我正在写一个mapreduce作业来测试一些计算。我把我的输入分割成Map，这样每个Map都做了微积分的一部分，结果将是一个（x，y）对的列表，我想把它刷新到一个sequencefile中。
Map部分运行良好，但当减速机启动时，我得到以下错误： Exception in thread "main" java.io.FileNotFoundException: File does not exist: hdfs://172.16.199.132:9000/user/hduser/FractalJob_1452257628594_410365359/out/reduce-out .
另一个观察结果是，只有当我使用多于map时，才会出现此错误。
这里更新的是我的Map器和减速机代码。

public static class RasterMapper extends Mapper<IntWritable, IntWritable, IntWritable, IntWritable> {
        private int imageS;
        private static Complex mapConstant;
        @Override
        public void setup(Context context) throws IOException {
            imageS = context.getConfiguration().getInt("image.size", -1);
            mapConstant = new Complex(context.getConfiguration().getDouble("constant.re", -1),
                    context.getConfiguration().getDouble("constant.im", -1));
        }
        @Override
        public void map(IntWritable begin, IntWritable end, Context context) throws IOException, InterruptedException {
            for (int x = (int) begin.get(); x < end.get(); x++) {
                for (int y = 0; y < imageS; y++) {
                    float hue = 0, brighness = 0;
                    int icolor = 0;
                    Complex z = new Complex(2.0 * (x - imageS / 2) / (imageS / 2),
                            1.33 * (y - imageS / 2) / (imageS / 2));
                    icolor = startCompute(generateZ(z), 0);
                    if (icolor != -1) {
                        brighness = 1f;
                    }
                    hue = (icolor % 256) / 255.0f;
                    Color color = Color.getHSBColor(hue, 1f, brighness);
                    try {
                        context.write(new IntWritable(x + y * imageS), new IntWritable(color.getRGB()));
                    } catch (Exception e) {
                        e.printStackTrace();
                    }
                }
            }
        }
        private static Complex generateZ(Complex z) {
            return (z.times(z)).plus(mapConstant);
        }
        private static int startCompute(Complex z, int color) {
            if (z.abs() > 4) {
                return color;
            } else if (color >= 255) {
                return -1;
            } else {
                color = color + 1;
                return startCompute(generateZ(z), color);
            }
        }
    }
    public static class ImageReducer extends Reducer<IntWritable, IntWritable, WritableComparable<?>, Writable> {
        private SequenceFile.Writer writer;
        @Override
        protected void cleanup(Context context) throws IOException, InterruptedException {
            writer.close();
        }
        @Override
        public void setup(Context context) throws IOException, InterruptedException {
            Configuration conf = context.getConfiguration();
            Path outDir = new Path(conf.get(FileOutputFormat.OUTDIR));
            Path outFile = new Path(outDir, "pixels-out");
            Option optPath = SequenceFile.Writer.file(outFile);
            Option optKey = SequenceFile.Writer.keyClass(IntWritable.class);
            Option optVal = SequenceFile.Writer.valueClass(IntWritable.class);
            Option optCom = SequenceFile.Writer.compression(CompressionType.NONE);
            try {
                writer = SequenceFile.createWriter(conf, optCom, optKey, optPath, optVal);
            } catch (Exception e) {
                e.printStackTrace();
            }
        }
        @Override
        public void reduce (IntWritable key,  Iterable<IntWritable>  value, Context context) throws IOException, InterruptedException {
                try{
                    writer.append(key, value.iterator().next());
                } catch (Exception e) {
                        e.printStackTrace();
                }
            }
        }

我希望你们能帮我。谢谢您！
编辑：

Job failed as tasks failed. failedMaps:1 failedReduces:0

仔细看我注意到的日志，我认为问题来自于我将数据输入Map的方式，我将图像大小分成几个序列文件，这样Map就可以从中读取数据并计算该区域像素的颜色。
这是我创建文件的方式：

try {
    int offset = 0;
    // generate an input file for each map task
    for (int i = 0; i < mapNr; ++i) {
        final Path file = new Path(input, "part" + i);
        final IntWritable begin = new IntWritable(offset);
        final IntWritable end = new IntWritable(offset + imgSize / mapNr);
        offset = (int) end.get();
        Option optPath = SequenceFile.Writer.file(file);
        Option optKey = SequenceFile.Writer.keyClass(IntWritable.class);
        Option optVal = SequenceFile.Writer.valueClass(IntWritable.class);
        Option optCom = SequenceFile.Writer.compression(CompressionType.NONE);
        SequenceFile.Writer writer = SequenceFile.createWriter(conf, optCom, optKey, optPath, optVal);
        try {
            writer.append(begin, end);
        } catch (Exception e) {
            e.printStackTrace();
        } finally {
            writer.close();
        }
        System.out.println("Wrote input for Map #" + i);
    }

日志文件：

16/01/10 19:06:04 INFO client.RMProxy: Connecting to ResourceManager at /172.16.199.132:8032
16/01/10 19:06:07 INFO input.FileInputFormat: Total input paths to process : 4
16/01/10 19:06:07 INFO mapreduce.JobSubmitter: number of splits:4
16/01/10 19:06:08 INFO mapreduce.JobSubmitter: Submitting tokens for job: job_1452444283951_0007
16/01/10 19:06:08 INFO impl.YarnClientImpl: Submitted application application_1452444283951_0007
16/01/10 19:06:08 INFO mapreduce.Job: The url to track the job: http://172.16.199.132:8088/proxy/application_1452444283951_0007/
16/01/10 19:06:08 INFO mapreduce.Job: Running job: job_1452444283951_0007
16/01/10 19:06:19 INFO mapreduce.Job: Job job_1452444283951_0007 running in uber mode : false
16/01/10 19:06:20 INFO mapreduce.Job:  map 0% reduce 0%
16/01/10 19:06:49 INFO mapreduce.Job: Task Id : attempt_1452444283951_0007_m_000002_0, Status : FAILED
16/01/10 19:06:49 INFO mapreduce.Job: Task Id : attempt_1452444283951_0007_m_000001_0, Status : FAILED
16/01/10 19:06:49 INFO mapreduce.Job: Task Id : attempt_1452444283951_0007_m_000000_0, Status : FAILED
16/01/10 19:06:49 INFO mapreduce.Job: Task Id : attempt_1452444283951_0007_m_000003_0, Status : FAILED
16/01/10 19:07:07 INFO mapreduce.Job:  map 25% reduce 0%
16/01/10 19:07:08 INFO mapreduce.Job:  map 50% reduce 0%
16/01/10 19:07:10 INFO mapreduce.Job: Task Id : attempt_1452444283951_0007_m_000001_1, Status : FAILED
16/01/10 19:07:11 INFO mapreduce.Job: Task Id : attempt_1452444283951_0007_m_000003_1, Status : FAILED
16/01/10 19:07:25 INFO mapreduce.Job: Task Id : attempt_1452444283951_0007_r_000000_0, Status : FAILED
16/01/10 19:07:32 INFO mapreduce.Job:  map 100% reduce 0%
16/01/10 19:07:32 INFO mapreduce.Job: Task Id : attempt_1452444283951_0007_m_000003_2, Status : FAILED
16/01/10 19:07:32 INFO mapreduce.Job: Task Id : attempt_1452444283951_0007_m_000001_2, Status : FAILED
16/01/10 19:07:33 INFO mapreduce.Job:  map 50% reduce 0%
16/01/10 19:07:43 INFO mapreduce.Job:  map 75% reduce 0%
16/01/10 19:07:44 INFO mapreduce.Job: Task Id : attempt_1452444283951_0007_r_000000_1, Status : FAILED
16/01/10 19:07:50 INFO mapreduce.Job:  map 100% reduce 100%
16/01/10 19:07:51 INFO mapreduce.Job: Job job_1452444283951_0007 failed with state FAILED due to: Task failed task_1452444283951_0007_m_000003
Job failed as tasks failed. failedMaps:1 failedReduces:0
16/01/10 19:07:51 INFO mapreduce.Job: Counters: 40
    File System Counters
        FILE: Number of bytes read=0
        FILE: Number of bytes written=3048165
        FILE: Number of read operations=0
        FILE: Number of large read operations=0
        FILE: Number of write operations=0
        HDFS: Number of bytes read=765
        HDFS: Number of bytes written=0
        HDFS: Number of read operations=12
        HDFS: Number of large read operations=0
        HDFS: Number of write operations=0
    Job Counters 
        Failed map tasks=9
        Failed reduce tasks=2
        Killed reduce tasks=1
        Launched map tasks=12
        Launched reduce tasks=3
        Other local map tasks=8
        Data-local map tasks=4
        Total time spent by all maps in occupied slots (ms)=239938
        Total time spent by all reduces in occupied slots (ms)=34189
        Total time spent by all map tasks (ms)=239938
        Total time spent by all reduce tasks (ms)=34189
        Total vcore-seconds taken by all map tasks=239938
        Total vcore-seconds taken by all reduce tasks=34189
        Total megabyte-seconds taken by all map tasks=245696512
        Total megabyte-seconds taken by all reduce tasks=35009536
    Map-Reduce Framework
        Map input records=3
        Map output records=270000
        Map output bytes=2160000
        Map output materialized bytes=2700018
        Input split bytes=441
        Combine input records=0
        Spilled Records=270000
        Failed Shuffles=0
        Merged Map outputs=0
        GC time elapsed (ms)=538
        CPU time spent (ms)=5520
        Physical memory (bytes) snapshot=643928064
        Virtual memory (bytes) snapshot=2537975808
        Total committed heap usage (bytes)=408760320
    File Input Format Counters 
        Bytes Read=324
Constructing image...
Exception in thread "main" java.io.FileNotFoundException: File does not exist: hdfs://172.16.199.132:9000/user/hduser/FractalJob_1452445557585_342741171/out/pixels-out
    at org.apache.hadoop.hdfs.DistributedFileSystem$22.doCall(DistributedFileSystem.java:1309)
    at org.apache.hadoop.hdfs.DistributedFileSystem$22.doCall(DistributedFileSystem.java:1301)
    at org.apache.hadoop.fs.FileSystemLinkResolver.resolve(FileSystemLinkResolver.java:81)
    at org.apache.hadoop.hdfs.DistributedFileSystem.getFileStatus(DistributedFileSystem.java:1301)
    at org.apache.hadoop.io.SequenceFile$Reader.<init>(SequenceFile.java:1752)
    at FractalJob.generateFractal(FractalJob.j..

配置如下：

conf.setInt("image.size", imgSize);
    conf.setDouble("constant.re", FractalJob.constant.re());
    conf.setDouble("constant.im", FractalJob.constant.im());
    Job job = Job.getInstance(conf);
    job.setJobName(FractalJob.class.getSimpleName());
    job.setJarByClass(FractalJob.class);
    job.setInputFormatClass(SequenceFileInputFormat.class);
    job.setOutputKeyClass(IntWritable.class);
    job.setOutputValueClass(IntWritable.class);
    job.setOutputFormatClass(SequenceFileOutputFormat.class);
    job.setMapperClass(RasterMapper.class);
    job.setReducerClass(ImageReducer.class);
    job.setNumReduceTasks(1);
    job.setSpeculativeExecution(false);
    final Path input = new Path(filePath, "in");
    final Path output = new Path(filePath, "out");
    FileInputFormat.setInputPaths(job, input);
    FileOutputFormat.setOutputPath(job, output);

1条答案

按热度按时间

wvmv3b1j1#

您不必担心创建自己的序列文件。mapreduce有一种自动执行的输出格式。
因此，在驱动程序类中，您将使用：

job.setOutputKeyClass(IntWritable.class);
job.setOutputValueClass(IntWritable.class);
job.setOutputFormatClass(SequenceFileOutputFormat.class);

然后在减速机上写下：

context.write(key, values.iterator().next());

并删除所有 setup 方法。
作为一种旁白，看起来你根本不需要减速机。如果您没有在reducer中进行任何计算，也没有对分组进行任何操作（我认为您没有），那么为什么不直接删除它呢？ job.setOutputFormatClass(SequenceFileOutputFormat.class) 将Map器输出写入序列文件。
如果只需要一个输出文件，请设置

job.setNumReduceTasks(1);

如果您的最终数据不大于1块大小，您将得到所需的输出。
值得注意的是，当前每个键只输出一个值—您应该确保需要这样做，如果不需要，还应该在reducer中包含一个循环来迭代这些值。

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赞(0）回复(0）举报 2021-05-30

sequencefile不是在hadoop中创建的

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