java - エラーの原因 java.lang.IndexOutOfBoundsException: インデックス: 0、サイズ: 0

Question

次のMapフェーズからプログラムをhadoopで書きました

public class ParallelIndexation {
    public static class Map extends MapReduceBase implements
            Mapper<LongWritable, Text, Text, LongWritable> {
        private final static LongWritable zero = new LongWritable(0);
        private Text word = new Text();

        public void map(LongWritable key, Text value,
                OutputCollector<Text, LongWritable> output, Reporter reporter)
                throws IOException {
            //DOMConfigurator.configure("/folder/log4j.xml");
            Configuration conf = new Configuration();
            int CountComputers;
            FileInputStream fstream = new FileInputStream(
                    "/export/hadoop-1.0.1/bin/countcomputers.txt");

            BufferedReader br = new BufferedReader(new InputStreamReader(fstream));
            String result=br.readLine();
            CountComputers=Integer.parseInt(result);
            input.close();
            fstream.close();
            Connection con = null;
            Statement st = null;
                ResultSet rs = null;    
               String url = "jdbc:postgresql://192.168.1.8:5432/NexentaSearch";
                String user = "postgres";
                String password = "valter89";
            ArrayList<String> paths = new ArrayList<String>();
            try
            {
                con = DriverManager.getConnection(url, user, password);
                        st = con.createStatement();
                        rs = st.executeQuery("select path from tasks order by id");
                while (rs.next()) { paths.add(rs.getString(1)); };
                PrintWriter zzz = null;
                    try
                    {
                            zzz = new PrintWriter(new FileOutputStream("/export/hadoop-1.0.1/bin/readwaysfromdatabase.txt"));
                    }
                    catch(FileNotFoundException e)
                    {
                            System.out.println("Error");
                            System.exit(0);
                    }
                    for (int i=0; i<paths.size(); i++)
                {
                    zzz.println("paths[i]=" + paths.get(i) + "\n");
                    }
                    zzz.close();

            }
            catch (SQLException e) 
            {
                System.out.println("Connection Failed! Check output console");
                e.printStackTrace();
            }
            String[] ConcatPaths = new String[CountComputers];
            int NumberOfElementConcatPaths = 0;
            if (paths.size() % CountComputers == 0) {
                for (int i = 0; i < CountComputers; i++) {
                    ConcatPaths[i] = paths.get(NumberOfElementConcatPaths);
                    NumberOfElementConcatPaths += paths.size() / CountComputers;
                    for (int j = 1; j < paths.size() / CountComputers; j++) {
                        ConcatPaths[i] += "\n"
                                + paths.get(i * paths.size() / CountComputers
                                        + j);
                    }
                }
            } else {
                NumberOfElementConcatPaths = 0;
                for (int i = 0; i < paths.size() % CountComputers; i++) {
                    ConcatPaths[i] = paths.get(NumberOfElementConcatPaths);
                    NumberOfElementConcatPaths += paths.size() / CountComputers
                            + 1;
                    for (int j = 1; j < paths.size() / CountComputers + 1; j++) {
                        ConcatPaths[i] += "\n"
                                + paths.get(i
                                        * (paths.size() / CountComputers + 1)
                                        + j);
                    }
                }
                for (int k = paths.size() % CountComputers; k < CountComputers; k++) {
                    ConcatPaths[k] = paths.get(NumberOfElementConcatPaths);
                    NumberOfElementConcatPaths += paths.size() / CountComputers;
                    for (int j = 1; j < paths.size() / CountComputers; j++) {
                        ConcatPaths[k] += "\n"
                                + paths.get((k - paths.size() % CountComputers)
                                        * paths.size() / CountComputers
                                        + paths.size() % CountComputers
                                        * (paths.size() / CountComputers + 1)
                                        + j);
                    }
                }
            }
            for (int i = 0; i < ConcatPaths.length; i++) {
                word.set(ConcatPaths[i]);
                output.collect(word, zero);
            }
        }
    }

実行の結果、次のメッセージを受け取りました

args[0]=/export/hadoop-1.0.1/bin/input
13/04/27 16:02:29 WARN mapred.JobClient: Use GenericOptionsParser for parsing the arguments. Applications should implement Tool for the same.
13/04/27 16:02:29 INFO mapred.FileInputFormat: Total input paths to process : 1
13/04/27 16:02:29 INFO mapred.JobClient: Running job: job_201304271556_0001
13/04/27 16:02:30 INFO mapred.JobClient:  map 0% reduce 0%
13/04/27 16:06:45 INFO mapred.JobClient:  map 50% reduce 0%
13/04/27 16:06:50 INFO mapred.JobClient: Task Id : attempt_201304271556_0001_m_000001_0, Status : FAILED
java.lang.IndexOutOfBoundsException: Index: 0, Size: 0
    at java.util.ArrayList.rangeCheck(ArrayList.java:604)
    at java.util.ArrayList.get(ArrayList.java:382)
    at org.myorg.ParallelIndexation$Map.map(ParallelIndexation.java:100)
    at org.myorg.ParallelIndexation$Map.map(ParallelIndexation.java:29)
    at org.apache.hadoop.mapred.MapRunner.run(MapRunner.java:50)
    at org.apache.hadoop.mapred.MapTask.runOldMapper(MapTask.java:436)
    at org.apache.hadoop.mapred.MapTask.run(MapTask.java:372)
    at org.apache.hadoop.mapred.Child$4.run(Child.java:255)
    at java.security.AccessController.doPrivileged(Native Method)
    at javax.security.auth.Subject.doAs(Subject.java:415)
    at org.apache.hadoop.security.UserGroupInformation.doAs(UserGroupInformation.java:1093)
    at org.apache.hadoop.mapred.Child.main(Child.java:249)

13/04/27 16:07:50 WARN mapred.JobClient: Error reading task outputmyhost2
13/04/27 16:07:50 WARN mapred.JobClient: Error reading task outputmyhost2
13/04/27 16:07:50 INFO mapred.JobClient: Job complete: job_201304271556_0001
13/04/27 16:07:50 INFO mapred.JobClient: Counters: 21
13/04/27 16:07:50 INFO mapred.JobClient:   Job Counters 
13/04/27 16:07:50 INFO mapred.JobClient:     Launched reduce tasks=1
13/04/27 16:07:50 INFO mapred.JobClient:     SLOTS_MILLIS_MAPS=37867
13/04/27 16:07:50 INFO mapred.JobClient:     Total time spent by all reduces waiting after reserving slots (ms)=0
13/04/27 16:07:50 INFO mapred.JobClient:     Total time spent by all maps waiting after reserving slots (ms)=0
13/04/27 16:07:50 INFO mapred.JobClient:     Launched map tasks=5
13/04/27 16:07:50 INFO mapred.JobClient:     Data-local map tasks=5
13/04/27 16:07:50 INFO mapred.JobClient:     SLOTS_MILLIS_REDUCES=24154
13/04/27 16:07:50 INFO mapred.JobClient:     Failed map tasks=1
13/04/27 16:07:50 INFO mapred.JobClient:   File Input Format Counters 
13/04/27 16:07:50 INFO mapred.JobClient:     Bytes Read=99
13/04/27 16:07:50 INFO mapred.JobClient:   FileSystemCounters
13/04/27 16:07:50 INFO mapred.JobClient:     HDFS_BYTES_READ=215
13/04/27 16:07:50 INFO mapred.JobClient:     FILE_BYTES_WRITTEN=21573
13/04/27 16:07:50 INFO mapred.JobClient:   Map-Reduce Framework
13/04/27 16:07:50 INFO mapred.JobClient:     Map output materialized bytes=6
13/04/27 16:07:50 INFO mapred.JobClient:     Combine output records=0
13/04/27 16:07:50 INFO mapred.JobClient:     Map input records=0
13/04/27 16:07:50 INFO mapred.JobClient:     Spilled Records=0
13/04/27 16:07:50 INFO mapred.JobClient:     Map output bytes=0
13/04/27 16:07:50 INFO mapred.JobClient:     Total committed heap usage (bytes)=160763904
13/04/27 16:07:50 INFO mapred.JobClient:     Map input bytes=0
13/04/27 16:07:50 INFO mapred.JobClient:     Combine input records=0
13/04/27 16:07:50 INFO mapred.JobClient:     Map output records=0
13/04/27 16:07:50 INFO mapred.JobClient:     SPLIT_RAW_BYTES=116
13/04/27 16:07:50 INFO mapred.JobClient: Job Failed: # of failed Map Tasks exceeded allowed limit. FailedCount: 1. LastFailedTask: task_201304271556_0001_m_000001
Exception in thread "main" java.io.IOException: Job failed!
    at org.apache.hadoop.mapred.JobClient.runJob(JobClient.java:1265)
    at org.myorg.ParallelIndexation.main(ParallelIndexation.java:183)
    at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method)
    at sun.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:57)
    at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:43)
    at java.lang.reflect.Method.invoke(Method.java:601)
    at org.apache.hadoop.util.RunJar.main(RunJar.java:156)

また、正常に実行されたプログラムのフェーズを Map に与えます (少なくとも、それが動作したデータベースから判断すると、少なくとも実行ログとして完全に理想的とは言えませんでしたが、必要なレコードがデータベースに入力されたにもかかわらず、おそらくそれが役立つでしょう）データベースからファイルへの方法を含むテキストファイルが入力され、1行に書き込まれ、文字で分割されました|（動作しないプログラムでは、明らかにテキストからこれらの方法がデータベースから直接読み取られます）

public class ParallelIndexation {
    public static class Map extends MapReduceBase implements
            Mapper<LongWritable, Text, Text, LongWritable> {
        private final static LongWritable zero = new LongWritable(0);
        private Text word = new Text();

        public void map(LongWritable key, Text value,
                OutputCollector<Text, LongWritable> output, Reporter reporter)
                throws IOException {
            String line = value.toString();
            int CountComputers;
            FileInputStream fstream = new FileInputStream(
                    "/usr/countcomputers.txt");

            BufferedReader br = new BufferedReader(new InputStreamReader(fstream));
            String result=br.readLine();
            CountComputers=Integer.parseInt(result);
            in.close();
            fstream.close();
            ArrayList<String> paths = new ArrayList<String>();
            StringTokenizer tokenizer = new StringTokenizer(line, "|");
            while (tokenizer.hasMoreTokens()) {
                paths.add(tokenizer.nextToken());
            }
            String[] ConcatPaths = new String[CountComputers];
            int NumberOfElementConcatPaths = 0;
            if (paths.size() % CountComputers == 0) {
                for (int i = 0; i < CountComputers; i++) {
                    ConcatPaths[i] = paths.get(NumberOfElementConcatPaths);
                    NumberOfElementConcatPaths += paths.size() / CountComputers;
                    for (int j = 1; j < paths.size() / CountComputers; j++) {
                        ConcatPaths[i] += "\n"
                                + paths.get(i * paths.size() / CountComputers
                                        + j);
                    }
                }
            } else {
                NumberOfElementConcatPaths = 0;
                for (int i = 0; i < paths.size() % CountComputers; i++) {
                    ConcatPaths[i] = paths.get(NumberOfElementConcatPaths);
                    NumberOfElementConcatPaths += paths.size() / CountComputers
                            + 1;
                    for (int j = 1; j < paths.size() / CountComputers + 1; j++) {
                        ConcatPaths[i] += "\n"
                                + paths.get(i
                                        * (paths.size() / CountComputers + 1)
                                        + j);
                    }
                }
                for (int k = paths.size() % CountComputers; k < CountComputers; k++) {
                    ConcatPaths[k] = paths.get(NumberOfElementConcatPaths);
                    NumberOfElementConcatPaths += paths.size() / CountComputers;
                    for (int j = 1; j < paths.size() / CountComputers; j++) {
                        ConcatPaths[k] += "\n"
                                + paths.get((k - paths.size() % CountComputers)
                                        * paths.size() / CountComputers
                                        + paths.size() % CountComputers
                                        * (paths.size() / CountComputers + 1)
                                        + j);
                    }
                }
            }
            for (int i = 0; i < ConcatPaths.length; i++) {
                word.set(ConcatPaths[i]);
                output.collect(word, zero);
            }
        }
    }

エラーを解消するのに役立ちます。エラーは行にあります

ConcatPaths[i] = paths.get(NumberOfElementConcatPaths);

おそらくpaths.sizeゼロに等しいからです。しかしarraylist paths、データベースからの読み取りの結果 (リクエストで指定されたテーブルは 6 つのレコードで完了) が満たされないのはなぜですか?

score 1 · Accepted Answer

どれが100行か言及していないので、まだ論理ルートを通過しようとしています.issueは並んでいます

ConcatPaths[i] = paths.get(NumberOfElementConcatPaths);

ここで、NumberOfElementConcatPaths はパスサイズのサイズを超えています。エラーが発生している行の前に NumberOfElementConcatPaths とパスのサイズを出力するだけです。あなたはそれをキャッチします

java - エラーの原因 java.lang.IndexOutOfBoundsException: インデックス: 0、サイズ: 0

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