Pool::__construct

(PHP 8.6+, True Async 1.0)

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

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

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

• Pool::acquire — Acquire a resource from the pool
• Pool::release — Release a resource back to the pool
• Pool::close — Close the pool