feat: use SimpleDataStore for album pages cache

this should have better lifecycle and use less memory over time, since
we can define max items in cache
at the moment hard-coded to 10 cached pages (inclusive of nojs version
if ever generated)

controllers/albumsController.js

@@ -296,7 +296,7 @@ self.disable = async (req, res, next) => {
         .first()
         .update('enabled', 0)
     }
-    utils.invalidateAlbumsCache([id])
+    utils.deleteStoredAlbumRenders([id])
     utils.invalidateStatsCache('albums')
 
     try {
@@ -387,7 +387,7 @@ self.edit = async (req, res, next) => {
     await utils.db.table('albums')
       .where(filter)
       .update(update)
-    utils.invalidateAlbumsCache([id])
+    utils.deleteStoredAlbumRenders([id])
     utils.invalidateStatsCache('albums')
 
     if (req.body.requestLink) {
@@ -676,7 +676,7 @@ self.addFiles = async (req, res, next) => {
     await utils.db.table('albums')
       .whereIn('id', albumids)
       .update('editedAt', Math.floor(Date.now() / 1000))
-    utils.invalidateAlbumsCache(albumids)
+    utils.deleteStoredAlbumRenders(albumids)
 
     await res.json({ success: true, failed })
   } catch (error) {

controllers/authController.js

@@ -317,7 +317,7 @@ self.deleteUser = async (req, res, next) => {
       await utils.db.table('albums')
         .whereIn('id', albumids)
         .del()
-      utils.invalidateAlbumsCache(albumids)
+      utils.deleteStoredAlbumRenders(albumids)
 
       // Unlink their archives
       await Promise.all(albums.map(async album => {

controllers/uploadController.js

@@ -926,7 +926,7 @@ self.storeFilesToDb = async (req, res, user, infoMap) => {
       await utils.db.table('albums')
         .whereIn('id', authorizedIds)
         .update('editedAt', Math.floor(Date.now() / 1000))
-      utils.invalidateAlbumsCache(authorizedIds)
+      utils.deleteStoredAlbumRenders(authorizedIds)
     }
   }
 

controllers/utilsController.js

@@ -12,6 +12,7 @@ const perms = require('./permissionController')
 const apiErrorsHandler = require('./handlers/apiErrorsHandler')
 const ClientError = require('./utils/ClientError')
 const ServerError = require('./utils/ServerError')
+const SimpleDataStore = require('./utils/SimpleDataStore')
 const config = require('./../config')
 const logger = require('./../logger')
 
@@ -59,7 +60,6 @@ const self = {
   thumbsSize: config.uploads.generateThumbs.size || 200,
   ffprobe: promisify(ffmpeg.ffprobe),
 
-  albumsCache: {},
   timezoneOffset: new Date().getTimezoneOffset(),
 
   retentions: {
@@ -68,6 +68,10 @@ const self = {
     default: {}
   },
 
+  albumRenderStore: new SimpleDataStore({
+    limit: 10,
+    strategy: SimpleDataStore.STRATEGIES[0]
+  }),
   contentDispositionStore: null
 }
 
@@ -678,7 +682,7 @@ self.bulkDeleteFromDb = async (field, values, user) => {
           .whereIn('id', albumids)
           .update('editedAt', Math.floor(Date.now() / 1000))
           .catch(logger.error)
-        self.invalidateAlbumsCache(albumids)
+        self.deleteStoredAlbumRenders(albumids)
       }
 
       // Purge Cloudflare's cache if necessary, but do not wait
@@ -769,10 +773,10 @@ self.bulkDeleteExpired = async (dryrun, verbose) => {
   return result
 }
 
-self.invalidateAlbumsCache = albumids => {
+self.deleteStoredAlbumRenders = albumids => {
   for (const albumid of albumids) {
-    delete self.albumsCache[albumid]
-    delete self.albumsCache[`${albumid}-nojs`]
+    self.albumRenderStore.delete(`${albumid}`)
+    self.albumRenderStore.delete(`${albumid}-nojs`)
   }
 }
 

routes/album.js

@@ -26,17 +26,13 @@ routes.get('/a/:identifier', async (req, res, next) => {
 
   let cacheid
   if (process.env.NODE_ENV !== 'development') {
-    // Cache ID - we initialize a separate cache for No-JS version
-    cacheid = nojs ? `${album.id}-nojs` : album.id
+    // Cache ID - we use a separate cache key for No-JS version
+    cacheid = `${album.id}${nojs ? '-nojs' : ''}`
 
-    if (!utils.albumsCache[cacheid]) {
-      utils.albumsCache[cacheid] = {
-        cache: null,
-        generating: false
-      }
-    }
-
-    if (!utils.albumsCache[cacheid].cache && utils.albumsCache[cacheid].generating) {
+    const cache = utils.albumRenderStore.get(cacheid)
+    if (cache) {
+      return res.send(cache)
+    } else if (cache === null) {
       return res.render('album-notice', {
         config,
         utils,
@@ -44,11 +40,9 @@ routes.get('/a/:identifier', async (req, res, next) => {
         album,
         notice: 'This album\'s public page is still being generated. Please try again later.'
       })
-    } else if (utils.albumsCache[cacheid].cache) {
-      return res.send(utils.albumsCache[cacheid].cache)
     }
 
-    utils.albumsCache[cacheid].generating = true
+    utils.albumRenderStore.hold(cacheid)
   }
 
   const files = await utils.db.table('files')
@@ -90,13 +84,16 @@ routes.get('/a/:identifier', async (req, res, next) => {
   }, (error, html) => {
     const data = error ? null : html
     if (cacheid) {
-      utils.albumsCache[cacheid].cache = data
-      utils.albumsCache[cacheid].generating = false
+      // Only store rendered page if it did not error out and album actually have files
+      if (data && files.length) {
+        utils.albumRenderStore.set(cacheid, data)
+      } else {
+        utils.albumRenderStore.delete(cacheid)
+      }
     }
 
     // Express should already send error to the next handler
-    if (error) return
-    return res.send(data)
+    if (!error) return res.send(data)
   })
 })