2 files changed, 270 insertions, 0 deletions

diff --git a/server/middlewares/cache/shared/api-cache.ts b/server/middlewares/cache/shared/api-cache.ts
new file mode 100644
index 000000000..f9f7b1b67
--- /dev/null
+++ b/server/middlewares/cache/shared/api-cache.ts
@@ -0,0 +1,269 @@
+// Thanks: https://github.com/kwhitley/apicache
+// We duplicated the library because it is unmaintened and prevent us to upgrade to recent NodeJS versions
+
+import * as express from 'express'
+import { OutgoingHttpHeaders } from 'http'
+import { isTestInstance, parseDurationToMs } from '@server/helpers/core-utils'
+import { logger } from '@server/helpers/logger'
+import { Redis } from '@server/lib/redis'
+import { HttpStatusCode } from '@shared/models'
+
+export interface APICacheOptions {
+  headerBlacklist?: string[]
+  excludeStatus?: HttpStatusCode[]
+}
+
+interface CacheObject {
+  status: number
+  headers: OutgoingHttpHeaders
+  data: any
+  encoding: BufferEncoding
+  timestamp: number
+}
+
+export class ApiCache {
+
+  private readonly options: APICacheOptions
+  private readonly timers: { [ id: string ]: NodeJS.Timeout } = {}
+
+  private index: { all: string[] } = { all: [] }
+
+  constructor (options: APICacheOptions) {
+    this.options = {
+      headerBlacklist: [],
+      excludeStatus: [],
+
+      ...options
+    }
+  }
+
+  buildMiddleware (strDuration: string) {
+    const duration = parseDurationToMs(strDuration)
+
+    return (req: express.Request, res: express.Response, next: express.NextFunction) => {
+      const key = Redis.Instance.getPrefix() + 'api-cache-' + req.originalUrl
+      const redis = Redis.Instance.getClient()
+
+      if (!redis.connected) return this.makeResponseCacheable(res, next, key, duration)
+
+      try {
+        redis.hgetall(key, (err, obj) => {
+          if (!err && obj && obj.response) {
+            return this.sendCachedResponse(req, res, JSON.parse(obj.response), duration)
+          }
+
+          return this.makeResponseCacheable(res, next, key, duration)
+        })
+      } catch (err) {
+        return this.makeResponseCacheable(res, next, key, duration)
+      }
+    }
+  }
+
+  private shouldCacheResponse (response: express.Response) {
+    if (!response) return false
+    if (this.options.excludeStatus.includes(response.statusCode)) return false
+
+    return true
+  }
+
+  private addIndexEntries (key: string) {
+    this.index.all.unshift(key)
+  }
+
+  private filterBlacklistedHeaders (headers: OutgoingHttpHeaders) {
+    return Object.keys(headers)
+      .filter(key => !this.options.headerBlacklist.includes(key))
+      .reduce((acc, header) => {
+        acc[header] = headers[header]
+
+        return acc
+      }, {})
+  }
+
+  private createCacheObject (status: number, headers: OutgoingHttpHeaders, data: any, encoding: BufferEncoding) {
+    return {
+      status,
+      headers: this.filterBlacklistedHeaders(headers),
+      data,
+      encoding,
+
+      // Seconds since epoch, used to properly decrement max-age headers in cached responses.
+      timestamp: new Date().getTime() / 1000
+    } as CacheObject
+  }
+
+  private cacheResponse (key: string, value: object, duration: number) {
+    const redis = Redis.Instance.getClient()
+
+    if (redis.connected) {
+      try {
+        redis.hset(key, 'response', JSON.stringify(value))
+        redis.hset(key, 'duration', duration + '')
+        redis.expire(key, duration / 1000)
+      } catch (err) {
+        logger.error('Cannot set cache in redis.', { err })
+      }
+    }
+
+    // add automatic cache clearing from duration, includes max limit on setTimeout
+    this.timers[key] = setTimeout(() => this.clear(key), Math.min(duration, 2147483647))
+  }
+
+  private accumulateContent (res: express.Response, content: any) {
+    if (!content) return
+
+    if (typeof content === 'string') {
+      res.locals.apicache.content = (res.locals.apicache.content || '') + content
+      return
+    }
+
+    if (Buffer.isBuffer(content)) {
+      let oldContent = res.locals.apicache.content
+
+      if (typeof oldContent === 'string') {
+        oldContent = Buffer.from(oldContent)
+      }
+
+      if (!oldContent) {
+        oldContent = Buffer.alloc(0)
+      }
+
+      res.locals.apicache.content = Buffer.concat(
+        [ oldContent, content ],
+        oldContent.length + content.length
+      )
+
+      return
+    }
+
+    res.locals.apicache.content = content
+  }
+
+  private makeResponseCacheable (res: express.Response, next: express.NextFunction, key: string, duration: number) {
+    const self = this
+
+    res.locals.apicache = {
+      write: res.write,
+      writeHead: res.writeHead,
+      end: res.end,
+      cacheable: true,
+      content: undefined,
+      headers: {}
+    }
+
+    // Patch express
+    res.writeHead = function () {
+      if (self.shouldCacheResponse(res)) {
+        res.setHeader('cache-control', 'max-age=' + (duration / 1000).toFixed(0))
+      } else {
+        res.setHeader('cache-control', 'no-cache, no-store, must-revalidate')
+      }
+
+      res.locals.apicache.headers = Object.assign({}, res.getHeaders())
+      return res.locals.apicache.writeHead.apply(this, arguments as any)
+    }
+
+    res.write = function (chunk: any) {
+      self.accumulateContent(res, chunk)
+      return res.locals.apicache.write.apply(this, arguments as any)
+    }
+
+    res.end = function (content: any, encoding: BufferEncoding) {
+      if (self.shouldCacheResponse(res)) {
+        self.accumulateContent(res, content)
+
+        if (res.locals.apicache.cacheable && res.locals.apicache.content) {
+          self.addIndexEntries(key)
+
+          const headers = res.locals.apicache.headers || res.getHeaders()
+          const cacheObject = self.createCacheObject(
+            res.statusCode,
+            headers,
+            res.locals.apicache.content,
+            encoding
+          )
+          self.cacheResponse(key, cacheObject, duration)
+        }
+      }
+
+      res.locals.apicache.end.apply(this, arguments as any)
+    } as any
+
+    next()
+  }
+
+  private sendCachedResponse (request: express.Request, response: express.Response, cacheObject: CacheObject, duration: number) {
+    const headers = response.getHeaders()
+
+    if (isTestInstance()) {
+      Object.assign(headers, {
+        'x-api-cache-cached': 'true'
+      })
+    }
+
+    Object.assign(headers, this.filterBlacklistedHeaders(cacheObject.headers || {}), {
+      // Set properly decremented max-age header
+      // This ensures that max-age is in sync with the cache expiration
+      'cache-control':
+        'max-age=' +
+        Math.max(
+          0,
+          (duration / 1000 - (new Date().getTime() / 1000 - cacheObject.timestamp))
+        ).toFixed(0)
+    })
+
+    // unstringify buffers
+    let data = cacheObject.data
+    if (data && data.type === 'Buffer') {
+      data = typeof data.data === 'number'
+        ? Buffer.alloc(data.data)
+        : Buffer.from(data.data)
+    }
+
+    // Test Etag against If-None-Match for 304
+    const cachedEtag = cacheObject.headers.etag
+    const requestEtag = request.headers['if-none-match']
+
+    if (requestEtag && cachedEtag === requestEtag) {
+      response.writeHead(304, headers)
+      return response.end()
+    }
+
+    response.writeHead(cacheObject.status || 200, headers)
+
+    return response.end(data, cacheObject.encoding)
+  }
+
+  private clear (target: string) {
+    const redis = Redis.Instance.getClient()
+
+    if (target) {
+      clearTimeout(this.timers[target])
+      delete this.timers[target]
+
+      try {
+        redis.del(target)
+      } catch (err) {
+        logger.error('Cannot delete %s in redis cache.', target, { err })
+      }
+
+      this.index.all = this.index.all.filter(key => key !== target)
+    } else {
+      for (const key of this.index.all) {
+        clearTimeout(this.timers[key])
+        delete this.timers[key]
+
+        try {
+          redis.del(key)
+        } catch (err) {
+          logger.error('Cannot delete %s in redis cache.', key, { err })
+        }
+      }
+
+      this.index.all = []
+    }
+
+    return this.index
+  }
+}
diff --git a/server/middlewares/cache/shared/index.ts b/server/middlewares/cache/shared/index.ts
new file mode 100644
index 000000000..c707eaf7a
--- /dev/null
+++ b/server/middlewares/cache/shared/index.ts
@@ -0,0 +1 @@
+export * from './api-cache'