一、kafka基本概念

      1、kafka是一個分散式的訊息快取系統
      2、kafka叢集中的伺服器都叫做broker
      3、kafka有兩類客戶端，一類叫producer（訊息生產者），一類叫做consumer（訊息消費者），客戶端和broker伺服器之間採用tcp協議連線
      4、kafka中不同業務系統的訊息可以通過topic進行區分，而且每一個訊息topic都會被分割槽，以分擔訊息讀寫的負載
      5、每一個分割槽都可以有多個副本，以防止資料的丟失
      6、某一個分割槽中的資料如果需要更新，都必須通過該分割槽所有副本中的leader來更新
      7、消費者可以分組，比如有兩個消費者組A和B，共同消費一個topic：order_info,A和B所消費的訊息不會重複
           比如 order_info 中有100個訊息，每個訊息有一個id,編號從0-99，那麼，如果A組消費0-49號，B組就消費50-99號
      8、消費者在具體消費某個topic中的訊息時，可以指定起始偏移量

二、kafka叢集安裝

1、解壓

2、修改server.properties
broker.id=1
zookeeper.connect=weekend05:2181,weekend06:2181,weekend07:2181

3、將zookeeper叢集啟動

4、在每一臺節點上啟動broker
bin/kafka-server-start.sh config/server.properties


5、在kafka叢集中建立一個topic
bin/kafka-topics.sh --create --zookeeper weekend05:2181 --replication-factor 3 --partitions 1 --topic order


6、用一個producer向某一個topic中寫入訊息
bin/kafka-console-producer.sh --broker-list weekend:9092 --topic order


7、用一個comsumer從某一個topic中讀取資訊
bin/kafka-console-consumer.sh --zookeeper weekend05:2181 --from-beginning --topic order


8、檢視一個topic的分割槽及副本狀態資訊
bin/kafka-topics.sh --describe --zookeeper weekend05:2181 --topic order

三、kafka與storm結合

首先來看一張業務流程圖

這裡，flume作為生產者客戶端，storm作為消費者客戶端

例子：下面，我們開發了一個簡單WordCount示例程式，從Kafka讀取訂閱的訊息行，通過空格拆分出單個單詞，然後再做詞頻統計計算

import java.util.Arrays;
import java.util.HashMap;
import java.util.Iterator;
import java.util.Map;
import java.util.Map.Entry;
import java.util.concurrent.atomic.AtomicInteger;

import org.apache.commons.logging.Log;
import org.apache.commons.logging.LogFactory;

import storm.kafka.BrokerHosts;//匯入storm-kafka-0.9.2-incubating.jar包
import storm.kafka.KafkaSpout;
import storm.kafka.SpoutConfig;
import storm.kafka.StringScheme;
import storm.kafka.ZkHosts;
import backtype.storm.Config;
import backtype.storm.LocalCluster;
import backtype.storm.StormSubmitter;
import backtype.storm.generated.AlreadyAliveException;
import backtype.storm.generated.InvalidTopologyException;
import backtype.storm.spout.SchemeAsMultiScheme;
import backtype.storm.task.OutputCollector;
import backtype.storm.task.TopologyContext;
import backtype.storm.topology.OutputFieldsDeclarer;
import backtype.storm.topology.TopologyBuilder;
import backtype.storm.topology.base.BaseRichBolt;
import backtype.storm.tuple.Fields;
import backtype.storm.tuple.Tuple;
import backtype.storm.tuple.Values;

public class MyKafkaTopology {

     public static class KafkaWordSplitter extends BaseRichBolt {

          private static final Log LOG = LogFactory.getLog(KafkaWordSplitter.class);
          private static final long serialVersionUID = 886149197481637894L;
          private OutputCollector collector;
         
          @Override
          public void prepare(Map stormConf, TopologyContext context,
                    OutputCollector collector) {
               this.collector = collector;              
          }

          @Override
          public void execute(Tuple input) {
               String line = input.getString(0);
               LOG.info("RECV[kafka -> splitter] " + line);
               String[] words = line.split("\\s+");
               for(String word : words) {
                    LOG.info("EMIT[splitter -> counter] " + word);
                    collector.emit(input, new Values(word, 1));
               }
               collector.ack(input);
          }

          @Override
          public void declareOutputFields(OutputFieldsDeclarer declarer) {
               declarer.declare(new Fields("word", "count"));         
          }
         
     }
    
     public static class WordCounter extends BaseRichBolt {

          private static final Log LOG = LogFactory.getLog(WordCounter.class);
          private static final long serialVersionUID = 886149197481637894L;
          private OutputCollector collector;
          private Map<String, AtomicInteger> counterMap;
         
          @Override
          public void prepare(Map stormConf, TopologyContext context,
                    OutputCollector collector) {
               this.collector = collector;    
               this.counterMap = new HashMap<String, AtomicInteger>();
          }

          @Override
          public void execute(Tuple input) {
               String word = input.getString(0);
               int count = input.getInteger(1);
               LOG.info("RECV[splitter -> counter] " + word + " : " + count);
               AtomicInteger ai = this.counterMap.get(word);
               if(ai == null) {
                    ai = new AtomicInteger();
                    this.counterMap.put(word, ai);
               }
               ai.addAndGet(count);
               collector.ack(input);
               LOG.info("CHECK statistics map: " + this.counterMap);
          }

          @Override
          public void cleanup() {
               LOG.info("The final result:");
               Iterator<Entry<String, AtomicInteger>> iter = this.counterMap.entrySet().iterator();
               while(iter.hasNext()) {
                    Entry<String, AtomicInteger> entry = iter.next();
                    LOG.info(entry.getKey() + "\t:\t" + entry.getValue().get());
               }
              
          }

          @Override
          public void declareOutputFields(OutputFieldsDeclarer declarer) {
               declarer.declare(new Fields("word", "count"));         
          }
     }
    
     public static void main(String[] args) throws AlreadyAliveException, InvalidTopologyException, InterruptedException {
          String zks = "h1:2181,h2:2181,h3:2181";
          String topic = "my-replicated-topic5";
          String zkRoot = "/storm"; // default zookeeper root configuration for storm
          String id = "word";
         
          BrokerHosts brokerHosts = new ZkHosts(zks);
          SpoutConfig spoutConf = new SpoutConfig(brokerHosts, topic, zkRoot, id);
          spoutConf.scheme = new SchemeAsMultiScheme(new StringScheme());
          spoutConf.forceFromStart = false;//該配置是指，如果該Topology因故障停止處理，下次正常執行時是否從Spout對應資料來源Kafka//中的該訂閱Topic的起始位置開始讀取，如果forceFromStart=true，則之前處理過的Tuple還要重新處理一遍，否則會從上次處理的位置//繼續處理，保證Kafka中的Topic資料不被重複處理，是在資料來源的位置進行狀態記錄
          spoutConf.zkServers = Arrays.asList(new String[] {"h1", "h2", "h3"});
          spoutConf.zkPort = 2181;
         
          TopologyBuilder builder = new TopologyBuilder();
          builder.setSpout("kafka-reader", new KafkaSpout(spoutConf), 5); // Kafka我們建立了一個5分割槽的Topic，這裡並行度設定為5
          builder.setBolt("word-splitter", new KafkaWordSplitter(), 2).shuffleGrouping("kafka-reader");
          builder.setBolt("word-counter", new WordCounter()).fieldsGrouping("word-splitter", new Fields("word"));
         
          Config conf = new Config();
         
          String name = MyKafkaTopology.class.getSimpleName();
          if (args != null && args.length > 0) {
               // Nimbus host name passed from command line
               conf.put(Config.NIMBUS_HOST, args[0]);
               conf.setNumWorkers(3);
               StormSubmitter.submitTopologyWithProgressBar(name, conf, builder.createTopology());
          } else {
               conf.setMaxTaskParallelism(3);
               LocalCluster cluster = new LocalCluster();
               cluster.submitTopology(name, conf, builder.createTopology());
               Thread.sleep(60000);
               cluster.shutdown();
          }
     }
}
 

四、kafka學習網址

學習官網：http://kafka.apache.org/documentation.html#introduction

storm+kafka+hdfs: http://shiyanjun.cn/archives/934.html