initial commit

Author: jkyberneees

get-keys.js

@@ -0,0 +1,14 @@
+const matcher = require('matcher')
+
+const getKeys = (cache, pattern) => new Promise((resolve) => {
+  if (pattern.indexOf('*') > -1) {
+    const args = [pattern, (_, res) => resolve(matcher(res, [pattern]))]
+    if (cache.store.name !== 'redis') {
+      args.shift()
+    }
+
+    cache.keys.apply(cache, args)
+  } else resolve([pattern])
+})
+
+module.exports = getKeys

index.js

@@ -0,0 +1,78 @@
+const CacheManager = require('cache-manager')
+const iu = require('middleware-if-unless')
+const ms = require('ms')
+const onEnd = require('on-http-end')
+const getKeys = require('./get-keys')
+
+const X_CACHE_EXPIRE = 'x-cache-expire'
+const X_CACHE_TIMEOUT = 'x-cache-timeout'
+const X_CACHE_HIT = 'x-cache-hit'
+
+const middleware = (opts) => async (req, res, next) => {
+  opts = Object.assign({
+    stores: [CacheManager.caching({ store: 'memory', max: 1000, ttl: 30 })]
+  }, opts)
+
+  // creating multi-cache instance
+  const mcache = CacheManager.multiCaching(opts.stores)
+
+  if (req.cacheDisabled) return
+
+  let { url, cacheAppendKey = req => '' } = req
+  cacheAppendKey = await cacheAppendKey(req)
+
+  const key = req.method + url + cacheAppendKey
+  // ref cache key on req object
+  req.cacheKey = key
+
+  // try to retrieve cached response
+  const cached = await get(mcache, key)
+
+  if (cached) {
+    // respond from cache if there is a hit
+    let { status, headers, data } = JSON.parse(cached)
+    if (typeof data === 'object' && data.type === 'Buffer') {
+      data = Buffer.from(data.data)
+    }
+    headers[X_CACHE_HIT] = '1'
+
+    // set cached response headers
+    Object.keys(headers).forEach(header => res.setHeader(header, headers[header]))
+
+    // send cached payload
+    req.cacheHit = true
+    res.statusCode = status
+    res.end(data)
+
+    return
+  }
+
+  onEnd(res, (payload) => {
+    // avoid double caching
+    if (req.cacheHit) return
+
+    if (payload.headers[X_CACHE_EXPIRE]) {
+      // support service level expiration
+      const keysPattern = payload.headers[X_CACHE_EXPIRE]
+      // delete keys on all cache tiers
+      opts.stores.forEach(cache => getKeys(cache, keysPattern).then(keys => mcache.del(keys)))
+    } else if (payload.headers[X_CACHE_TIMEOUT]) {
+      // we need to cache response
+      mcache.set(req.cacheKey, JSON.stringify(payload), {
+        // @NOTE: cache-manager uses seconds as TTL unit
+        // restrict to min value "1 second"
+        ttl: Math.max(ms(payload.headers[X_CACHE_TIMEOUT]), 1000) / 1000
+      })
+    }
+  })
+
+  return next()
+}
+
+const get = (cache, key) => new Promise((resolve) => {
+  cache.getAndPassUp(key, (_, res) => {
+    resolve(res)
+  })
+})
+
+module.exports = iu(middleware)