Handle concurrent requests in cache middleware

1 files changed, 33 insertions, 20 deletions

diff --git a/server/middlewares/cache.ts b/server/middlewares/cache.ts
index c589ef683..bf6659687 100644
--- a/server/middlewares/cache.ts
+++ b/server/middlewares/cache.ts
@@ -1,39 +1,52 @@
 import * as express from 'express'
+import * as AsyncLock from 'async-lock'
 import { Redis } from '../lib/redis'
 import { logger } from '../helpers/logger'
 
+const lock = new AsyncLock({ timeout: 5000 })
+
 function cacheRoute (lifetime: number) {
   return async function (req: express.Request, res: express.Response, next: express.NextFunction) {
-    const cached = await Redis.Instance.getCachedRoute(req)
+    const redisKey = Redis.Instance.buildCachedRouteKey(req)
+
+    await lock.acquire(redisKey, async (done) => {
+      const cached = await Redis.Instance.getCachedRoute(req)
 
-    // Not cached
-    if (!cached) {
-      logger.debug('Not cached result for route %s.', req.originalUrl)
+      // Not cached
+      if (!cached) {
+        logger.debug('Not cached result for route %s.', req.originalUrl)
 
-      const sendSave = res.send.bind(res)
+        const sendSave = res.send.bind(res)
 
-      res.send = (body) => {
-        if (res.statusCode >= 200 && res.statusCode < 400) {
-          const contentType = res.getHeader('content-type').toString()
-          Redis.Instance.setCachedRoute(req, body, lifetime, contentType, res.statusCode)
-               .catch(err => logger.error('Cannot cache route.', { err }))
+        res.send = (body) => {
+          if (res.statusCode >= 200 && res.statusCode < 400) {
+            const contentType = res.getHeader('content-type').toString()
+            Redis.Instance.setCachedRoute(req, body, lifetime, contentType, res.statusCode)
+                 .then(() => done())
+                 .catch(err => {
+                   logger.error('Cannot cache route.', { err })
+                   return done(err)
+                 })
+          }
+
+          return sendSave(body)
         }
 
-        return sendSave(body)
+        return next()
       }
 
-      return next()
-    }
+      if (cached.contentType) res.contentType(cached.contentType)
 
-    if (cached.contentType) res.contentType(cached.contentType)
+      if (cached.statusCode) {
+        const statusCode = parseInt(cached.statusCode, 10)
+        if (!isNaN(statusCode)) res.status(statusCode)
+      }
 
-    if (cached.statusCode) {
-      const statusCode = parseInt(cached.statusCode, 10)
-      if (!isNaN(statusCode)) res.status(statusCode)
-    }
+      logger.debug('Use cached result for %s.', req.originalUrl)
+      res.send(cached.body).end()
 
-    logger.debug('Use cached result for %s.', req.originalUrl)
-    return res.send(cached.body).end()
+      return done()
+    })
   }
 }