apache/hadoop · error · IOException

Unknown processor {} (valid processors: xml, binary, stats)

Error message

Unknown processor {} (valid processors: xml, binary, stats)

What it means

The offline edits viewer ('hdfs oev') chooses its output visitor from the -processor option. 'binary' is dispatched early (it writes raw output and takes the filename directly); all other processors open the output stream first and this factory accepts only 'xml' and 'stats' (case-insensitive). Any other value falls through to IOException('Unknown processor ... (valid processors: xml, binary, stats)').

Source

Thrown at hadoop-hdfs-project/hadoop-hdfs/src/main/java/org/apache/hadoop/hdfs/tools/offlineEditsViewer/OfflineEditsVisitorFactory.java:69

    OfflineEditsVisitor vis;
    OutputStream fout = Files.newOutputStream(Paths.get(filename));
    OutputStream out = null;
    try {
      if (!printToScreen) {
        out = fout;
      }
      else {
        OutputStream outs[] = new OutputStream[2];
        outs[0] = fout;
        outs[1] = System.out;
        out = new TeeOutputStream(outs);
      }
      if(StringUtils.equalsIgnoreCase("xml", processor)) {
        vis = new XmlEditsVisitor(out);
      } else if(StringUtils.equalsIgnoreCase("stats", processor)) {
        vis = new StatisticsEditsVisitor(out);
      } else {
        throw new IOException("Unknown processor " + processor +
          " (valid processors: xml, binary, stats)");
      }
      out = fout = null;
      return vis;
    } finally {
      IOUtils.closeStream(fout);
      IOUtils.closeStream(out);
    }
  }
}

View on GitHub (pinned to 2add963021)

Solutions

Use exactly one of xml, binary, or stats as the -p/-processor value (matching is case-insensitive).
Echo the variable before running to catch empty or whitespace-padded values in scripts.
Run 'hdfs oev -h' for the current option set of your Hadoop version.

Example fix

# before
hdfs oev -i edits_in_progress -o /tmp/edits.xml -p XMLS
# Unknown processor XMLS (valid processors: xml, binary, stats)

# after
hdfs oev -i edits_in_progress -o /tmp/edits.xml -p xml

Defensive patterns

Strategy: validation

Validate before calling

Set<String> VALID = Set.of("xml", "binary", "stats");
String processor = opts.valueOf("-p").trim().toLowerCase(Locale.ROOT);
if (!VALID.contains(processor)) {
  throw new IllegalArgumentException(
      "processor must be one of xml, binary, stats; got '" + processor + "'");
}
OfflineEditsViewer.run(args);

Try / catch

try {
  OfflineEditsVisitorFactory.getEditsVisitor(outFile, processor, printToScreen);
} catch (IOException e) {
  if (e.getMessage().startsWith("Unknown processor")) {
    throw new IllegalArgumentException(
        "Valid oev processors are xml, binary, stats", e);
  }
  throw e;
}

Prevention

Normalize the processor variable (trim + lowercase) before passing it to oev.
Fail scripts early when the processor variable is empty instead of letting '-p' receive garbage.

When it happens

Trigger: Running 'hdfs oev -i edits -o out.xml -p <value>' where value is not xml/binary/stats — e.g. 'XML ' with a trailing space from shell quoting, 'json', or a typo like 'stat'.

Common situations: Scripts parameterizing the processor variable with an empty or misspelled value; users assuming a JSON or text processor exists; whitespace introduced by variable expansion ('$PROC' unset).

Related errors

AI-assisted analysis of apache/hadoop@2add963021 (2026-08-22). Data as JSON: /api/errors/cdcd465dbc5f2f4e. Report an issue: GitHub.