Rate Limiting

The library integrates with Symfony Rate Limiter to manage how often the data source is contacted when cache entries expire.

Integration

The library uses Symfony\Component\RateLimiter\RateLimiterFactoryInterface. This allows the manager to create specific limiters dynamically based on the rate_limit_key provided in the options.

Example with Symfony Rate Limiter

use Symfony\Component\RateLimiter\RateLimiterFactory;
use Symfony\Component\RateLimiter\Storage\InMemoryStorage;

$factory = new RateLimiterFactory([
    'id' => 'my_api',
    'policy' => 'token_bucket',
    'limit' => 5,
    'rate' => ['interval' => '10 seconds'],
], new InMemoryStorage());

// Pass the factory, not a specific limiter
$manager = new AsyncCacheManager(
    AsyncCacheManager::configure($cache)
        ->withRateLimiter($factory)
        ->build()
);

How It Interacts with Cache

When a cache item is stale and a refresh is needed: 1. The manager checks if a rate_limit_key is provided in CacheOptions. 2. It uses the factory to create/get a limiter for that key: $factory->create($rate_limit_key). 3. It calls ->consume(1) on that limiter. 4. If Accepted: The pipeline continues to fetch fresh data. 5. If Rejected: - If serve_stale_if_limited is true and stale data exists in the context, the stale data is returned immediately. - Otherwise, a RateLimitException is thrown.

Manual Reset

If you need to manually reset the limit for a specific key (e.g. after an administrative action), use the manager:

$manager->resetRateLimit('user_123');

Benefit of Symfony Integration

By using Symfony Rate Limiter, you gain access to various storage backends (Redis, Database, PHP-APC) and sophisticated policies (Token Bucket, Fixed Window, Sliding Window) without additional configuration in this library.