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<?php |
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namespace JVelasco\CircuitBreaker\AvailabilityStrategy; |
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use JVelasco\CircuitBreaker\AvailabilityStrategy; |
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use JVelasco\CircuitBreaker\StorageException; |
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class TimeBackoff implements AvailabilityStrategy |
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{ |
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const ATTEMPTS_KEY = "attempts"; |
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const LAST_ATTEMPT_TIME_KEY = "last_attempt"; |
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/** @var Storage */ |
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protected $storage; |
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/** @var BackoffStrategy */ |
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private $backoffStrategy; |
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/** @var int */ |
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protected $maxFailures; |
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/** @var int initial time to wait in milliseconds */ |
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protected $baseWaitTime; |
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/** @var int */ |
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private $maxWaitTime; |
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public function __construct( |
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Storage $storage, |
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BackoffStrategy $backoffStrategy, |
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int $maxFailures, |
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int $baseWaitTime, |
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int $maxWaitTime |
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) { |
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$this->storage = $storage; |
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$this->maxFailures = $maxFailures; |
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$this->baseWaitTime = $baseWaitTime; |
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$this->backoffStrategy = $backoffStrategy; |
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$this->maxWaitTime = $maxWaitTime; |
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} |
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public function isAvailable(string $serviceName): bool |
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{ |
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try { |
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if ($this->storage->numberOfFailures($serviceName) < $this->maxFailures) { |
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return true; |
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} |
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$attempt = $this->getLastAttempt($serviceName); |
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if ($this->millisecondsSinceLastAttempt($serviceName) > $this->waitTime($attempt)) { |
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$this->saveAttempt($serviceName, $attempt+1); |
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return true; |
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} |
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return false; |
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} catch (StorageException $ex) { |
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return true; |
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} |
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} |
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public function getId(): string |
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{ |
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return $this->backoffStrategy->id(); |
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} |
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private function getLastAttemptTime(string $serviceName): int |
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{ |
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$lastTryTimestamp = $this->storage->getStrategyData( |
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$this, |
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$serviceName, |
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self::LAST_ATTEMPT_TIME_KEY |
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); |
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return $lastTryTimestamp ? $lastTryTimestamp : $this->now(); |
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} |
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private function getLastAttempt($serviceName): int |
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{ |
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return (int) $this->storage->getStrategyData($this, $serviceName, self::ATTEMPTS_KEY); |
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} |
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private function millisecondsSinceLastAttempt(string $serviceName): int |
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{ |
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$lastAttempt = $this->getLastAttemptTime($serviceName); |
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return $this->now() - $lastAttempt; |
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} |
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private function now(): int |
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{ |
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return floor(microtime(true) * 1000); |
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} |
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private function waitTime($attempt): int |
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{ |
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return min( |
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$this->backoffStrategy->waitTime($attempt, $this->baseWaitTime), |
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$this->maxWaitTime |
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); |
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} |
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private function saveAttempt(string $serviceName, int $attempt) |
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{ |
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$this->storage->saveStrategyData( |
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$this, |
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$serviceName, |
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self::ATTEMPTS_KEY, |
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$attempt |
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); |
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$this->storage->saveStrategyData( |
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$this, |
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$serviceName, |
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self::LAST_ATTEMPT_TIME_KEY, |
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$this->now() |
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); |
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$this->storage->resetFailuresCounter($serviceName); |
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} |
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} |
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j-velasco /
php-circuit-breaker
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