Apache Storm 简明教程

Apache Storm in Yahoo! Finance

Yahoo! Finance 是互联网领先的商业新闻和财务数据网站。它是 Yahoo! 的一部分，可以提供任何人均可访问的财务新闻、市场统计数据、国际市场数据和关于财务资源的其他信息。

若您是一位注册的 Yahoo! 用户，那么您可以定制 Yahoo! Finance 来利用它的某些服务内容。Yahoo! Finance API 用于查询 Yahoo! 上的财务数据。

此 API 显示的数据比实时数据延迟 15 分钟，每 1 分钟更新一次其数据库，用于访问当前的股票相关信息。现在我们来了解一个公司的实时场景，并了解如何在股票价值低于 100 时发出警报。

Spout Creation

喷口的目的是获取公司详细信息并将价格发送给螺栓。您可以使用以下程序代码来创建一个喷口。

Coding: YahooFinanceSpout.java

import java.util.*;
import java.io.*;
import java.math.BigDecimal;

//import yahoofinace packages
import yahoofinance.YahooFinance;
import yahoofinance.Stock;

import backtype.storm.tuple.Fields;
import backtype.storm.tuple.Values;

import backtype.storm.topology.IRichSpout;
import backtype.storm.topology.OutputFieldsDeclarer;

import backtype.storm.spout.SpoutOutputCollector;
import backtype.storm.task.TopologyContext;

public class YahooFinanceSpout implements IRichSpout {
   private SpoutOutputCollector collector;
   private boolean completed = false;
   private TopologyContext context;

   @Override
   public void open(Map conf, TopologyContext context, SpoutOutputCollector collector){
      this.context = context;
      this.collector = collector;
   }

   @Override
   public void nextTuple() {
      try {
         Stock stock = YahooFinance.get("INTC");
         BigDecimal price = stock.getQuote().getPrice();

         this.collector.emit(new Values("INTC", price.doubleValue()));
         stock = YahooFinance.get("GOOGL");
         price = stock.getQuote().getPrice();

         this.collector.emit(new Values("GOOGL", price.doubleValue()));
         stock = YahooFinance.get("AAPL");
         price = stock.getQuote().getPrice();

         this.collector.emit(new Values("AAPL", price.doubleValue()));
      } catch(Exception e) {}
   }

   @Override
   public void declareOutputFields(OutputFieldsDeclarer declarer) {
      declarer.declare(new Fields("company", "price"));
   }

   @Override
   public void close() {}

   public boolean isDistributed() {
      return false;
   }

   @Override
   public void activate() {}

   @Override
   public void deactivate() {}

   @Override
   public void ack(Object msgId) {}

   @Override
   public void fail(Object msgId) {}

   @Override
   public Map<String, Object> getComponentConfiguration() {
      return null;
   }

}

Bolt Creation

此处，螺栓的目的是处理给定公司的价格（当价格低于 100 时）。它使用 Java Map 对象将截止价格限制警报设置为 true （当股票价格低于 100 时）；否则为 false。完整的程序代码如下所示 −

Coding: PriceCutOffBolt.java

import java.util.HashMap;
import java.util.Map;

import backtype.storm.tuple.Fields;
import backtype.storm.tuple.Values;

import backtype.storm.task.OutputCollector;
import backtype.storm.task.TopologyContext;

import backtype.storm.topology.IRichBolt;
import backtype.storm.topology.OutputFieldsDeclarer;

import backtype.storm.tuple.Tuple;

public class PriceCutOffBolt implements IRichBolt {
   Map<String, Integer> cutOffMap;
   Map<String, Boolean> resultMap;

   private OutputCollector collector;

   @Override
   public void prepare(Map conf, TopologyContext context, OutputCollector collector) {
      this.cutOffMap = new HashMap <String, Integer>();
      this.cutOffMap.put("INTC", 100);
      this.cutOffMap.put("AAPL", 100);
      this.cutOffMap.put("GOOGL", 100);

      this.resultMap = new HashMap<String, Boolean>();
      this.collector = collector;
   }

   @Override
   public void execute(Tuple tuple) {
      String company = tuple.getString(0);
      Double price = tuple.getDouble(1);

      if(this.cutOffMap.containsKey(company)){
         Integer cutOffPrice = this.cutOffMap.get(company);

         if(price < cutOffPrice) {
            this.resultMap.put(company, true);
         } else {
            this.resultMap.put(company, false);
         }
      }

      collector.ack(tuple);
   }

   @Override
   public void cleanup() {
      for(Map.Entry<String, Boolean> entry:resultMap.entrySet()){
         System.out.println(entry.getKey()+" : " + entry.getValue());
      }
   }

   @Override
   public void declareOutputFields(OutputFieldsDeclarer declarer) {
      declarer.declare(new Fields("cut_off_price"));
   }

   @Override
   public Map<String, Object> getComponentConfiguration() {
      return null;
   }

}

Submitting a Topology

这是 YahooFinanceSpout.java 和 PriceCutOffBolt.java 相互连接并产生拓扑的主应用程序。以下程序代码演示了如何提交拓扑。

Coding: YahooFinanceStorm.java

import backtype.storm.tuple.Fields;
import backtype.storm.tuple.Values;

import backtype.storm.Config;
import backtype.storm.LocalCluster;
import backtype.storm.topology.TopologyBuilder;

public class YahooFinanceStorm {
   public static void main(String[] args) throws Exception{
      Config config = new Config();
      config.setDebug(true);

      TopologyBuilder builder = new TopologyBuilder();
      builder.setSpout("yahoo-finance-spout", new YahooFinanceSpout());

      builder.setBolt("price-cutoff-bolt", new PriceCutOffBolt())
         .fieldsGrouping("yahoo-finance-spout", new Fields("company"));

      LocalCluster cluster = new LocalCluster();
      cluster.submitTopology("YahooFinanceStorm", config, builder.createTopology());
      Thread.sleep(10000);
      cluster.shutdown();
   }
}

Building and Running the Application

完整的应用程序有三个 Java 代码。它们如下：

YahooFinanceSpout.java
PriceCutOffBolt.java
YahooFinanceStorm.java

可以通过以下命令构建应用程序 −

javac -cp “/path/to/storm/apache-storm-0.9.5/lib/*”:”/path/to/yahoofinance/lib/*” *.java

可以通过以下命令运行应用程序 −

javac -cp “/path/to/storm/apache-storm-0.9.5/lib/*”:”/path/to/yahoofinance/lib/*”:.
YahooFinanceStorm

Output

输出将类似于以下内容 −

GOOGL : false
AAPL : false
INTC : true