apache/hadoop · error · RuntimeException

Class not found: {}

Error message

Class not found: {}

What it means

Error "Class not found: {}" thrown in apache/hadoop.

Source

Thrown at hadoop-tools/hadoop-streaming/src/main/java/org/apache/hadoop/streaming/mapreduce/StreamInputFormat.java:80

    context.progress();

    // Open the file and seek to the start of the split
    Path path = split.getPath();
    FileSystem fs = path.getFileSystem(conf);
    // open the file
    final FutureDataInputStreamBuilder builder = fs.openFile(path);
    FutureIO.propagateOptions(builder, conf,
        MRJobConfig.INPUT_FILE_OPTION_PREFIX,
        MRJobConfig.INPUT_FILE_MANDATORY_PREFIX);
    FSDataInputStream in = FutureIO.awaitFuture(builder.build());

    // Factory dispatch based on available params..
    Class readerClass;

    {
      readerClass = StreamUtil.goodClassOrNull(conf, c, null);
      if (readerClass == null) {
        throw new RuntimeException("Class not found: " + c);
      }
    }
    Constructor ctor;

    try {
      ctor = readerClass.getConstructor(new Class[] { FSDataInputStream.class,
          FileSplit.class, TaskAttemptContext.class, Configuration.class,
          FileSystem.class });
    } catch (NoSuchMethodException nsm) {
      throw new RuntimeException(nsm);
    }

    RecordReader<Text, Text> reader;
    try {
      reader = (RecordReader<Text, Text>) ctor.newInstance(new Object[] { in,
          split, context, conf, fs });
    } catch (Exception nsm) {
      throw new RuntimeException(nsm);

View on GitHub (pinned to 2add963021)

Solutions

1. Add the named class to the job classpath or fix the configured class name.

When it happens

Trigger: The record reader class named in the streaming configuration cannot be found on the task classpath.

Common situations: See trigger scenarios.

AI-assisted analysis of apache/hadoop@2add963021 (2026-08-22). Data as JSON: /api/errors/5c41d3e23a47c337. Report an issue: GitHub.