What causes "mongodbio.Write: invalid option: %v" in apache/beam?

Fix the invalid input the option validates (positive BatchSize, sane Ordered flag)

mongodbio.Write: invalid option: %v

Error message

mongodbio.Write: invalid option: %v

What it means

mongodbio.Write validates each variadic WriteOption by invoking it; if an option func returns an error, Write panics at graph-construction time because options are expected to be statically valid. Note Write also infers the _id field index from the element type via structx tags right after.

Source

Thrown at sdks/go/pkg/beam/io/mongodbio/write.go:86

//   - Ordered: whether to execute the writes in order. Defaults to true
func Write(
	s beam.Scope,
	uri string,
	database string,
	collection string,
	col beam.PCollection,
	opts ...WriteOptionFn,
) beam.PCollection {
	s = s.Scope("mongodbio.Write")

	option := &WriteOption{
		BatchSize: defaultWriteBatchSize,
		Ordered:   defaultWriteOrdered,
	}

	for _, opt := range opts {
		if err := opt(option); err != nil {
			panic(fmt.Sprintf("mongodbio.Write: invalid option: %v", err))
		}
	}

	t := col.Type().Type()
	idIndex := structx.FieldIndexByTag(t, bsonTag, "_id")

	var keyed beam.PCollection

	if idIndex == -1 {
		pre := beam.ParDo(s, createIDFn, col)
		keyed = beam.Reshuffle(s, pre)
	} else {
		keyed = beam.ParDo(
			s,
			newExtractIDFn(idIndex),
			col,
			beam.TypeDefinition{Var: beam.XType, T: t.Field(idIndex).Type},
		)

View on GitHub (pinned to 12126d8942)

Solutions

Fix the invalid input the option validates (positive BatchSize, sane Ordered flag)
Inspect custom WriteOption funcs for validation bugs
Validate batch size / ordering config before calling Write
Wrap construction in recover() to surface the message cleanly

Example fix

// before
opt := func(o *mongodbio.WriteOption) error {
    o.BatchSize = cfg.BatchSize // 0
    return nil
}
// after
opt := func(o *mongodbio.WriteOption) error {
    if cfg.BatchSize <= 0 {
        return fmt.Errorf("batchSize must be > 0, got %d", cfg.BatchSize)
    }
    o.BatchSize = cfg.BatchSize
    return nil
}

Defensive patterns

Strategy: validation

Validate before calling

func validateWriteOption(o *mongodbio.WriteOption) error {
    if o.BatchSize <= 0 { return fmt.Errorf("BatchSize must be > 0") }
    return nil
}

Try / catch

defer func() { if r := recover(); r != nil { log.Fatalf("Write options invalid: %v", r) } }()

Prevention

Validate batch-size/ordering flags before building the pipeline
Test custom WriteOption funcs like any other code
Prefer library option constructors over ad-hoc closures

When it happens

Trigger: Passing a custom func(*WriteOption) error that returns non-nil, e.g. a WithBatchSize helper rejecting non-positive batch sizes or an invalid Ordered combination, when calling Write.

Common situations: Options sourced from config flags (batch size 0 or negative); custom option funcs with buggy validation; conflicting options like generate-ID plus an existing _id tag mishandled.

Understand the failure class

Background: "Must be a positive integer", "Invalid value", "Unsupported": the invalid-argument-value error family, when a library rejects the value you pass — this error's family across 35 libraries.

Related errors

AI-assisted analysis of apache/beam@12126d8942 (2026-09-13). Data as JSON: /api/errors/be8b173d3eb5967a. Report an issue: GitHub.