With the increasing use of client-side caching, developers often encounter situations where multiple JavaScript requests are made concurrently and can lead to cache conflicts. These conflicts occur when multiple requests to fetch the same resource are made simultaneously, and each request tries to write the result to the cache.

The JavaScript Cache API provides a way to cache responses to network requests and enables offline access to web applications. However, it does not handle cache conflicts out-of-the-box. In this blog post, we will explore how to handle cache conflicts when dealing with concurrent requests using the JavaScript Cache API.

Understanding cache conflicts

To understand cache conflicts, let’s consider a scenario where two concurrent requests are made to fetch the same resource from the cache. Both requests will check if the resource is present in the cache and, if not, make a network request to fetch it.

If both requests find that the resource is not in the cache, they will both initiate separate network requests to fetch the resource. When the responses arrive, each request will try to write the response to the cache. This is where the conflict occurs, as only one request should write the response to the cache while the other request should use the cached response.

Solution: Using a mutex lock

To handle cache conflicts, we can use a mutual exclusive (mutex) lock mechanism. A mutex lock ensures that only one request can write to the cache at a time, while other requests wait for the lock to be released.

Here’s an example of how to implement a mutex lock in JavaScript:

const lock = new Promise((resolve) => {
  // Acquire the lock and resolve when unlocked
  // You can use any mechanism to implement the lock
  // For example, using a flag or using a more sophisticated locking mechanism
  acquireLock(resolve);
});

async function fetchResource(request) {
  // Wait until the lock is released
  await lock;

  const cache = await caches.open('my-cache');
  const cachedResponse = await cache.match(request);

  if (cachedResponse) {
    return cachedResponse; // Return the cached response
  }

  const networkResponse = await fetch(request);
  cache.put(request, networkResponse.clone());

  // Release the lock once the response is written to the cache
  releaseLock();

  return networkResponse;
}

In the code above, the lock promise is used as a mutex lock. The acquireLock function is responsible for acquiring the lock, and the releaseLock function releases the lock after the response is written to the cache.

By using this mutex lock mechanism, we ensure that only one request can write to the cache at a time, preventing cache conflicts.

Conclusion

When working with the JavaScript Cache API and dealing with concurrent requests, cache conflicts can occur if multiple requests try to write to the cache simultaneously. To handle these conflicts, we can use a mutex lock mechanism to ensure that only one request can write to the cache at a time.

By implementing a mutex lock, we can prevent cache conflicts and ensure consistent caching behavior in our web applications.

#references #JavaScript #Cache-API