> For the complete documentation index, see [llms.txt](https://docs.roadrunner.dev/docs/llms.txt). Markdown versions of documentation pages are available by appending `.md` to page URLs; this page is available as [Markdown](https://docs.roadrunner.dev/docs/php-worker/manual-scaling.md).

# Manual workers scaling

## Introduction

Use `Spiral\RoadRunner\WorkerPool` to add or remove workers through [Goridge RPC](/docs/php-worker/rpc.md). RoadRunner v3 retains these PHP calls.

### Limitations

* This feature is not available when running RoadRunner in debug mode (`pool.debug=true`).
* A pool can hold at most 2048 workers. The initial `num_workers` value cannot exceed 500.
* A removal selects a free worker. It does not interrupt an active request or remove the last worker.
* When an automatic allocator is active, workers above the base `num_workers` count are subject to its idle removal rules, including manually added workers.

### Usage

Add or remove a worker from the HTTP pool:

{% code title="worker.php" %}

```php
use Spiral\RoadRunner\WorkerPool;
use Spiral\Goridge\RPC\RPC;

$rpc = RPC::create('tcp://127.0.0.1:6001');
$pool = new WorkerPool($rpc);

// Add a worker to the pool.
$pool->addWorker('http');

// Remove a worker from the pool.
$pool->removeWorker('http');
```

{% endcode %}

### List of supported plugins

* `http`, `grpc`, `temporal`, `centrifuge`, `tcp`, `jobs`.

For automatic allocation, see [automatic worker scaling](/docs/php-worker/auto-scaling.md).