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Apache Spark技术实战之1 -- KafkaWordCount
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概要
Spark应用开发实践性非常强,很多时候可能都会将时间花费在环境的搭建和运行上,如果有一个比较好的指导将会大大的缩短应用开发流程。Spark Streaming中涉及到和许多第三方程序的整合,源码中的例子如何真正跑起来,文档不是很多也不详细。
本篇主要讲述如何运行KafkaWordCount,这个需要涉及Kafka集群的搭建,还是说的越仔细越好。
搭建Kafka集群
步骤1:下载kafka 0.8.1及解压
wget https://www.apache.org/dyn/closer.cgi?path=/kafka/0.8.1.1/kafka_2.10-0.8.1.1.tgztar zvxf kafka_2.10-0.8.1.1.tgzcd kafka_2.10-0.8.1.1
步骤2:启动zookeeper
bin/zookeeper-server-start.sh config/zookeeper.properties
步骤3:修改配置文件config/server.properties,添加如下内容
host.name=localhost# Hostname the broker will advertise to producers and consumers. If not set, it uses the# value for "host.name" if configured. Otherwise, it will use the value returned from# java.net.InetAddress.getCanonicalHostName().advertised.host.name=localhost
步骤4:启动Kafka server
bin/kafka-server-start.sh config/server.properties
步骤5:创建topic
bin/kafka-topics.sh --create --zookeeper localhost:2181 --replication-factor 1 --partitions 1 --topic test
检验topic创建是否成功
bin/kafka-topics.sh --list --zookeeper localhost:2181
如果正常返回test
步骤6:打开producer,发送消息
bin/kafka-console-producer.sh --broker-list localhost:9092 --topic test ##启动成功后,输入以下内容测试This is a messageThis is another message
步骤7:打开consumer,接收消息
bin/kafka-console-consumer.sh --zookeeper localhost:2181 --topic test --from-beginning###启动成功后,如果一切正常将会显示producer端输入的内容This is a messageThis is another message
运行KafkaWordCount
KafkaWordCount源文件位置 examples/src/main/scala/org/apache/spark/examples/streaming/KafkaWordCount.scala
尽管里面有使用说明,见下文,但如果不是事先对Kafka有一定的了解的话,决然不知道这些参数是什么意思,也不知道该如何填写。
/** * Consumes messages from one or more topics in Kafka and does wordcount. * Usage: KafkaWordCount * is a list of one or more zookeeper servers that make quorum * is the name of kafka consumer group * is a list of one or more kafka topics to consume from * is the number of threads the kafka consumer should use * * Example: * `$ bin/run-example * org.apache.spark.examples.streaming.KafkaWordCount zoo01,zoo02,zoo03 * my-consumer-group topic1,topic2 1` */object KafkaWordCount { def main(args: Array[String]) { if (args.length < 4) { System.err.println("Usage: KafkaWordCount ") System.exit(1) } StreamingExamples.setStreamingLogLevels() val Array(zkQuorum, group, topics, numThreads) = args val sparkConf = new SparkConf().setAppName("KafkaWordCount") val ssc = new StreamingContext(sparkConf, Seconds(2)) ssc.checkpoint("checkpoint") val topicpMap = topics.split(",").map((_,numThreads.toInt)).toMap val lines = KafkaUtils.createStream(ssc, zkQuorum, group, topicpMap).map(_._2) val words = lines.flatMap(_.split(" ")) val wordCounts = words.map(x => (x, 1L)) .reduceByKeyAndWindow(_ + _, _ - _, Minutes(10), Seconds(2), 2) wordCounts.print() ssc.start() ssc.awaitTermination() }}
讲清楚了写这篇博客的主要原因之后,来看一看该如何运行KafkaWordCount
步骤1:停止运行刚才的kafka-console-producer和kafka-console-consumer
步骤2:运行KafkaWordCountProducer
bin/run-example org.apache.spark.examples.streaming.KafkaWordCountProducer localhost:9092 test 3 5
解释一下参数的意思,localhost:9092表示producer的地址和端口, test表示topic,3表示每秒发多少条消息,5表示每条消息中有几个单词
步骤3:运行KafkaWordCount
bin/run-example org.apache.spark.examples.streaming.KafkaWordCount localhost:2181 test-consumer-group test 1
解释一下参数, localhost:2181表示zookeeper的监听地址,test-consumer-group表示consumer-group的名称,必须和$KAFKA_HOME/config/consumer.properties中的group.id的配置内容一致,test表示topic,1表示线程数。