文章目錄
- 一、MapReduce
- 二、MapReduce開發環境搭建
-
- 2.1、Maven環境
- 2.2、手動導入Jar包
- 三、MapReduce單詞計數源碼分析
-
- 3.1、打開WordCount.java
- 3.2、源碼分析
-
- 3.2.1、MapReduce單詞計數源碼 : Map任務
- 3.2.2、MapReduce單詞計數源碼 : Reduce任務
- 3.2.3、MapReduce單詞計數源碼 : main 函數
- 四、MapReduce API介紹
-
- 4.1、MapReduce程式子產品 : Main 函數
- 4.2、MapReduce程式子產品: Mapper
- 4.3、MapReduce程式子產品: Reducer
- 五、MapReduce執行個體
-
- 5.1、流程(Mapper、Reducer、Main、打包運作)
- 5.2、執行個體1:按日期通路統計次數:
- 5.3、執行個體2:按使用者通路次數排序
一、MapReduce
MapReduce是Google提出的一個軟體架構,用于大規模資料集(大于1TB)的并行運算。概念“Map(映射)”和“Reduce(歸納)”,及他們的主要思想,都是從函數式程式設計語言借來的,還有從矢量程式設計語言借來的特性。
目前的軟體實作是指定一個Map(映射)函數,用來把一組鍵值對映射成一組新的鍵值對,指定并發的Reduce(歸納)函數,用來保證所有映射的鍵值對中的每一個共享相同的鍵組。
二、MapReduce開發環境搭建
環境準備: Java, Intellij IDEA, Maven
開發環境搭建方式
java安裝連結及步驟:https://www.cnblogs.com/de-ming/p/13909440.html
2.1、Maven環境
添加依賴
https://search.maven.org/artifact/org.apache.hadoop/hadoop-client/3.1.4/jar
添加源碼
2.2、手動導入Jar包
Hadoop安裝包連結:https://pan.baidu.com/s/1teHwnBH2Qm6F7iWZ3q-hSQ
提取碼:cgnb
建立一個java工程
然後,搜JobClient.class,點選’Choose Sources’
這樣就OK了,可以看到JobClient.java
三、MapReduce單詞計數源碼分析
3.1、打開WordCount.java
打開:https://mvnrepository.com/artifact/org.apache.hadoop/hadoop-mapreduce-examples/3.1.4,複制Maven裡面的内容
粘貼到源碼
搜尋WordCount
3.2、源碼分析
3.2.1、MapReduce單詞計數源碼 : Map任務
3.2.2、MapReduce單詞計數源碼 : Reduce任務
3.2.3、MapReduce單詞計數源碼 : main 函數
設定必要參數及組裝MapReduce程式
四、MapReduce API介紹
- 一般MapReduce都是由Mapper, Reducer 及main 函數組成。
- Mapper程式一般完成鍵值對映射操作;
- Reducer 程式一般完成鍵值對聚合操作;
- Main函數則負責組裝Mapper,Reducer及必要的配置;
- 高階程式設計還涉及到設定輸入輸出檔案格式、設定Combiner、Partitioner優化程式等;
4.1、MapReduce程式子產品 : Main 函數
4.2、MapReduce程式子產品: Mapper
- org.apache.hadoop.mapreduce.Mapper
4.3、MapReduce程式子產品: Reducer
- org.apache.hadoop.mapreduce.Reducer
五、MapReduce執行個體
5.1、流程(Mapper、Reducer、Main、打包運作)
- 參考WordCount程式,修改Mapper;
- 直接複制 Reducer程式;
- 直接複制Main函數,并做相應修改;
- 編譯打包 ;
- 上傳Jar包;
- 上傳資料;
- 運作程式;
- 檢視運作結果;
5.2、執行個體1:按日期通路統計次數:
1、參考WordCount程式,修改Mapper;
(這裡建立一個java程式,然後把下面(1、2、3步代碼)複制到類裡)
public static class SpiltMapper
extends Mapper<Object, Text, Text, IntWritable> {
private final static IntWritable one = new IntWritable(1);
private Text word = new Text();
//value: email_address | date
public void map(Object key, Text value, Context context
) throws IOException, InterruptedException {
String[] data = value.toString().split("\\|",-1); //
word.set(data[1]); //
context.write(word, one);
}
}
2、直接複制 Reducer程式;
public static class IntSumReducer
extends Reducer<Text,IntWritable,Text,IntWritable> {
private IntWritable result = new IntWritable();
public void reduce(Text key, Iterable<IntWritable> values,
Context context
) throws IOException, InterruptedException {
int sum = 0;
for (IntWritable val : values) {
sum += val.get();
}
result.set(sum);
context.write(key, result);
}
}
3、直接複制Main函數,并做相應修改;
public static void main(String[] args) throws Exception {
Configuration conf = new Configuration();
String[] otherArgs = new GenericOptionsParser(conf, args).getRemainingArgs();
if (otherArgs.length < 2) {
System.err.println("Usage: wordcount <in> [<in>...] <out>");
System.exit(2);
}
Job job = Job.getInstance(conf, "word count");
job.setJarByClass(CountByDate.class); //我們的主類是CountByDate
job.setMapperClass(SpiltMapper.class); //mapper:我們修改為SpiltMapper
job.setCombinerClass(IntSumReducer.class);
job.setReducerClass(IntSumReducer.class);
job.setOutputKeyClass(Text.class);
job.setOutputValueClass(IntWritable.class);
for (int i = 0; i < otherArgs.length - 1; ++i) {
FileInputFormat.addInputPath(job, new Path(otherArgs[i]));
}
FileOutputFormat.setOutputPath(job,
new Path(otherArgs[otherArgs.length - 1]));
System.exit(job.waitForCompletion(true) ? 0 : 1);
}
4、編譯打包 (jar打包)
build出現錯誤及解決辦法:
完成
5/6、上傳jar包&資料
email_log_with_date.txt資料包連結:https://pan.baidu.com/s/1HfwHCfmvVdQpuL-MPtpAng
提取碼:cgnb
上傳資料包(注意開啟hdfs):
上傳OK(浏覽器:
master:50070
檢視)
7、運作程式
(注意開啟yarn)
上傳完成後:
(
master:8088
)
8、檢視結果
(
master:50070
)
5.3、執行個體2:按使用者通路次數排序
Mapper、Reducer、Main程式
SortByCountFirst.Mapper
package demo;
import org.apache.hadoop.conf.Configuration;
import org.apache.hadoop.fs.Path;
import org.apache.hadoop.io.IntWritable;
import org.apache.hadoop.io.Text;
import org.apache.hadoop.mapreduce.Job;
import org.apache.hadoop.mapreduce.Mapper;
import org.apache.hadoop.mapreduce.Reducer;
import org.apache.hadoop.mapreduce.lib.input.FileInputFormat;
import org.apache.hadoop.mapreduce.lib.output.FileOutputFormat;
import org.apache.hadoop.util.GenericOptionsParser;
import java.io.IOException;
public class SortByCountFirst {
//1、修改Mapper
public static class SpiltMapper
extends Mapper<Object, Text, Text, IntWritable> {
private final static IntWritable one = new IntWritable(1);
private Text word = new Text();
//value: email_address | date
public void map(Object key, Text value, Context context
) throws IOException, InterruptedException {
String[] data = value.toString().split("\\|",-1);
word.set(data[0]);
context.write(word, one);
}
}
//2、直接複制 Reducer程式,不用修改
public static class IntSumReducer
extends Reducer<Text,IntWritable,Text,IntWritable> {
private IntWritable result = new IntWritable();
public void reduce(Text key, Iterable<IntWritable> values,
Context context
) throws IOException, InterruptedException {
int sum = 0;
for (IntWritable val : values) {
sum += val.get();
}
result.set(sum);
context.write(key, result);
}
}
//3、直接複制Main函數,并做相應修改;
public static void main(String[] args) throws Exception {
Configuration conf = new Configuration();
String[] otherArgs = new GenericOptionsParser(conf, args).getRemainingArgs();
if (otherArgs.length < 2) {
System.err.println("Usage: demo.SortByCountFirst <in> [<in>...] <out>");
System.exit(2);
}
Job job = Job.getInstance(conf, "sort by count first ");
job.setJarByClass(SortByCountFirst.class); //我們的主類是CountByDate
job.setMapperClass(SpiltMapper.class); //mapper:我們修改為SpiltMapper
job.setCombinerClass(IntSumReducer.class);
job.setReducerClass(IntSumReducer.class);
job.setOutputKeyClass(Text.class);
job.setOutputValueClass(IntWritable.class);
for (int i = 0; i < otherArgs.length - 1; ++i) {
FileInputFormat.addInputPath(job, new Path(otherArgs[i]));
}
FileOutputFormat.setOutputPath(job,
new Path(otherArgs[otherArgs.length - 1]));
System.exit(job.waitForCompletion(true) ? 0 : 1);
}
}
SortByCountSecond.Mapper
package demo;
import org.apache.hadoop.conf.Configuration;
import org.apache.hadoop.fs.Path;
import org.apache.hadoop.io.IntWritable;
import org.apache.hadoop.io.Text;
import org.apache.hadoop.mapreduce.Job;
import org.apache.hadoop.mapreduce.Mapper;
import org.apache.hadoop.mapreduce.Reducer;
import org.apache.hadoop.mapreduce.lib.input.FileInputFormat;
import org.apache.hadoop.mapreduce.lib.output.FileOutputFormat;
import org.apache.hadoop.util.GenericOptionsParser;
import java.io.IOException;
public class SortByCountSecond {
//1、修改Mapper
public static class SpiltMapper
extends Mapper<Object, Text, IntWritable, Text> {
private IntWritable count = new IntWritable(1);
private Text word = new Text();
//value: email_address \t count
public void map(Object key, Text value, Context context
) throws IOException, InterruptedException {
String[] data = value.toString().split("\t",-1);
word.set(data[0]);
count.set(Integer.parseInt(data[1]));
context.write(count,word);
}
}
//2、直接複制 Reducer程式,不用修改
public static class ReverseReducer
extends Reducer<IntWritable,Text,Text,IntWritable> {
public void reduce(IntWritable key, Iterable<Text> values,
Context context
) throws IOException, InterruptedException {
for (Text val : values) {
context.write(val,key);
}
}
}
//3、直接複制Main函數,并做相應修改;
public static void main(String[] args) throws Exception {
Configuration conf = new Configuration();
String[] otherArgs = new GenericOptionsParser(conf, args).getRemainingArgs();
if (otherArgs.length < 2) {
System.err.println("Usage: demo.SortByCountFirst <in> [<in>...] <out>");
System.exit(2);
}
Job job = Job.getInstance(conf, "sort by count first ");
job.setJarByClass(SortByCountSecond.class); //我們的主類是CountByDate
job.setMapperClass(SpiltMapper.class); //mapper:我們修改為SpiltMapper
// job.setCombinerClass(IntSumReducer.class);
job.setReducerClass(ReverseReducer.class);
job.setMapOutputKeyClass(IntWritable.class);
job.setMapOutputValueClass(Text.class);
job.setOutputKeyClass(Text.class);
job.setOutputValueClass(IntWritable.class);
for (int i = 0; i < otherArgs.length - 1; ++i) {
FileInputFormat.addInputPath(job, new Path(otherArgs[i]));
}
FileOutputFormat.setOutputPath(job,
new Path(otherArgs[otherArgs.length - 1]));
System.exit(job.waitForCompletion(true) ? 0 : 1);
}
}
然後打包上傳
yarn jar sortbycount.jar demo.SortByCountSecond -Dmapreduce.job.queuename=prod email_log_with_date.txt sortbycountfirst_output00
yarn jar sortbycount.jar demo.SortByCountSecond -Dmapreduce.job.queuename=prod email_log_with_date.txt sortbycountfirst_output00 sortbycountsecond_output00