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[[http-client]]
=== Configure the HTTP client

Elasticsearch-php uses https://github.com/elastic/elastic-transport-php[elastic-transport-php]
for managing the HTTP tranport. This is an HTTP client provided by Elastic
that can be configured to use any https://www.php-fig.org/psr/psr-18/[PSR-18] client library.

Elasticsearch-php uses Guzzle as default HTTP client but you can specify
any other client using the `setHttpClient()` function, as follows:


[source,php]
----
use Symfony\Component\HttpClient\Psr18Client;

$client = ClientBuilder::create()
    ->setHttpClient(new Psr18Client)
    ->build();
----

For instance, in this example we used the https://symfony.com/doc/current/http_client.html[Symfony HTTP Client].

[discrete]
==== Setting the client options

If you want you can set the options for a specific PSR-18 client
using the `ClientBuilder::setHttpClientOptions($options)` method.
The `$options` is an array of key:value options that are 
specifics to the HTTP client used.

For instance, if you are using Guzzle (default) and you need to use a
https://docs.guzzlephp.org/en/stable/request-options.html#proxy[proxy]
you can use the following settings:

[source,php]
----
$client = ClientBuilder::create()
    ->setHttpClientOptions([
        'proxy' => 'http://localhost:8125'
    ])
    ->build();
----


[discrete]
==== Configuring the HTTP async client

Elasticsearch-php can works using an asyncronous HTTP client that implements
the https://github.com/php-http/httplug/blob/master/src/HttpAsyncClient.php[HttpAsyncClient] interface
of the http://httplug.io/[HTTPlug] project.

Unfortunately, there is not yet a PSR standard for HTTP async client.
We used the HTTPlug interface that is quite simple, as follows:

[source,php]
----
namespace Http\Client;

use Http\Promise\Promise;
use Psr\Http\Message\RequestInterface; // PSR-7 response

interface HttpAsyncClient
{
    /**
     * @return Promise
     */
    public function sendAsyncRequest(RequestInterface $request);
}
----

You can enable the HTTP async in elasticsearch-php using the `setAsync()` function,
as follows:

[source,php]
----
$client = ClientBuilder::create()
    ->build();

$client->setAsync(true);

$promise = [];
for ($i=0; $i<10; $i++) {
    $promise[] = $client->index([
        'index' => 'my-index'
        'body' => [
            'foo' => base64_encode(random_bytes(24))
        ]
    ]);
}
----

The previous example stores 10 random documents using the HTTP asyncronous feature.
The `$promise` response is an object of https://github.com/php-http/promise/blob/master/src/Promise.php[promises/a+]
interface.

A promise represents a single result of an asynchronous operation.
It is not necessarily available at a specific time, but should become in the future.

If you need to know the response you can just call the `wait()` function,
as follows:

[source,php]
----
$promise = $client->index([
    'index' => 'my-index',
    'body' => [
        'foo' => 'bar'
    ]
]);
$result = $promise->wait();
print_r($result->asArray());
----

The `wait()` function block the execution until we will recevie the
HTTP response from {es}.

Instead of waiting, you can handle things asynchronously using the
`then()` function, as follows:

[source,php]
----
use Psr\Http\Message\ResponseInterface; // PSR-7

$promise = $client->index([
    'index' => 'my-index',
    'body' => [
        'foo' => 'bar'
    ]
]);

$promise->then(
    // The success callback
    function (ResponseInterface $response) {
        // Success
        // insert here the logic for managing the response
        return $response;
    },
    // The failure callback
    function (\Exception $exception) {
        // Error
        throw $exception;
    }
);
----

More information about Promise are available at the
https://docs.php-http.org/en/latest/components/promise.html[HTTPlug documentation page].