apache/hadoop · error · IOException

incomplete data, input length is: {}

Error message

incomplete data, input length is: {}

What it means

BufferPuller.moveData() validates each incoming KV chunk: after handling an aside buffer for oversized records, it requires at least the 8-byte KV header (keyLength int + valueLength int) in the remaining input. One to seven leftover bytes means a partial/corrupt record boundary, and it throws IOException('incomplete data, input length is: N'). It signals misalignment between the producer and consumer of the native buffer channel, not a user config error.

Source

Thrown at hadoop-mapreduce-project/hadoop-mapreduce-client/hadoop-mapreduce-client-nativetask/src/main/java/org/apache/hadoop/mapred/nativetask/handlers/BufferPuller.java:164

    if (null != asideBuffer && asideBuffer.length() > 0) {
      if (asideBuffer.remaining() > 0) {
        final byte[] output = asideBuffer.getByteBuffer().array();
        final int write = Math.min(asideBuffer.remaining(), input.remaining());
        input.get(output, asideBuffer.position(), write);
        asideBuffer.position(asideBuffer.position() + write);
      }

      if (asideBuffer.remaining() == 0) {
        asideBuffer.position(0);
      }
    }

    if (input.remaining() == 0) {
      return true;
    }

    if (input.remaining() < KV_HEADER_LENGTH) {
      throw new IOException("incomplete data, input length is: " + input.remaining());
    }
    final int position = input.position();
    final int keyLength = input.getInt();
    final int valueLength = input.getInt();
    input.position(position);
    final int kvLength = keyLength + valueLength + KV_HEADER_LENGTH;
    final int remaining = input.remaining();

    if (kvLength > remaining) {
      if (null == asideBuffer || asideBuffer.capacity() < kvLength) {
        asideBuffer = new InputBuffer(BufferType.HEAP_BUFFER, kvLength);
      }
      asideBuffer.rewind(0, kvLength);

      input.get(asideBuffer.array(), 0, remaining);
      asideBuffer.position(remaining);
    }
    return true;

View on GitHub (pinned to 2add963021)

Solutions

1. Verify that all nodes and the submitted job use the same Hadoop/nativetask build (no mixed-version rolling upgrade)
2. If custom INativeSerializer/Deserializer pairs are in play, check that serialized KV framing (8-byte header + payload) matches on both sides
3. Re-run the job; persistent occurrences on specific nodes point to a bad native install or hardware - inspect the affected NodeManager

try {
  boolean done = puller.moveData();
} catch (IOException e) {
  if (e.getMessage() != null && e.getMessage().startsWith("incomplete data")) {
    // framing/truncation between producer and native consumer:
    // verify version alignment and serializer framing; do not silently retry corrupt data
    throw new IOException("nativetask KV framing error; check jar/so alignment", e);
  }
  throw e;
}

When it happens

Trigger: The upstream writer and BufferPuller disagree on record framing: serializer length drift between producer/consumer versions, truncated buffer handoff, or corrupted intermediate data on the reduce side of the nativetask pipeline.

Common situations: Mixed Hadoop versions between job artifacts and the cluster's nativetask library during rolling upgrades; custom serializers emitting a different header layout than the deserializer expects; memory/hardware corruption of spill files.

Related errors

• incomplete data, input length is: {}
• output buffer not set
• We expect to read {}, but we actually read: {}
• FileMetadata not match key:" + key
• no such method

AI-assisted analysis of apache/hadoop@2add963021 (2026-08-22). Data as JSON: /api/errors/5f5d346e17068191. Report an issue: GitHub.