Random MaxListenersExceededWarning when serving the project with dev server

[dukedhx]

Version

3.11.0

Reproduction link

https://github.com/Autodesk-Forge/forge-digital-catalog

Environment info

Environment Info:

  System:
    OS: macOS High Sierra 10.13.6
    CPU: (8) x64 Intel(R) Core(TM) i7-6820HQ CPU @ 2.70GHz
  Binaries:
    Node: 10.9.0 - /usr/local/bin/node
    Yarn: Not Found
    npm: 6.2.0 - /usr/local/bin/npm
  Browsers:
    Chrome: 77.0.3865.75
    Firefox: 62.0
    Safari: 12.1.1
  npmPackages:
    @vue/babel-helper-vue-jsx-merge-props:  1.0.0 
    @vue/babel-plugin-transform-vue-jsx:  1.0.0 
    @vue/babel-preset-app:  3.11.0 
    @vue/babel-preset-jsx:  1.1.0 
    @vue/babel-sugar-functional-vue:  1.0.0 
    @vue/babel-sugar-inject-h:  1.0.0 
    @vue/babel-sugar-v-model:  1.0.0 
    @vue/babel-sugar-v-on:  1.1.0 
    @vue/cli-overlay:  3.11.0 
    @vue/cli-plugin-babel: 3.11.0 => 3.11.0 
    @vue/cli-plugin-eslint: 3.11.0 => 3.11.0 
    @vue/cli-plugin-pwa: 3.11.0 => 3.11.0 
    @vue/cli-service: 3.11.0 => 3.11.0 
    @vue/cli-shared-utils:  3.11.0 
    @vue/component-compiler-utils:  3.0.0 
    @vue/preload-webpack-plugin:  1.1.1 
    @vue/test-utils: 1.0.0-beta.29 => 1.0.0-beta.29 
    @vue/web-component-wrapper:  1.2.0 
    eslint-plugin-vue: 5.2.3 => 5.2.3 
    eslint-plugin-vuetify: 1.0.0-beta.3 => 1.0.0-beta.3 
    vue: 2.6.10 => 2.6.10 
    vue-cli-plugin-axios: 0.0.4 => 0.0.4 
    vue-cli-plugin-vuetify: 0.6.3 => 0.6.3 
    vue-eslint-parser:  2.0.3 
    vue-hot-reload-api:  2.3.4 
    vue-i18n: 8.14.1 => 8.14.1 
    vue-loader:  15.7.1 
    vue-mq: 1.0.1 => 1.0.1 
    vue-router: 3.1.3 => 3.1.3 
    vue-style-loader:  4.1.2 
    vue-template-compiler: 2.6.10 => 2.6.10 
    vue-template-es2015-compiler:  1.9.1 
    vuejs-logger: 1.5.3 => 1.5.3 
    vuetify: 2.0.17 => 2.0.17 
    vuetify-loader: 1.3.0 => 1.3.0 
    vuex: 3.1.1 => 3.1.1 
  npmGlobalPackages:
    @vue/cli: 3.2.1

Steps to reproduce

run "vue-cli-service serve" and got multiple MaxListenersExceededWarning during compilation - this seems to be on and off but 9 out 10 the warnings would be thrown like below:

40% building 48/58 modules 10 active ...s/@mdi/font/css/materialdesignicons.css(node:1761) MaxListenersExceededWarning: Possible EventEmitter memory leak detected. 11 VElement listeners added. Use emitter.setMaxListeners() to increase limit (node:1761) MaxListenersExceededWarning: Possible EventEmitter memory leak detected. 11 VElement listeners added. Use emitter.setMaxListeners() to increase limit (node:1761) MaxListenersExceededWarning: Possible EventEmitter memory leak detected. 11 VElement listeners added. Use emitter.setMaxListeners() to increase limit 40%

What is expected?

No MaxListenersExceededWarning should be thrown

What is actually happening?

The project seems to be compiled and the dev serve seems to run as expected despite the warnings

[zangxx66]

I have same problem

[mattgreenfield]

I am also experiencing this. I don't know if it's related but I am also using Vuetify

[glazjoon]

Also experiencing this and also using Vuetify

[GalvinGao]

Also experiencing this and I'm also using Vuetify here, specifically vuetify@2.2.34.

By adding require('events').EventEmitter.defaultMaxListeners = 50; in vue.config.js (source) I'm able to ignore this warning because I couldn't fix it and it's polluting my console output all around.

Still need a real fix for this.

Edit: I've only got one entry in the devServer.proxy section in my vue.config.js

[tohanian]

Also experiencing this with Vuetify. In my case it's caused specifically by adding a 10th proxy object in vue.config.js to devServer.proxy. The warning does not occur with 9 or fewer kv pairs in devServer.proxy.

Not seeing any info related to this in the relevant docs.

[hitautodestruct]

It's Nov 2022 and I'm also getting this 🤕

(node:28946) MaxListenersExceededWarning: Possible EventEmitter memory leak detected. 11 upgrade listeners added to [Server]. Use emitter.setMaxListeners() to increase limit
(Use `node --trace-warnings ...` to show where the warning was created)