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<?php
namespace Aws;
use Aws\Exception\AwsException;
use GuzzleHttp\Promise;
use GuzzleHttp\Promise\PromisorInterface;
use GuzzleHttp\Promise\RejectedPromise;
/**
* "Waiters" are associated with an AWS resource (e.g., EC2 instance), and poll
* that resource and until it is in a particular state.
* The Waiter object produces a promise that is either a.) resolved once the
* waiting conditions are met, or b.) rejected if the waiting conditions cannot
* be met or has exceeded the number of allowed attempts at meeting the
* conditions. You can use waiters in a blocking or non-blocking way, depending
* on whether you call wait() on the promise.
* The configuration for the waiter must include information about the operation
* and the conditions for wait completion.
*/
class Waiter implements PromisorInterface
{
/** @var AwsClientInterface Client used to execute each attempt. */
private $client;
/** @var string Name of the waiter. */
private $name;
/** @var array Params to use with each attempt operation. */
private $args;
/** @var array Waiter configuration. */
private $config;
/** @var array Default configuration options. */
private static $defaults = ['initDelay' => 0, 'before' => null];
/** @var array Required configuration options. */
private static $required = [
'acceptors',
'delay',
'maxAttempts',
'operation',
];
/**
* The array of configuration options include:
*
* - acceptors: (array) Array of acceptor options
* - delay: (int) Number of seconds to delay between attempts
* - maxAttempts: (int) Maximum number of attempts before failing
* - operation: (string) Name of the API operation to use for polling
* - before: (callable) Invoked before attempts. Accepts command and tries.
*
* @param AwsClientInterface $client Client used to execute commands.
* @param string $name Waiter name.
* @param array $args Command arguments.
* @param array $config Waiter config that overrides defaults.
*
* @throws \InvalidArgumentException if the configuration is incomplete.
*/
public function __construct(
AwsClientInterface $client,
$name,
array $args = [],
array $config = []
) {
$this->client = $client;
$this->name = $name;
$this->args = $args;
// Prepare and validate config.
$this->config = $config + self::$defaults;
foreach (self::$required as $key) {
if (!isset($this->config[$key])) {
throw new \InvalidArgumentException(
'The provided waiter configuration was incomplete.'
);
}
}
if ($this->config['before'] && !is_callable($this->config['before'])) {
throw new \InvalidArgumentException(
'The provided "before" callback is not callable.'
);
}
}
public function promise()
{
return Promise\coroutine(function () {
$name = $this->config['operation'];
for ($state = 'retry', $attempt = 1; $state === 'retry'; $attempt++) {
// Execute the operation.
$args = $this->getArgsForAttempt($attempt);
$command = $this->client->getCommand($name, $args);
try {
if ($this->config['before']) {
$this->config['before']($command, $attempt);
}
$result = (yield $this->client->executeAsync($command));
} catch (AwsException $e) {
$result = $e;
}
// Determine the waiter's state and what to do next.
$state = $this->determineState($result);
if ($state === 'success') {
yield $command;
} elseif ($state === 'failed') {
$msg = "The {$this->name} waiter entered a failure state.";
if ($result instanceof \Exception) {
$msg .= ' Reason: ' . $result->getMessage();
}
yield new RejectedPromise(new \RuntimeException($msg));
} elseif ($state === 'retry'
&& $attempt >= $this->config['maxAttempts']
) {
$state = 'failed';
yield new RejectedPromise(new \RuntimeException(
"The {$this->name} waiter failed after attempt #{$attempt}."
));
}
}
});
}
/**
* Gets the operation arguments for the attempt, including the delay.
*
* @param $attempt Number of the current attempt.
*
* @return mixed integer
*/
private function getArgsForAttempt($attempt)
{
$args = $this->args;
// Determine the delay.
$delay = ($attempt === 1)
? $this->config['initDelay']
: $this->config['delay'];
if (is_callable($delay)) {
$delay = $delay($attempt);
}
// Set the delay. (Note: handlers except delay in milliseconds.)
if (!isset($args['@http'])) {
$args['@http'] = [];
}
$args['@http']['delay'] = $delay * 1000;
return $args;
}
/**
* Determines the state of the waiter attempt, based on the result of
* polling the resource. A waiter can have the state of "success", "failed",
* or "retry".
*
* @param mixed $result
*
* @return string Will be "success", "failed", or "retry"
*/
private function determineState($result)
{
foreach ($this->config['acceptors'] as $acceptor) {
$matcher = 'matches' . ucfirst($acceptor['matcher']);
if ($this->{$matcher}($result, $acceptor)) {
return $acceptor['state'];
}
}
return $result instanceof \Exception ? 'failed' : 'retry';
}
/**
* @param result $result Result or exception.
* @param array $acceptor Acceptor configuration being checked.
*
* @return bool
*/
private function matchesPath($result, array $acceptor)
{
return !($result instanceof ResultInterface)
? false
: $acceptor['expected'] == $result->search($acceptor['argument']);
}
/**
* @param result $result Result or exception.
* @param array $acceptor Acceptor configuration being checked.
*
* @return bool
*/
private function matchesPathAll($result, array $acceptor)
{
if (!($result instanceof ResultInterface)) {
return false;
}
$actuals = $result->search($acceptor['argument']) ?: [];
foreach ($actuals as $actual) {
if ($actual != $acceptor['expected']) {
return false;
}
}
return true;
}
/**
* @param result $result Result or exception.
* @param array $acceptor Acceptor configuration being checked.
*
* @return bool
*/
private function matchesPathAny($result, array $acceptor)
{
if (!($result instanceof ResultInterface)) {
return false;
}
$actuals = $result->search($acceptor['argument']) ?: [];
foreach ($actuals as $actual) {
if ($actual == $acceptor['expected']) {
return true;
}
}
return false;
}
/**
* @param result $result Result or exception.
* @param array $acceptor Acceptor configuration being checked.
*
* @return bool
*/
private function matchesStatus($result, array $acceptor)
{
if ($result instanceof ResultInterface) {
return $acceptor['expected'] == $result['@metadata']['statusCode'];
} elseif ($result instanceof AwsException && $response = $result->getResponse()) {
return $acceptor['expected'] == $response->getStatusCode();
} else {
return false;
}
}
/**
* @param result $result Result or exception.
* @param array $acceptor Acceptor configuration being checked.
*
* @return bool
*/
private function matchesError($result, array $acceptor)
{
if ($result instanceof AwsException) {
return $result->isConnectionError()
|| $result->getAwsErrorCode() == $acceptor['expected'];
}
return false;
}
}