Pool::__construct

Create a new resource pool.

Pool::__construct ​

(PHP 8.6+, True Async 1.0)

php
public Pool::__construct(
    callable $factory,
    ?callable $destructor = null,
    ?callable $healthcheck = null,
    ?callable $beforeAcquire = null,
    ?callable $beforeRelease = null,
    int $min = 0,
    int $max = 10,
    int $healthcheckInterval = 0
)

Creates a new resource pool. The pool manages a set of reusable objects (connections, clients, file descriptors, etc.), automatically creating and destroying them as needed.

Parameters ​

factory : A factory function for creating a new resource. Called each time the pool needs a new resource and the current count is less than max. Must return a ready-to-use resource.

destructor : A function for properly destroying a resource. Called when the pool is closed or when a resource is removed (e.g., after a failed health check). null --- the resource is simply removed from the pool without additional actions.

healthcheck : A resource health check function. Takes a resource, returns bool. true --- the resource is healthy, false --- the resource will be destroyed and replaced. null --- no health check is performed.

beforeAcquire : A hook called before a resource is handed out. Takes the resource. Can be used to prepare the resource (e.g., reset state). null --- no hook.

beforeRelease : A hook called before a resource is returned to the pool. Takes the resource, returns bool. If it returns false, the resource is destroyed instead of being returned to the pool. null --- no hook.

min : The minimum number of resources in the pool. When the pool is created, min resources are created immediately. Default is 0.

max : The maximum number of resources in the pool. When the limit is reached, acquire() calls block until a resource is released. Default is 10.

healthcheckInterval : The interval for background resource health checks in milliseconds. 0 --- background checking is disabled (check only on acquire).

Examples ​

Example #1 PDO connection pool ​

php
<?php

use Async\Pool;

$pool = new Pool(
    factory: function(): PDO {
        return new PDO('mysql:host=localhost;dbname=app', 'user', 'pass', [
            PDO::ATTR_ERRMODE => PDO::ERRMODE_EXCEPTION,
        ]);
    },
    destructor: function(PDO $pdo): void {
        // PDO is closed automatically when removed
    },
    healthcheck: function(PDO $pdo): bool {
        try {
            $pdo->query('SELECT 1');
            return true;
        } catch (\Throwable) {
            return false;
        }
    },
    min: 2,
    max: 20,
    healthcheckInterval: 30000 // check every 30 seconds
);

$conn = $pool->acquire();
$result = $conn->query('SELECT * FROM users');
$pool->release($conn);

Example #2 Pool with hooks ​

php
<?php

use Async\Pool;

$pool = new Pool(
    factory: fn() => new RedisClient('127.0.0.1', 6379),
    destructor: fn(RedisClient $r) => $r->close(),
    beforeAcquire: function(RedisClient $r): void {
        $r->select(0); // reset to default database
    },
    beforeRelease: function(RedisClient $r): bool {
        // If the connection is broken — destroy the resource
        return $r->isConnected();
    },
    max: 5
);

See Also ​