我有两个发送电子邮件的服务，Postmark和SendGrid。我使用工厂模式是为了具有可扩展性和灵活性。
EmailProviderInterface

namespace App\Services\Notifications;

interface EmailProviderInterface
{
    public function sendEmail(string $to, string $templateName, array $data);
}

PostMarkEmailService

<?php

namespace App\Services\Notifications;

use App\Traits\SendEmailTrait;

class PostmarkEmailService implements EmailProviderInterface
{
    use SendEmailTrait;

    /**
     * send email using postmark
     *
     * @param string $to
     * @param string $templateName
     * @param array $data
     * @return array
     */
    public function sendEmail(string $to, string $templateName, array $data): array
    {

        $templateInfo = $this->getHtmlRender($templateName, $data);
        if (!$templateInfo['success']) {
            return $templateInfo;
        }
        
        try {
            // implement logic calling external api and passing the html

            return $this->successHandler();
        } catch (\Exception $e) {
            return $this->handleErrors($e);
        }
    }
}

SendGridEmailService

<?php

namespace App\Services\Notifications;

use App\Traits\SendEmailTrait;

class SendGridEmailService implements EmailProviderInterface
{

    use SendEmailTrait;

    /**
     * Send Email Using SendGrid
     *
     * @param string $to
     * @param string $templateName
     * @param array $data
     * @return array
     */
    public function sendEmail(string $to, string $templateName, array $data): array
    {

        $templateInfo = $this->getHtmlRender($templateName, $data);
        if (!$templateInfo['success']) {
            return $templateInfo;
        }
        try {
            // implement logic calling external api and passing the html

            return $this->successHandler();
        } catch (\Exception $e) {
            return $this->handleErrors($e);
        }
    }
}

这是EmailServiceProvider将使用它：

<?php

namespace App\Services\Notifications;

class EmailServiceProvider
{
    private EmailProviderInterface $emailProvider;

    public function __construct(bool $highPriority = true)
    {
        if ($highPriority) {
            $this->emailProvider = new PostmarkEmailService();
        } else {
            $this->emailProvider = new SendGridEmailService();
        }
    }

    /**
     * Send email using the email provider
     *
     * @param string $to
     * @param string $templateName
     * @param array $data
     * @return array
     */
    public function sendMail(string $to, string $templateName, array $data): array
    {
        return $this->emailProvider->sendEmail($to, $templateName, $data);
    }

}

我需要实现一个带有重试机制的负载均衡器（使用循环策略）。这将在EmailService提供程序上操作，以便在PostMark和SendGrid服务之间进行交换。
如果要实现一个队列，如何应用这样的负载均衡器？