hadoop - 如何将系统属性传递给 hadoop 中的映射函数

Question

有没有一种方法可以将系统参数(例如 -Dmy_param=XXX)传递给 hadoop map reduce 框架中的映射函数。将作业提交到 hadoop 集群是通过 .setJarByClass() 完成的。在映射器中，我必须创建配置，所以我想让它可配置，所以我认为通过属性文件的标准方式就可以了。只是在设置属性的地方努力传递参数。另一种方法是将属性文件添加到提交的 jar。有人有解决这个问题的经验吗？

Answer 1

如果您还没有在您的工作中使用过它，您可以尝试使用 GenericOptionsParser、Tool 和 ToolRunner 来运行 Hadoop 作业。

注意:MyDriver 扩展 Configured 并实现 Tool。而且，运行你的工作使用这个

hadoop -jar somename.jar MyDriver -D your.property=value arg1 arg2

欲了解更多信息，check this link .

这是我为您准备的一些示例代码:

public class MyDriver extends Configured implements Tool {

  public static class MyDriverMapper extends Mapper<LongWritable, Text, LongWritable, NullWritable> {

    protected void map(LongWritable key, Text value, Context context)
      throws IOException, InterruptedException {
      // In the mapper you can retrieve any configuration you've set
      // while starting the job from the terminal as shown below

      Configuration conf = context.getConfiguration();
      String yourPropertyValue = conf.get("your.property");
    }
  }

  public static class MyDriverReducer extends Reducer<LongWritable, NullWritable, LongWritable, NullWritable> {

    protected void reduce(LongWritable key, Iterable<NullWritable> values, Context context) 
      throws IOException, InterruptedException {
      // --- some code ---
    }
  }

  public static void main(String[] args) throws Exception {
    int exitCode = ToolRunner.run(new MyDriver(), args);
    System.exit(exitCode);
  }

  @Override
  public int run(String[] args) throws Exception {
    Configuration conf = getConf();
    // if you want you can get/set to conf here too.
    // your.property can also be file location and after
    // you retrieve the properties and set them one by one to conf object.

    // --other code--//
    Job job = new Job(conf, "My Sample Job");
    // --- other code ---//
    return (job.waitForCompletion(true) ? 0 : 1);
  }
}