a-simple-fs-cache.js

const fs = require('fs')
const path = require('path')
const cacheManager = require('cache-manager')
const fsStoreHash = require('cache-manager-fs-hash')
const CACHE_KEY = 'foo'
const STORAGE_PATH = (process.env.IS_OFFLINE) ? path.join(__dirname, '../tmp') : '/tmp'
const SECONDS = 60
const MINUTES = 60
const ONE_HOUR = SECONDS * MINUTES
const mbOfStorage = 512
/* initialize caching on disk */
const diskCache = cacheManager.caching({
  store: fsStoreHash,
  options: {
    /* TTL in seconds */
    ttl: ONE_HOUR,
    /* max size in bytes on disk */
    // maxsize: mbOfStorage * 1000 * 1000,
    path: STORAGE_PATH,
  }
})

async function usage() {
  const hasCache = await diskCache.get(CACHE_KEY)
  if (hasCache && hasCache.length) {
    /* If cache NOT empty return it */
    // console.log('Using cached value', hasCache)
    return hasCache
  }
  // else do fetch
  const data = await getStuff()
  // Then save cache
  console.log('Saving value')
  await diskCache.set(CACHE_KEY, data)
}

function getCacheSize(filePath) {
  return new Promise((resolve, reject) => {
    fs.stat(filePath, (err, stats) => {
      if (err) {
        return resolve({ sizeInBytes: 0, sizeInMB: 0 })
      }
      const byteSize = stats.size
      const megaByteSize = byteSize / (1024 * 1024)
      return resolve({
        sizeInBytes: byteSize,
        sizeInMB: megaByteSize
      })
    })
  })
}

package.json

{
  "dependencies": {
    "cache-manager": "^3.4.0",
    "cache-manager-fs-hash": "0.0.9"
  }
}