at 18:44
You didn’t solve the problem, you just hid the warning about it. – bfontaine Jul 21 '23 at 16:44

score 0 · Answer 5 · edited Dec 01 '20 at 16:02

0

Try to use:

require('events').EventEmitter.defaultMaxListeners = Infinity;

edited Dec 01 '20 at 16:02

turivishal

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answered Feb 11 '20 at 14:13

Malik Jehangir Riaz

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score -3 · Answer 6 · answered Apr 22 '20 at 15:46

this is Extension to @Félix Brunet answer

Reason - there is code hidden in your app

How to find -

Strip/comment code and execute until you reach error
check log file

Eg - In my case i created 30 instances of winston log Unknowingly and it started giving error

Note : if u supress this error , it will come again afetr 3..4 days

AKM The Gamer · Answer 7 · 2020-08-15T13:05:53.620

-3

It also happened to me

I use this code and it worked

require('events').EventEmitter.defaultMaxListeners = infinity;

Try it out. It may help

Thanks

edited Aug 15 '20 at 13:05

answered Aug 12 '20 at 11:13

AKM The Gamer

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Update the [existing answer](https://stackoverflow.com/a/60170831/735926) instead of copy/pasting it. – bfontaine Jul 21 '23 at 16:43

How to "emitter.setMaxListeners()"?

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