如果我们需要通过编程的方式来获取到TopicMetadataRequest请求到 def findLeader(topic: String): Unit = {

val consumer = connect("www.iteblog.com", 9092)

val req = TopicMetadataRequest(TopicMetadataRequest.CurrentVersion,

0, kafkaGroupId, List(topic))

val topicMetadataResponse = consumer.send(req)

val topicsMetadataSet = topicMetadataResponse.topicsMetadata

topicsMetadataSet.foreach { topicMetadata =>

println(topicMetadata.topic)

val metadataSet = topicMetadata.partitionsMetadata

metadataSet.foreach { metadata =>

val partitionId = metadata.partitionId

val isr = metadata.isr.map(_.connectionString).mkString("[", ",", "]")

val replicas = metadata.replicas.map(_.connectionString).mkString("[", ",", "]")

val leader = metadata.leader.map (_.connectionString).get

println(s"\tPartition: $partitionId, Leader: $leader Replicas: $replicas ISR: $isr")

}

}

}

TopicMetadataRequest是一个case class，其各个参数如下： case class TopicMetadataRequest(val versionId: Short,

val correlationId: Int,

val clientId: String,

val topics: Seq[String])

构造完成TopicMetadataRequest之后，通过SimpleConsumer的send方法发送请求，然后返回TopicMetadataResponse对象，其中就包含了Topic各个分区的相关信息，我们运行这个函数，可以得到以下的信息： iteblog

Partition: 0, Leader: www.iteblog.com:9091 Replicas: [www.iteblog.com:9091] ISR: [www.iteblog.com:9091]

Partition: 1, Leader: www.iteblog.com:9097 Replicas: [www.iteblog.com:9097] ISR: [www.iteblog.com:9097]

Partition: 2, Leader: www.iteblog.com:9095 Replicas: [www.iteblog.com:9095] ISR: [www.iteblog.com:9095]

Partition: 3, Leader: www.iteblog.com:9096 Replicas: [www.iteblog.com:9096] ISR: [www.iteblog.com:9096]

Partition: 4, Leader: www.iteblog.com:9094 Replicas: [www.iteblog.com:9094] ISR: [www.iteblog.com:9094]

Partition: 5, Leader: www.iteblog.com:9092 Replicas: [www.iteblog.com:9092] ISR: [www.iteblog.com:9092]

Partition: 6, Leader: www.iteblog.com:9093 Replicas: [www.iteblog.com:9093] ISR: [www.iteblog.com:9093]

这个输出是不是很熟悉，是的，输出的结果类似于运行以下的Kafka自带系统命令： [iteblog@www.iteblog.com kafka]$ ./bin/kafka-topics.sh --topic iteblog --describe \

--zookeeper www.iteblog.com

Topic:iteblog PartitionCount:7 ReplicationFactor:2 Configs:

Topic: iteblog Partition: 0 Leader: 1 Replicas: 1 Isr: 1

Topic: iteblog Partition: 1 Leader: 7 Replicas: 7 Isr: 7

Topic: iteblog Partition: 2 Leader: 5 Replicas: 5 Isr: 5

Topic: iteblog Partition: 3 Leader: 6 Replicas: 6 Isr: 6

Topic: iteblog Partition: 4 Leader: 4 Replicas: 4 Isr: 4

Topic: iteblog Partition: 5 Leader: 2 Replicas: 2 Isr: 2

Topic: iteblog Partition: 6 Leader: 3 Replicas: 3 Isr: 3

如果我们设置空的topic的列表，如：TopicMetadataRequest(TopicMetadataRequest.CurrentVersion, 0, kafkaGroupId, Seq())，那么我们可以获取Kafka server中所有Topic的信息。