apache/druid · error · IllegalStateException

Illegal segmentId format [%s]

Error message

Illegal segmentId format [%s]

What it means

Thrown by SinglePhaseParallelIndexTaskRunner.allocateNewSegment when SegmentId.tryParse fails to parse the stored next-segment-ID string from the sequence's allocation list. Segment IDs in the allocation state are expected to be parseable 'dataSource_interval_version_partition' strings; an unparseable value means the stored allocation state is corrupt or was written by incompatible code.

Source

Thrown at indexing-service/src/main/java/org/apache/druid/indexing/common/task/batch/parallel/SinglePhaseParallelIndexTaskRunner.java:244

      if (prevSegmentId == null) {
        prevSegmentIdIndex = -1;
        segmentIds = v == null ? new ArrayList<>() : v;
      } else {
        segmentIds = v;
        if (segmentIds == null) {
          throw new ISE("Can't find previous segmentIds for sequence[%s]", sequenceName);
        }
        prevSegmentIdIndex = segmentIds.indexOf(prevSegmentId);
        if (prevSegmentIdIndex == -1) {
          throw new ISE("Can't find previously allocated segmentId[%s] for sequence[%s]", prevSegmentId, sequenceName);
        }
      }
      final int nextSegmentIdIndex = prevSegmentIdIndex + 1;
      final SegmentIdWithShardSpec newSegmentId;
      if (nextSegmentIdIndex < segmentIds.size()) {
        SegmentId segmentId = SegmentId.tryParse(dataSource, segmentIds.get(nextSegmentIdIndex));
        if (segmentId == null) {
          throw new ISE("Illegal segmentId format [%s]", segmentIds.get(nextSegmentIdIndex));
        }
        newSegmentId = new SegmentIdWithShardSpec(
            segmentId.getDataSource(),
            segmentId.getInterval(),
            segmentId.getVersion(),
            new BuildingNumberedShardSpec(segmentId.getPartitionNum())
        );
      } else {
        final int partitionNum = Counters.getAndIncrementInt(partitionNumCountersPerInterval, intervalAndVersion.lhs);
        newSegmentId = new SegmentIdWithShardSpec(
            dataSource,
            intervalAndVersion.lhs,
            intervalAndVersion.rhs,
            new BuildingNumberedShardSpec(partitionNum)
        );
        segmentIds.add(newSegmentId.toString());
      }
      segmentIdHolder.setValue(newSegmentId);

View on GitHub (pinned to 9b90983fd2)

Solutions

1. Restart/resubmit the supervisor task to rebuild the allocation list from scratch
2. Inspect the stored segmentIds (overlord logs / task storage) to find the malformed entry and its origin
3. Verify all Druid nodes and extensions run the same version
4. If state is persisted in an external metadata store, clean the corrupt rows for this task and retry

Example fix

// before: unvalidated stored ID passed to tryParse
SegmentId segmentId = SegmentId.tryParse(dataSource, segmentIds.get(nextSegmentIdIndex));
// after: validate format before storing
String id = segmentIds.get(nextSegmentIdIndex);
if (!SEGMENT_ID_PATTERN.matcher(id).matches()) { log.warn("dropping malformed id %s", id); }

// validate stored segment IDs parse before use
for (String id : segmentIds) {
  if (SegmentId.tryParse(dataSource, id) == null) {
    throw new IllegalStateException("corrupt allocation entry: " + id);
  }
}

static boolean isParseableSegmentId(String dataSource, String id) {
  return id != null && SegmentId.tryParse(dataSource, id) != null;
}

catch (ISE e) {
  if (e.getMessage().startsWith("Illegal segmentId format")) {
    log.error("corrupt allocation state: %s", e.getMessage());
    resubmitSupervisor(taskSpec); // rebuild state
  } else throw e;
}

When it happens

Trigger: The segmentIds list for a sequence contains a malformed entry (e.g., manually edited task state, corrupted metadata, or an ID written by a different Druid version with an incompatible format) and nextSegmentIdIndex points at it.

Common situations: Upgrading Druid across versions while a batch task's state persists; restoring task state from backups; custom extensions writing non-standard segment IDs into allocation maps.

Understand the failure class

Background: "invalid id" errors: invalid identifier format — why libraries reject IDs before lookup, and how to fix them — this error's family across 37 libraries.

Related errors

• Could not find interval for timestamp [%s]
• Can't find previously allocated segmentId[%s] for sequence[%
• Unable to parse row [%s]
• Unable to parse row [%s]
• JavaScript parsed value [%s] must be in {key: value} format!

AI-assisted analysis of apache/druid@9b90983fd2 (2026-09-07). Data as JSON: /api/errors/7253d8daa8f063e4. Report an issue: GitHub.