Implementing a 5-Hour Cache With Node.js Using Node-Cache

To implement a caching mechanism in a Node.js application that refreshes every 5 hours, you can use various caching strategies. In this example, I’ll demonstrate how to use the node-cache library to set up such a cache. This library allows you to store key-value pairs in memory and automatically refresh them based on a time-to-live (TTL) setting.

Firstly, you'll need to install the node-cache package:

npm install node-cache

Next, you can create a caching mechanism like this:

const NodeCache = require('node-cache');

// Create a new cache instance
// TTL is set to 5 hours (in seconds)
const myCache = new NodeCache({ stdTTL: 18000, checkperiod: 3600 });

// A function to populate cache with some data
function loadDataIntoCache() {
  // Fetch or compute the data you want to cache
  const data = fetchOrComputeData();

  // Store data in the cache with a specific key
  myCache.set('myKey', data);
}

// Fetch or compute data
function fetchOrComputeData() {
  // Replace this with actual logic to fetch data from a database, API, etc.
  return { value: 'This is cached data' };
}

// Refresh the cache every 5 hours
function scheduleCacheRefresh() {
  // Refresh immediately
  loadDataIntoCache();

  // Set an interval to refresh the cache every 5 hours
  setInterval(() => {
    console.log('Refreshing cache...');
    loadDataIntoCache();
  }, 18000 * 1000); // 18000 seconds in milliseconds
}

// Retrieve data from cache function
function getCachedData(key) {
  const value = myCache.get(key);
  if (value) {
    console.log('Cache hit. Returning cached data...');
    return value;
  }

  console.log('Cache miss. Loading data...');
  const data = fetchOrComputeData();
  myCache.set(key, data);
  return data;
}

// Example usage: schedule the cache refresh to start caching and refreshing the data
scheduleCacheRefresh();

// Example usage: get data from the cache
const cachedData = getCachedData('myKey');
console.log(cachedData);

Explanation

1. NodeCache Initialization: We create a new cache with a TTL of 5 hours (18,000 seconds) and a check period to clean old cache entries.

2. Data Loading Function: loadDataIntoCache function fetches data and stores it in the cache. This function could be used to fetch from a database, API, or any other source.

3. Schedule Cache Refresh: We create an interval that calls loadDataIntoCache every 5 hours to refresh the data.

4. Retrieve Data from Cache: The getCachedData function tries to get data from the cache. If it’s not available, it fetches new data, stores it, and returns it.

This implementation is quite basic and suited for simple use cases. For more advanced use cases, consider using distributed caching solutions like Redis or Memcached, especially when scaling across multiple instances of your Node.js application.