parallel/docs/workers.md

title	permalink
Workers	/workers

Worker

Worker provides a simple interface for executing PHP code in parallel in a separate PHP process or thread. Classes implementing Task are used to define the code to be run in parallel.

<?php

namespace Amp\Parallel\Worker;

use Amp\Promise;

/**
 * An interface for a parallel worker thread that runs a queue of tasks.
 */
interface Worker
{
    /**
     * Checks if the worker is running.
     *
     * @return bool True if the worker is running, otherwise false.
     */
    public function isRunning(): bool;

    /**
     * Checks if the worker is currently idle.
     *
     * @return bool
     */
    public function isIdle(): bool;

    /**
     * Enqueues a task to be executed by the worker.
     *
     * @param Task $task The task to enqueue.
     *
     * @return \Amp\Promise<mixed> Resolves with the return value of Task::run().
     */
    public function enqueue(Task $task): Promise;

    /**
     * @return \Amp\Promise<int> Exit code.
     */
    public function shutdown(): Promise;

    /**
     * Immediately kills the context.
     */
    public function kill();
}

Task

The Task interface has a single run() method that gets invoked in the worker to dispatch the work that needs to be done. The run() method can be written using blocking code since the code is executed in a separate process or thread. The method may also be asynchronous, returning a Promise or Generator that is run as a coroutine.

<?php

namespace Amp\Parallel\Worker;

/**
 * A runnable unit of execution.
 */
interface Task
{
    /**
     * Runs the task inside the caller's context.
     *
     * Does not have to be a coroutine, can also be a regular function returning a value.
     *
     * @param Environment
     *
     * @return mixed|\Amp\Promise|\Generator
     */
    public function run(Environment $environment);
}

Task instances are serialize'd in the main process and unserialize'd in the worker. That means that all data that is passed between the main process and a worker needs to be serializable.

Environment

The passed Environment allows to persist data between multiple tasks executed by the same worker, e.g. database connections or file handles, without resorting to globals for that. Additionally Environment allows setting a TTL for entries, so can be used as a cache.

<?php

namespace Amp\Parallel\Worker;

interface Environment extends \ArrayAccess
{
    /**
     * @param string $key
     *
     * @return bool
     */
    public function exists(string $key): bool;

    /**
     * @param string $key
     *
     * @return mixed|null Returns null if the key does not exist.
     */
    public function get(string $key);

    /**
     * @param string $key
     * @param mixed $value Using null for the value deletes the key.
     * @param int $ttl Number of seconds until data is automatically deleted. Use 0 for unlimited TTL.
     */
    public function set(string $key, $value, int $ttl = null);

    /**
     * @param string $key
     */
    public function delete(string $key);

    /**
     * Removes all values.
     */
    public function clear();
}