apache/hadoop · error · IllegalArgumentException

Input Iterator not markable

Error message

Input Iterator not markable

What it means

Error "Input Iterator not markable" thrown in apache/hadoop.

Source

Thrown at hadoop-mapreduce-project/hadoop-mapreduce-client/hadoop-mapreduce-client-core/src/main/java/org/apache/hadoop/mapreduce/MarkableIterator.java:45

/**
 * <code>MarkableIterator</code> is a wrapper iterator class that 
 * implements the {@link MarkableIteratorInterface}.
 * 
 */
@InterfaceAudience.Public
@InterfaceStability.Evolving
public class MarkableIterator<VALUE> 
  implements MarkableIteratorInterface<VALUE> {

  MarkableIteratorInterface<VALUE> baseIterator;

  /**
   * Create a new iterator layered on the input iterator
   * @param itr underlying iterator that implements MarkableIteratorInterface
   */
  public MarkableIterator(Iterator<VALUE> itr)  {
    if (!(itr instanceof MarkableIteratorInterface)) {
      throw new IllegalArgumentException("Input Iterator not markable");
    }
    baseIterator = (MarkableIteratorInterface<VALUE>) itr;
  }

  @Override
  public void mark() throws IOException {
    baseIterator.mark();
  }

  @Override
  public void reset() throws IOException {
    baseIterator.reset();
  }

  @Override
  public void clearMark() throws IOException {
    baseIterator.clearMark();
  }

View on GitHub (pinned to 2add963021)

Solutions

1. The underlying iterator does not support mark/reset; wrap the input in a markable iterator or avoid operations requiring reset.

When it happens

Trigger: Thrown at hadoop-mapreduce-project/hadoop-mapreduce-client/hadoop-mapreduce-client-core/src/main/java/org/apache/hadoop/mapreduce/MarkableIterator.java:45 when the library encounters an invalid state.

Common situations: See trigger scenarios.

AI-assisted analysis of apache/hadoop@2add963021 (2026-08-22). Data as JSON: /api/errors/ce206497d87e0b0f. Report an issue: GitHub.