server/middlewares/cache.ts

   1 import * as express from 'express'
   2 import * as AsyncLock from 'async-lock'
   3 import { parseDurationToMs } from '../helpers/core-utils'
   4 import { Redis } from '../lib/redis'
   5 import { logger } from '../helpers/logger'
   6
   7 const lock = new AsyncLock({ timeout: 5000 })
   8
   9 function cacheRoute (lifetimeArg: string | number) {
  10   const lifetime = parseDurationToMs(lifetimeArg)
  11
  12   return async function (req: express.Request, res: express.Response, next: express.NextFunction) {
  13     const redisKey = Redis.Instance.generateCachedRouteKey(req)
  14
  15     try {
  16       await lock.acquire(redisKey, async (done) => {
  17         const cached = await Redis.Instance.getCachedRoute(req)
  18
  19         // Not cached
  20         if (!cached) {
  21           logger.debug('No cached results for route %s.', req.originalUrl)
  22
  23           const sendSave = res.send.bind(res)
  24           const redirectSave = res.redirect.bind(res)
  25
  26           res.send = (body) => {
  27             if (res.statusCode >= 200 && res.statusCode < 400) {
  28               const contentType = res.get('content-type')
  29
  30               Redis.Instance.setCachedRoute(req, body, lifetime, contentType, res.statusCode)
  31                    .then(() => done())
  32                    .catch(err => {
  33                      logger.error('Cannot cache route.', { err })
  34                      return done(err)
  35                    })
  36             } else {
  37               done()
  38             }
  39
  40             return sendSave(body)
  41           }
  42
  43           res.redirect = url => {
  44             done()
  45
  46             return redirectSave(url)
  47           }
  48
  49           return next()
  50         }
  51
  52         if (cached.contentType) res.set('content-type', cached.contentType)
  53
  54         if (cached.statusCode) {
  55           const statusCode = parseInt(cached.statusCode, 10)
  56           if (!isNaN(statusCode)) res.status(statusCode)
  57         }
  58
  59         logger.debug('Use cached result for %s.', req.originalUrl)
  60         res.send(cached.body).end()
  61
  62         return done()
  63       })
  64     } catch (err) {
  65       logger.error('Cannot serve cached route.', { err })
  66       return next()
  67     }
  68   }
  69 }
  70
  71 // ---------------------------------------------------------------------------
  72
  73 export {
  74   cacheRoute
  75 }