Disable http disk cache and implempent in-memory image cache (#2498)

* Disable http disk cache and implempent in-memory image cache

* Add comment about removing URL scheme prefix

Co-authored-by: PikachuEXE <pikachuexe@gmail.com>

* Add early return to clean up the code

* Rewrite cache expiry logic with fallbacks

* Move this change behind a CLI argument --experiments-disable-disk-cache

* Replace CLI flag with a GUI setting

* Improve warning message styling

* ! Fix incompatibility with latest settings code

* Use CSS instead of sass for the experimental settings

* Return the error as JSON instead of throwing it

* Inline restart prompt label and option names and values

* Mention crash risk and recommend backups in the warning

Co-authored-by: PikachuEXE <pikachuexe@gmail.com>

_scripts/dev-runner.js

@@ -53,10 +53,12 @@ async function restartElectron() {
 
   electronProcess = spawn(electron, [
     path.join(__dirname, '../dist/main.js'),
-    // '--enable-logging', Enable to show logs from all electron processes
+    // '--enable-logging', // Enable to show logs from all electron processes
     remoteDebugging ? '--inspect=9222' : '',
-    remoteDebugging ? '--remote-debugging-port=9223' : '',
-  ])
+    remoteDebugging ? '--remote-debugging-port=9223' : ''
+  ],
+    // { stdio: 'inherit' } // required for logs to actually appear in the stdout
+  )
 
   electronProcess.on('exit', (code, _) => {
     if (code === relaunchExitCode) {

src/main/ImageCache.js

@@ -0,0 +1,73 @@
+// cleanup expired images once every 5 mins
+const CLEANUP_INTERVAL = 300_000
+
+// images expire after 2 hours if no expiry information is found in the http headers
+const FALLBACK_MAX_AGE = 7200
+
+export class ImageCache {
+  constructor() {
+    this._cache = new Map()
+
+    setInterval(this._cleanup.bind(this), CLEANUP_INTERVAL)
+  }
+
+  add(url, mimeType, data, expiry) {
+    this._cache.set(url, { mimeType, data, expiry })
+  }
+
+  has(url) {
+    return this._cache.has(url)
+  }
+
+  get(url) {
+    const entry = this._cache.get(url)
+
+    if (!entry) {
+      // this should never happen as the `has` method should be used to check for the existence first
+      throw new Error(`No image cache entry for ${url}`)
+    }
+
+    return {
+      data: entry.data,
+      mimeType: entry.mimeType
+    }
+  }
+
+  _cleanup() {
+    // seconds since 1970-01-01 00:00:00
+    const now = Math.trunc(Date.now() / 1000)
+
+    for (const [key, entry] of this._cache.entries()) {
+      if (entry.expiry <= now) {
+        this._cache.delete(key)
+      }
+    }
+  }
+}
+
+/**
+ * Extracts the cache expiry timestamp of image from HTTP headers
+ * @param {Record<string, string>} headers
+ * @returns a timestamp in seconds
+ */
+export function extractExpiryTimestamp(headers) {
+  const maxAgeRegex = /max-age=([0-9]+)/
+
+  const cacheControl = headers['cache-control']
+  if (cacheControl && maxAgeRegex.test(cacheControl)) {
+    let maxAge = parseInt(cacheControl.match(maxAgeRegex)[1])
+
+    if (headers.age) {
+      maxAge -= parseInt(headers.age)
+    }
+
+    // we don't need millisecond precision, so we can store it as seconds to use less memory
+    return Math.trunc(Date.now() / 1000) + maxAge
+  } else if (headers.expires) {
+    // https://developer.mozilla.org/en-US/docs/Web/HTTP/Headers/Expires
+
+    return Math.trunc(Date.parse(headers.expires) / 1000)
+  } else {
+    return Math.trunc(Date.now() / 1000) + FALLBACK_MAX_AGE
+  }
+}

src/main/index.js

@@ -1,12 +1,14 @@
 import {
   app, BrowserWindow, dialog, Menu, ipcMain,
-  powerSaveBlocker, screen, session, shell, nativeTheme
+  powerSaveBlocker, screen, session, shell, nativeTheme, net, protocol
 } from 'electron'
 import path from 'path'
 import cp from 'child_process'
 
 import { IpcChannels, DBActions, SyncEvents } from '../constants'
 import baseHandlers from '../datastores/handlers/base'
+import { extractExpiryTimestamp, ImageCache } from './ImageCache'
+import { existsSync } from 'fs'
 
 if (process.argv.includes('--version')) {
   app.exit()
@@ -49,6 +51,17 @@ function runApp() {
   app.commandLine.appendSwitch('enable-file-cookies')
   app.commandLine.appendSwitch('ignore-gpu-blacklist')
 
+  // command line switches need to be added before the app ready event first
+  // that means we can't use the normal settings system as that is asynchonous,
+  // doing it synchronously ensures that we add it before the event fires
+  const replaceHttpCache = existsSync(`${app.getPath('userData')}/experiment-replace-http-cache`)
+  if (replaceHttpCache) {
+    // the http cache causes excessive disk usage during video playback
+    // we've got a custom image cache to make up for disabling the http cache
+    // experimental as it increases RAM use in favour of reduced disk use
+    app.commandLine.appendSwitch('disable-http-cache')
+  }
+
   // See: https://stackoverflow.com/questions/45570589/electron-protocol-handler-not-working-on-windows
   // remove so we can register each time as we run the app.
   app.removeAsDefaultProtocolClient('freetube')
@@ -149,6 +162,113 @@ function runApp() {
       })
     })
 
+    if (replaceHttpCache) {
+      // in-memory image cache
+
+      const imageCache = new ImageCache()
+
+      protocol.registerBufferProtocol('imagecache', (request, callback) => {
+        // Remove `imagecache://` prefix
+        const url = decodeURIComponent(request.url.substring(13))
+        if (imageCache.has(url)) {
+          const cached = imageCache.get(url)
+
+          // eslint-disable-next-line node/no-callback-literal
+          callback({
+            mimeType: cached.mimeType,
+            data: cached.data
+          })
+          return
+        }
+
+        const newRequest = net.request({
+          method: request.method,
+          url
+        })
+
+        // Electron doesn't allow certain headers to be set:
+        // https://www.electronjs.org/docs/latest/api/client-request#requestsetheadername-value
+        // also blacklist Origin and Referrer as we don't want to let YouTube know about them
+        const blacklistedHeaders = ['content-length', 'host', 'trailer', 'te', 'upgrade', 'cookie2', 'keep-alive', 'transfer-encoding', 'origin', 'referrer']
+
+        for (const header of Object.keys(request.headers)) {
+          if (!blacklistedHeaders.includes(header.toLowerCase())) {
+            newRequest.setHeader(header, request.headers[header])
+          }
+        }
+
+        newRequest.on('response', (response) => {
+          const chunks = []
+          response.on('data', (chunk) => {
+            chunks.push(chunk)
+          })
+
+          response.on('end', () => {
+            const data = Buffer.concat(chunks)
+
+            const expiryTimestamp = extractExpiryTimestamp(response.headers)
+            const mimeType = response.headers['content-type']
+
+            imageCache.add(url, mimeType, data, expiryTimestamp)
+
+            // eslint-disable-next-line node/no-callback-literal
+            callback({
+              mimeType,
+              data: data
+            })
+          })
+
+          response.on('error', (error) => {
+            console.error('image cache error', error)
+
+            // error objects don't get serialised properly
+            // https://stackoverflow.com/a/53624454
+
+            const errorJson = JSON.stringify(error, (key, value) => {
+              if (value instanceof Error) {
+                return {
+                  // Pull all enumerable properties, supporting properties on custom Errors
+                  ...value,
+                  // Explicitly pull Error's non-enumerable properties
+                  name: value.name,
+                  message: value.message,
+                  stack: value.stack
+                }
+              }
+
+              return value
+            })
+
+            // eslint-disable-next-line node/no-callback-literal
+            callback({
+              statusCode: response.statusCode ?? 400,
+              mimeType: 'application/json',
+              data: Buffer.from(errorJson)
+            })
+          })
+        })
+
+        newRequest.end()
+      })
+
+      const imageRequestFilter = { urls: ['https://*/*', 'http://*/*'] }
+      session.defaultSession.webRequest.onBeforeRequest(imageRequestFilter, (details, callback) => {
+        // the requests made by the imagecache:// handler to fetch the image,
+        // are allowed through, as their resourceType is 'other'
+        if (details.resourceType === 'image') {
+          // eslint-disable-next-line node/no-callback-literal
+          callback({
+            redirectURL: `imagecache://${encodeURIComponent(details.url)}`
+          })
+        } else {
+          // eslint-disable-next-line node/no-callback-literal
+          callback({})
+        }
+      })
+
+      // --- end of `if experimentsDisableDiskCache` ---
+    }
+
     await createWindow()
 
     if (isDev) {

src/renderer/components/experimental-settings/experimental-settings.css

@@ -0,0 +1,6 @@
+.experimental-warning {
+  text-align: center;
+  font-weight: bold;
+  padding-left: 4%;
+  padding-right: 4%
+}

src/renderer/components/experimental-settings/experimental-settings.js

@@ -0,0 +1,73 @@
+import { closeSync, existsSync, openSync, rmSync } from 'fs'
+import Vue from 'vue'
+import { mapActions } from 'vuex'
+import FtSettingsSection from '../ft-settings-section/ft-settings-section.vue'
+import FtFlexBox from '../ft-flex-box/ft-flex-box.vue'
+import FtToggleSwitch from '../ft-toggle-switch/ft-toggle-switch.vue'
+import FtPrompt from '../ft-prompt/ft-prompt.vue'
+
+export default Vue.extend({
+  name: 'ExperimentalSettings',
+  components: {
+    'ft-settings-section': FtSettingsSection,
+    'ft-flex-box': FtFlexBox,
+    'ft-toggle-switch': FtToggleSwitch,
+    'ft-prompt': FtPrompt
+  },
+  data: function () {
+    return {
+      replaceHttpCacheLoading: true,
+      replaceHttpCache: false,
+      replaceHttpCachePath: '',
+      showRestartPrompt: false
+    }
+  },
+  mounted: function () {
+    this.getUserDataPath().then((userData) => {
+      this.replaceHttpCachePath = `${userData}/experiment-replace-http-cache`
+
+      this.replaceHttpCache = existsSync(this.replaceHttpCachePath)
+      this.replaceHttpCacheLoading = false
+    })
+  },
+  methods: {
+    updateReplaceHttpCache: function () {
+      this.replaceHttpCache = !this.replaceHttpCache
+
+      if (this.replaceHttpCache) {
+        // create an empty file
+        closeSync(openSync(this.replaceHttpCachePath, 'w'))
+      } else {
+        rmSync(this.replaceHttpCachePath)
+      }
+    },
+
+    handleRestartPrompt: function (value) {
+      this.replaceHttpCache = value
+      this.showRestartPrompt = true
+    },
+
+    handleReplaceHttpCache: function (value) {
+      this.showRestartPrompt = false
+
+      if (value === null || value === 'no') {
+        this.replaceHttpCache = !this.replaceHttpCache
+        return
+      }
+
+      if (this.replaceHttpCache) {
+        // create an empty file
+        closeSync(openSync(this.replaceHttpCachePath, 'w'))
+      } else {
+        rmSync(this.replaceHttpCachePath)
+      }
+
+      const { ipcRenderer } = require('electron')
+      ipcRenderer.send('relaunchRequest')
+    },
+
+    ...mapActions([
+      'getUserDataPath'
+    ])
+  }
+})

src/renderer/components/experimental-settings/experimental-settings.vue

@@ -0,0 +1,30 @@
+<template>
+  <ft-settings-section
+    :title="$t('Settings.Experimental Settings.Experimental Settings')"
+  >
+    <p class="experimental-warning">
+      {{ $t('Settings.Experimental Settings.Warning') }}
+    </p>
+    <ft-flex-box>
+      <ft-toggle-switch
+        tooltip-position="top"
+        :label="$t('Settings.Experimental Settings.Replace HTTP Cache')"
+        :compact="true"
+        :default-value="replaceHttpCache"
+        :disabled="replaceHttpCacheLoading"
+        :tooltip="$t('Tooltips.Experimental Settings.Replace HTTP Cache')"
+        @change="handleRestartPrompt"
+      />
+    </ft-flex-box>
+    <ft-prompt
+      v-if="showRestartPrompt"
+      :label="$t('Settings[\'The app needs to restart for changes to take effect. Restart and apply change?\']')"
+      :option-names="[$t('Yes'), $t('No')]"
+      :option-values="['yes', 'no']"
+      @click="handleReplaceHttpCache"
+    />
+  </ft-settings-section>
+</template>
+
+<script src="./experimental-settings.js" />
+<style scoped src="./experimental-settings.css" />

src/renderer/components/ft-toggle-switch/ft-toggle-switch.js

@@ -26,6 +26,10 @@ export default Vue.extend({
     tooltip: {
       type: String,
       default: ''
+    },
+    tooltipPosition: {
+      type: String,
+      default: 'bottom-left'
     }
   },
   data: function () {

src/renderer/components/ft-toggle-switch/ft-toggle-switch.vue

@@ -27,7 +27,7 @@
       <ft-tooltip
         v-if="tooltip !== ''"
         class="selectTooltip"
-        position="bottom-left"
+        :position="tooltipPosition"
         :tooltip="tooltip"
       />
     </label>

src/renderer/views/Settings/Settings.js

@@ -13,6 +13,7 @@ import DistractionSettings from '../../components/distraction-settings/distracti
 import ProxySettings from '../../components/proxy-settings/proxy-settings.vue'
 import SponsorBlockSettings from '../../components/sponsor-block-settings/sponsor-block-settings.vue'
 import ParentControlSettings from '../../components/parental-control-settings/parental-control-settings.vue'
+import ExperimentalSettings from '../../components/experimental-settings/experimental-settings.vue'
 
 export default Vue.extend({
   name: 'Settings',
@@ -30,7 +31,8 @@ export default Vue.extend({
     'proxy-settings': ProxySettings,
     'sponsor-block-settings': SponsorBlockSettings,
     'download-settings': DownloadSettings,
-    'parental-control-settings': ParentControlSettings
+    'parental-control-settings': ParentControlSettings,
+    'experimental-settings': ExperimentalSettings
   },
   computed: {
     usingElectron: function () {

src/renderer/views/Settings/Settings.vue

@@ -23,6 +23,8 @@
     <parental-control-settings />
     <hr>
     <sponsor-block-settings />
+    <hr v-if="usingElectron">
+    <experimental-settings v-if="usingElectron" />
   </div>
 </template>
 

static/locales/en-US.yaml

@@ -406,6 +406,10 @@ Settings:
     Download Behavior: Download Behavior
     Download in app: Download in app
     Open in web browser: Open in web browser
+  Experimental Settings:
+    Experimental Settings: Experimental Settings
+    Warning: These settings are experimental, they make cause crashes while enabled. Making backups is highly recommended. Use at your own risk!
+    Replace HTTP Cache: Replace HTTP Cache
 About:
   #On About page
   About: About
@@ -774,6 +778,8 @@ Tooltips:
   Privacy Settings:
     Remove Video Meta Files: When enabled, FreeTube automatically deletes meta files created during video playback,
       when the watch page is closed.
+  Experimental Settings:
+    Replace HTTP Cache: Disables Electron's disk based HTTP cache and enables a custom in-memory image cache. Will lead to increased RAM usage.
 
 # Toast Messages
 Local API Error (Click to copy): Local API Error (Click to copy)