要使用Alpakka Kafka流永远不会终止，您可以使用RestartSource操作符将流包装在一个可以自动重启的Source中。这样，即使流因为某些错误而终止，它也会自动重新启动。

下面是一个示例代码，演示如何使用Alpakka Kafka和Akka Streams创建一个永不终止的流：

import akka.actor.ActorSystem
import akka.kafka.ConsumerMessage.CommittableMessage
import akka.kafka.scaladsl.Consumer
import akka.kafka.scaladsl.Consumer.DrainingControl
import akka.kafka.{ConsumerSettings, Subscriptions}
import akka.stream.{ActorMaterializer, RestartSettings}
import akka.stream.scaladsl.{RestartSource, Sink, Source}
import org.apache.kafka.clients.consumer.ConsumerConfig
import org.apache.kafka.common.serialization.StringDeserializer

import scala.concurrent.duration._

object AlpakkaKafkaExample extends App {
  implicit val system: ActorSystem = ActorSystem("AlpakkaKafkaExample")
  implicit val materializer: ActorMaterializer = ActorMaterializer()

  // Kafka consumer settings
  val consumerSettings: ConsumerSettings[String, String] =
    ConsumerSettings(system, new StringDeserializer, new StringDeserializer)
      .withBootstrapServers("localhost:9092")
      .withGroupId("my-group")
      .withProperty(ConsumerConfig.AUTO_OFFSET_RESET_CONFIG, "earliest")

  // Define the Kafka topic to consume from
  val topic = "my-topic"

  // Create a Source that will restart automatically if it fails
  val restartSource: Source[CommittableMessage[String, String], DrainingControl[CommittableMessage[String, String]]] =
    RestartSource.onFailuresWithBackoff(
      RestartSettings(minBackoff = 3.seconds, maxBackoff = 30.seconds, randomFactor = 0.2)
    ) { () =>
      // Create a Kafka consumer source
      val consumerSource: Source[CommittableMessage[String, String], Consumer.Control] =
        Consumer.committableSource(consumerSettings, Subscriptions.topics(topic))

      // Define the processing logic
      consumerSource.map { msg =>
        // Process the Kafka message here
        println(s"Received message: ${msg.record.value()}")
        msg
      }
    }

  // Define the Sink to commit the consumed messages
  val commitSink: Sink[CommittableMessage[String, String], Unit] =
    Consumer.commitSink(consumerSettings)

  // Connect the Source to the Sink and run the stream
  restartSource.to(commitSink).run()
}

在上面的示例中，我们使用了RestartSource.onFailuresWithBackoff操作符，它会将我们的Kafka消费者流包装在一个可以自动重启的Source中。我们还设置了一些重启策略参数，例如最小和最大重试间隔。

这样，如果Kafka流因为某种原因（例如网络故障，Kafka服务器故障等）终止，它将自动重新启动并继续消费消息。

请注意，上述示例假设您已经正确配置了Kafka和Alpakka Kafka，并且Kafka服务器正在运行在localhost:9092上，且有一个名为my-topic的主题可用。您还需要在项目的依赖项中包含必要的Alpakka Kafka和Akka Streams库。