mongooseCache.ts

/**
 * This file is responsible for caching mongo model instance for specific time.
 * Usage example:
 * Store.findOne(query, fields).cacheResults(1 * 60).exec(); // it'll cache result for specified seconds
 * Store.findOne(query, fields).removeCache().exec(); // it'll remove any existing cache
*/

// @ts-nocheck

import mongoose from 'mongoose';
import redisClient from './redisClient';

mongoose.Query.prototype.cacheResults = function (time: number) {
  this.cache_results = true;
  this.cacheTimeSeconds = time;
  return this;
};

mongoose.Query.prototype.removeCached = function () {
  this.remove_cached = true;
  return this;
};
mongoose.Query.prototype.getCacheKey = function () {
  const key = JSON.stringify({
    collectionName: this.mongooseCollection.name,
    op: this.op,
    options: this.getOptions(),
    filter: this.getFilter(),
    projection: this.projection(),
    populatedPaths: this.getPopulatedPaths(),
  });
  return key;
};
const exec = mongoose.Query.prototype.exec;

mongoose.Query.prototype.exec = async function () {
  if (this.remove_cached) {
    // remove_cached is true so remove cache for the key
    const key = this.getCacheKey();
    redisClient.del(key);
  }
  if (this.cache_results) {
    // cache_results is true so cache result for the key
    const key = this.getCacheKey();

    const cachedResults = await redisClient.get(key);

    if (cachedResults) {
      // if you found cached results return it;
      const result = JSON.parse(cachedResults);

      const options = this.getOptions();
      const projection = this.projection();
      // create model instance again from the results so that you get all the model functionalities with cached data
      return Array.isArray(result)
        ? // eslint-disable-next-line new-cap
        result.map((document) => new this.model(document, projection, options))
        : // eslint-disable-next-line new-cap
        new this.model(result, projection, options);
    } else {
      // get results from Database then cache it
      const result = await exec.apply(this, arguments);
      redisClient.set(key, JSON.stringify(result), 'EX', this.cacheTimeSeconds);

      return result;
    }
  } else {
    return exec.apply(this, arguments);
  }
};

Thanks but, not working with populate ?

I am trying to implement exactly the same logic in my app but
const result = await exec.apply(this, arguments);
this part of the code is giving me null in case of findOne and find calls even when matching documents are present in the DB
any idea how to overcome this problem?