apache/druid · critical · org.apache.druid.java.util.common.IOE

Failed to write to file: %s. Current size of file: %d

Error message

Failed to write to file: %s. Current size of file: %d

What it means

LegacyFileWriteOutBytes.flush pushes its buffered bytes through Channels.writeFully to the file channel; an IOException is wrapped in IOE naming the file path and current size. It indicates the backing file could not be written to during segment persistence.

Source

Thrown at processing/src/main/java/org/apache/druid/segment/writeout/LegacyFileWriteOutBytes.java:67

    this.writeOutBytes = 0L;
  }

  private void flushIfNeeded(int bytesNeeded) throws IOException
  {
    if (buffer.remaining() < bytesNeeded) {
      flush();
    }
  }

  @Override
  public void flush() throws IOException
  {
    buffer.flip();
    try {
      Channels.writeFully(ch, buffer);
    }
    catch (IOException e) {
      throw new IOE(e, "Failed to write to file: %s. Current size of file: %d", file.getAbsolutePath(), writeOutBytes);
    }
    buffer.clear();
  }

  @Override
  public void write(int b) throws IOException
  {
    flushIfNeeded(1);
    buffer.put((byte) b);
    writeOutBytes++;
  }

  @Override
  public void writeInt(int v) throws IOException
  {
    flushIfNeeded(Integer.BYTES);
    buffer.putInt(v);
    writeOutBytes += Integer.BYTES;

View on GitHub (pinned to 9b90983fd2)

Solutions

1. Check disk space/quota on the druid intermediate persist directory and clean or expand storage.
2. Verify file and directory permissions and that the mount/volume is healthy.
3. Review OS logs for underlying I/O errors and fix hardware/filesystem issues.
4. Rerun the task after fixing; treat the partially written file as invalid and rebuild it.

Example fix

// before
legacyWriteOutBytes.write(data); // IOE when disk full
// after
if (new File(baseDir).getUsableSpace() < data.length * 2L) {
  throw new IOException("not enough space in " + baseDir);
}
legacyWriteOutBytes.write(data);

if (baseDir.getUsableSpace() < estimatedSize) { throw new IOException("insufficient space: " + baseDir); }

try { legacy.write(data); } catch (IOException e) { log.error(e, "legacy write failed [%s]", e.getMessage()); throw e; }

When it happens

Trigger: write(), writeTo(), readFully(), flushIfNeeded() or asInputStream() triggering flush while the channel write fails: disk full, I/O error, volume unavailable, permission revoked.

Common situations: Full or failing disk on the intermediate persist dir; NFS/network storage outage; permission changes after task start; inode/device errors on long-running peons.

Understand the failure class

Background: "failed to write file", "Could not save figure", "Error saving remote file" — file write failed: causes and fixes across languages and libraries — this error's family across 38 libraries.

Related errors

• Failed to write to file: %s. Current size of file: %d
• Failed to write partial info file for segment[%s]
• Exception while writing distribution file for interval [%s],
• Exception during serialization of lookups using file [%s]
• Failed to mount partial metadata for segment[%s]

AI-assisted analysis of apache/druid@9b90983fd2 (2026-09-07). Data as JSON: /api/errors/56780512f033ac22. Report an issue: GitHub.