Nuxt huge memory usage / leakage and how to prevent

Question

I'm on Nuxt v2.13 and Vuetify v2 , also using keep-alive in my default layout. As my app got bigger and bigger , I noticed the memory problem more and more so that my app needs at least around 4GB RAM on cloud server to be built and work properly. I dug around and found scattered pieces, so decided to share them and discuss the solutions.

Please answer each one according to their #numbers

#1 - NuxtLink (vue-router) memory leakage : others found that there may be a leakage in vue-router ; also because the DOM associated with the nuxt-link will be prefetched, there also may be a high usage in memory. So someone suggested to use html anchor instead of nuxt-link like this:

<template>
  <a href="/mypage" @click.prevent="goTo('mypage')">my page link</a>
</template>

<script>
export default{
  methods:{
    goTo(link){
      this.$router.push(link)
    }
  }
}
</script>

what do you think about this approach ?? and what about Vuetify to props as they work like nuxt-link?

<template>
  <v-card to="/mypage" ></v-card>
</template>

#2 - Dynamic component load : As my app is bidirectional and customizable by .env file , i had to lazy load many of my components dynamically and conditionally like this:

<template>
  <component :is="mycomp" />
</template>

<script>
export default{
  computed:{
    mycomp(){
      return import()=>(`@/components/${process.env.SITE_DIR}/mycomp.vue`)
    }
  }
}
</script>

will this cause high memory usage/leakage ??

# 3 - Nuxt Event Bus : beside normal this.$emit() in my components, sometimes I had to use $nuxt.$emit() . i remove them all in beforeDestroy hook :

<script>
export default{
  created:{
    this.$nuxt.$on('myevent', ()=>{
      // do something
    }
  },
  beforeDestroy(){
    this.$nuxt.$off('myevent')
  }
}
</script>

but someone told me that listeners on created hook will be SSR and won't be removed in CSR beforeDestroy hook. so what should i do? add if(process.client){} to created ??

# 4 - Global Plugins : I found this issue and also this doc . i added my plugins/packages globally as mentioned in this question . So is the vue.use() a problem ? should i use inject instead? how?

// vue-product-zoomer package
import Vue from 'vue'
import ProductZoomer from 'vue-product-zoomer'
Vue.use(ProductZoomer)

# 5 - Vee Validate leakage : I read here about it , is this really cause leakage? I'm using Vee Validate v3 :

my veevalidate.js that added globally to nuxt.config.js

import Vue from 'vue'
import {  ValidationObserver, ValidationProvider, setInteractionMode } from 'vee-validate'
import { localize } from 'vee-validate';
import en from 'vee-validate/dist/locale/en.json';
import fa from 'vee-validate/dist/locale/fa.json';

localize({
    en,
    fa
});

setInteractionMode('eager')

let LOCALE = "fa";
Object.defineProperty(Vue.prototype, "locale", {
    configurable: true,
    get() {
        return LOCALE;
    },
    set(val) {
        LOCALE = val;
        localize(val);
    }
});

Vue.component('ValidationProvider', ValidationProvider);
Vue.component("ValidationObserver", ValidationObserver);

my veevalidate mixin that added to each page/component had use veevalidate . ( I used a mixin because I needed to use my vuex state lang )

import { required, email , alpha , alpha_spaces , numeric , confirmed , password } from 'vee-validate/dist/rules'
import { extend } from 'vee-validate'

export default {
    mounted() {
        extend("required", {
            ...required,
            message: `{_field_} ${this.lang.error_required}`
        });
        extend("email", {
            ...email,
            message: `{_field_} ${this.lang.error_email}`
        });
        extend("alpha", {
            ...alpha,
            message: `{_field_} ${this.lang.error_alpha}`
        });
        extend("alpha_spaces", {
            ...alpha_spaces,
            message: `{_field_} ${this.lang.error_alpha_spaces}`
        });
        extend("numeric", {
            ...numeric,
            message: `{_field_} ${this.lang.error_numeric}`
        });
        extend("confirmed", {
            ...confirmed,
            message: `{_field_} ${this.lang.error_confirmed}`
        });
        extend("decimal", {
            validate: (value, { decimals = '*', separator = '.' } = {}) => {
                if (value === null || value === undefined || value === '') {
                    return {
                        valid: false
                    };
                }
                if (Number(decimals) === 0) {
                    return {
                        valid: /^-?\d*$/.test(value),
                    };
                }
                const regexPart = decimals === '*' ? '+' : `{1,${decimals}}`;
                const regex = new RegExp(`^[-+]?\\d*(\\${separator}\\d${regexPart})?([eE]{1}[-]?\\d+)?$`);
        
                return {
                    valid: regex.test(value),
                };
            },
            message: `{_field_} ${this.lang.error_decimal}`
        })
    }
}

# 6 - Keep-Alive : As I mentioned before I'm using keep-alive in my app and that it self cache many things and may not destroy/remove plugins and event listeners.

# 7 - setTimeout : is there any need to use clearTimeout to do data clearing ??

# 8 - Remove Plugins/Packages : in this Doc it is mentioned that some plugins/packages won't be removed even after component being destroyed , how can I find those ??

here are my packages and nuxt.config

// package.json
{
  "name": "nuxt",
  "version": "1.0.0",
  "private": true,
  "scripts": {
    "dev": "nuxt",
    "build": "nuxt build",
    "start": "nuxt start",
    "generate": "nuxt generate"
  },
  "dependencies": {
    "@nuxt/http": "^0.6.0",
    "@nuxtjs/auth": "^4.9.1",
    "@nuxtjs/axios": "^5.11.0",
    "@nuxtjs/device": "^1.2.7",
    "@nuxtjs/google-gtag": "^1.0.4",
    "@nuxtjs/gtm": "^2.4.0",
    "chart.js": "^2.9.3",
    "cookie-universal-nuxt": "^2.1.4",
    "jquery": "^3.5.1",
    "less-loader": "^6.1.2",
    "nuxt": "^2.13.0",
    "nuxt-user-agent": "^1.2.2",
    "v-viewer": "^1.5.1",
    "vee-validate": "^3.3.7",
    "vue-chartjs": "^3.5.0",
    "vue-cropperjs": "^4.1.0",
    "vue-easy-dnd": "^1.10.2",
    "vue-glide-js": "^1.3.14",
    "vue-persian-datetime-picker": "^2.2.0",
    "vue-product-zoomer": "^3.0.1",
    "vue-slick-carousel": "^1.0.6",
    "vue-sweetalert2": "^3.0.5",
    "vue2-editor": "^2.10.2",
    "vuedraggable": "^2.24.0",
    "vuetify": "^2.3.9"
  },
  "devDependencies": {
    "@fortawesome/fontawesome-free": "^5.15.1",
    "@mdi/font": "^5.9.55",
    "@nuxtjs/dotenv": "^1.4.1",
    "css-loader": "^3.6.0",
    "flipclock": "^0.10.8",
    "font-awesome": "^4.7.0",
    "node-sass": "^4.14.1",
    "noty": "^3.2.0-beta",
    "nuxt-gsap-module": "^1.2.1",
    "sass-loader": "^8.0.2"
  }
}

//nuxt.config.js
const env = require('dotenv').config()
const webpack = require('webpack')

export default {
  mode: 'universal',

  loading: {
    color: 'green',
    failedColor: 'red',
    height: '3px'
  },
  router: {
    // base: process.env.NUXT_BASE_URL || '/' 
  },
  head: {
    title: process.env.SITE_TITLE + ' | ' + process.env.SITE_SHORT_DESC || '',
    meta: [
      { charset: 'utf-8' },
      { name: 'viewport', content: 'width=device-width, initial-scale=1' },
      { hid: 'keywords', name: 'keywords', content: process.env.SITE_KEYWORDS || '' },
      { hid: 'description', name: 'description', content: process.env.SITE_DESCRIPTION || '' },
      { hid: 'robots', name: 'robots', content: process.env.SITE_ROBOTS || '' },
      { hid: 'googlebot', name: 'googlebot', content: process.env.SITE_GOOGLE_BOT || '' },
      { hid: 'bingbot', name: 'bingbot', content: process.env.SITE_BING_BOT || '' },
      { hid: 'og:locale', name: 'og:locale', content: process.env.SITE_OG_LOCALE || '' },
      { hid: 'og:type', name: 'og:type', content: process.env.SITE_OG_TYPE || '' },
      { hid: 'og:title', name: 'og:title', content: process.env.SITE_OG_TITLE || '' },
      { hid: 'og:description', name: 'og:description', content: process.env.SITE_OG_DESCRIPTION || '' },
      { hid: 'og:url', name: 'og:url', content: process.env.SITE_OG_URL || '' },
      { hid: 'og:site_name', name: 'og:site_name', content: process.env.SITE_OG_SITENAME || '' },
      { hid: 'theme-color', name: 'theme-color', content: process.env.SITE_THEME_COLOR || '' },
      { hid: 'msapplication-navbutton-color', name: 'msapplication-navbutton-color', content: process.env.SITE_MSAPP_NAVBTN_COLOR || '' },
      { hid: 'apple-mobile-web-app-status-bar-style', name: 'apple-mobile-web-app-status-bar-style', content: process.env.SITE_APPLE_WM_STATUSBAR_STYLE || '' },
      { hid: 'X-UA-Compatible', 'http-equiv': 'X-UA-Compatible', content: process.env.SITE_X_UA_Compatible || '' }
    ],
    link: [
      { rel: 'icon', type: 'image/x-icon', href: process.env.SITE_FAVICON },
      // { rel: 'shortcut icon', type: 'image/x-icon', href: process.env.SITE_FAVICON },
      { rel: 'canonical', href: process.env.SITE_REL_CANONICAL },
      // { rel: 'stylesheet', href: 'https://cdn.jsdelivr.net/npm/[email protected]/css/font-awesome.min.css' },
    ]
  },
  css: [
      '~/assets/scss/style.scss',
      '~/assets/scss/media.scss',
      '~/assets/scss/customization.scss',
      '~/assets/scss/sweetalert.scss',
      '~/assets/scss/noty.scss',
      '~/assets/scss/flipclock.scss',
      '~/assets/scss/glide.scss',
      '~/assets/scss/sorting.scss',
      '~/assets/scss/cropper.scss',
      '~/assets/scss/transitions.scss',
      '~/assets/scss/product-zoom.scss',
      'vue-slick-carousel/dist/vue-slick-carousel.css'
  ],
  plugins: [
      'plugins/mixins/reqerrors.js',
      'plugins/mixins/user.js',
      'plugins/mixins/language.js',
      'plugins/mixins/shopinfo.js',
      'plugins/mixins/formattedprice.js',
      'plugins/mixins/utils.js',
      'plugins/mixins/cms.js',
      'plugins/mixins/client.js',
      'plugins/mixins/cart.js',
      'plugins/axios.js',
      'plugins/veevalidate.js',
      'plugins/noty.js',
      'plugins/glide.js',
      '@plugins/vuetify',
      '@plugins/vuedraggable',
      '@plugins/vuedraggable',
      '@plugins/vue-slick-carousel.js',
      {src: 'plugins/vuepersiandatepicker.js', mode: 'client'},
      {src: 'plugins/cropper.js', mode: 'client'},
      {src: 'plugins/vue-product-zoomer.js', mode: 'client'},
      {src: 'plugins/vueeditor.js', mode: 'client'},
  ],
  buildModules: [
    '@nuxtjs/dotenv',
    'nuxt-gsap-module'
  ],
  modules: [
    '@nuxtjs/axios',
    '@nuxtjs/auth',
    '@nuxtjs/device',
    ['vue-sweetalert2/nuxt',
      {
        confirmButtonColor: '#29BF12',
        cancelButtonColor: '#FF3333'
      }
    ],
    'cookie-universal-nuxt',
    '@nuxtjs/gtm',
    '@nuxtjs/google-gtag',
    'nuxt-user-agent',
  ],

  gtm: {
    id: process.env.GOOGLE_TAGS_ID,
    debug: false
  },
  'google-gtag': {
    id: process.env.GOOGLE_ANALYTICS_ID,
    debug: false
  },
  gsap: {
    extraPlugins: {
      cssRule: false,
      draggable: false,
      easel: false,
      motionPath: false,
      pixi: false,
      text: false,
      scrollTo: false,
      scrollTrigger: false
    },
    extraEases: {
      expoScaleEase: false,
      roughEase: false,
      slowMo: true,
    }
  },
  axios: {
    baseURL: process.env.BASE_URL,
  },
  auth: {
      strategies: {
        local: {
          endpoints: {
            login: { url: 'auth/login', method: 'post', propertyName: 'token' },
            logout: { url: 'auth/logout', method: 'post' },
            user: { url: 'auth/info', method: 'get', propertyName: '' }
          }
        }
      },
      redirect: {
        login: '/login',
        home: '',
        logout: '/login'
      },
      cookie: {
        prefix: 'auth.',
        options: {
          path: '/',
          maxAge: process.env.AUTH_COOKIE_MAX_AGE
        }
      }
  },

  publicRuntimeConfig: {
    gtm: {
      id: process.env.GOOGLE_TAGS_ID
    },
    'google-gtag': {
      id: process.env.GOOGLE_ANALYTICS_ID,
    }
  },
  build: {
    transpile: ['vee-validate/dist/rules'],
    plugins: [
      new webpack.ProvidePlugin({
        '$': 'jquery',
        jQuery: "jquery",
        "window.jQuery": "jquery",
        '_': 'lodash'
      }),
      new webpack.IgnorePlugin(/^\.\/locale$/, /moment$/)
    ],
    postcss: {
      preset: {
        features: {
          customProperties: false,
        },
      },
    },
    loaders: {
      scss: {
        prependData: `$theme_colors: ("theme_body_color":"${process.env.THEME_BODY_COLOR}","theme_main_color":"${process.env.THEME_MAIN_COLOR}","theme_main_color2":"${process.env.THEME_MAIN_COLOR2}","theme_side_color":"${process.env.THEME_SIDE_COLOR}","theme_side_color2":"${process.env.THEME_SIDE_COLOR2}","theme_link_color":"${process.env.THEME_LINK_COLOR}");`
      }
    },
  }
}

Answer 1

I think it is time to share my understanding (even though it's little):

#1 as vue-router use prefetch there may be heavy memory usage depending on number of links. in my case there are not many so I let them be, there is also an option to disable prefetch in nuxt so if your app is super busy or you have hundreds of links in a single page better to disable prefetch:

// locally
<nuxt-link to="/" no-prefetch>link</nuxt-link>

// globally in nuxt.config.js
router: {
  prefetchLinks: false
}

#2 I didn't found any problem with dynamic components

#3 not with $nuxt.$on but I experienced it (event listener not being removed) when used window.addEventListener in created hook. so better moved all listeners to client side (beforeMount or mounted) as much as possible

#4 as I mentioned in a comment above I removed global plugins/css as much as I could for a lighter init and used them locally , but about Vue.use() memory leakage, that was my misunderstanding !! in nuxt doc is said that:

Don't use Vue.use(), Vue.component(), and globally, don't plug anything in Vue inside this function, dedicated to Nuxt injection. It will cause memory leak on server-side.

So using Vue.use() inside injection function may cause memory leakage not Vue.use() itself.

As for others still no answer