vitessio/vitess · error · ErrPartSize

%w, currently set to %s

Error message

%w, currently set to %s

What it means

calculateUploadPartSize validates the configured part size bounds for S3 backups. When the resolved part size (or the minPartSize setting) falls below the minimum allowed (5MiB) or minPartSize exceeds the max (5GiB), it returns ErrPartSize wrapped with the current value.

Source

Thrown at go/vt/mysqlctl/s3backupstorage/s3.go:298

		defaultUploadPartSize = 5 * 1024 * 1024 // 5MiB
		minUploadPartSize     = 5 * 1024 * 1024 // 5MiB - S3 requirement
		maxUploadParts        = 10000           // S3 limit
	)

	// Calculate s3 upload part size using the source filesize
	partSizeBytes = defaultUploadPartSize
	if filesize > 0 {
		minimumPartSize := float64(filesize) / float64(maxUploadParts)
		// Round up to ensure large enough partsize
		calculatedPartSizeBytes := int64(math.Ceil(minimumPartSize))
		if calculatedPartSizeBytes > partSizeBytes {
			partSizeBytes = calculatedPartSizeBytes
		}
	}

	if minPartSize != 0 && partSizeBytes < minPartSize {
		if minPartSize > MaxPartSize || minPartSize < minUploadPartSize { // 5GiB and 5MiB respectively
			return 0, fmt.Errorf(
				"%w, currently set to %s",
				ErrPartSize, humanize.IBytes(uint64(minPartSize)),
			)
		}
		partSizeBytes = int64(minPartSize)
	}

	return
}

// Wait is part of the backupstorage.BackupHandle interface.
func (bh *S3BackupHandle) Wait() {
	bh.waitGroup.Wait()
}

// EndBackup is part of the backupstorage.BackupHandle interface.
func (bh *S3BackupHandle) EndBackup(ctx context.Context) error {
	if bh.readOnly {

View on GitHub (pinned to 01a25a7d17)

Solutions

1. Set the part-size config value to at least 5MiB (5242880 bytes)
2. Ensure minPartSize is not greater than 5GiB (5368709120 bytes)
3. Check the units in your config — values are in bytes, not MiB/GiB
4. Fix the underlying ErrPartSize root cause message (it is wrapped here with 'currently set to' context)

Example fix

// before
backup_storage_part_size: 1048576 // 1MiB, below 5MiB minimum
// after
backup_storage_part_size: 5242880 // 5MiB minimum

const minUploadPartSize = 5 * 1024 * 1024
const MaxPartSize = 5 * 1024 * 1024 * 1024
partSize := cfg.BackupStoragePartSize
if partSize < minUploadPartSize || partSize > MaxPartSize {
    return fmt.Errorf("part size %d outside [%d, %d]", partSize, minUploadPartSize, MaxPartSize)
}

partSize, err := storage.calculateUploadPartSize(...)
if errors.Is(err, s3backupstorage.ErrPartSize) {
    log.Error("invalid backup part size config", slog.Any("error", err))
    return err
}

When it happens

Trigger: Running a backup (AddFile path) with S3BackupStorage where backup_storage_part_size / minPartSize configuration is smaller than 5MiB or minPartSize is larger than 5GiB; also triggered in tests exercising edge cases.

Common situations: Operators setting backup_storage_part_size to tiny values to save bandwidth; misconfigured environment producing minPartSize outside [5MiB, 5GiB]; unit mistakes (bytes vs MiB) in config.

Related errors

• --s3-backup-storage-bucket required
• ErrPartSize
• AddFile cannot be called on read-only backup
• EndBackup cannot be called on read-only backup
• AbortBackup cannot be called on read-only backup

AI-assisted analysis of vitessio/vitess@01a25a7d17 (2026-09-01). Data as JSON: /api/errors/30f079f0592e8168. Report an issue: GitHub.