Possible memory leak?

[mihai-iorga]

I am trying for several days to figure out the following error:

Warning: Possible EventEmitter memory leak detected. 11 wakeup listeners added. Use emitter.setMaxListeners() to increase limit
    at _addListener (events.js:259:19)
    at Connection.addListener (events.js:275:10)
    at Connection.Readable.on (_stream_readable.js:687:35)
    at Connection.once (events.js:301:8)
    at Connection._send (/opt/push/server/releases/20170202150908/node_modules/http2/lib/protocol/connection.js:356:10)
    at runCallback (timers.js:649:20)
    at tryOnImmediate (timers.js:622:5)
    at processImmediate [as _immediateCallback] (timers.js:594:5)`

After a long period of debugging (not that memory leaks warnings are debug-able), I think I found from where this error is coming from, server is up and no warnings in the last 24 hours.

I have added after this._connection:

this._connection.setMaxListeners(0);

I know this is not the solution (infinite listeners is a bad idea), but I am tired of figuring out what the hell is happening there, maybe a second pair of eyes can see the leak.

GNU/Linux
NodeJS 6.9.4
NPM 3.10.10

I do not have a reproducible code that emits that warning because it happens once every now and then.
If this only happens to me, then my bad, sorry.

[haozxuan]

@mihai-iorga I have this Warning too, because InternalServerError i update module version 2.1.1 to 2.1.3, InternalServerError is gone, but this Warning make me worry about this module stable? if no perfect solution i will back to 2.1.1 and use pem file. :|

[jdrydn]

Hmm. Given this:

var apn = require('apn');
var path = require('path');

var service = new apn.Provider({
  token: {
    key: path.join(__dirname, 'APNsAuthKey_KEY_ID.p8'),
    keyId: 'KEY_ID',
    teamId: 'TEAM_ID',
  },
  production: true,
});

while(true) {}

No warnings about memory leaks appears. But update that to send a single notification:

var apn = require('apn');
var path = require('path');

var service = new apn.Provider({
  token: {
    key: path.join(__dirname, 'APNsAuthKey_KEY_ID.p8'),
    keyId: 'KEY_ID',
    teamId: 'TEAM_ID',
  },
  production: true,
});

var notification = new apn.Notification();
notification.topic = 'com.someimportantcompany.myapp';
notification.alert = 'Hello, world!';

service.send(notification, 'push-notification-id').then(function (reply) {
  console.log(JSON.stringify(reply, null, 2));
});

I get a successful output, and roughly 10 minutes later I get the warning about a possible memory leak:

{
  "sent": [
    {
      "device": "push-notification-id"
    }
  ],
  "failed": []
}
(node) warning: possible EventEmitter memory leak detected. 11 wakeup listeners added. Use emitter.setMaxListeners() to increase limit.
Trace
    at Connection.addListener (events.js:239:17)
    at Connection.Readable.on (_stream_readable.js:680:33)
    at Connection.once (events.js:265:8)
    at Connection._send (/Users/james/Sites/apns-test/node_modules/http2/lib/protocol/connection.js:356:10)
    at processImmediate [as _immediateCallback] (timers.js:383:17)

Given the error message is quite specific "11 wakeup listeners added" searching this repo for "wakeup" reveals the only place this event is listened on:

node-apn/lib/client.js

Line 14 in 61495d2

this.endpointManager.on("wakeup", () => {

function Client (options) {
    this.config = config(options);

    this.endpointManager = new EndpointManager(this.config);
    this.endpointManager.on("wakeup", () => {
        ...
    });

    ...
}

My guess would be new Client() is being called multiple times?

[jdrydn]

To add:

Sending to N devices in series doesn't impact on the number of listeners (after sending to 3 or 4 devices, 10ish minutes later the warning still appears stating "11 wakeup listeners added".

Sending a device token 1 notification every 30 seconds doesn't trigger any warnings at all, after 10ish minutes, suggesting it's related to inactivity?

Sending a device token 1 notification every 15 minutes triggers a warning after 10ish minutes each time.

[jdrydn]

To also add:

Obviously this bug is coming from this line in http2, if you see this list of issues you can see it's happened to other people with other events and the only way they've solved it is with 'setMaxListeners(0)' to "fix" it.

Fortunately, this is only occurs because it's a once event. My guess is it goes from 10 to 11 at that moment, which is why it's never gone higher than 11 (for me, at least).

[mihai-iorga]

Nope, I think it's from NodeJS itself check here and here.

The fix will land in Node 6.10.0 ..

[jeacott1]

+1 seeing this too.

[JacopoDaeli]

+1

[extempl]

Actually, not fixed in 7.5.0

[emretekince]

+1

[Removed-5an]

I have the same issue! node 7.5.

[edengol]

I switched to node 6.10.0 and still get the error using apn 2.1.3 some minutes after sending a notification.

[jacktuck]

Same issue 7.4.0

2017-03-08T16:43:56.568176535Z (node:7) MaxListenersExceededWarning: Possible EventEmitter memory leak detected. 11 wakeup listeners added. Use emitter.setMaxListeners() to increase limit

[debjeetsarkar]

+1

[sbat]

+1
node 6.10.0 on AWS Elastic Beanstalk
apn 2.1.3 dependency of https://github.com/appfeel/node-pushnotifications

After adding this._connection.setMaxListeners(20); after Line 88 in endpoint.js i get still the warning.

[emretekince]

I have just switched to Firebase.