apache/hadoop · error · UnsupportedOperationException

the wrapped stream does not support setting the drop-behind

Error message

the wrapped stream does not support setting the drop-behind caching setting.

What it means

Error "the wrapped stream does not support setting the drop-behind caching setting." thrown in apache/hadoop.

Source

Thrown at hadoop-common-project/hadoop-common/src/main/java/org/apache/hadoop/fs/FSDataOutputStream.java:156

      wrappedStream.flush();
    }
  }
  
  @Override  // Syncable
  public void hsync() throws IOException {
    if (wrappedStream instanceof Syncable) {
      ((Syncable)wrappedStream).hsync();
    } else {
      wrappedStream.flush();
    }
  }

  @Override
  public void setDropBehind(Boolean dropBehind) throws IOException {
    try {
      ((CanSetDropBehind)wrappedStream).setDropBehind(dropBehind);
    } catch (ClassCastException e) {
      throw new UnsupportedOperationException("the wrapped stream does " +
          "not support setting the drop-behind caching setting.");
    }
  }

  /**
   * Get the IO Statistics of the nested stream, falling back to
   * empty statistics if the stream does not implement the interface
   * {@link IOStatisticsSource}.
   * @return an IOStatistics instance.
   */
  @Override
  public IOStatistics getIOStatistics() {
    return IOStatisticsSupport.retrieveIOStatistics(wrappedStream);
  }

  /**
   * Invoke {@code abort()} on the wrapped stream if it
   * is Abortable, otherwise raise an

View on GitHub (pinned to 2add963021)

Solutions

1. Only set drop-behind on output streams whose wrapped stream supports it.
2. Guard with a capability check and skip the setting when unsupported.

When it happens

Trigger: Thrown at hadoop-common-project/hadoop-common/src/main/java/org/apache/hadoop/fs/FSDataOutputStream.java:156 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/1ae91af0de7c8541. Report an issue: GitHub.