apache/hadoop · error · RuntimeException

{err}

Error message

{err}

What it means

SimulatedDataNodes.printUsageExit() prints the offending message, prints the USAGE text, then rethrows the message as a RuntimeException, terminating the tool. The main producer is run(): 'Not enough arguments' when fewer than 2 command line args are given. The message text you see is whatever err was passed in.

Source

Thrown at hadoop-tools/hadoop-dynamometer/hadoop-dynamometer-infra/src/main/java/org/apache/hadoop/tools/dynamometer/SimulatedDataNodes.java:83

 */
public class SimulatedDataNodes extends Configured implements Tool {

  // Set this arbitrarily large (100TB) since we don't care about storage
  // capacity
  private static final long STORAGE_CAPACITY = 100 * 2L << 40;
  private static final String USAGE = "Usage: "
      + "org.apache.hadoop.tools.dynamometer.SimulatedDataNodes "
      + "bpid blockListFile1 [ blockListFileN ... ]\n"
      + "   bpid should be the ID of the block pool to which these DataNodes "
      + "belong.\n"
      + "   Each blockListFile specified should contain a list of blocks to "
      + "be served by one DataNode.\n"
      + "   See the Javadoc of this class for more detail.";

  static void printUsageExit(String err) {
    System.out.println(err);
    System.out.println(USAGE);
    throw new RuntimeException(err);
  }

  public static void main(String[] args) throws Exception {
    SimulatedDataNodes datanodes = new SimulatedDataNodes();
    ToolRunner.run(new HdfsConfiguration(), datanodes, args);
  }

  public int run(String[] args) throws Exception {
    if (args.length < 2) {
      printUsageExit("Not enough arguments");
    }
    String bpid = args[0];
    List<Path> blockListFiles = new ArrayList<>();
    for (int i = 1; i < args.length; i++) {
      blockListFiles.add(new Path(args[i]));
    }

    URI defaultFS = FileSystem.getDefaultUri(getConf());

View on GitHub (pinned to 2add963021)

Solutions

1. Invoke as: hadoop jar ... SimulatedDataNodes <bpid> <blockListFile1> [blockListFile2 ...]
2. Verify globs for the block list files expand to at least one existing file before the call
3. Check that a preceding option parser is not swallowing the positional arguments

Example fix

# before
SimulatedDataNodes bp-123
# after: bpid plus at least one block list file
SimulatedDataNodes bp-123 /tmp/blocks/dn0.out /tmp/blocks/dn1.out

if (args.length < 2) {
  System.err.println("usage: SimulatedDataNodes <bpid> <blockListFile...>");
  System.exit(2);
}

When it happens

Trigger: Launching org.apache.hadoop.tools.dynamometer.SimulatedDataNodes with 0 or 1 arguments. The tool requires args[0] = block pool id (bpid) and args[1..N] = block listing files, one per simulated DataNode, so args.length < 2 always lands here.

Common situations: Forgetting the bpid in a wrapper script, or a shell glob for the block list files expanding to zero files so only the bpid survives.

Related errors

• "Unexpected argument " + args[nextArgIndex]
• Bad argument: {}
• Expect either -getlevel or -setlevel
• No arguments specified
• Must specify either -getlevel or -setlevel

AI-assisted analysis of apache/hadoop@2add963021 (2026-08-22). Data as JSON: /api/errors/d79acb158a98c7d2. Report an issue: GitHub.