Laravel Cache::grace() return stale and dispatch revalidate #php

gracemacro.php

<?php

/**
 * Graceful cache retrieval and updating macro.
 *
 * First, tries to retrieve the cached value. If not found, uses a grace value.
 * Schedules a background job for updating the cache if grace value is found.
 *
 * @param  string  $key      The cache key to retrieve.
 * @param  int  $ttl      Time to live for the cache, in seconds.
 * @param  callable  $callback Function to call for generating cache value.
 * @return mixed           The cached data or fresh data from the callback.
 *
 * Pseudocode:
 * 1. Attempt to retrieve the value from the cache using the provided key.
 *    - If the value exists, return it.
 * 2. If the value is not in the cache, attempt to retrieve the grace value.
 * 3. If the grace value exists:
 *    - Schedule a background job to update the main cache value using the callback.
 *    - Return the grace value.
 * 4. If the grace value does not exist:
 *    - Execute the callback to generate a new value.
 *    - Return the new value.
 *
 * Usage Example:
 * Suppose you want to cache user data and refresh it every 10 minutes. You can use the 'grace' macro like this:
 *
 * $userData = Cache::grace('user_'. $userId, 600, function () use ($userId) {
 *     // Code to fetch user data from database or external service
 *     return User::find($userId);
 * });
 *
 * This will try to get 'user_$userId' from the cache. If it's not found, it will try to use the grace value.
 * If neither is available, it will fetch the user data using the provided callback and cache it for future requests.
 */
Cache::macro('grace', function ($key, $ttl, $callback) {
    // Attempt to retrieve the cached value for the given key.
    $value = Cache::get($key);

    // If the cached value exists, return it immediately.
    if ($value !== null) {
        return $value;
    }

    // Retrieve a fallback value (grace value) from the cache.
    $graceValue = Cache::get('grace.'.$key);

    // If grace value exists, schedule a background job to refresh the cache.
    if ($graceValue !== null) {
        // The cache will be updated after the response is sent to the user.
        // App::terminating(fn () => Cache::put($key, $callback(), $ttl));
        dispatch(function () use ($key, $ttl, $callback) {
            Cache::put($key, $callback(), $ttl);
            Cache::put('grace.'.$key, $callback(), $ttl * 2);
        });
    }

    // Return the grace value or, if not present, execute the callback for a fresh result.
    return $graceValue ?? $callback();
});