Question

Mapper无法从多个目录中读取文件。有人可以帮忙吗？我需要在每个映射器中读取一个文件。我添加了多个输入路径并实现了自定义的WholeFileInputFormat，WholeFileRecordReader。在map方法中，我不需要输入键。我确保每张地图都可以读取整个文件。

命令行：hadoop jar AutoProduce.jar Autoproduce / input_a / input_b / output 我指定了两个输入路径---- 1.input_a; 2.input_b;

运行方法片段：

Job job = new Job(getConf());
job.setInputFormatClass(WholeFileInputFormat.class);
FileInputFormat.setInputPaths(job, new Path(args[0]), new Path(args[1]));
FileOutputFormat.setOutputPath(job, new Path(args[2]));

map method snippets：

public void map(NullWritable key, BytesWritable value, Context context){
    FileSplit fileSplit = (FileSplit) context.getInputSplit();
    System.out.println("Directory :" + fileSplit.getPath().toString());
    ......
}

自定义WholeFileInputFormat：

class WholeFileInputFormat extends FileInputFormat<NullWritable, BytesWritable> {
    @Override
    protected boolean isSplitable(JobContext context, Path file) {
        return false;
    }

    @Override
    public RecordReader<NullWritable, BytesWritable> createRecordReader(
        InputSplit split, TaskAttemptContext context) throws IOException,
        InterruptedException {

        WholeFileRecordReader reader = new WholeFileRecordReader();
        reader.initialize(split, context);
        return reader;
    }
}

自定义WholeFileRecordReader：

class WholeFileRecordReader extends RecordReader<NullWritable, BytesWritable> {
    private FileSplit fileSplit;
    private Configuration conf;
    private BytesWritable value = new BytesWritable();
    private boolean processed = false;

    @Override
    public void initialize(InputSplit split, TaskAttemptContext context)
    throws IOException, InterruptedException {
        this.fileSplit = (FileSplit) split;
        this.conf = context.getConfiguration();
    }

    @Override
    public boolean nextKeyValue() throws IOException, InterruptedException {
        if (!processed) {

            byte[] contents = new byte[(int) fileSplit.getLength()];
            Path file = fileSplit.getPath();
            FileSystem fs = file.getFileSystem(conf);
            FSDataInputStream in = null;
            try {
                in = fs.open(file);
                IOUtils.readFully(in, contents, 0, contents.length);
                value.set(contents, 0, contents.length);
            } finally {
                IOUtils.closeStream(in);
            }
            processed = true;
            return true;
        }
        return false;
    }
    @Override
    public NullWritable getCurrentKey() throws IOException,InterruptedException {
        return NullWritable.get();
    }

    @Override
    public BytesWritable getCurrentValue() throws IOException,InterruptedException {
        return value;
    }

    @Override
    public float getProgress() throws IOException {
        return processed ? 1.0f : 0.0f;
    }

    @Override
    public void close() throws IOException {
        // do nothing
    }
}

问题：

设置两个输入路径后，所有map任务只从一个目录读取文件..

提前致谢。

Answer 1

您必须在驱动程序中使用MultipleInputs而不是FileInputFormat。所以你的代码应该是：

MultipleInputs.addInputPath(job, new Path(args[0]), <Input_Format_Class_1>);
MultipleInputs.addInputPath(job, new Path(args[1]), <Input_Format_Class_2>);
.
.
.
MultipleInputs.addInputPath(job, new Path(args[N-1]), <Input_Format_Class_N>);

因此，如果您想使用WholeFileInputFormat作为第一个输入路径而使用TextInputFormat作为第二个输入路径，则必须按以下方式使用它：

MultipleInputs.addInputPath(job, new Path(args[0]), WholeFileInputFormat.class);
MultipleInputs.addInputPath(job, new Path(args[1]), TextInputFormat.class);

希望这适合你！

Hadoop：Mapper没有从多个输入路径读取文件

1 个答案: