compilerPass.php

<?php

class FactoryCompilerPass implements CompilerPassInterface
{
    public function process(ContainerBuilder $container)
    {
        $predisClientId = $container->getParameter('predis_client_id');

        if (!$container->hasDefinition($predisClientId)) {
            throw new ServiceNotFoundException($predisClientId);
        }

        $container->setAlias('predis_client', $predisClientId);
    }
}