如何通过 Alpakka 创建多个分区

Question

我正在尝试创建一个简单的生产者，它使用配置提供的一些分区创建一个主题。

根据Alpakka Producer Setting Doc，org.apache.kafka.clients.producer.ProducerConfig 中的任何属性都可以在kafka-clients 部分中设置。并且，num.partitions 中有一个 num.partitions 属性，正如在 Producer API Doc 中所评论的那样。

因此，我将该属性添加到我的application.conf 文件中，如下所示：

topic = "topic"
topic = ${?TOPIC}

# Properties for akka.kafka.ProducerSettings can be
# defined in this section or a configuration section with
# the same layout.
akka.kafka.producer {
  # Tuning parameter of how many sends that can run in parallel.
  parallelism = 100
  parallelism = ${?PARALLELISM}

  # Duration to wait for `KafkaConsumer.close` to finish.
  close-timeout = 20s

  # Fully qualified config path which holds the dispatcher configuration
  # to be used by the producer stages. Some blocking may occur.
  # When this value is empty, the dispatcher configured for the stream
  # will be used.
  use-dispatcher = "akka.kafka.default-dispatcher"

  # The time interval to commit a transaction when using the `Transactional.sink` or `Transactional.flow`
  eos-commit-interval = 100ms

  # Properties defined by org.apache.kafka.clients.producer.ProducerConfig
  # can be defined in this configuration section.
  kafka-clients {
    bootstrap.servers = "my-kafka:9092"
    bootstrap.servers = ${?BOOTSTRAPSERVERS}
    num.partitions = "3"
    num.partitions = ${?NUM_PARTITIONS}
  }
}

生产者应用代码如下：

object Main extends App {

  val config = ConfigFactory.load()

  implicit val system: ActorSystem = ActorSystem("producer")
  implicit val materializer: Materializer = ActorMaterializer()

  val producerConfigs = config.getConfig("akka.kafka.producer")
  val producerSettings = ProducerSettings(producerConfigs, new StringSerializer, new StringSerializer)

  val topic = config.getString("topic")

  val done: Future[Done] =
    Source(1 to 100000)
      .map(_.toString)
      .map(value => new ProducerRecord[String, String](topic, value))
      .runWith(Producer.plainSink(producerSettings))

  implicit val ec: ExecutionContextExecutor = system.dispatcher
  done onComplete  {
    case Success(_) => println("Done"); system.terminate()
    case Failure(err) => println(err.toString); system.terminate()
  }

}

但是，这不起作用。 Producer 使用单个分区而不是我通过配置设置的 3 个分区创建主题：

num.partitions = "3"

最后，Kafkacat 输出如下：

~$ kafkacat -b my-kafka:9092 -L
Metadata for all topics (from broker -1: my-kafka:9092/bootstrap):
 3 brokers:
  broker 2 at my-kafka-2.my-kafka-headless.default:9092
  broker 1 at my-kafka-1.my-kafka-headless.default:9092
  broker 0 at my-kafka-0.my-kafka-headless.default:9092
 1 topics:
  topic "topic" with 1 partitions:
    partition 0, leader 2, replicas: 2, isrs: 2

怎么了？是否可以使用 Alpakka 从 kafka-clients 部分的 Kafka Producer API 设置属性？

Answer 1

# org.apache.kafka.clients.producer.ProducerConfig 定义的属性

#可以在这个配置部分定义。

正如上面所说，ProducerConfig 用于生产者设置，而不是代理设置，这就是 num.partitions 的含义（我认为您迷失在 Apache Kafka 文档中显示的哪个表中...滚动到顶部以查看正确的标题）。

没有办法从生产者那里设置主题的分区...您需要使用AdminClient 类来创建主题，并且分区的数量是那里的参数，而不是配置属性。

示例代码

val props = new Properties()
props.setProperty(AdminClientConfig.BOOTSTRAP_SERVERS_CONFIG, "localhost:9092")

val adminClient = AdminClient.create(props)

val numPartitions = 3
val replicationFactor = 3.toShort
val newTopic = new NewTopic("new-topic-name", numPartitions, replicationFactor)
val configs = Map(TopicConfig.COMPRESSION_TYPE_CONFIG -> "gzip")
// settings some configs
newTopic.configs(configs.asJava)

adminClient.createTopics(List(newTopic).asJavaCollection)

然后你就可以启动生产者了

Answer 2

主题似乎是由 Default 创建的，这是 Kafka 的默认行为。如果是这种情况，您需要在 server.properties 文件中为您的代理定义默认分区数。

# The default number of log partitions per topic. More partitions allow greater
# parallelism for consumption, but this will also result in more files across
# the brokers.
num.partitions=3