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<?php
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namespace React\Dns\Query;
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use React\Promise\Promise;
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/**
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* Send DNS queries over a UDP or TCP/IP stream transport.
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*
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* This class will automatically choose the correct transport protocol to send
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* a DNS query to your DNS server. It will always try to send it over the more
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* efficient UDP transport first. If this query yields a size related issue
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* (truncated messages), it will retry over a streaming TCP/IP transport.
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*
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* For more advanced usages one can utilize this class directly.
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* The following example looks up the `IPv6` address for `reactphp.org`.
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*
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* ```php
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* $executor = new SelectiveTransportExecutor($udpExecutor, $tcpExecutor);
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*
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* $executor->query(
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* new Query($name, Message::TYPE_AAAA, Message::CLASS_IN)
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* )->then(function (Message $message) {
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* foreach ($message->answers as $answer) {
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* echo 'IPv6: ' . $answer->data . PHP_EOL;
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* }
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* }, 'printf');
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* ```
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*
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* Note that this executor only implements the logic to select the correct
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* transport for the given DNS query. Implementing the correct transport logic,
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* implementing timeouts and any retry logic is left up to the given executors,
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* see also [`UdpTransportExecutor`](#udptransportexecutor) and
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* [`TcpTransportExecutor`](#tcptransportexecutor) for more details.
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*
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* Note that this executor is entirely async and as such allows you to execute
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* any number of queries concurrently. You should probably limit the number of
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* concurrent queries in your application or you're very likely going to face
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* rate limitations and bans on the resolver end. For many common applications,
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* you may want to avoid sending the same query multiple times when the first
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* one is still pending, so you will likely want to use this in combination with
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* a `CoopExecutor` like this:
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*
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* ```php
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* $executor = new CoopExecutor(
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* new SelectiveTransportExecutor(
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* $datagramExecutor,
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* $streamExecutor
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* )
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* );
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* ```
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*/
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class SelectiveTransportExecutor implements ExecutorInterface
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{
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private $datagramExecutor;
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private $streamExecutor;
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public function __construct(ExecutorInterface $datagramExecutor, ExecutorInterface $streamExecutor)
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{
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$this->datagramExecutor = $datagramExecutor;
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$this->streamExecutor = $streamExecutor;
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}
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public function query(Query $query)
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{
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$stream = $this->streamExecutor;
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$pending = $this->datagramExecutor->query($query);
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return new Promise(function ($resolve, $reject) use (&$pending, $stream, $query) {
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$pending->then(
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$resolve,
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function ($e) use (&$pending, $stream, $query, $resolve, $reject) {
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if ($e->getCode() === (\defined('SOCKET_EMSGSIZE') ? \SOCKET_EMSGSIZE : 90)) {
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$pending = $stream->query($query)->then($resolve, $reject);
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} else {
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$reject($e);
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}
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}
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);
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}, function () use (&$pending) {
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$pending->cancel();
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$pending = null;
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});
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}
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}
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