出于测试目的，我有一个包含 2000 个图像 URI(字符串)的数组，我使用此函数异步下载。经过一些谷歌搜索、测试和尝试后，我想出了 2 个它们都可以工作的函数(老实说 downloadFilesAsync2 抛出一个 InvalidArgumentException在最后一行)。

downloadFilesAsync2 函数基于 GuzzleHttp\Promise\EachPromise 类，downloadFilesAsync1 基于 GuzzleHttp\Pool 类。

这两个函数都很好地异步下载了 2000 个文件，同时限制了 10 个线程。

我知道它们有效，但除此之外别无其他。我想知道是否有人可以解释这两种方法，一种是否比另一种更好，含义等。

// for the purpose of this question i've reduced the array to 5 files!
$uris = array /
  "https://cdn.enchufix.com/media/catalog/product/u/n/unix-48120.jpg",
  "https://cdn.enchufix.com/media/catalog/product/u/n/unix-48120-01.jpg",
  "https://cdn.enchufix.com/media/catalog/product/u/n/unix-48120-02.jpg",
  "https://cdn.enchufix.com/media/catalog/product/u/n/unix-48120-03.jpg",
  "https://cdn.enchufix.com/media/catalog/product/u/n/unix-48120-04.jpg",
);

function downloadFilesAsync2(array $uris, string $dir, $overwrite=true) {
    $client   = new \GuzzleHttp\Client();
    $requests = array();
    foreach ($uris as $i => $uri) {
        $loc = $dir . DIRECTORY_SEPARATOR . basename($uri);
        if ($overwrite && file_exists($loc)) unlink($loc);
        $requests[] = new GuzzleHttp\Psr7\Request('GET', $uri, ['sink' => $loc]);
        echo "Downloading $uri to $loc" . PHP_EOL;
    }
    $pool = new \GuzzleHttp\Pool($client, $requests, [
        'concurrency' => 10,
        'fulfilled' => function (\Psr\Http\Message\ResponseInterface $response, $index) {
            // this is delivered each successful response
            echo 'success: '.$response->getStatusCode().PHP_EOL;
        },
        'rejected' => function ($reason, $index) {
            // this is delivered each failed request
            echo 'failed: '.$reason.PHP_EOL;
        },
    ]);
    $promise = $pool->promise();  // Start transfers and create a promise
    $promise->wait();   // Force the pool of requests to complete.
}

function downloadFilesAsync1(array $uris, string $dir, $overwrite=true) {
    $client = new \GuzzleHttp\Client();
    $promises = (function () use ($client, $uris, $dir, $overwrite) {
        foreach ($uris as $uri) {
            $loc = $dir . DIRECTORY_SEPARATOR . basename($uri);
            if ($overwrite && file_exists($loc)) unlink($loc);
            yield $client->requestAsync('GET', $uri, ['sink' => $loc]);
            echo "Downloading $uri to $loc" . PHP_EOL;
        }
    })();
    (new \GuzzleHttp\Promise\EachPromise(
        $promises, [
        'concurrency' => 10,
        'fulfilled'   => function (\Psr\Http\Message\ResponseInterface $response) {
            //            echo "\t=>\tDONE! status:" . $response->getStatusCode() . PHP_EOL;
        },
        'rejected'    => function ($reason, $index) {
            echo 'ERROR => ' . strtok($reason->getMessage(), "\n") . PHP_EOL;
        },
    ])
    )->promise()->wait();
}

最佳答案

首先，我将解决 downloadFilesAsync2 中的 InvalidArgumentException方法。这种方法实际上有两个问题。两者都与此有关:

$requests[] = $client->request('GET', $uri, ['sink' => $loc]);

第一个问题是 Client::request()是一个同步实用方法，它包装了 $client->requestAsync()->wait() . $client->request()将返回 Psr\Http\Message\ResponseInterface 的实例，结果 $requests[]实际上会填充 ResponseInterface实现。这就是最终导致 InvalidArgumentException 作为 $requests 的原因不包含任何 Psr\Http\Message\RequestInterface的，异常是从 Pool::__construct() 中抛出的.

此方法的更正版本应包含看起来更像的代码:

$requests = [
    new Request('GET', 'www.google.com', [], null, 1.1),
    new Request('GET', 'www.ebay.com', [], null, 1.1),
    new Request('GET', 'www.cnn.com', [], null, 1.1),
    new Request('GET', 'www.red.com', [], null, 1.1),
];

$pool = new Pool($client, $requests, [
    'concurrency' => 10,
    'fulfilled' => function(ResponseInterface $response) {
        // do something
    },
    'rejected' => function($reason, $index) {
        // do something error handling
    },
    'options' => ['sink' => $some_location,],
]);

$promise = $pool->promise();
$promise->wait();

要回答您的第二个问题“这两种方法有什么区别”，答案很简单，没有。为了解释这一点，让我复制并粘贴 Pool::__construct() :

/**
 * @param ClientInterface $client   Client used to send the requests.
 * @param array|\Iterator $requests Requests or functions that return
 *                                  requests to send concurrently.
 * @param array           $config   Associative array of options
 *     - concurrency: (int) Maximum number of requests to send concurrently
 *     - options: Array of request options to apply to each request.
 *     - fulfilled: (callable) Function to invoke when a request completes.
 *     - rejected: (callable) Function to invoke when a request is rejected.
 */
public function __construct(
    ClientInterface $client,
    $requests,
    array $config = []
) {
    // Backwards compatibility.
    if (isset($config['pool_size'])) {
        $config['concurrency'] = $config['pool_size'];
    } elseif (!isset($config['concurrency'])) {
        $config['concurrency'] = 25;
    }

    if (isset($config['options'])) {
        $opts = $config['options'];
        unset($config['options']);
    } else {
        $opts = [];
    }

    $iterable = \GuzzleHttp\Promise\iter_for($requests);
    $requests = function () use ($iterable, $client, $opts) {
        foreach ($iterable as $key => $rfn) {
            if ($rfn instanceof RequestInterface) {
                yield $key => $client->sendAsync($rfn, $opts);
            } elseif (is_callable($rfn)) {
                yield $key => $rfn($opts);
            } else {
                throw new \InvalidArgumentException('Each value yielded by '
                    . 'the iterator must be a Psr7\Http\Message\RequestInterface '
                    . 'or a callable that returns a promise that fulfills '
                    . 'with a Psr7\Message\Http\ResponseInterface object.');
            }
        }
    };

    $this->each = new EachPromise($requests(), $config);
}

现在，如果我们将其与 downloadFilesAsync1 中代码的简化版本进行比较方法:

$promises = (function () use ($client, $uris) {
    foreach ($uris as $uri) {
        yield $client->requestAsync('GET', $uri, ['sink' => $some_location]);
    }
})();
(new \GuzzleHttp\Promise\EachPromise(
    $promises, [
    'concurrency' => 10,
    'fulfilled'   => function (\Psr\Http\Message\ResponseInterface $response) {
        // do something
    },
    'rejected'    => function ($reason, $index) {
        // do something
    },
])
)->promise()->wait();

在这两个示例中，都有一个生成器生成解析为 ResponseInterface 实例的 promise 该生成器连同配置数组(已完成的可调用、已拒绝的可调用、并发)也被送入 EachPromise 的新实例中。 .

总结:

1. downloadFilesAsync1在功能上与使用 Pool 相同只是没有内置到 Pool::__construct() 中的错误检查.

2. downloadFilesAsync2 中有一些错误当 Pool 时，这将导致文件在收到 InvalidArgumentException 之前以同步方式下载。被实例化。

我唯一的建议是:使用您觉得更直观的那个。

关于php - Guzzle HTTP客户端多线程下载文件 : EachPromises vs Pool objects，我们在Stack Overflow上找到一个类似的问题： https://stackoverflow.com/questions/51361739/