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vendor/symfony/mailer/Transport/RoundRobinTransport.php

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+<?php
+
+/*
+ * This file is part of the Symfony package.
+ *
+ * (c) Fabien Potencier <fabien@symfony.com>
+ *
+ * For the full copyright and license information, please view the LICENSE
+ * file that was distributed with this source code.
+ */
+
+namespace Symfony\Component\Mailer\Transport;
+
+use Symfony\Component\Mailer\Envelope;
+use Symfony\Component\Mailer\Exception\TransportException;
+use Symfony\Component\Mailer\Exception\TransportExceptionInterface;
+use Symfony\Component\Mailer\SentMessage;
+use Symfony\Component\Mime\RawMessage;
+
+/**
+ * Uses several Transports using a round robin algorithm.
+ *
+ * @author Fabien Potencier <fabien@symfony.com>
+ */
+class RoundRobinTransport implements TransportInterface
+{
+    /**
+     * @var \SplObjectStorage<TransportInterface, float>
+     */
+    private \SplObjectStorage $deadTransports;
+    private array $transports = [];
+    private int $retryPeriod;
+    private int $cursor = -1;
+
+    /**
+     * @param TransportInterface[] $transports
+     */
+    public function __construct(array $transports, int $retryPeriod = 60)
+    {
+        if (!$transports) {
+            throw new TransportException(sprintf('"%s" must have at least one transport configured.', static::class));
+        }
+
+        $this->transports = $transports;
+        $this->deadTransports = new \SplObjectStorage();
+        $this->retryPeriod = $retryPeriod;
+    }
+
+    public function send(RawMessage $message, ?Envelope $envelope = null): ?SentMessage
+    {
+        $exception = null;
+
+        while ($transport = $this->getNextTransport()) {
+            try {
+                return $transport->send($message, $envelope);
+            } catch (TransportExceptionInterface $e) {
+                $exception ??= new TransportException('All transports failed.');
+                $exception->appendDebug(sprintf("Transport \"%s\": %s\n", $transport, $e->getDebug()));
+                $this->deadTransports[$transport] = microtime(true);
+            }
+        }
+
+        throw $exception ?? new TransportException('No transports found.');
+    }
+
+    public function __toString(): string
+    {
+        return $this->getNameSymbol().'('.implode(' ', array_map('strval', $this->transports)).')';
+    }
+
+    /**
+     * Rotates the transport list around and returns the first instance.
+     */
+    protected function getNextTransport(): ?TransportInterface
+    {
+        if (-1 === $this->cursor) {
+            $this->cursor = $this->getInitialCursor();
+        }
+
+        $cursor = $this->cursor;
+        while (true) {
+            $transport = $this->transports[$cursor];
+
+            if (!$this->isTransportDead($transport)) {
+                break;
+            }
+
+            if ((microtime(true) - $this->deadTransports[$transport]) > $this->retryPeriod) {
+                $this->deadTransports->detach($transport);
+
+                break;
+            }
+
+            if ($this->cursor === $cursor = $this->moveCursor($cursor)) {
+                return null;
+            }
+        }
+
+        $this->cursor = $this->moveCursor($cursor);
+
+        return $transport;
+    }
+
+    protected function isTransportDead(TransportInterface $transport): bool
+    {
+        return $this->deadTransports->contains($transport);
+    }
+
+    protected function getInitialCursor(): int
+    {
+        // the cursor initial value is randomized so that
+        // when are not in a daemon, we are still rotating the transports
+        return mt_rand(0, \count($this->transports) - 1);
+    }
+
+    protected function getNameSymbol(): string
+    {
+        return 'roundrobin';
+    }
+
+    private function moveCursor(int $cursor): int
+    {
+        return ++$cursor >= \count($this->transports) ? 0 : $cursor;
+    }
+}