Pool::tryAcquire

(PHP 8.6+, True Async 1.0)

public Pool::tryAcquire(): mixed

Attempts to acquire a resource from the pool without blocking. If a free resource is available or the max limit has not been reached, returns the resource immediately. Otherwise, returns null.

Parameters

This method takes no parameters.

Return Value

Returns a resource from the pool or null if no free resources are available and the maximum limit has been reached.

Examples

Example #1 Attempting to acquire a resource

<?php

use Async\Pool;

$pool = new Pool(
    factory: fn() => new PDO('mysql:host=localhost;dbname=app', 'user', 'pass'),
    max: 5
);

$conn = $pool->tryAcquire();

if ($conn === null) {
    echo "All connections are busy, try again later\n";
} else {
    try {
        $result = $conn->query('SELECT COUNT(*) FROM orders');
        echo "Orders: " . $result->fetchColumn() . "\n";
    } finally {
        $pool->release($conn);
    }
}

Example #2 Fallback when pool is unavailable

<?php

use Async\Pool;

$pool = new Pool(
    factory: fn() => new CacheClient('127.0.0.1', 11211),
    max: 3
);

function getData(Pool $pool, string $key): mixed
{
    $client = $pool->tryAcquire();

    if ($client === null) {
        // Cache unavailable — query database directly
        return fetchFromDatabase($key);
    }

    try {
        return $client->get($key) ?? fetchFromDatabase($key);
    } finally {
        $pool->release($client);
    }
}

Documentation