feat: in-memory caching of content-disposition

please read config.sample.js
ignore if not serving files with node or not having the option turned on

config.sample.js

@@ -38,11 +38,25 @@ module.exports = {
 
   /*
     If you serve files with node, you can optionally choose to set Content-Disposition header
-    into their original file names. This allows users to save files into their original file names.
+    with their original file names. This allows users to download files into their original file names.
 
-    This will query the DB every time users access uploaded files as there's no caching mechanism.
+    "contentDispositionOptions" configures in-memory caching options,
+    as it would otherwise have to query database every single time.
+
+    If enabled, but "contentDispositionOptions" is missing, it will use these defaults:
+    { limit: 50, strategy: 'lastGetTime' }
   */
   setContentDisposition: false,
+  contentDispositionOptions: {
+    limit: 50,
+    /*
+      Available strategies: lastGetTime, getsCount
+
+      lastGetTime: when cache store exceeds limit, remove cache with oldest access time
+      getsCount: when cache store exceeds limit, remove cache with fewest access count
+    */
+    strategy: 'lastGetTime'
+  },
 
   /*
     If you serve files with node, you can optionally choose to

controllers/utils/SimpleDataStore.js

@@ -0,0 +1,124 @@
+const STRATEGIES = [
+  'lastGetTime',
+  'getsCount'
+]
+
+class SimpleDataStore {
+  #store
+  #limit
+  #strategy
+
+  constructor (options = {}) {
+    if (typeof options !== 'object') {
+      throw new TypeError('Missing options object.')
+    }
+
+    if (!Number.isFinite(options.limit) || options.limit <= 1) {
+      throw new TypeError('Limit must be a finite number that is at least 2.')
+    }
+
+    if (!STRATEGIES.includes(options.strategy)) {
+      throw new TypeError(`Strategy must be one of these: ${STRATEGIES.map(s => `"${s}"`).join(', ')}.`)
+    }
+
+    this.#store = new Map()
+    this.#limit = options.limit
+    this.#strategy = options.strategy
+  }
+
+  clear () {
+    return this.#store.clear()
+  }
+
+  delete (key) {
+    return this.#store.delete(key)
+  }
+
+  get (key) {
+    const entry = this.#store.get(key)
+    if (typeof entry === 'undefined') return entry
+
+    switch (this.#strategy) {
+      case STRATEGIES[0]:
+        entry.stratval = Date.now()
+        break
+      case STRATEGIES[1]:
+        entry.stratval++
+        break
+    }
+
+    this.#store.set(key, entry)
+    return entry.value
+  }
+
+  getStalest () {
+    let stalest = null
+    switch (this.#strategy) {
+      // both "lastGetTime" and "getsCount" simply must find lowest value
+      // to determine the stalest entry
+      case STRATEGIES[0]:
+      case STRATEGIES[1]:
+        for (const entry of this.#store) {
+          if (!stalest || entry[1].stratval < stalest[1].stratval) {
+            stalest = entry
+          }
+        }
+        break
+    }
+
+    // return its key only
+    return stalest[0]
+  }
+
+  set (key, value) {
+    if (this.#store.size >= this.#limit) {
+      const stalest = this.getStalest()
+      if (stalest) {
+        this.#store.delete(stalest)
+      }
+    }
+
+    let stratval
+    switch (this.#strategy) {
+      case STRATEGIES[0]:
+        stratval = Date.now()
+        break
+      case STRATEGIES[1]:
+        stratval = 0
+        break
+    }
+
+    return this.#store.set(key, { value, stratval }) && true
+  }
+
+  get limit () {
+    return this.#limit
+  }
+
+  set limit (_) {
+    throw Error('This property is read-only.')
+  }
+
+  get size () {
+    return this.#store.size
+  }
+
+  set size (_) {
+    throw Error('This property is read-only.')
+  }
+
+  get strategy () {
+    return this.#strategy
+  }
+
+  set strategy (_) {
+    throw Error('This property is read-only.')
+  }
+
+  get store () {
+    // return shallow copy
+    return new Map(this.#store)
+  }
+}
+
+module.exports = SimpleDataStore

controllers/utilsController.js

@@ -66,7 +66,9 @@ const self = {
     enabled: false,
     periods: {},
     default: {}
-  }
+  },
+
+  contentDispositionStore: null
 }
 
 // Remember old renderer, if overridden, or proxy to default renderer
@@ -654,11 +656,15 @@ self.bulkDeleteFromDb = async (field, values, user) => {
         })
       }
 
-      // Push album ids
       unlinked.forEach(file => {
+        // Push album ids
         if (file.albumid && !albumids.includes(file.albumid)) {
           albumids.push(file.albumid)
         }
+        // Delete form Content-Disposition store if used
+        if (self.contentDispositionStore) {
+          self.contentDispositionStore.delete(file.name)
+        }
       })
 
       // Push unlinked files

lolisafe.js

@@ -139,6 +139,13 @@ const overrideContentTypes = contentTypes && contentTypes.length && function (re
 
 const initServeStaticUploads = (opts = {}) => {
   if (config.setContentDisposition) {
+    const SimpleDataStore = require('./controllers/utils/SimpleDataStore')
+    utils.contentDispositionStore = new SimpleDataStore(
+      config.contentDispositionOptions || {
+        limit: 50,
+        strategy: 'lastGetTime'
+      }
+    )
     opts.preSetHeaders = async (res, req, path, stat) => {
       try {
         // Do only if accessing files from uploads' root directory (i.e. not thumbs, etc.)
@@ -146,20 +153,33 @@ const initServeStaticUploads = (opts = {}) => {
         const relpath = path.replace(paths.uploads, '')
         if (relpath.indexOf('/', 1) === -1 && req.method === 'GET') {
           const name = relpath.substring(1)
-          const _file = await utils.db.table('files')
-            .where('name', name)
-            .select('original')
-            .first()
-          res.set('Content-Disposition', contentDisposition(_file.original, { type: 'inline' }))
+          let original = utils.contentDispositionStore.get(name)
+          if (!original) {
+            original = await utils.db.table('files')
+              .where('name', name)
+              .select('original')
+              .first()
+              .then(_file => {
+                utils.contentDispositionStore.set(name, _file.original)
+                return _file.original
+              })
+          }
+          if (original) {
+            res.set('Content-Disposition', contentDisposition(original, { type: 'inline' }))
+          }
         }
       } catch (error) {
         logger.error(error)
       }
     }
     // serveStatic is provided with @bobbywibowo/serve-static, a fork of express/serve-static.
-    // The fork allows specifying an async setHeaders function by the name preSetHeaders.
-    // It will await the said function before creating 'send' stream to client.
+    // The fork allows specifying an async function by the name preSetHeaders,
+    // which it will await before creating 'send' stream to client.
+    // This is necessary due to database queries being async tasks,
+    // and express/serve-static not having the functionality by default.
     safe.use('/', require('@bobbywibowo/serve-static')(paths.uploads, opts))
+    logger.debug('Inititated SimpleDataStore for Content-Disposition: ' +
+      `{ limit: ${utils.contentDispositionStore.limit}, strategy: "${utils.contentDispositionStore.strategy}" }`)
   } else {
     safe.use('/', express.static(paths.uploads, opts))
   }