What causes "Failed to close task iterable" in apache/iceberg?

Inspect the logged IOException's cause for the underlying storage problem.

Failed to close task iterable

Error message

Failed to close task iterable

What it means

In BaseRewriteDataFilesAction.execute(), the iterable of FileScanTasks produced during planning is closed in a finally block. If closing throws an IOException, this warning is logged. The rewrite proceeds — the warning only reports failure to release underlying resources (e.g. open file handles) held by the task iterable.

Solutions

Inspect the logged IOException's cause for the underlying storage problem.
Verify storage connectivity/permissions and object-store health at close time.
Re-run the rewrite action after storage issues are resolved — the warning usually doesn't block the rewrite itself.
If reproducible, check for leaked/closed-twice streams in custom FileIO implementations.

Defensive patterns

Strategy: try-catch

Try / catch

try {
  rewriteAction.execute();
} catch (RuntimeException e) {
  if (e.getCause() instanceof IOException) {
    LOG.warn("storage issue during rewrite; verify storage health and re-run", e);
  }
  throw e;
}

Prevention

Ensure stable connectivity to the object store
Verify FileIO implementations close streams correctly once
Check storage permissions for read/close operations
Re-run actions after transient storage errors

When it happens

Trigger: fileScanTasks.close() throws IOException during the finally block of execute(), typically because an underlying reader/input stream over data files cannot be closed cleanly.

Common situations: Object-store connection errors while closing read streams; underlying Hadoop FileSystem issues; interrupted IO during shutdown of the scan; flaky network to storage.

Understand the failure class

Background: "failed to read file", EACCES, ENOENT and "could not read <path>" errors: when a program can't read a file from disk — this error's family across 49 libraries.

Related errors

AI-assisted analysis of apache/iceberg@86d9c8fc54 (2026-09-12). Data as JSON: /api/errors/090524ce3e1407d5. Report an issue: GitHub.

Appendix: source

Thrown at core/src/main/java/org/apache/iceberg/actions/BaseRewriteDataFilesAction.java:242

    }

    long startingSnapshotId = table.currentSnapshot().snapshotId();
    try {
      fileScanTasks =
          table
              .newScan()
              .useSnapshot(startingSnapshotId)
              .caseSensitive(caseSensitive)
              .ignoreResiduals()
              .filter(filter)
              .planFiles();
    } finally {
      try {
        if (fileScanTasks != null) {
          fileScanTasks.close();
        }
      } catch (IOException ioe) {
        LOG.warn("Failed to close task iterable", ioe);
      }
    }

    Map<StructLikeWrapper, Collection<FileScanTask>> groupedTasks =
        groupTasksByPartition(fileScanTasks.iterator());
    Map<StructLikeWrapper, Collection<FileScanTask>> filteredGroupedTasks =
        groupedTasks.entrySet().stream()
            .filter(kv -> kv.getValue().size() > 1)
            .collect(Collectors.toMap(Map.Entry::getKey, Map.Entry::getValue));

    // Nothing to rewrite if there's only one DataFile in each partition.
    if (filteredGroupedTasks.isEmpty()) {
      return RewriteDataFilesActionResult.empty();
    }
    // Split and combine tasks under each partition
    List<CombinedScanTask> combinedScanTasks =
        filteredGroupedTasks.values().stream()
            .map(

View on GitHub (pinned to 86d9c8fc54)