Support lazy download thumbnails

server/lib/files-cache/shared/abstract-permanent-file-cache.ts

@@ -0,0 +1,119 @@
+import express from 'express'
+import { LRUCache } from 'lru-cache'
+import { logger } from '@server/helpers/logger'
+import { LRU_CACHE, STATIC_MAX_AGE } from '@server/initializers/constants'
+import { downloadImageFromWorker } from '@server/lib/worker/parent-process'
+import { HttpStatusCode } from '@shared/models'
+import { Model } from 'sequelize'
+
+type ImageModel = {
+  fileUrl: string
+  filename: string
+  onDisk: boolean
+
+  isOwned (): boolean
+  getPath (): string
+
+  save (): Promise<Model>
+}
+
+export abstract class AbstractPermanentFileCache <M extends ImageModel> {
+  // Unsafe because it can return paths that do not exist anymore
+  private readonly filenameToPathUnsafeCache = new LRUCache<string, string>({
+    max: LRU_CACHE.FILENAME_TO_PATH_PERMANENT_FILE_CACHE.MAX_SIZE
+  })
+
+  protected abstract getImageSize (image: M): { width: number, height: number }
+  protected abstract loadModel (filename: string): Promise<M>
+
+  constructor (private readonly directory: string) {
+
+  }
+
+  async lazyServe (options: {
+    filename: string
+    res: express.Response
+    next: express.NextFunction
+  }) {
+    const { filename, res, next } = options
+
+    if (this.filenameToPathUnsafeCache.has(filename)) {
+      return res.sendFile(this.filenameToPathUnsafeCache.get(filename), { maxAge: STATIC_MAX_AGE.SERVER })
+    }
+
+    const image = await this.loadModel(filename)
+    if (!image) return res.status(HttpStatusCode.NOT_FOUND_404).end()
+
+    if (image.onDisk === false) {
+      if (!image.fileUrl) return res.status(HttpStatusCode.NOT_FOUND_404).end()
+
+      try {
+        await this.downloadRemoteFile(image)
+      } catch (err) {
+        logger.warn('Cannot process remote image %s.', image.fileUrl, { err })
+
+        return res.status(HttpStatusCode.NOT_FOUND_404).end()
+      }
+    }
+
+    const path = image.getPath()
+    this.filenameToPathUnsafeCache.set(filename, path)
+
+    return res.sendFile(path, { maxAge: STATIC_MAX_AGE.LAZY_SERVER }, (err: any) => {
+      if (!err) return
+
+      this.onServeError({ err, image, next, filename })
+    })
+  }
+
+  private async downloadRemoteFile (image: M) {
+    logger.info('Download remote image %s lazily.', image.fileUrl)
+
+    await this.downloadImage({
+      filename: image.filename,
+      fileUrl: image.fileUrl,
+      size: this.getImageSize(image)
+    })
+
+    image.onDisk = true
+    image.save()
+      .catch(err => logger.error('Cannot save new image disk state.', { err }))
+  }
+
+  private onServeError (options: {
+    err: any
+    image: M
+    filename: string
+    next: express.NextFunction
+  }) {
+    const { err, image, filename, next } = options
+
+    // It seems this actor image is not on the disk anymore
+    if (err.status === HttpStatusCode.NOT_FOUND_404 && !image.isOwned()) {
+      logger.error('Cannot lazy serve image %s.', filename, { err })
+
+      this.filenameToPathUnsafeCache.delete(filename)
+
+      image.onDisk = false
+      image.save()
+        .catch(err => logger.error('Cannot save new image disk state.', { err }))
+    }
+
+    return next(err)
+  }
+
+  private downloadImage (options: {
+    fileUrl: string
+    filename: string
+    size: { width: number, height: number }
+  }) {
+    const downloaderOptions = {
+      url: options.fileUrl,
+      destDir: this.directory,
+      destName: options.filename,
+      size: options.size
+    }
+
+    return downloadImageFromWorker(downloaderOptions)
+  }
+}