memcached-store.js

const _ = require('lodash');

export default class MemcachedStore {
  constructor (memcached, { keyPrefix, ttl = 15 * 60 }) {
    this.memcached = memcached;
    this.keyPrefix = keyPrefix;
    this.ttl = ttl;
    this.queuedGets = {};
  }

  toCacheKey(key) {
    if (!this.keyPrefix) return key;
    return `${this.keyPrefix}:${key}`;
  }

  get(key) {
    const cacheKey = this.toCacheKey(key);
    return new Promise((resolve, reject) => {
      if (Object.keys(this.queuedGets).length === 0) {
        process.nextTick(this.executeMulti.bind(this));
      }
      if (!this.queuedGets[cacheKey]) {
        this.queuedGets[cacheKey] = { resolves: [], rejects: [] };
      }
      this.queuedGets[cacheKey].resolves.push(resolve);
      this.queuedGets[cacheKey].rejects.push(reject);
    });
  }

  executeMulti() {
    const gets = this.queuedGets;
    this.queuedGets = {};
    console.log(_.mapValues(gets, ({ key }) => key));
    this.memcached.getMulti(Object.keys(gets), (err, data) => {
      if (err) {
        _.mapValues(gets, ({ rejects }) => rejects.forEach(r => r(err)));
        return;
      }
      _.toPairs(gets).forEach(
        ([key, { resolves }]) => resolves.forEach(r => r(data[key]))
      );
    });
  }

  set (key, value, ttl) {
    ttl = ttl || this.ttl;
    const cacheKey = this.toCacheKey(key);
    return new Promise((resolve, reject) => {
      this.memcached.set(cacheKey, value, ttl, (err) => {
        if (err) {
          reject(err);
          return;
        }
        resolve();
      });
    });
  }
}