1<?php
2
3/*
4 * This file is part of the Symfony package.
5 *
6 * (c) Fabien Potencier <fabien@symfony.com>
7 *
8 * For the full copyright and license information, please view the LICENSE
9 * file that was distributed with this source code.
10 */
11
12namespace Symfony\Component\Mailer\Transport;
13
14use Symfony\Component\Mailer\Envelope;
15use Symfony\Component\Mailer\Exception\TransportException;
16use Symfony\Component\Mailer\Exception\TransportExceptionInterface;
17use Symfony\Component\Mailer\SentMessage;
18use Symfony\Component\Mime\RawMessage;
19
20/**
21 * Uses several Transports using a round robin algorithm.
22 *
23 * @author Fabien Potencier <fabien@symfony.com>
24 */
25class RoundRobinTransport implements TransportInterface
26{
27    private $deadTransports;
28    private $transports = [];
29    private $retryPeriod;
30    private $cursor = -1;
31
32    /**
33     * @param TransportInterface[] $transports
34     */
35    public function __construct(array $transports, int $retryPeriod = 60)
36    {
37        if (!$transports) {
38            throw new TransportException(sprintf('"%s" must have at least one transport configured.', static::class));
39        }
40
41        $this->transports = $transports;
42        $this->deadTransports = new \SplObjectStorage();
43        $this->retryPeriod = $retryPeriod;
44    }
45
46    public function send(RawMessage $message, Envelope $envelope = null): ?SentMessage
47    {
48        while ($transport = $this->getNextTransport()) {
49            try {
50                return $transport->send($message, $envelope);
51            } catch (TransportExceptionInterface $e) {
52                $this->deadTransports[$transport] = microtime(true);
53            }
54        }
55
56        throw new TransportException('All transports failed.');
57    }
58
59    public function __toString(): string
60    {
61        return $this->getNameSymbol().'('.implode(' ', array_map('strval', $this->transports)).')';
62    }
63
64    /**
65     * Rotates the transport list around and returns the first instance.
66     */
67    protected function getNextTransport(): ?TransportInterface
68    {
69        if (-1 === $this->cursor) {
70            $this->cursor = $this->getInitialCursor();
71        }
72
73        $cursor = $this->cursor;
74        while (true) {
75            $transport = $this->transports[$cursor];
76
77            if (!$this->isTransportDead($transport)) {
78                break;
79            }
80
81            if ((microtime(true) - $this->deadTransports[$transport]) > $this->retryPeriod) {
82                $this->deadTransports->detach($transport);
83
84                break;
85            }
86
87            if ($this->cursor === $cursor = $this->moveCursor($cursor)) {
88                return null;
89            }
90        }
91
92        $this->cursor = $this->moveCursor($cursor);
93
94        return $transport;
95    }
96
97    protected function isTransportDead(TransportInterface $transport): bool
98    {
99        return $this->deadTransports->contains($transport);
100    }
101
102    protected function getInitialCursor(): int
103    {
104        // the cursor initial value is randomized so that
105        // when are not in a daemon, we are still rotating the transports
106        return mt_rand(0, \count($this->transports) - 1);
107    }
108
109    protected function getNameSymbol(): string
110    {
111        return 'roundrobin';
112    }
113
114    private function moveCursor(int $cursor): int
115    {
116        return ++$cursor >= \count($this->transports) ? 0 : $cursor;
117    }
118}
119