apache/hadoop · error · IllegalArgumentException

${className} is not an instance of Seekable or PositionedRea

Error message

${className} is not an instance of Seekable or PositionedReadable

What it means

Error "${className} is not an instance of Seekable or PositionedReadable" thrown in apache/hadoop.

Source

Thrown at hadoop-common-project/hadoop-common/src/main/java/org/apache/hadoop/fs/FSDataInputStream.java:62

@InterfaceAudience.Public
@InterfaceStability.Stable
public class FSDataInputStream extends DataInputStream
    implements Seekable, PositionedReadable, 
      ByteBufferReadable, HasFileDescriptor, CanSetDropBehind, CanSetReadahead,
      HasEnhancedByteBufferAccess, CanUnbuffer, StreamCapabilities,
      ByteBufferPositionedReadable, IOStatisticsSource {
  /**
   * Map ByteBuffers that we have handed out to readers to ByteBufferPool 
   * objects
   */
  private final IdentityHashStore<ByteBuffer, ByteBufferPool>
    extendedReadBuffers
      = new IdentityHashStore<>(0);

  public FSDataInputStream(InputStream in) {
    super(in);
    if( !(in instanceof Seekable) || !(in instanceof PositionedReadable) ) {
      throw new IllegalArgumentException(in.getClass().getCanonicalName() +
          " is not an instance of Seekable or PositionedReadable");
    }
  }
  
  /**
   * Seek to the given offset.
   *
   * @param desired offset to seek to
   */
  @Override
  public void seek(long desired) throws IOException {
    ((Seekable)in).seek(desired);
  }

  /**
   * Get the current position in the input stream.
   *
   * @return current position in the input stream

View on GitHub (pinned to 2add963021)

Solutions

1. Wrap the stream only if the underlying stream implements Seekable or PositionedReadable.
2. Use a filesystem open() call that returns a compliant stream instead of wrapping an arbitrary InputStream.

When it happens

Trigger: Thrown at hadoop-common-project/hadoop-common/src/main/java/org/apache/hadoop/fs/FSDataInputStream.java:62 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/dceabb8413458fe3. Report an issue: GitHub.