apache/druid · error · SegmentLoadingException

Failed to write partial info file for segment[%s]

Error message

Failed to write partial info file for segment[%s]

What it means

When a segment is loaded for a partial-load rule, SegmentLocalCacheManager rewrites the on-disk info file so it carries the current rule's wrapped loadSpec before mounting. If that rewrite fails with an IOException, it is wrapped in this SegmentLoadingException.

Source

Thrown at server/src/main/java/org/apache/druid/segment/loading/SegmentLocalCacheManager.java:1089

                wrapper.getFingerprint()
            );
          }
          // Rule couldn't be applied, nothing partial materialized, so hand back the plain segment; the
          // announcement layer will fall back to segment.getSize() for loadedBytes.
          return dataSegment;
        }

        final ReservedPartial reserved = findOrReservePartial(dataSegment, rangeReader);
        try {
          final PartialSegmentMetadataCacheEntry metadata = reserved.metadata();
          // findOrReservePartial only invokes reservePartial (which writes the info file) on the fresh-reserve
          // branch. On the find-existing branch the info file on disk still carries the PRIOR rule's wrapped
          // load spec, so a rule swap here would apply in memory only. Rewrite unconditionally before mount.
          try {
            rewriteInfoFile(dataSegment);
          }
          catch (IOException e) {
            throw new SegmentLoadingException(
                e,
                "Failed to write partial info file for segment[%s]",
                dataSegment.getId()
            );
          }
          try {
            metadata.mount(reserved.location());
          }
          catch (IOException e) {
            throw new SegmentLoadingException(
                e,
                "Failed to mount partial metadata for segment[%s]",
                dataSegment.getId()
            );
          }
          final PartialSegmentFileMapperV10 mapper = metadata.getFileMapper();
          if (mapper == null) {
            throw DruidException.defensive(

View on GitHub (pinned to 9b90983fd2)

Solutions

1. Check disk space and filesystem health on the segment cache location (druid.segmentCache.locations).
2. Fix permissions/ownership on the cache info directory so the historical can write info files.
3. Ensure the cache location directories exist and are writable at startup; remount if offline.
4. After fixing the disk, let the coordinator re-queue the segment load.

final File infoDir = new File(location.getPath(), "info_dir");
if (!infoDir.canWrite() || infoDir.getFreeSpace() < MIN_FREE_BYTES) {
  throw new IllegalStateException("Cache location not writable or low on disk: " + infoDir);
}

try {
  cacheManager.loadPartial(segment, rule);
} catch (SegmentLoadingException e) {
  if (e.getCause() instanceof IOException ioe && ioe.getMessage() != null && ioe.getMessage().contains("info file")) {
    alertDiskProblem(e); // check disk space/permissions before retrying
  } else {
    throw e;
  }
}

When it happens

Trigger: loadPartial path calls rewriteInfoFile(dataSegment) and the underlying file write throws (disk full, permissions, location offline, missing directory).

Common situations: Cache disk full or read-only filesystem; cache directory permissions changed; info-hierarchy directory deleted underneath a running historical; disk hardware failure.

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 to file: %s. Current size of file: %d
• 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/12fc214eec39b2fc. Report an issue: GitHub.