Changes between Initial Version and Version 1 of waue/2011/0426_4_6

Timestamp:

Apr 25, 2011, 3:55:44 PM (13 years ago)

Author:

waue

Comment:

--

waue/2011/0426_4_6

@@ +1 @@
+{{{
+#!html
+<div style="text-align: center; color:#151B8D"><big style="font-weight: bold;"><big><big>
+ITRI HBase 進階課程 
+</big></big></big></div> <div style="text-align: center; color:#7E2217"><big style="font-weight: bold;"><big>
+HBase 範例
+</big></big></div>
+}}}
+
+[wiki:waue/2011/0426_4_5 上一關 < ] 第六關 [wiki:waue/2011/0426_4_7 > 下一關]
+
+ = 範例六：WordCountHBase = 
+
+ == 說明：  ==
+
+ * 此程式碼將輸入路徑的檔案內的字串取出做字數統計,再將結果塞回HTable內
+ * 請注意在將hbase 等函式庫放入hadoop 的lib 目錄後，必須重新啟動hbase 與 hadoop 再執行此範例程式才不會出現錯誤
+
+{{{
+$ bin/hadoop dfs -mkdir input
+$ bin/hadoop dfs -put README.txt input
+$ bin/hadoop jar ItriMenu.jar CountToHBaseReducer input
+}}}
+
+ == 注意： ==
+
+1.      在hdfs 上來源檔案的路徑為 "/user/$YOUR_NAME/input"
+
+        請注意必須先放資料到此hdfs上的資料夾內，且此資料夾內只能放檔案，不可再放資料夾
+
+2.      運算完後，程式將執行結果放在hbase的wordcount資料表內
+
+
+
+ == 程式碼 ==
+
+{{{
+#!java
+
+package itri;
+
+
+import java.io.IOException;
+
+import org.apache.hadoop.conf.Configuration;
+import org.apache.hadoop.fs.Path;
+import org.apache.hadoop.hbase.client.Put;
+import org.apache.hadoop.hbase.mapreduce.TableOutputFormat;
+import org.apache.hadoop.hbase.mapreduce.TableReducer;
+import org.apache.hadoop.hbase.util.Bytes;
+import org.apache.hadoop.io.IntWritable;
+import org.apache.hadoop.io.LongWritable;
+import org.apache.hadoop.io.Text;
+import org.apache.hadoop.mapreduce.Job;
+import org.apache.hadoop.mapreduce.Mapper;
+import org.apache.hadoop.mapreduce.lib.input.FileInputFormat;
+import org.apache.hadoop.mapreduce.lib.input.TextInputFormat;
+import org.apache.hadoop.util.GenericOptionsParser;
+
+public class CountToHBaseReducer {
+        public static class HtMap extends
+                        Mapper<LongWritable, Text, Text, IntWritable> {
+                private IntWritable one = new IntWritable(1);
+
+                public void map(LongWritable key, Text value, Context context)
+                                throws IOException, InterruptedException {
+                        // 輸入的字串先轉換成小寫再用空白區隔
+                        String s[] = value.toString().toLowerCase().trim().split(" ");
+                        for (String m : s) {
+                                // 寫入到輸出串流
+                                context.write(new Text(m), one);
+                        }
+                }
+        }
+
+        // TableReducer<KEYIN,VALUEIN,KEYOUT>
+        // 原本為 TableReducer<Text, IntWritable, NullWritable >
+        // 但在此改成 LongWritable 也可以
+        // 因此證明在此的Class可以很多,org.apache.hadoop.io.* 內有write()的Writable class應該皆可
+        public static class HtReduce extends
+                        TableReducer<Text, IntWritable, LongWritable> {
+
+                public void reduce(Text key, Iterable<IntWritable> values,
+                                Context context) throws IOException, InterruptedException {
+                        int sum = 0;
+                        for (IntWritable i : values) {
+                                sum += i.get();
+                        }
+
+                        // org.apache.hadoop.hbase.client.Put
+                        // Used to perform Put operations for a single row.
+                        // new Put(byte[] row)
+                        Put put = new Put(Bytes.toBytes(key.toString()));
+
+                        // add(byte[] family, byte[] qualifier, byte[] value)
+                        // 在main設定output format class 為 TableOutputFormat
+                        // TableReducer 內有定義 output Key class 必須為 Put 或 Delete
+                        put.add(Bytes.toBytes("content"), Bytes.toBytes("word"), Bytes
+                                        .toBytes(key.toString()));
+                        put.add(Bytes.toBytes("content"), Bytes.toBytes("count"), Bytes
+                                        .toBytes(String.valueOf(sum)));
+
+                        // NullWritable.get(): Returns the single instance of this class.
+                        // NullWritable.write(): Serialize the fields of this object to out.
+                        context.write(new LongWritable(), put);
+                        // context.write(NullWritable.get(), put)
+                }
+        }
+
+        public static void main(String argv[]) throws Exception {
+//              String[] argc = {"input"};      argv = argc ; // in hdfs
+                
+                Configuration conf = new Configuration();
+                String[] otherArgs = new GenericOptionsParser(conf, argv)
+                                .getRemainingArgs();
+                if (otherArgs.length < 1) {
+                        System.out.println("CountToHBaseReducer <inHdfsDir> ");
+                        return;
+                }
+                
+                String input = otherArgs[0];
+                
+                String tablename = "wordcounthbase";
+
+
+                // OUTPUT_TABLE = "hbase.mapred.outputtable"
+                // conf.set 用於設定 如 core-site.xml 的 name 與 value
+                // 告訴程式 hbase.mapred.outputtable --> wordcount
+                conf.set(TableOutputFormat.OUTPUT_TABLE, tablename);
+                // 建立hbase 的table 否則沒先建立會出錯
+                CreateTable.createHBaseTable(tablename, "content");
+
+                Job job = new Job(conf, "WordCount table with " + input);
+
+                job.setJarByClass(CountToHBaseReducer.class);
+
+                job.setMapperClass(HtMap.class);
+                job.setReducerClass(HtReduce.class);
+                // 此範例的輸出為 <Text,IntWritable> 因此其實可以省略宣告
+                // set{Map|Reduce}Output{Key|Value}Class()
+                job.setMapOutputKeyClass(Text.class);
+                job.setMapOutputValueClass(IntWritable.class);
+                // InputFormat 只有一個子介面
+                // FileInputFormat <-(SequenceFileInputFormat,TextInputFormat)
+                // 其中TextInputFormat 最常用 ，預設輸入為 LongWritable,Text
+                // 另外HBase 則設計了一個子類別 TableInputFormat
+                job.setInputFormatClass(TextInputFormat.class);
+                // TAbleOutputFormat
+                // 宣告此行則可使 reduce 輸出為 HBase 的table
+                job.setOutputFormatClass(TableOutputFormat.class);
+
+                // 原本設定輸入檔案為 Config.setInputPath(Path) 卻改為
+                // FileInputFormat.addInputPath(Job, Path()) 的設計，
+                // 猜測應該是考慮某些檔案操作並不需要跑mapreduce的Job，因此提到外面
+                FileInputFormat.addInputPath(job, new Path(input));
+
+                System.exit(job.waitForCompletion(true) ? 0 : 1);
+        }
+}
+}}}
+
+= 執行測試 =
+
+{{{
+$ /opt/hbase/bin/hbase shell
+hbase(main):x:0> list
+wordcount                                                                                                     
+1 row(s) in 0.0240 seconds
+hbase(main):x:0> scan 'wordcount'
+.....
+ zeller                      column=content:count, timestamp=1285674576293, value=1                           
+ zero                        column=content:count, timestamp=1285674576293, value=8                           
+ zero,                       column=content:count, timestamp=1285674576293, value=2                           
+ zero-compressed             column=content:count, timestamp=1285674576293, value=1              
+.....
+hbase(main):x:0> exit
+}}}