thanos-io/thanos · warning

block has no meta file

Error message

block %s has no meta file

What it means

After listing the bucket, fetchMetadata classifies blocks flagged as partial by the lister and records per-block errors "block %s has no meta file", incrementing resp.noMetas. This is a per-block (not fatal) error meaning a block directory exists in the bucket but its meta.json is absent — typically because the block is still being uploaded (partial block).

Solutions

1. If the block is still being uploaded, wait for the upload to finish and re-sync — partial blocks resolve on their own.
2. Delete the leftover partial block directory from the bucket if its uploader crashed.
3. Check the uploader/compactor logs for failed uploads and re-run the upload.
4. Enable IgnoreBlockList or block list filtering to skip known-partial blocks during sync if desired.

Example fix

// before: leftover partial block in bucket with no meta.json
// s3://my-bucket/01ARZ3NDEKTSV4RRFFQ69G5FAV/ (only index + chunks, no meta.json)
// after: remove the partial block
aws s3 rm s3://my-bucket/01ARZ3NDEKTSV4RRFFQ69G5FAV --recursive

// Before treating as fatal: list blocks and check for meta.json presence
_, partial, err := lister.GetActiveAndPartialBlockIDs(ctx, ch)
if err == nil && len(partial) > 0 {
    // exclude partial blocks or wait for uploads to finish
}

metas, err := fetcher.FetchMetadata(ctx, filtered)
if err != nil {
    if strings.Contains(err.Error(), "has no meta file") {
        // per-block warning: log the block ULIDs, skip them, retry sync later
    } else {
        return err
    }
}

When it happens

Trigger: fetchMetadata encounters a block ULID in partialBlocks (GetActiveAndPartialBlockIDs returned isPartial=true): the block dir exists but meta.json is missing/not yet uploaded.

Common situations: Concurrent upload in progress (uploader writes dir and index before meta.json); crashed/interrupted upload leaving an empty block dir; manually deleted meta.json; another process mid-upload during sync.

Understand the failure class

Background: "File not found" and ENOENT errors: why libraries can't find a file that should exist — this error's family across 50 libraries.

Related errors

• meta.json unmarshal
• sync before first pass of downsampling
• sync before second pass of downsampling
• sync before retention
• create meta fetcher

AI-assisted analysis of thanos-io/thanos@35b8b99117 (2026-09-07). Data as JSON: /api/errors/bbfd195327e76acc. Report an issue: GitHub.

Appendix: source

Thrown at pkg/block/fetcher.go:599

	}

	var partialBlocks map[ulid.ULID]bool
	var err error
	// Workers scheduled, distribute blocks.
	eg.Go(func() error {
		defer close(activeBlocksCh)
		partialBlocks, err = f.blockIDsLister.GetActiveAndPartialBlockIDs(ctx, activeBlocksCh)
		return err
	})

	if err := eg.Wait(); err != nil {
		return nil, errors.Wrap(err, "BaseFetcher: iter bucket")
	}

	mtx.Lock()
	for blockULID, isPartial := range partialBlocks {
		if isPartial {
			resp.partial[blockULID] = errors.Errorf("block %s has no meta file", blockULID)
			resp.noMetas++
		}
	}
	mtx.Unlock()

	if len(resp.metaErrs) > 0 {
		return resp, nil
	}

	// Only for complete view of blocks update the cache.

	cached := &sync.Map{}
	for id, m := range resp.metas {
		cached.Store(id, m)
	}

	modifiedTimestamps := make(map[ulid.ULID]time.Time, len(resp.modifiedTimestamps))
	maps.Copy(modifiedTimestamps, resp.modifiedTimestamps)

View on GitHub (pinned to 35b8b99117)