What causes "bundle size must be greater than 0" in apache/beam?

Pass a strictly positive byte size, e.g. mongodbio.WithReadBundleSize(64 * 1024 * 1024).

bundle size must be greater than 0

Error message

bundle size must be greater than 0

What it means

WithReadBundleSize is a ReadOption for the Beam MongoDB connector that sets the target byte size of each read bundle. It rejects non-positive values because a zero or negative bundle size makes splitting the _id range meaningless. The error is returned when the option function is applied to ReadOption.

Source

Thrown at sdks/go/pkg/beam/io/mongodbio/read_option.go:54

	return func(o *ReadOption) error {
		o.BucketAuto = bucketAuto
		return nil
	}
}

// WithReadFilter configures the ReadOption to use the provided filter.
func WithReadFilter(filter bson.M) ReadOptionFn {
	return func(o *ReadOption) error {
		o.Filter = filter
		return nil
	}
}

// WithReadBundleSize configures the ReadOption to use the provided bundle size in bytes.
func WithReadBundleSize(bundleSize int64) ReadOptionFn {
	return func(o *ReadOption) error {
		if bundleSize <= 0 {
			return errors.New("bundle size must be greater than 0")
		}

		o.BundleSize = bundleSize
		return nil
	}
}

View on GitHub (pinned to 12126d8942)

Solutions

Pass a strictly positive byte size, e.g. mongodbio.WithReadBundleSize(64 * 1024 * 1024).
If the value comes from config or flags, validate it is > 0 before constructing the ReadOptions and provide a sane default (e.g. 64MB).
Check that the parsed config value did not silently become 0 due to a parse failure.

Example fix

// before
opts = append(opts, mongodbio.WithReadBundleSize(bundleSize)) // bundleSize == 0 from missing flag
// after
if bundleSize <= 0 {
    bundleSize = 64 * 1024 * 1024
}
opts = append(opts, mongodbio.WithReadBundleSize(bundleSize))

Defensive patterns

Strategy: validation

Validate before calling

if bundleSize <= 0 {
    return fmt.Errorf("bundleSize must be > 0, got %d", bundleSize)
}
opts = append(opts, mongodbio.WithReadBundleSize(bundleSize))

Try / catch

if err := mongodbio.Read(scope, db, collection, opts...); err != nil {
    return fmt.Errorf("mongodbio read options invalid: %w", err)
}

Prevention

Give bundle-size flags/env vars a positive default (e.g. 64MB).
Validate all numeric options at pipeline-argument parsing time.
Distinguish clearly between bundle size and batch size config fields to avoid mixups.

When it happens

Trigger: Passing mongodbio.WithReadBundleSize(0) or a negative value into the options slice of mongodbio.Read (or ReadList), which applies each option and fails on the first invalid one.

Common situations: Bundle size read from config/CLI flags with a zero default that was never set; int64 conversion of a value that failed parsing to 0; copy-paste where the user meant to set batch size, not bundle size.

Understand the failure class

Background: "Invalid value" and "allowed values are" config errors: what your library rejected and how to fix it — this error's family across 41 libraries.

Related errors

AI-assisted analysis of apache/beam@12126d8942 (2026-09-13). Data as JSON: /api/errors/85692d7310b12b25. Report an issue: GitHub.