*/ private readonly \SplQueue $queue; /** * @param positive-int $concurrencyLimit */ public function __construct(private readonly int $concurrencyLimit) { /** @psalm-suppress DocblockTypeContradiction */ if ($this->concurrencyLimit <= 0) { throw new \ValueError('The concurrency limit must be a positive integer'); } $this->queue = new \SplQueue(); } public function handleRequest(Request $request, RequestHandler $requestHandler): Response { if (++$this->pendingRequests > $this->concurrencyLimit) { $deferred = new DeferredFuture(); $this->queue->push($deferred); $deferred->getFuture()->await(); } try { return $requestHandler->handleRequest($request); } finally { --$this->pendingRequests; if (!$this->queue->isEmpty()) { $this->queue->shift()->complete(); } } } }